Electrolyte, battery and electric device

Abstract

The application relates to an electrolyte, a battery and a power utilization device. The electrolyte comprises a first additive and a second additive, the first additive comprises fluoroethylene carbonate, and the second additive comprises 2-[N,N-bis(trifluoromethane alkyl sulfone) amino] pyridine. Through the interaction of the first additive and the second additive, the electrolyte can not only reduce the loss of active lithium, but also can better form a film on the surface of a negative electrode sheet, so that the battery has higher initial charge-discharge efficiency, energy density and better cycle stability.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to an electrolyte, a battery, and an electrical device. Background Technology

[0002] With the rapid development of new energy technologies, the requirements for the capacity and energy efficiency of energy storage batteries are becoming increasingly stringent. To improve battery energy efficiency, the specific surface area of ​​the negative electrode is typically increased to enhance the number of reactive sites on the graphite surface. Simultaneously, the particle size of the negative electrode is reduced to increase the lithium intercalation rate in the graphite, thereby improving the energy efficiency of the electrode assembly. However, as the specific surface area of ​​the negative electrode increases, side reactions between the negative electrode and the electrolyte increase during battery formation and film formation. This leads to the consumption of more active lithium, resulting in a loss of battery capacity, thus causing lower initial efficiency and poorer cycle performance. Summary of the Invention

[0003] In view of this, this application provides an electrolyte, a battery, and an electrical device. The electrolyte, through the interaction of a first additive and a second additive, reduces the loss of active lithium and can form a film on the surface of the negative electrode, so that the battery has both high initial charge-discharge efficiency, energy density, and good cycle stability.

[0004] This application provides an electrolyte comprising: a first additive and a second additive, wherein the first additive comprises fluoroethylene carbonate and the second additive comprises 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine.

[0005] Furthermore, if the mass fraction of the first additive is a and the mass fraction of the second additive is b, then the electrolyte satisfies the relationship: 1 < a / b ≤ 10.

[0006] Furthermore, the mass fraction 'a' of the first additive is in the range of 0.1% ≤ a ≤ 3%.

[0007] Furthermore, the mass fraction b of the second additive is in the range of 0.05% ≤ b ≤ 2%.

[0008] This application also provides a battery, the battery including an electrode assembly and an electrolyte provided in this application, the electrode assembly including a negative electrode sheet; the electrolyte is used to wet at least a portion of the electrode assembly.

[0009] Further, in the electrolyte, the mass fraction of the first additive is a, and the mass fraction of the second additive is b; the negative electrode sheet includes a negative electrode current collector layer and a negative electrode material layer stacked together, the negative electrode material layer includes active particles, and the specific surface area of ​​the active particles is S. Therefore, the battery satisfies the relationship: 0.2 g / m³. 2≤100(a+b) / S≤8g / m 2 .

[0010] Furthermore, the specific surface area S of the active particles is in the range of 0.8 m². 2 / g≤S≤2.5m 2 / g.

[0011] Further, in the electrolyte, the mass fraction of the first additive is a, and the mass fraction of the second additive is b; the negative electrode sheet includes a negative electrode current collector layer and a negative electrode material layer stacked together, the negative electrode material layer includes active particles, and the median particle size of the active particles is D. Then the battery satisfies the relationship: 3μm≤D / 100(a+b)≤16μm.

[0012] Furthermore, the median particle size D of the active particles is in the range of 5μm≤D≤20μm.

[0013] This application also provides an electrical device, which includes a device body and a battery provided in this application, wherein the battery supplies power to the device body.

[0014] In this application, the electrolyte includes a first additive and a second additive. The first additive includes fluoroethylene carbonate and is a film-forming additive. When the electrolyte is applied to a battery and the battery is being formed, the first additive undergoes a reduction reaction and decomposes. The decomposition products form an SEI film on the surface of the negative electrode. The SEI film formed by the first additive has a stable structure, resulting in good cycle performance of the battery under both low and high temperature environments. Furthermore, during the charge-discharge cycle of the battery, the first additive can repair the SEI film to maintain the stability of the interfacial film formed by the first additive on the surface of the negative electrode. However, in the first additive, the carbon-fluorine bonds in the fluoroethylene carbonate are easily broken, making it easy to separate fluoride ions and ethylene carbonate molecules from the first additive. Fluoride ions easily combine with active ions in the electrolyte, such as lithium ions, to form lithium fluoride, thereby consuming the active lithium ions in the electrolyte and reducing the battery's initial charge-discharge efficiency and energy density. Furthermore, the electrolyte of this application also includes a second additive, which comprises 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine. The trifluoromethyl group in 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine has a strong electron-withdrawing effect, causing the electron cloud density of the second additive to be biased towards the trifluoromethyl molecule. Since the electronegativity of the nitrogen atom is greater than that of the carbon atom, during initial film formation, the CN bond in the second additive breaks to form a pyridine carbocation and N,N-bistrifluoromethanesulfonyl. When the first and second additives are mixed and distributed in the electrolyte, the pyridine carbocation combines with fluoride ions to form 2-fluoropyridine, thereby reducing the free fluoride ions in the electrolyte and slowing down the combination of fluoride ions with lithium ions. This prevents fluoride ions from consuming lithium ions in the electrolyte, resulting in a higher initial charge / discharge efficiency and energy density for the battery. Furthermore, 2-fluoropyridine exhibits higher reactivity than the first additive, making it easier to decompose and form a film on the surface of the negative electrode. Additionally, N,N-bis(trifluoromethanesulfonyl) can promote the ring-opening and decomposition of ethylene carbonate molecules into a film. In other words, the combination of the first and second additives allows for better film formation on the surface of the negative electrode during the initial film formation process, resulting in a composite interfacial film containing inorganic and organic components such as N, F, and C, thus enhancing the battery's cycle stability. Moreover, the interfacial film formed on the surface of the negative electrode by the first and second additives contains a higher proportion of inorganic components, further contributing to the battery's high-temperature cycle stability. The electrolyte of this application, through the interaction of the first and second additives, reduces the loss of active lithium and effectively forms a film on the surface of the negative electrode, resulting in a battery that combines high initial charge-discharge efficiency, energy density, and good cycle stability. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementations of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a battery according to an embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the structure of an electrical device according to an embodiment of this application;

[0018] Figure 3 This is a circuit block diagram of an electrical device according to an embodiment of this application.

