Secondary battery and electronic device comprising same

Abstract

Provided are a secondary battery and an electronic device comprising same. The secondary battery comprises a negative electrode sheet and an electrolyte. The electrolyte comprises a compound represented by formula I. Based on the total mass of the electrolyte, the mass percentage content of the compound represented by formula I is WI％, where WI is from 0.05 to 50. The negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The thickness of a single side of the negative electrode material layer is D μm. A plurality of recesses are arranged on a surface of the negative electrode material layer. The depth of a single recess is d μm, where d < D, and 0.005 ≤ WI / d ≤ 5. The secondary battery has improved high-temperature cycling performance and low-temperature discharge performance.

Description

Secondary batteries and electronic devices containing them

[0001] This application claims priority to Chinese Patent Application No. 202411214635.1, filed on August 30, 2024, entitled "Secondary Battery and Electronic Device Containing the Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device comprising the same. Background Technology

[0003] Electrochemical devices (lithium-ion batteries) are widely used in many fields such as 3C electronic products, electric vehicles, and energy storage power stations due to their high energy density, high power density, low self-discharge, no memory effect, and long cycle life. As the application scope of lithium-ion batteries continues to expand and their application scenarios become more diverse, the market is placing higher demands on the electrochemical performance of lithium-ion batteries. Summary of the Invention

[0004] The purpose of this application is to provide a secondary battery and an electronic device comprising the same, to improve the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. The specific technical solution is as follows:

[0005] A first aspect of this application provides a secondary battery comprising a negative electrode and an electrolyte, said electrolyte comprising a compound represented by Formula I:

[0006] Wherein, R is selected from unsubstituted or Ra-substituted C2 to C6 alkyl groups, unsubstituted or Ra-substituted C6 to C12 aryl groups, and unsubstituted or Ra-substituted C5 to C12 nitrogen-containing heteroaryl groups; each Ra is independently selected from halogens or halogen-substituted C1 to C3 alkyl groups, and each halogen is independently selected from fluorine, chlorine, or bromine; based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is W. I %, W I The value is 0.05 to 50, preferably 1 to 35; the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the thickness of the negative electrode material layer on one side is D μm, the surface of the negative electrode material layer is provided with a plurality of recesses, the depth of a single recess is d μm, d < D, 0.005 ≤ W I / d≤5. In the secondary battery of this application, the electrolyte includes the compound shown in Formula I, the surface of the negative electrode material layer is provided with multiple recesses, and W is adjusted. I and W I A value of / d within the above range is beneficial for simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of secondary batteries.

[0007] In one embodiment of this application, 0.1 ≤ d / D ≤ 0.5. By adjusting the value of d / D within the above range, this application can better utilize the function of the recess and improve lithium plating, thereby enabling the secondary battery to have better high-temperature cycle performance and low-temperature discharge performance.

[0008] In one embodiment of this application, along the thickness direction of the negative electrode sheet, the minimum distance between the outer contours of the orthographic projections of two adjacent recesses is L μm, where 50 ≤ L ≤ 300. Adjusting the value of L within the range of this application allows the recesses to have a suitable distribution density, facilitating the processing of the secondary battery, while also better utilizing the function of the recesses to further improve the high-temperature cycle performance of the secondary battery, while also taking into account the low-temperature discharge performance of the secondary battery.

[0009] In one embodiment of this application, 0.005 ≤ W I / L≤1. Regulate W I The value of / L is within the scope of this application, which enables the compound shown in Formula I to perform better, while avoiding excessive reaction of the compound shown in Formula I in the non-recessed region, thus avoiding the formation of a thicker SEI film, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0010] In one embodiment of this application, 100 ≤ D ≤ 400. By adjusting the value of D within the above range, this application can increase the volumetric energy density of the secondary battery while also taking into account the kinetic performance of the secondary battery, ensuring that the secondary battery has good low-temperature discharge performance.

[0011] In one embodiment of this application, the plurality of recesses are distributed in a stripe pattern along the thickness direction of the negative electrode sheet. The orthographic projection of a single recess includes a stripe shape, and the width D1mm of the orthographic projection of a single recess is 0.02mm to 0.5mm. By adjusting the value of D1 within the above range, this application enables the secondary battery to simultaneously possess better high-temperature cycle performance and low-temperature discharge performance.

[0012] In one embodiment of this application, along the thickness direction of the negative electrode sheet, the total area of ​​the orthogonal projection of the plurality of recesses is S1, and the area of ​​the negative electrode material layer on one side is S2, where 0.1 ≤ S1 / S2 ≤ 0.8. By adjusting the value of S1 / S2 within the above range, this application enables the secondary battery to simultaneously possess better high-temperature cycle performance and low-temperature discharge performance.

[0013] In one embodiment of this application, the compound represented by Formula I includes at least one of the following compounds:

[0014] The electrolyte includes compounds of Formula I within the above-mentioned range, which can better exert the synergistic effect with the concave portion of the negative electrode, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0015] In one embodiment of this application, the electrolyte further includes a fluorinated lithium salt additive, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate. Based on the total mass of the electrolyte, the mass percentage of the fluorinated lithium salt additive is W. L %, W L The concentration is from 0.01 to 1, preferably from 0.1 to 0.7. The electrolyte includes a fluorinated lithium salt additive and adjusts the W... L When the value is within the above range, it can synergistically participate in the film-forming reaction to form a more stable SEI film, thereby further improving the cycle stability of the secondary battery, enhancing the high-temperature cycle performance of the secondary battery, and taking into account the low-temperature discharge performance of the secondary battery.

[0016] In one embodiment of this application, 0.5 ≤ W I / W L ≤300. This application regulates W I / W L Within the above range, the synergistic effect of the compound shown in Formula I in the electrolyte, the fluorinated lithium salt additive, and the concave portion of the negative electrode sheet can be better utilized, further improving the high-temperature cycle performance of the secondary battery while also taking into account the low-temperature discharge performance of the secondary battery.

[0017] In one embodiment of this application, the electrolyte further includes at least one of a polycyano compound or a sulfur-containing oxygen double bond compound; the polycyano compound includes at least one of the following compounds: succinic anionyl nitrile, glutaronitrile, methylglutaronitrile, adiponitrile, heptanonitrile, octanoic anionyl nitrile, azelonitrile, sebacate, 1,3,5-pentanetrionitrile, 1,3,6-hexanetrionitrile; the sulfur-containing oxygen double bond compound includes at least one of the following compounds: 1,3-propanesulfonic acid lactone, 2,4-butanesulfonic acid lactone, 1,4-butanesulfonic acid lactone, vinyl sulfate, 1,3-propanediol sulfate; based on the total mass of the electrolyte, the total mass percentage of the polycyano compound and the sulfur-containing oxygen double bond compound is W. CNSO %, W CNSO The value is 0.1 to 15, preferably 1 to 10; 0.1 ≤ W I / W CNSO ≤40. The electrolyte includes the above-mentioned types of polycyano compounds and / or sulfur-containing oxygen double bond compounds and regulates W. CNSO and W I / W CNSOWhen the value is within the above range, the side reactions of the positive electrode can be suppressed, thereby further improving the high-temperature cycle stability of the secondary battery. This is beneficial for the compound shown in Formula I in the electrolyte and the concave part of the negative electrode to better exert a synergistic effect, further improving the high-temperature cycle performance of the secondary battery, while also taking into account the low-temperature discharge performance of the secondary battery.

[0018] A second aspect of this application provides an electronic device comprising a secondary battery as described in any of the foregoing embodiments. Therefore, the electronic device provided by this application has excellent performance.

[0019] This application provides a secondary battery and an electronic device comprising the same. The secondary battery includes a negative electrode and an electrolyte, the electrolyte comprising a compound represented by Formula I; based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is W. I %, W I The thickness is 0.05 to 50; the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the thickness of the single-sided negative electrode material layer is D μm, and the surface of the negative electrode material layer is provided with multiple recesses, the depth of a single recess is d μm, d < D, 0.005 ≤ W I / d≤5. In the secondary battery of this application, the electrolyte includes the compound shown in Formula I, the surface of the negative electrode material layer is provided with multiple recesses, and W is adjusted. I and W I A value of / d within the above range is beneficial for simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of secondary batteries.