[0019] Explanation of reference numerals in the attached figures:

[0020] 100-Battery, 110-Electrode assembly, 111-Negative electrode, 112-Separator, 113-Positive electrode, 120-Electrolyte, 200-Electrical equipment, 210-Equipment body. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0023] In this document, references to "embodiment" or "implementation" mean that a particular feature, structure, or characteristic described in connection with an embodiment or implementation may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] With the rapid development of new energy technologies, the requirements for the capacity and energy efficiency of energy storage batteries are becoming increasingly stringent. To improve battery energy efficiency, the specific surface area of ​​the negative electrode is typically increased to enhance the number of reactive sites on the graphite surface. Simultaneously, the particle size of the negative electrode is reduced to increase the lithium intercalation rate in the graphite, thereby improving the energy efficiency of the electrode assembly. However, as the specific surface area of ​​the negative electrode increases, side reactions between the negative electrode and the electrolyte increase during battery formation and film formation. This leads to the consumption of more active lithium, resulting in a loss of battery capacity, thus causing lower initial efficiency and poorer cycle performance.

[0025] Specifically, during the formation of the SEI film in a battery, additives in the electrolyte decompose on the negative electrode surface to form a film, which consumes a certain amount of active lithium, leading to capacity loss. Therefore, a solution is needed to increase the specific surface area of ​​the negative electrode and reduce its particle size without deteriorating the battery's initial efficiency and cycle performance.

[0026] Understandably, in the terminology of this application, "SEI membrane" refers to Solid Electrolyte Interface membrane, which is located at the interface between the battery electrode (e.g., the negative electrode) and the electrolyte.

[0027] Please see Figure 1 This application provides an electrolyte 120, which includes a first additive and a second additive. The first additive includes fluoroethylene carbonate, and the second additive includes 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine.

[0028] Understandably, the electrolyte 120 is applied to the battery 100, and the battery 100 includes an electrode assembly 110, the electrolyte 120 being used to wet at least a portion of the electrode assembly 110, the electrode assembly 110 including a negative electrode 111.

[0029] Understandably, the structural formula of 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine is...

[0030] In this embodiment, the electrolyte 120 includes a first additive and a second additive. The first additive includes fluoroethylene carbonate and is a film-forming additive. When the electrolyte 120 is applied to the battery 100 and the battery 100 is being formed, the first additive undergoes a reduction reaction and decomposes. The decomposition products form an SEI film on the surface of the negative electrode 111. The SEI film structure formed by the first additive is stable, enabling the battery 100 to have good cycle performance in both low-temperature and high-temperature environments. Furthermore, during the charge-discharge cycle of the battery 100, the first additive can repair the SEI film to maintain the stability of the interface film formed by the first additive on the surface of the negative electrode 111. However, in the first additive, the carbon-fluorine bonds in the fluoroethylene carbonate are easily broken, making it easy to separate fluoride ions and ethylene carbonate molecules from the first additive. Fluoride ions easily combine with active ions such as lithium ions in the electrolyte 120 to form lithium fluoride, thereby consuming the active lithium ions in the electrolyte 120 and reducing the first charge-discharge efficiency and energy density of the battery 100. Furthermore, the electrolyte 120 in this embodiment further includes a second additive, which comprises 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine. The trifluoromethyl group in 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine has a strong electron-withdrawing effect, causing the electron cloud density of the second additive to be biased towards the trifluoromethyl molecule. Since the electronegativity of the nitrogen atom is greater than that of the carbon atom, during initial film formation, the CN bond in the second additive breaks to form a pyridine carbocation and N,N-bistrifluoromethanesulfonyl. When the first and second additives are mixed and distributed in the electrolyte 120, the pyridine carbocation combines with fluoride ions to form 2-fluoropyridine, thereby reducing the free fluoride ions in the electrolyte 120 and slowing down the combination of fluoride ions with lithium ions. This prevents fluoride ions from consuming lithium ions in the electrolyte 120, thus enabling the battery 100 to have higher initial charge / discharge efficiency and energy density. Furthermore, 2-fluoropyridine exhibits higher reactivity than the first additive, making it easier to decompose and form a film on the surface of the negative electrode 111. Additionally, N,N-bis(trifluoromethanesulfonyl) can promote the ring-opening and decomposition of ethylene carbonate molecules into a film. In other words, the combination of the first and second additives allows for better film formation on the surface of the negative electrode 111 during the initial film formation process of the battery 100, resulting in a composite interfacial film containing inorganic and organic components such as N, F, and C. This enhances the cycle stability of the battery 100. Moreover, the interfacial film formed on the surface of the negative electrode 111 by the first and second additives contains a higher proportion of inorganic components, further contributing to the battery 100's superior high-temperature cycle stability.In this embodiment, the electrolyte 120, through the interaction of the first additive and the second additive, reduces the loss of active lithium and can form a film on the surface of the negative electrode 111, so that the battery 100 has both high initial charge and discharge efficiency, energy density and good cycle stability.

[0031] Understandably, in the terminology of this application, "formation" refers to the process of activating the active materials of the positive electrode 113 and negative electrode 111 inside the battery 100 after its manufacture by means of a certain charging and discharging method, thereby improving the charging and discharging performance and the comprehensive performance of the battery 100, such as self-discharge and storage.

[0032] Understandably, in the terminology of this application, a higher "reactivity" indicates a greater likelihood of a reaction occurring. For example, during the charging process of battery 100, the potential of the positive electrode 113 increases, while the potential of the negative electrode 111 decreases. If the reduction potential on the negative electrode 111 side is higher, it indicates that the reduction decomposition reaction occurs more preferentially on the negative electrode 111. In this embodiment, the product 2-fluoropyridine formed by the reaction of pyridine carbocations and fluoride ions has a higher reduction potential on the negative electrode 111 side compared to the first additive.

[0033] Specifically, the reduction potential of the first additive on the negative electrode 111 side is about 1.2V, the reduction potential of the second additive on the negative electrode 111 side is about 1.5V and about 1.98V, and the reduction potential of 2-fluoropyridine, the product formed by the first additive and the second additive, on the negative electrode 111 side is higher than 1.2V.

[0034] In some embodiments, if the mass fraction of the first additive is a and the mass fraction of the second additive is b, then the electrolyte 120 satisfies the relationship: 1 < a / b ≤ 10.

[0035] Specifically, the value of a / b can be, but is not limited to, 1.5, 2, 2.5, 3, 3.6, 4, 4.7, 5, 5.5, 6, 6.5, 7, 7.3, 8, 8.6, 9, 9.6 and 10.

[0036] Understandably, in the electrolyte 120, the mass fraction of the first additive is greater than the mass fraction of the second additive.