[0020] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0022] Figure 1 is a schematic cross-sectional view of the negative electrode sheet along the thickness direction in one embodiment of this application;

[0023] Figure 2 is a schematic diagram of the structure of a single-sided negative electrode material layer according to one embodiment of this application;

[0024] Figure 3 is a schematic diagram of the structure of a single-sided negative electrode material layer according to another embodiment of this application. Detailed Implementation

[0025] 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. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] It should be noted that, in the specific embodiments of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application; however, the secondary battery in this application is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0027] A first aspect of this application provides a secondary battery comprising a negative electrode and an electrolyte, the electrolyte comprising a compound represented by Formula I:

[0028] Wherein, R is selected from unsubstituted or Ra-substituted C2 to C6 alkyl groups, unsubstituted or Ra-substituted C6 to C12 aryl groups, and unsubstituted or Ra-substituted C5 to C12 nitrogen-containing heteroaryl groups; Ra is independently selected from halogens or halogen-substituted C1 to C3 alkyl groups, and the halogens are independently selected from fluorine, chlorine, or bromine; based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is W. I %, W I The value is from 0.05 to 50, preferably from 1 to 35, for example, W. I The value can be 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 12, 15, 18, 20, 22, 25, 28, 30, 33, 35, 38, 40, 42, 45, 48, 50, or a range of any two of these values; the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The thickness of the single-sided negative electrode material layer is D μm, and the surface of the negative electrode material layer is provided with multiple recesses, the depth of a single recess being d μm, d < D, 0.005 ≤ W. I / d≤5, for example W IThe value of / d can be 0.005, 0.008, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.7, 3, 3.3, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, or a range of any two values. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved. For example, as shown in FIG1, the negative electrode sheet 210 includes a negative electrode current collector 211 and a negative electrode material layer 212 disposed on two surfaces of the negative electrode current collector. The thickness of the single-sided negative electrode material layer 212 is D μm, and a plurality of recesses 214 are disposed on the surface of the negative electrode material layer 212. The depth of a single recess 214 is d μm, where d < D.

[0029] The inventors discovered that at high temperatures, the electrolyte in a secondary battery is consumed rapidly during cycling. Multiple recesses on the surface of the negative electrode material layer can accelerate the flow, wetting, and diffusion of the electrolyte within the negative electrode, enhancing the cycling stability of the secondary battery in a low-electrolyte state and thus improving its high-temperature cycling performance. However, the presence of multiple recesses on the negative electrode can lead to localized electrolyte accumulation. During formation, this results in more localized electrolyte reactions, leading to higher local impedance and hindered ion transport, thus reducing the low-temperature discharge capacity and affecting the battery's low-temperature discharge performance. Adding the compound shown in Formula I to the electrolyte can form a thin, highly ion-conductive interface layer rich in elements such as lithium, sulfur, and fluorine at the interface of the negative electrode recesses, accelerating ion conduction and thereby increasing the low-temperature discharge capacity and performance of the secondary battery. When W I When the value of W is too small, for example less than 0.05, the content of the compound shown in Formula I is too low to improve the low-temperature discharge performance of the secondary battery; when W I When the value of W is too large, for example, greater than 50, the content of the compound shown in Formula I is relatively high, and the thickness of the solid electrolyte interphase (SEI) film formed is significantly increased, which is not conducive to ion transport, and thus not conducive to improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. I When the value of / d is too small, for example, less than 0.005, the compound shown in Formula I cannot exert its effect, making it difficult to improve the low-temperature discharge performance of the secondary battery; when W IWhen the value of / d is too large, for example, greater than 5, the compound shown in Formula I reacts excessively, resulting in an excessively thick SEI film formed on the surface of the negative electrode, which is detrimental to improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. In the secondary battery of this application, the electrolyte includes the compound shown in Formula I, and the surface of the negative electrode material layer is provided with multiple recesses, and W is adjusted. I and W I A value of / d within the above range is beneficial for simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. In this application, "high temperature" refers to a temperature greater than or equal to 45°C, and "low temperature" refers to a temperature less than or equal to -10°C.