[0037] When the electrolyte 120 satisfies the relationship 1 < a / b ≤ 10, the mass fractions of the first additive and the second additive in the electrolyte 120 are both within a reasonable range, and the mass fraction of the first additive is greater than the mass fraction of the second additive. On the one hand, during the formation stage of the battery 100, the first additive and the second additive are compounded, and the number of pyridine carbocations separated from the second additive and the number of N,N-bis(trifluoromethanesulfonyl) are both within a reasonable range. The pyridine carbocations of the second additive combine with the fluoride ions separated from the first additive to reduce the free fluoride ions in the electrolyte 120, thereby enabling the battery 100 to have a higher first charge and discharge efficiency and energy density. Furthermore, the product 2-fluoropyridine, formed by the combination of the first and second additives, exhibits higher reactivity than the first additive, making it easier to decompose and form a film on the surface of the negative electrode 111. Additionally, N,N-bis(trifluoromethanesulfonyl) can promote the ring-opening and decomposition of ethylene carbonate molecules into a film. In other words, the combination of the first and second additives allows for better film formation on the surface of the negative electrode 111 during the initial film formation process of the battery 100, resulting in a composite interfacial film containing inorganic and organic elements such as N, F, and C, thus enhancing the cycle stability of the battery 100. On the other hand, during subsequent charge-discharge cycles of the battery 100, the first additive can promptly repair the SEI film to maintain its structural integrity, thereby ensuring the cycle stability of the battery 100. When the a / b value is too high, the mass fraction of the first additive in the electrolyte 120 is too large, or the mass fraction of the second additive is too small. Although the first additive can promote the formation of the SEI film, it separates too many fluoride ions, while the second additive separates too few pyridine ions. The pyridine ions are insufficient to combine with the fluoride ions, resulting in free fluoride ions remaining in the electrolyte 120. These fluoride ions will combine with lithium ions in the electrolyte 120 to form lithium fluoride, causing lithium ion loss in the electrolyte 120. Consequently, when the electrolyte 120 is applied to the battery 100, the initial charge-discharge efficiency and energy density of the battery 100 are low. When the a / b value is too small, the mass fraction of the first additive in the electrolyte 120 is too small, or the mass fraction of the second additive is too large. When the mass fraction of the first additive is too small, it is difficult for the first additive to repair the SEI film during subsequent charge-discharge cycles of the battery 100, thereby reducing the structural stability of the SEI film and resulting in poor cycle stability of the battery 100.When the mass fraction of the second additive is too high, the second additive separates out too much 2-fluoropyridine. The pyridine carbocation in the second additive forms too much 2-fluoropyridine with the fluoride ions in the first additive, which will increase the impedance of the interfacial film between the negative electrode 111 and the electrolyte 120, thereby reducing the energy efficiency of the battery 100.

[0038] In some embodiments, the mass fraction 'a' of the first additive is in the range of 0.1% ≤ a ≤ 3%.

[0039] Specifically, the mass fraction a of the first additive can be, but is not limited to, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, and 3%.

[0040] When the mass fraction 'a' of the first additive is within the range of 0.1% ≤ a ≤ 3%, the mass fraction 'a' of the first additive is within a reasonable range. In the electrolyte 120, the mass proportion of the first additive is within a reasonable range. On one hand, during the formation stage of the battery 100 and subsequent charge-discharge cycles, the first additive can work in conjunction with the second additive to form an SEI film on the surface of the negative electrode 111. Furthermore, the first additive can repair the SEI film, giving it better structural stability. On the other hand, it can prevent the first additive from separating out excessive fluoride ions and from losing excessive lithium ions. Therefore, when the electrolyte 120 is applied to the battery 100, the battery 100 exhibits both high initial charge-discharge efficiency, high energy density, and good cycle stability. When the mass fraction 'a' of the first additive is too high, its mass proportion in the electrolyte 120 is too large. This results in an excessive amount of fluoride ions released from the first additive. Even if the electrolyte 120 includes the second additive, it is difficult for these fluoride ions to combine with all the fluoride ions separated from the first additive, leaving a large number of free fluoride ions in the electrolyte 120. This will deplete the lithium ions in the electrolyte 120, thereby reducing the initial charge / discharge efficiency and energy density of the battery 100. Conversely, when the mass fraction 'a' of the first additive is too low, its mass proportion in the electrolyte 120 is too small. In subsequent charge / discharge cycles of the battery 100, the first additive is insufficient to repair the SEI film, thus reducing the structural stability of the SEI film and resulting in poor cycle stability of the battery 100.

[0041] In some embodiments, the mass fraction b of the second additive is in the range of 0.05% ≤ b ≤ 2%.

[0042] Specifically, the mass fraction b of the second additive can be, but is not limited to, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, 1.5%, 1.7%, 1.8%, and 2%.

[0043] When the mass fraction b of the second additive is within the range of 0.05% ≤ b ≤ 2%, the mass fraction b of the second additive is within a reasonable range. Therefore, the mass proportion of the second additive in the electrolyte 120 is within a reasonable range, and the amount of pyridine carbocations and N,N-bis(trifluoromethanesulfonyl) separated from the second additive is within a reasonable range. On the one hand, the pyridine carbocations can combine with the fluoride ions separated from the first additive to form 2-fluoropyridine, thereby consuming the free fluoride ions in the electrolyte 120, avoiding excessive loss of lithium ions by the first additive during film formation, and avoiding excessive generation of 2-fluoropyridine which would increase the internal resistance of the battery 100. As a result, when the electrolyte 120 is applied to the battery 100, the battery 100 has higher initial charge-discharge efficiency, energy density, and energy efficiency. On the other hand, N,N-bis(trifluoromethanesulfonyl) can promote the ring-opening and film formation of ethylene carbonate molecules decomposed from the first additive. In other words, the combination of the first and second additives can better decompose and form a film on the surface of the negative electrode 111 during the initial film formation process of the battery 100, forming a composite interfacial film containing inorganic and organic substances such as N, F, and C, thus giving the battery 100 better cycle stability. When the mass fraction b of the second additive is too large, the mass proportion of the second additive in the electrolyte 120 is too large. The pyridine carbocations in the second additive and the fluoride ions in the first additive form excessive 2-fluoropyridine, which will increase the impedance of the interfacial film between the negative electrode 111 and the electrolyte 120, thereby reducing the energy efficiency of the battery 100 and deteriorating the rate performance of the battery 100. When the mass fraction b of the second additive is too small, the mass proportion of the second additive in the electrolyte 120 is too small, resulting in too few pyridine ions separated by the second additive. This means that the pyridine ions can only combine with a small portion of the fluoride ions. In other words, there are still a lot of free fluoride ions in the electrolyte 120, which causes the fluoride ions to combine with and consume the lithium ions in the electrolyte 120, reducing the first charge-discharge efficiency and energy density of the battery 100 when the electrolyte 120 is applied.

[0044] Preferably, the mass fraction b of the second additive is in the range of 0.01% ≤ b ≤ 1%.

[0045] Optionally, the electrolyte 120 further includes a solvent used to dissolve the first additive and the second additive. The solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and ethylene glycol dimethyl ether.

[0046] Optionally, the electrolyte 120 further includes a lithium salt dissolved in a solvent. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium tetrafluoroborate, and lithium trifluoromethanesulfonylimide. The lithium salt has a high lithium content to provide active lithium ions to the electrolyte 120, thereby increasing the energy density of the battery 100 when the electrolyte 120 is used.