[0030] In one embodiment of this application, 0.1 ≤ d / D ≤ 0.5. For example, the value of d / D can be 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, or a range of any two values ​​therein. By adjusting the value of d / D within the above range, this application can better utilize the function of the recessed portion, while ensuring the ratio of negative electrode capacity per unit area to positive electrode capacity per unit area (CB value) of the secondary battery, improving lithium plating, and thus enabling the secondary battery to have better high-temperature cycle performance and low-temperature discharge performance.

[0031] In one embodiment of this application, along the thickness direction of the negative electrode sheet, the minimum distance between the outer contours of the orthographic projections of two adjacent recesses is L μm, where 50 ≤ L ≤ 300. For example, the value of L can be 50, 55, 60, 65, 70, 80, 90, 100, 110, 120, 130, 150, 160, 180, 190, 200, 210, 220, 240, 250, 260, 270, 280, 290, 300, or a range of any two values ​​therein. In this application, the minimum distance L between the outer contours of the orthographic projections of two adjacent recesses can be the same or different, as long as the purpose of this application is achieved. Adjusting the value of L within the range of this application allows the recesses to have a suitable distribution density, facilitating the processing technology of the secondary battery, while better utilizing the function of the recesses, further improving the high-temperature cycle performance of the secondary battery, and simultaneously taking into account the low-temperature discharge performance of the secondary battery.

[0032] In one embodiment of this application, 0.005 ≤ W I / L≤1, for example W IThe value of / L can be 0.005, 0.008, 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range of any two of these values. Adjusting W I The value of / L is within the scope of this application, which enables the compound shown in Formula I to perform better, while avoiding excessive reaction of the compound shown in Formula I in the non-recessed region, thus avoiding the formation of a thicker SEI film, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0033] In one embodiment of this application, 100 ≤ D ≤ 400. For example, the value of D can be 100, 110, 120, 130, 150, 160, 180, 190, 200, 210, 220, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 350, 360, 380, 390, 400, or a range of any two values ​​therein. By adjusting the value of D within the above range, this application can increase the volumetric energy density of the secondary battery while also taking into account the kinetic performance of the secondary battery, ensuring that the secondary battery has good low-temperature discharge performance.

[0034] In one embodiment of this application, multiple recesses are distributed in a stripe pattern along the thickness direction of the negative electrode sheet. The orthographic projection of a single recess includes a stripe shape, and the width D1mm of the orthographic projection of a single recess is 0.02mm to 0.5mm. For example, the value of D1 can be 0.02, 0.03, 0.05, 0.06, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.23, 0.25, 0.27, 0.3, 0.32, 0.35, 0.37, 0.38, 0.4, 0.42, 0.43, 0.45, 0.46, 0.47, 0.48, 0.5, or a range of any two values ​​therein. By controlling the value of D1 within the above range, this application can obtain good processability and simultaneously promote the more complete action of the Formula I molecule on the recessed area, thereby enabling the secondary battery to have better high-temperature cycle performance and low-temperature discharge performance.

[0035] In this application, multiple recesses are distributed in a stripe pattern. Multiple recesses can be arranged along the width direction of the negative electrode sheet, along the length direction of the negative electrode sheet, or simultaneously along both the width and length directions of the negative electrode sheet. In this application, the width D1 of the orthographic projection of a single recess is the maximum value of the orthographic projection width. When multiple recesses are distributed in a stripe pattern, the width D1 of the stripes in the orthographic projection of two adjacent recesses can be the same or different, and the length of the stripes can be the same or different, as long as the purpose of this application is achieved. This application does not have a particular limitation on the length of the stripes; it can be designed according to the size of the negative electrode sheet, as long as the purpose of this application is achieved.

[0036] Specifically, as shown in Figure 2, the surface of the negative electrode material layer 212 is provided with multiple recesses 214. These recesses 214 are distributed in a striped pattern, and one side of the orthographic projection of a single recess 214 is parallel to one side of the negative electrode sheet 210. The orthographic projection of a single recess 214 is a narrow, elongated rectangle with a width of D1 and a minimum spacing of L between adjacent rectangles. It can be understood that, as shown in Figure 3, the multiple recesses 214 are distributed in a striped pattern, and there is an angle between one side of the orthographic projection of a single recess 214 and one side of the negative electrode sheet 210. The orthographic projection of a single recess 214 is a narrow, elongated rectangle with a width of D1 and a minimum spacing of L between adjacent rectangles, with different lengths. This application does not particularly limit the size of the aforementioned angle, as long as it achieves the purpose of this application. For example, the angle is 25° to 65°. The dimensions, number, and shape of the recesses in Figures 2 and 3 are merely examples and do not limit the scope of protection of this application.

[0037] In one embodiment of this application, along the thickness direction of the negative electrode sheet, the total area of ​​the orthogonal projection of multiple recesses is S1, and the area of ​​the single-sided negative electrode material layer is S2, where 0.1 ≤ S1 / S2 ≤ 0.8. For example, S1 / S2 can be 0.1, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, or a range of any two values ​​therein. By adjusting the value of S1 / S2 within the above range, this application can control the proportion of recesses within a reasonable range, allowing the recesses to fully perform their function, thereby enabling the secondary battery to simultaneously possess better high-temperature cycle performance and low-temperature discharge performance.

[0038] This application does not impose any particular limitation on the preparation method of the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the preparation method of the negative electrode sheet may include, but is not limited to, the following steps: setting a negative electrode material layer on one surface of the negative electrode current collector, then repeatedly setting a negative electrode material layer on the other surface of the negative electrode current collector, and then etching a recess on the surface of the double-sided negative electrode material layer by laser process to obtain the negative electrode sheet.

[0039] This application does not impose any particular restrictions on the methods for controlling d, L, D1, and S1, as long as the purpose of this application can be achieved. For example, the magnitudes of d, L, D1, and S1 can be controlled by laser technology.

[0040] In one embodiment of this application, the compound represented by Formula I includes at least one of the following compounds:

[0041] The electrolyte includes compounds of Formula I within the above-mentioned range, which can better exert the synergistic effect with the concave portion of the negative electrode, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0042] In one embodiment of this application, the electrolyte further includes a fluorinated lithium salt additive, which includes at least one of lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate; the mass percentage of the fluorinated lithium salt additive is W based on the total mass of the electrolyte. L %, W L It is 0.01 to 1, preferably 0.1 to 0.7, for example W L The value can be 0.01, 0.02, 0.03, 0.05, 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range of any two of these values. The electrolyte includes fluorinated lithium salt additives and adjusts W... L When the value is within the above range, it can synergistically participate in the film-forming reaction to form a more stable SEI film, thereby further improving the cycle stability of the secondary battery, enhancing the high-temperature cycle performance of the secondary battery, and taking into account the low-temperature discharge performance of the secondary battery.

[0043] In one embodiment of this application, 0.5 ≤ W I / W L ≤300, for example W I / W LThe value can be 0.5, 1, 2, 5, 10, 20, 30, 50, 60, 80, 100, 120, 130, 150, 160, 180, 190, 200, 210, 220, 240, 250, 260, 270, 280, 290, 300, or a range of any two of these values. This application regulates W... I / W L Within the above range, the synergistic effect of the compound shown in Formula I in the electrolyte, the fluorinated lithium salt additive, and the concave portion of the negative electrode sheet can be better utilized, further improving the high-temperature cycle performance of the secondary battery while also taking into account the low-temperature discharge performance of the secondary battery.