[0047] This application also provides a battery 100, which includes an electrode assembly 110 and an electrolyte 120 provided in this application. The electrode assembly 110 includes a negative electrode 111. The electrolyte 120 is used to wet at least a portion of the electrode assembly 110.

[0048] Optionally, in some embodiments, the battery 100 is a lithium-ion battery.

[0049] Understandably, the electrode assembly 110 also includes a positive electrode 113. During the charging process of the battery 100, lithium ions are released from the positive electrode 113 and embedded into the negative electrode 111 through the electrolyte 120; during the discharging process of the battery 100, lithium ions are released from the negative electrode 111 and embedded into the positive electrode 113 through the electrolyte 120.

[0050] In the battery 100 provided in this embodiment, the electrolyte 120 is used to wet at least a portion of the electrode assembly 110 to achieve ion transport between the electrolyte 120 and the electrode assembly 110. The electrolyte 120 includes a first additive and a second additive. The second additive can promptly consume the fluoride ions separated by the first additive, so that even if the negative electrode 111 has a large specific surface area, the combination of fluoride ions and lithium ions can be slowed down, thereby avoiding the consumption of active lithium in the battery 100. The battery 100 has high initial charge-discharge efficiency and energy density. In addition, the first additive and the second additive are combined to form a composite interface film containing inorganic and organic substances such as N, F, and C on the surface of the negative electrode 111, so that the battery 100 has good cycle stability.

[0051] Optionally, the electrode assembly 110 further includes a diaphragm 112, and the positive electrode 113, the diaphragm 112 and the negative electrode 111 are stacked together.

[0052] Optionally, in the electrolyte 120, the mass fraction a of the first additive and the mass fraction b of the second additive satisfy the relationship: 0.15% ≤ a + b ≤ 5%.

[0053] Understandably, a+b can characterize the ratio of the total mass of the first additive and the second additive to the mass of the electrolyte 120.

[0054] Specifically, the value of a+b can be, but is not limited to, 0.15%, 0.8%, 1%, 1.2%, 1.9%, 2%, 2.3%, 2.7%, 3%, 3.2%, 3.6%, 4%, 4.2%, 4.7%, and 5%.

[0055] In this embodiment, when the mass fractions a of the first additive and b of the second additive satisfy 0.15% ≤ a + b ≤ 5%, the mass fractions a of the first additive and b of the second additive are within a reasonable range in the electrolyte 120. The combination of the first additive and the second additive can slow down the combination of fluoride ions separated from the first additive with lithium ions in the electrolyte 120, thus avoiding excessive consumption of lithium ions. It can also form a stable SEI film on the surface of the negative electrode 111, thereby enabling the battery 100 to have high energy density, first charge / discharge efficiency, and energy efficiency. When the value of a + b is too large, the sum of the mass fractions a of the first additive and b of the second additive is too large. When the mass fraction a of the first additive is too high, it may lead to excessive fluoride ions separated from the first additive. Even if the content of the second additive is high, it is difficult to slow down the combination of fluoride ions with lithium ions. In addition, if the mass fraction of the second additive is large enough, the product formed by the second additive and fluoride ions will also increase the impedance of the battery 100, thereby reducing the energy efficiency of the battery 100. When the value of a+b is too small, the sum of the mass fractions a of the first additive and b of the second additive is too small. This results in insufficient amounts of the first additive and / or the second additive. When the first additive is insufficient, the electrolyte 120 has difficulty forming an SEI film on the surface of the negative electrode 111, and during subsequent charge-discharge cycles, the first additive cannot repair the SEI film in time, thus reducing the cycle stability of the battery 100. When the second additive is insufficient, it has difficulty binding the fluoride ions detached from the first additive, thus failing to slow down the consumption of active lithium in the electrolyte 120, resulting in lower initial charge-discharge efficiency and energy density of the battery 100.

[0056] In some embodiments, the negative electrode 111 includes a negative electrode current collector layer and a negative electrode material layer stacked together. The negative electrode material layer includes active particles with a specific surface area S, wherein the specific surface area S of the active particles ranges from 0.8 μm. 2 / g≤S≤2.5m 2 / g.

[0057] Specifically, the specific surface area S of the active particles can be, but is not limited to, 0.8 m². 2 / g, 0.9m 2 / g、1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g、2m 2 / g, 2.2m 2 / g, 2.4m 2 / g and 2.5m 2 / g etc.

[0058] Optionally, in some embodiments, the active particles are graphite particles.

[0059] Understandably, the larger the specific surface area of ​​the active particles, the more sites the negative electrode material layer has that can be used for lithium insertion or delithiation, and the more active sites there are on the negative electrode material layer. When the electrolyte 120 wets the negative electrode sheet 111, the electrolyte 120 is more likely to undergo side reactions with lithium ions at the active sites of the negative electrode material layer.

[0060] Understandably, the number of active particles is multiple.

[0061] Understandably, S represents the total area per unit mass of the active particles.

[0062] In this embodiment, the specific surface area S of the active particles is within the range of 0.8 m². 2 / g≤S≤2.5m 2At a specific surface area S of / g, the active particles are within a reasonable range, and the negative electrode material layer has a large number of active sites, which can reduce the rate at which lithium ions are inserted into or extracted from the negative electrode 111 in the electrolyte 120. In other words, the lithium insertion efficiency of the negative electrode 111 is high, thereby giving the battery 100 a high energy efficiency. Furthermore, it avoids the active particles having an excessively large specific surface area, which would accelerate the combination of fluoride ions separated from the first additive with lithium ions, thus enabling the battery 100 to possess high energy efficiency, initial charge / discharge efficiency, and energy density. When the specific surface area S of the active particles is too large, there are too many active sites in the negative electrode material layer. When the electrolyte 120 wets the negative electrode sheet 111, fluoride ions separated from the first additive in the electrolyte 120 easily combine with lithium ions at the active sites. In other words, the more active sites the negative electrode material layer has, the easier it is for fluoride ions to combine with lithium ions, thereby aggravating the loss of lithium ions in the electrolyte 120 and resulting in lower initial charge-discharge efficiency and energy density of the battery 100. When the specific surface area S of the active particles is too small, there are too few active sites in the negative electrode material layer. In other words, the lithium intercalation efficiency of the negative electrode sheet 111 is low, resulting in lower energy efficiency of the battery 100.

[0063] In some embodiments, in the electrolyte 120, the mass fraction of the first additive is a, and the mass fraction of the second additive is b; the battery 100 satisfies the relationship: 0.2 g / m 2 ≤100(a+b) / S≤8g / m 2 .