[0044] In one embodiment of this application, the electrolyte further includes at least one of a polycyanate compound or a sulfur-containing oxygen double bond compound; the polycyanate compound includes at least one of the following compounds: succinic acid nitrile, glutaronitrile, methylglutaronitrile, adiponitrile, heptanonitrile, octanoic acid nitrile, azelonitrile, sebaconitrile, 1,3,5-pentanetrionitrile, 1,3,6-hexanetrionitrile; the sulfur-containing oxygen double bond compound includes at least one of the following compounds: 1,3-propanesulfonic acid lactone, 2,4-butanesulfonic acid lactone, 1,4-butanesulfonic acid lactone, vinyl sulfate, 1,3-propanediol sulfate; based on the total mass of the electrolyte, the total mass percentage of the polycyanate compound and the sulfur-containing oxygen double bond compound is W. CNSO %, W CNSO The value is 0.1 to 15, preferably 1 to 10, for example, W CNSO The value can be 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, or a range of any two of these values; 0.1 ≤ W I / W CNSO ≤40, for example, W I / W CNSO The value can be 0.1, 0.2, 0.5, 1, 1.5, 2, 3, 5, 6, 8, 10, 12, 13, 15, 16, 18, 20, 22, 23, 25, 26, 28, 30, 32, 33, 35, 36, 38, 39, 40, or a range of any two of these values. The electrolyte includes the aforementioned types of polycyano compounds and / or sulfur-containing oxygen double bond compounds, and the W value is adjusted accordingly. CNSO and W I / W CNSOWhen the value is within the above range, the side reactions of the positive electrode can be suppressed, thereby further improving the high-temperature cycle stability of the secondary battery. This is beneficial for the compound shown in Formula I in the electrolyte and the concave part of the negative electrode to better exert a synergistic effect, further improving the high-temperature cycle performance of the secondary battery, while also taking into account the low-temperature discharge performance of the secondary battery.

[0045] In one embodiment of this application, the electrolyte further includes a polycyanate compound; the mass percentage of the polycyanate compound is 0.1% to 15%, preferably 1% to 10%, based on the total mass of the electrolyte. In one embodiment of this application, the electrolyte further includes a sulfur-containing oxygen double bond compound; the mass percentage of the sulfur-containing oxygen double bond compound is 0.1% to 15%, preferably 1% to 10%, based on the total mass of the electrolyte. In one embodiment of this application, the electrolyte further includes a polycyanate compound and a sulfur-containing oxygen double bond compound, wherein the mass ratio of the polycyanate compound to the sulfur-containing oxygen double bond compound is 1:(0.5 to 1.5).

[0046] In this application, the electrolyte also includes an electrolyte salt and a non-aqueous solvent. This application does not impose any particular limitation on the electrolyte salt, as long as it achieves the purpose of this application. For example, the electrolyte salt may include, but is not limited to, at least one of LiPF6, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. This application does not impose any particular limitation on the content of the electrolyte salt in the electrolyte, as long as it achieves the purpose of this application. For example, based on the mass of the electrolyte, the mass percentage content of the electrolyte salt is 8% to 15%.

[0047] This application does not impose any particular limitation on non-aqueous solvents, as long as they can achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage of non-aqueous solvents may be from 19% to 91%.

[0048] In one embodiment of this application, the electrolyte comprises a compound of Formula I, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the compound of Formula I and the electrolyte salt, based on the total mass of the electrolyte, are as shown above, and the mass percentage of the non-aqueous solvent is 35% to 91%. The secondary battery using the electrolyte of this application, comprising the compound of Formula I, exhibits improved high-temperature cycling performance and low-temperature discharge performance.

[0049] In one embodiment of this application, the electrolyte comprises a compound of Formula I, a fluorinated lithium salt additive, an electrolyte salt, and a non-aqueous solvent. The mass percentages of the compound of Formula I, the fluorinated lithium salt additive, and the electrolyte salt, based on the total mass of the electrolyte, are as shown above, and the mass percentage of the non-aqueous solvent is 34% to 91%. The secondary battery using the electrolyte of this application, comprising the compound of Formula I and the fluorinated lithium salt additive, exhibits further improved high-temperature cycling performance and low-temperature discharge performance.

[0050] In one embodiment of this application, the electrolyte comprises at least one of the compounds represented by Formula I, a polycyano compound, or a sulfur-containing oxygen double bond compound, an electrolyte salt, and a non-aqueous solvent. Based on the total mass of the electrolyte, the total mass percentages of the compound represented by Formula I, the polycyano compound, and the sulfur-containing oxygen double bond compound, and the mass percentage of the electrolyte salt are as shown above, while the mass percentage of the non-aqueous solvent is 20% to 91%. The secondary battery using the electrolyte of this application, comprising the compound represented by Formula I and at least one of the polycyano compound or a sulfur-containing oxygen double bond compound, exhibits further improved high-temperature cycling performance and low-temperature discharge performance.

[0051] In one embodiment of this application, the electrolyte comprises a compound of Formula I, at least one of a fluorinated lithium salt additive, a polycyano compound, or a sulfur-containing oxygen double bond compound, an electrolyte salt, and a non-aqueous solvent. The total mass percentages of the compound of Formula I, the fluorinated lithium salt additive, the polycyano compound, and the sulfur-containing oxygen double bond compound, and the electrolyte salt, based on the total mass of the electrolyte, are as shown above. The mass percentage of the non-aqueous solvent is 19% to 91%. The secondary battery using the electrolyte of this application, comprising the compound of Formula I, the fluorinated lithium salt additive, and at least one of a polycyano compound or a sulfur-containing oxygen double bond compound, exhibits further improved high-temperature cycling performance and low-temperature discharge performance.

[0052] In this application, there are no particular limitations on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors. For example, the composite current collector can be a lithium copper composite current collector, a carbon copper composite current collector, a nickel copper composite current collector, a titanium copper composite current collector, etc. There are no particular limitations on the thickness of the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the thickness of the negative electrode current collector can be from 4 μm to 15 μm.

[0053] The negative electrode material layer includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Or at least one of Li-Al alloys.

[0054] In some embodiments of this application, the negative electrode material layer may further include a conductive agent and a binder. This application does not particularly limit the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0055] In some embodiments of this application, a conductive agent, a binder, and a thickener may also be included. This application does not particularly limit the types of conductive agents and thickeners, as long as they achieve the purpose of this application. For example, the conductive agent and binder may be at least one of the aforementioned conductive agents and binders. The thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, binder, and thickener in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0056] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, which can be a conductive layer commonly used in the art. For example, the conductive layer may include a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0057] In this application, the secondary battery further includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the term "surface" here can refer to the entire surface area of ​​the positive current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0058] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0059] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this application. For example, the positive electrode active material may include, but is not limited to, lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0060] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it may include at least one of the aforementioned conductive agents and binders. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0061] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the positive electrode material layer can be 30 μm to 120 μm.

[0062] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0063] In this application, the secondary battery also includes a separator. This application does not impose any particular limitation on the separator, as long as it achieves the purpose of this application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0064] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0065] Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials. In some embodiments of this application, the inorganic layer includes inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0066] In this application, there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 3 μm to 30 μm.

[0067] In this application, the secondary battery also includes a casing for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the casing; it can be a casing known in the art, as long as it achieves the purpose of this application. For example, the casing can be a rigid casing or a flexible casing. The material of the rigid casing can be metal; this application does not limit the type of metal and can use known metal rigid casings, as long as they achieve the purpose of this application. The flexible casing can be a metal plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0068] The fabrication process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the fabrication process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. Alternatively, stacking the positive electrode sheet, separator, and negative electrode sheet in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the secondary battery. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the secondary battery.

[0069] This application does not impose any particular limitation on the type of secondary battery, which may include any device in which an electrochemical reaction occurs. For example, secondary batteries may include, but are not limited to: lithium metal secondary batteries, lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries.

[0070] A second aspect of this application provides an electronic device comprising a secondary battery as described in any of the foregoing embodiments. The secondary battery provided by this application exhibits excellent high-temperature cycling performance and low-temperature discharge performance, thereby giving the electronic device a long service life.

[0071] This application does not specifically limit the type of electronic device; it can be any electronic device known in the prior art. In some embodiments of this application, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0072] Example

[0073] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0074] Test methods and equipment:

[0075] Dimension measurement:

[0076] d, D: The cross-section of the negative electrode sheet along the thickness direction is obtained by ion polishing. The cross-section of the negative electrode sheet is observed and measured under a scanning electron microscope. The depth d of a single concave part and the thickness D of the single-sided negative electrode material layer are measured.