[0064] Specifically, the value of 100(a+b) / S can be, but is not limited to, 0.2 g / m 2 0.8g / m 2 1g / m 2 1.4g / m 2 2g / m 2 2.2g / m 2 2.5g / m 2 3g / m 2 3.5g / m 2 4g / m 2 4.5g / m 2 5g / m 2 5.5g / m 2 6g / m 2 6.4g / m 2 7g / m 2 7.2g / m 2 7.5g / m 2 and 8g / m 2 wait.

[0065] In this embodiment, when the battery 100 satisfies the relationship 0.2g / m 2 ≤100(a+b) / S≤8g / m 2In the battery 100, the mass fraction a of the first additive, the mass fraction b of the second additive, and the specific surface area S of the active particles are all within a reasonable range. When the specific surface area S of the active particles is within a reasonable range, there are more active sites on the negative electrode material layer, which can reduce the rate at which lithium ions are inserted into or extracted from the negative electrode sheet 111 in the electrolyte 120. In other words, the lithium insertion efficiency of the negative electrode sheet 111 is high, thereby giving the battery 100 a high energy efficiency. In addition, since the mass fractions of the first additive and the second additive are both within a reasonable range, the second additive can combine with the fluoride ions separated from the first additive to prevent free fluoride ions from combining with lithium ions on the active sites, thereby reducing side reactions between the electrolyte 120 and the negative electrode material layer, reducing lithium ion loss in the electrolyte 120, and thus giving the battery 100 a high initial charge-discharge efficiency and energy density. Correspondingly, when the specific surface area of ​​the active particles is small, the amount of the first and second additives required during battery formation is less. If the first and second additives are excessive, the SEI film on the surface of the negative electrode 111 may thicken, slowing down lithium-ion migration and affecting the energy efficiency of the battery 100. When the specific surface area of ​​the active particles is large, the SEI film formed on the surface of the negative electrode 111 should be larger and thicker, correspondingly requiring an increase in the amount of the first and second additives. If the mass content of the first and second additives is small, the first and second additives cannot form a complete SEI film on the surface of the negative electrode 111 for interface protection, resulting in poor interface stability of the SEI film and reducing the cycle stability of the battery 100. When 100(a+b) / S is too large, the sum of the mass fractions a of the first additive and b of the second additive is too large, or the specific surface area S of the active particles is too small. Although the combination of the first and second additives can reduce the consumption of active lithium in the electrolyte 120, excessive amounts of the first and second additives may increase the internal resistance of the battery 100. Furthermore, the small specific surface area of ​​the active particles results in a slow lithium intercalation rate on the negative electrode 111, ultimately leading to low energy efficiency of the battery 100. Conversely, when 100(a+b) / S is too small, the sum of the mass fractions a of the first additive and b of the second additive is too small, or the specific surface area S of the active particles is too large. This results in a faster lithium intercalation rate on the negative electrode 111, giving the battery 100 higher energy efficiency. However, the side reactions between the negative electrode 111 and the electrolyte 120 increase, consuming too many active lithium ions in the electrolyte 120, resulting in poor initial charge-discharge efficiency and cycle performance of the battery 100.

[0066] In some embodiments, the median particle size D of the active particles ranges from 5 μm to D to 20 μm.

[0067] Specifically, the median particle size D of the active particles can be, but is not limited to, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm and 20μm.

[0068] Understandably, the particle size of the active particles is the maximum radial dimension of the active particles. Further, the particle size of the active particles is the diameter of the active particles.

[0069] Understandably, the median particle size of the active particles is the particle size corresponding to 50% of the total mass of particles smaller than this size on the particle size distribution curve of the active particles.

[0070] Understandably, the smaller the median particle size of the active particles, the larger the area of ​​the active particles exposed on the negative electrode material layer. The more sites the negative electrode material layer has that can be used for lithium insertion or delithiation, the more active sites there are on the negative electrode material layer. When the electrolyte 120 wets the negative electrode sheet 111, the electrolyte 120 is more likely to undergo side reactions with lithium ions at the active sites of the negative electrode material layer.

[0071] In this embodiment, when the median particle size D of the active particles meets the range of 5μm≤D≤20μm, the median particle size D of the active particles is within a reasonable range. Therefore, the number of active sites in the negative electrode material layer is within a reasonable range, facilitating the insertion and extraction of lithium ions. It also avoids increased side reactions between the negative electrode material layer and the electrolyte 120 due to excessive active sites, thus enabling the battery 100 to possess high energy efficiency, initial charge / discharge efficiency, and energy density, and exhibiting good cycle performance. When the median particle size D of the active particles is too large, the specific surface area of ​​the active particles is relatively small. Therefore, when the electrolyte 120 wets the negative electrode sheet 111, there are fewer channels and sites for lithium ions to insert into the negative electrode material layer, resulting in lower lithium insertion efficiency of the negative electrode sheet 111 and reducing the cycle performance and energy efficiency of the battery 100. When the median particle size D of the active particles is too small, the specific surface area of ​​the active particles is relatively large. When the electrolyte 120 wets the negative electrode 111, the fluoride ions separated from the first additive in the electrolyte 120 are more likely to combine with lithium ions at the active sites. In other words, the more active sites the negative electrode material layer has, the easier it is for fluoride ions to combine with lithium ions, thereby aggravating the loss of lithium ions in the electrolyte 120 and resulting in a lower first charge and discharge efficiency and energy density of the battery 100.

[0072] In some embodiments, in the electrolyte 120, the mass fraction of the first additive is a, and the mass fraction of the second additive is b; the negative electrode 111 includes a negative electrode current collector layer and a negative electrode material layer stacked together, the negative electrode material layer includes active particles, and the median particle size of the active particles is D, then the battery 100 satisfies the relationship: 3μm≤D / 100(a+b)≤16μm.

[0073] Specifically, the value of D / 100(a+b) can be, but is not limited to, 3μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm and 16μm.

[0074] When the battery 100 satisfies the relationship 3μm≤D / 100(a+b)≤16μm, the mass fraction a of the first additive, the mass fraction b of the second additive, and the median particle size D of the active particles are all within a reasonable range. On the one hand, the combination of the first and second additives can slow down the combination of fluoride ions separated from the first additive with lithium ions in the electrolyte 120, thus avoiding excessive consumption of lithium ions. It can also form a stable SEI film on the surface of the negative electrode 111, thereby enabling the battery 100 to have both high energy density, high initial charge-discharge efficiency, and high energy efficiency. On the other hand, the median particle size of the active particles being within a reasonable range enables the negative electrode 111 to have a high lithium insertion rate. Furthermore, because the first and second additives are provided in the electrolyte 120, the side reactions between the negative electrode 111 and the electrolyte 120 can be avoided due to the increase in active sites in the negative electrode material layer. This results in the battery 100 having high cycle stability and high energy efficiency. Correspondingly, when the median particle size of the active particles is small, the delithiation and lithiation rates of the negative electrode material layer are faster. However, the structural stability of the active particles is relatively poor, requiring more first and second additives to form a stable SEI film at the interface between the negative electrode 111 and the electrolyte 120, thereby improving the cycle stability of the battery 100. However, the content of the first and second additives should not be excessive to avoid forming an overly thick SEI film on the surface of the negative electrode 111, which would reduce the lithium-ion transport efficiency at the interface of the negative electrode 111 and decrease the energy efficiency of the battery 100. When the value of D / 100(a+b) is too large, the median particle size D of the active particles is too large, or the sum of the mass fractions a of the first additive and b of the second additive is too small. When the median particle size of the active particles is too large, when the electrolyte 120 wets the negative electrode 111, there are fewer channels and sites for lithium ions to embed into the negative electrode material layer, resulting in lower lithium embedding efficiency of the negative electrode 111 and reducing the cycle performance and energy efficiency of the battery 100. When the sum of the mass fractions a of the first additive and b of the second additive is too small, if the first additive is too small, the electrolyte 120 has difficulty forming an SEI film on the surface of the negative electrode 111, and in subsequent charge-discharge cycles, the first additive has difficulty repairing the SEI film in time, thereby reducing the cycle stability of the battery 100. If the second additive is too small, the second additive has difficulty binding the fluoride ions detached from the first additive, thus making it difficult to slow down the consumption of active lithium in the electrolyte 120, resulting in lower initial charge-discharge efficiency and energy density of the battery 100.When the value of D / 100(a+b) is too small, the median particle size D of the active particles is too small, or the sum of the mass fraction a of the first additive and the mass fraction b of the second additive is too large. When the median particle size of the active particles is too small, the specific surface area of ​​the active particles is too large. When the electrolyte 120 wets the negative electrode 111, the fluoride ions separated from the first additive in the electrolyte 120 are more likely to combine with lithium ions at the active sites. In other words, the more active sites the negative electrode material layer has, the easier it is for fluoride ions to combine with lithium ions, thereby aggravating the loss of lithium ions in the electrolyte 120, resulting in a lower first charge and discharge efficiency and energy density of the battery 100. When the sum of the mass fraction a of the first additive and the mass fraction b of the second additive is too large, the excessive mass fraction a of the first additive may lead to excessive fluoride ions separated from the first additive. Even if the content of the second additive is large, it is difficult to slow down the combination of fluoride ions and lithium ions. In addition, if the mass fraction of the second additive is large enough, the product formed by the second additive and fluoride ions will also increase the impedance of the battery 100, thereby reducing the energy efficiency of the battery 100.

[0075] The technical solution of this application will be further described below with reference to several embodiments:

[0076] Examples 1 to 10, Comparative Examples 1 to 7:

[0077] 1. Preparation of electrolyte 120:

[0078] In an argon atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were uniformly mixed at a mass ratio of 1:1:1. The dried electrolyte lithium salt, lithium hexafluorophosphate, was dissolved in the solvent until fully dissolved, with a lithium salt concentration of 1 mol / L. Then, a first additive and a second additive were added. The first additive was fluoroethylene carbonate, and the second additive was 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine, to obtain electrolytes 120 of Examples 1 to 10 and Comparative Examples 1 to 7. The mass fractions a and b of the first additive in electrolytes 120 of Examples 1 to 10 and Comparative Examples 1 to 7 are shown in Table 1.

[0079] 2. Preparation of negative electrode sheet 111:

[0080] The negative electrode active particles, artificial graphite, thickener sodium carboxymethyl cellulose (CMC), conductive carbon black (Super-P), and binder styrene-butadiene rubber latex (SBR) were mixed in a mass ratio of 96:2:1:1. Deionized water was added to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred evenly. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector layer (copper foil) with a thickness of 6 μm. After drying, a negative electrode material layer was obtained. After further cold pressing, slitting, and cutting, negative electrode sheets 111 of Examples 1 to 10 and Comparative Examples 1 to 7 were obtained. The single-sided thickness of the negative electrode material layer was 70 μm. The specific surface area S and median particle size D of the active particles in the negative electrode sheets 111 of Examples 1 to 10 and Comparative Examples 1 to 7 are shown in Table 1.

[0081] Furthermore, the values ​​of a / b, 100(a+b) / S, and D / 100(a+b) are shown in Table 1.

[0082] 3. Preparation of positive electrode 113:

[0083] Lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and PVDF binder were mixed at a mass ratio of 97.2:2.3:0.5. Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 60 wt%, which was stirred evenly. The positive electrode slurry was then uniformly coated onto one surface of a 10 μm thick positive electrode current collector layer (aluminum foil). After drying, the positive electrode material layer was obtained. Following further cold pressing, slitting, and cutting, positive electrode sheet 113 was obtained. The single-sided thickness of the positive electrode material layer was 100 μm.

[0084] 4. Preparation of diaphragm 112:

[0085] A 16µm polyethylene (PE) film is used as the diaphragm 112.

[0086] 5. Assembly of Battery 100:

[0087] The positive electrode 113, separator 112, and negative electrode 111 are stacked in sequence, with the separator 112 acting as a separator between the positive electrode 113 and the negative electrode 111. Then, they are wound into a bare electrode assembly 110. After welding the tabs, the bare battery 100 is placed in an outer packaging shell, dried, and then injected with the electrolyte 120. After vacuum sealing, standing, formation, and shaping, the implementation batteries 1 to 10 and the comparative batteries 1 to 7 are finally prepared.

[0088] In this embodiment, the electrolyte 120 and negative electrode 111 of Example 1 are assembled in the experimental battery 1, the electrolyte 120 and negative electrode 111 of Example 2 are assembled in the experimental battery 2, the electrolyte 120 and negative electrode 111 of Comparative Example 1 are assembled in the control battery 1, the electrolyte 120 and negative electrode 111 of Comparative Example 2 are assembled in the control battery 2, and so on.

[0089] Table 1: Performance parameters of electrolyte 120 and active particles of Examples 1 to 10 and Comparative Examples 1 to 7.

[0090]

[0091]

[0092] Battery 100 performance test:

[0093] Charge-discharge cycle test:

[0094] The aforementioned experimental batteries 1 to 10 and control batteries 1 to 7 were subjected to constant current charge-discharge cycle tests on a charge-discharge apparatus at a test temperature of 45°C. The charge-discharge rate was 1C (the magnitude of the charge-discharge current is usually expressed by the charge-discharge rate, and the calculation formula for the charge-discharge current is: charge-discharge current = charge-discharge rate × rated capacity of battery 100). The charge-discharge voltage window was 2.5V to 3.65V (i.e., the charging cut-off voltage of battery 100 is 3.65V, and the discharging cut-off voltage of battery 100 is 2.5V). The capacity retention rate and energy efficiency of experimental batteries 1 to 10 and control batteries 1 to 7 after 800 cycles were calculated. The values ​​of the initial coulombic efficiency, capacity retention rate, and energy efficiency of experimental batteries 1 to 10 and control batteries 1 to 7 at 45°C, after 800 cycles are shown in Table 2.

[0095] The calculation formulas are as follows: Capacity retention rate after the nth cycle = (Discharge capacity after the nth cycle / Discharge capacity of the first cycle) × 100%; Energy efficiency of the nth cycle = (Discharge energy of the nth cycle / Charge energy of the nth cycle) × 100%. Specifically, the initial coulombic efficiency = Energy efficiency of the first cycle = Discharge energy of the first cycle / Charge energy of the first cycle.

[0096] A complete charge-discharge cycle is usually referred to as one full charge-discharge cycle. This means that the battery 100 is first charged from 2.5V to 3.65V, and then discharged from 3.65V back to 2.5V, thus forming one charge-discharge cycle. N cycles are the number of times the above process is repeated.

[0097] Table 2: Performance parameters of implementation batteries 1 to 10 and comparative batteries 1 to 7:

[0098]

[0099] Understandably, the initial coulombic efficiency characterizes the initial charge-discharge efficiency of the battery 100.

[0100] Please refer to Tables 1 and 2. Data from Examples 1 to 3 and Comparative Examples 1 to 3 show that, under the same conditions, the electrolytes 120 in Examples 1 to 3 all include both a first additive and a second additive. Furthermore, the mass fraction b of the second additive in the electrolytes 120 of Examples 1 to 3 meets a reasonable range. The electrolyte 120 in Comparative Example 1 only includes the first additive and does not include the second additive. The mass fraction of the second additive in the electrolyte 120 of Comparative Example 2 is too high, and the mass fraction of the second additive in Comparative Example 3 is too low. This results in the initial coulombic efficiency of Implemented Batteries 1 to 3 being higher than that of Comparative Batteries 1 to 3. The capacity retention rates of Implemented Batteries 1 to 3 at 45°C and after 800 cycles at 1P are also higher than those of Comparative Batteries 1 to 3 at 45°C and after 800 cycles at 1P. The energy efficiency of batteries 1 to 3 after 800 cycles at 45°C and 1P is higher than that of control batteries 1 and 2 after 800 cycles at 45°C and 1P. The energy efficiency of control battery 3 is also higher after 800 cycles at 45°C and 1P. This is because the electrolyte 120 of all examples 1 to 3 includes a second additive and the mass fraction of the second additive is within a reasonable range. During the formation stage of the battery 100, the first additive and the second additive are combined. The number of pyridine carbocations separated by the second additive and the number of N,N-bis(trifluoromethanesulfonyl) are both within a reasonable range. The pyridine carbocations of the second additive combine with the fluoride ions separated by the first additive to reduce the free fluoride ions in the electrolyte 120, thereby giving the battery 100 a higher first charge / discharge efficiency and energy density. Furthermore, the product 2-fluoropyridine, formed by the combination of the first and second additives, exhibits higher reactivity than the first additive, making it easier to decompose and form a film on the surface of the negative electrode 111. Additionally, N,N-bis(trifluoromethanesulfonyl) can promote the ring-opening and decomposition of ethylene carbonate molecules into a film, further enhancing the decomposition and film formation of the first and second additives on the surface of the negative electrode 111. This maintains the stability of the SEI film, resulting in high capacity retention and energy efficiency for batteries 1 to 3 after 800 cycles at 45°C and 1P. Moreover, the first and second additives form a composite interfacial film containing inorganic and organic elements such as N, F, and C on the surface of the negative electrode 111, contributing to the good cycle stability of the battery 100. When the mass fraction of the second additive is too high, the second additive separates out too much 2-fluoropyridine. The pyridine carbocation in the second additive forms too much 2-fluoropyridine with the fluoride ions in the first additive, which will increase the impedance of the interface film between the negative electrode 111 and the electrolyte 120, thereby making the energy efficiency of the control battery 2 too low.When the mass fraction of the second additive is too small, there are too few pyridine ions separated from the second additive. The pyridine ions are insufficient to combine with fluoride ions one by one, resulting in the presence of free fluoride ions in the electrolyte 120. The fluoride ions will combine with lithium ions in the electrolyte 120 to form lithium fluoride, causing the loss of lithium ions in the electrolyte 120. As a result, when the electrolyte 120 is applied to the battery 100, the initial charge-discharge efficiency and energy density of the battery 100 are relatively low.

[0101] Data from Examples 2, 4, and 5 show that the electrolytes 120 in Examples 2, 4, and 5 all include a first additive, and the mass fraction of the first additive is within a reasonable range. Furthermore, the values ​​of a / b, 100(a+b) / S, and D / 100(a+b) are all within reasonable ranges, resulting in high energy efficiency and cycle performance for Implemented Batteries 2, 4, and 5. Further, under the same conditions, as the mass fraction of the first additive increases, the initial coulombic efficiency of the corresponding battery 100 first increases and then decreases. The capacity retention rate of battery 100 at 45°C and 1P for 800 cycles shows an increasing trend, but the energy efficiency of the corresponding battery 100 shows a decreasing trend. This is because, with the mass fraction of the second additive remaining constant, as the mass fraction of the first additive increases, the amount of fluoride ions separated by the first additive increases. During the formation stage of the battery 100, the pyridine cations separated by the second additive combine with fluoride ions one by one to slow down the consumption of lithium ions in the electrolyte 120 by fluoride ions. When the mass fraction of the first additive is small, the pyridine ions separated from the second additive can quickly combine with the fluoride ions separated from the first additive, thereby avoiding lithium ion consumption and improving the initial coulombic efficiency and capacity retention of the battery 100. As the mass fraction of the first additive increases, the product formed by the combination of the fluoride ions separated from the first additive and the pyridine ions of the second additive increases the internal resistance of the battery 100 and reduces the initial coulombic efficiency of the battery 100. Correspondingly, during the charge-discharge cycle of the battery 100, the product 2-fluoropyridine formed by the combination of fluoride ions and pyridine ions will increase the impedance of the interfacial film between the negative electrode 111 and the electrolyte 120, thereby causing the energy efficiency of the implemented batteries 4, 2, and 5 to gradually decrease.

[0102] Similarly, as can be seen from the data of Example 8 and Comparative Example 5, under the same conditions, the mass fraction 'a' of the first additive in Example 8 is within a reasonable range, while the mass fraction of the first additive in Comparative Example 5 is too small. This results in the first coulombic efficiency, capacity retention rate at 45°C and 1P for 800 cycles, and energy efficiency after 800 cycles at 45°C and 1P being higher than those of the comparative battery 5. This is because, in the comparative battery 5, the mass fraction of the first additive is too small. Although this reduces the consumption of lithium ions by fluorine ions separated by the first additive, it also makes it impossible for the first additive to be compounded with the second additive. The first additive and the second additive are difficult to form a stable SEI film on the surface of the negative electrode 111. Furthermore, in the subsequent charge and discharge cycles of the battery 100, the first additive is also difficult to repair the SEI film, increasing the internal resistance of the battery 100 and reducing the capacity retention rate and energy efficiency of the comparative battery 5.

[0103] As can be seen from the data of Examples 6, 7, and Comparative Example 4, when the specific surface area and median particle size of the active particles are the same, the battery 100 can have a higher first charge-discharge efficiency and energy density by adjusting the mass fraction of the first additive and the mass fraction of the second additive. Specifically, in Examples 6 and 7, 100(a+b) / S is within a reasonable range, while in Comparative Example 4, the value of 100(a+b) / S is too large. This causes the following: Although the combination of the first additive and the second additive can reduce the consumption of active lithium in the electrolyte 120, if there is too much of the first additive and the second additive, it may increase the internal resistance of the battery 100. Furthermore, the specific surface area of ​​the active particles is too small, resulting in a slower lithium insertion rate of the negative electrode 111, and ultimately, the energy efficiency of the battery 100 is too low, thus making the final energy efficiency of the comparative battery 4 too low.

[0104] Data from Examples 9, 10, and Comparative Example 6 show that the median particle size and D / 100(a+b) of the active particles in Examples 9 and 10 are within reasonable ranges. However, the median particle size and D / 100(a+b) of the active particles in Comparative Example 6 are too small, resulting in higher initial coulombic efficiencies for Implemented Battery 9 and Implemented Battery 10 compared to Comparative Battery 6. Furthermore, Implemented Battery 9 and Implemented Battery 10 exhibit higher capacity retention at 45°C and 1P for 800 cycles than Comparative Battery 6 at the same temperature. The energy retention rate of batteries 9 and 10 after 800 cycles at 45°C and 1P is higher than that of the control battery 6 after 800 cycles at 45°C and 1P. This is because the number of active sites in the negative electrode material layer is within a reasonable range, which facilitates the insertion and extraction of lithium ions and avoids the increase of side reactions between the negative electrode material layer and the electrolyte 120 due to excessive active sites. As a result, battery 100 has high energy efficiency, first charge-discharge efficiency, and energy density, and battery 100 has good cycle performance. When the median particle size of the active particles is too small, when the electrolyte 120 wets the negative electrode sheet 111, fluoride ions separated from the first additive in the electrolyte 120 are more likely to combine with lithium ions at the active sites. In other words, the more active sites there are in the negative electrode material layer, the easier it is for fluoride ions to combine with lithium ions, thereby aggravating the loss of lithium ions in the electrolyte 120, resulting in lower first charge-discharge efficiency and energy density of battery 100.

[0105] Similarly, as can be seen from the data of Example 8 and Comparative Example 7, the median particle size and D / 100(a+b) value of the active particles in Example 8 are within a reasonable range, while the median particle size and D / 100(a+b) value of the active particles in Comparative Example 7 are too large, resulting in the first coulombic efficiency of the implemented battery 8 being higher than that of the comparative battery 7. Furthermore, the capacity retention rate of the implemented battery 8 after 800 cycles at 45°C and 1P is higher than that of the comparative battery 7 after 800 cycles at 45°C and 1P. Battery 8 has a higher energy efficiency than the control battery 7 after 800 cycles at 45°C and 1P. This is because the number of active sites in the negative electrode material layer is within a reasonable range, facilitating lithium ion insertion and extraction. It also avoids increased side reactions between the negative electrode material layer and the electrolyte 120 due to excessive active sites. This results in battery 100 having high energy efficiency, initial charge / discharge efficiency, and energy density, and good cycle performance. When the median particle size of the active particles is too large, there are fewer channels and sites for lithium ions to insert into the negative electrode material layer when the electrolyte 120 wets the negative electrode sheet 111. This leads to lower lithium insertion efficiency of the negative electrode sheet 111 and reduces the cycle performance and energy efficiency of battery 100.

[0106] Please see Figure 2 and Figure 3 This application also provides an electrical device 200, which includes a device body 210 and a battery 100 provided in this application, wherein the battery 100 supplies power to the device body 210.

[0107] Understandably, the battery 100 is electrically connected to the device body 210.

[0108] In this embodiment, the battery 100 has high initial charge-discharge efficiency, energy density, and energy efficiency, which enables the battery 100 to provide stable power to the device body 210, thereby improving the user experience.

[0109] Optionally, the electrical device 200 in this application embodiment can be, but is not limited to, portable electronic devices such as mobile phones, tablets, laptops, desktop computers, smart bracelets, smartwatches, e-readers, and game consoles. It can also be a vehicle such as a car, truck, sedan, van, freight train, high-speed train, or electric vehicle. Furthermore, it can be various household appliances. Figure 2 The electrical equipment 200 in this embodiment is an energy storage battery cabinet.

[0110] It is understood that the electrical device 200 described in this embodiment is merely one form of the electrical device 200 used by the battery 100, and should not be construed as a limitation on the electrical device 200 provided in this application, nor should it be construed as a limitation on the electrical device 200 provided in various embodiments of this application.

[0111] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises a first additive and a second additive, wherein the first additive is fluoroethylene carbonate and the second additive is 2-[N,N-bis(trifluoromethanesulfonyl)amino]pyridine; the mass fraction of the first additive is a and the mass fraction of the second additive is b, and the electrolyte satisfies the relationship: 1 < a / b ≤ 10; the mass fraction a of the first additive is in the range of 0.1% ≤ a ≤ 3%; and the mass fraction b of the second additive is in the range of 0.05% ≤ b ≤ 2%.

2. A battery, characterized in that, The battery includes: Electrode assembly, the electrode assembly including a negative electrode sheet; and The electrolyte of claim 1 is used to wet at least a portion of the electrode assembly; in the electrolyte, the mass fraction of the first additive is a, and the mass fraction of the second additive is b; the negative electrode sheet includes a negative current collector layer and a negative electrode material layer stacked together, the negative electrode material layer includes active particles, and the specific surface area of ​​the active particles is S, then the battery satisfies the relationship: 0.2 g / m³ 2 ≤100(a+b) / S≤8g / m 2 If the median particle size of the active particles is D, then the battery satisfies the following relationship: 3μm≤D / 100(a+b)≤16μm.

3. The battery according to claim 2, characterized in that, The specific surface area S of the active particles is in the range of 0.8 m². 2 / g≤S≤2.5m 2 / g.

4. The battery according to claim 2, characterized in that, The median particle size D of the active particles is in the range of 5μm≤D≤20μm.

5. An electrical appliance, characterized in that, The electrical equipment includes: The equipment itself; and The battery according to any one of claims 2 to 4, wherein the battery supplies power to the device body.

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