[0077] D1, L, S1: Place the negative electrode material layer of the negative electrode sheet face up under a VHX5000 microscope with the magnification set to 50 to 200 times; take a picture of the surface of the negative electrode material layer; use microscope software to measure the width D1 of the orthographic projection of a single concave part and the minimum distance L between the outer contours of the orthographic projections of two adjacent concave parts; integrate and sum the orthographic projection areas of the concave parts in the image to obtain S1.

[0078] For each of the above dimensions, 10 points were measured and the average value was taken as the final result.

[0079] High-temperature cycling performance test:

[0080] The lithium-ion battery was placed in a 45°C constant temperature chamber and charged to 4.48V with a constant current of 4.5C. Then it was charged to 0.05C with a constant voltage at 4.48V and discharged to 3.0V with a constant current of 1C. This is one charge-discharge cycle. The initial discharge capacity was recorded as C1. The above method was repeated for 800 charge-discharge cycles. The discharge capacity after the 800th cycle was recorded as C800.

[0081] Capacity retention rate at 45℃ = (C800 / C1) × 100%.

[0082] Low-temperature discharge performance test:

[0083] Place the lithium-ion battery in a high-low temperature chamber, adjust the temperature to 25°C, and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Discharge the lithium-ion battery to 3.0V at a current of 0.5C, then charge it to 4.5V at a current of 0.5C, and then charge it at the same voltage until the current equals 0.05C. Again at 25°C, discharge it to 3.0V at a current of 0.5C; record this discharge capacity as the initial discharge capacity. At 25°C, charge it to 4.5V at a current of 0.5C, and then charge it at the same voltage until the current equals 0.05C. Then, place the lithium-ion battery at -10°C and let it stand for 30 minutes to allow the battery temperature to match the ambient temperature. At -10°C, discharge it to 3.0V at a current of 0.5C; record this discharge capacity as the low-temperature discharge capacity.

[0084] -10℃ low-temperature discharge capacity retention rate = (low-temperature discharge capacity / initial discharge capacity) × 100%.

[0085] Example 1-1

[0086] <Preparation of Negative Electrode Sheets>

[0087] Artificial graphite (negative electrode active material), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97.4:1.4:1.2. Deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil current collector and dried at 120°C to obtain a negative electrode sheet with a single-sided coating of negative electrode material. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 120°C, the sheet was cold-pressed, and then recesses were etched on the surface of the double-sided negative electrode material layer using laser processing technology. After cutting and welding tabs, a negative electrode sheet with a size of 78 mm × 875 mm was obtained for use. Wherein, d = 10 μm, D = 100 μm, L = 100 μm, D1 = 0.1 mm, and S1 / S2 = 0.5.

[0088] <Preparation of the positive electrode>

[0089] LiCoO2 (positive electrode active material), Super P (conductive agent), and polyvinylidene fluoride (PVDF) (binder) were mixed in a mass ratio of 97.9:0.9:1.2. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. The slurry was then stirred uniformly under vacuum to obtain the positive electrode slurry. This slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector. The foil was then dried at 120°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode material. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material. After drying at 120°C, the sheet was cold-pressed, cut, and had tabs welded to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm for later use. The thickness of the single-sided positive electrode material layer was 90 μm.

[0090] <Preparation of Electrolyte>

[0091] In an environment with a water content of less than 10 ppm, dimethyl carbonate, diethyl carbonate, and ethylene carbonate are mixed in a mass ratio of 1:1:1 to obtain a non-aqueous solvent. Then, compound I-1 (as shown in Formula I) and electrolyte salt LiPF6 are added to the non-aqueous solvent and mixed thoroughly to obtain the electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage W of the compound shown in Formula I is... I The content is 0.05%, the mass percentage of electrolyte salt is 12.5%, and the remainder is a non-aqueous solvent.

[0092] <Isolation membrane>

[0093] A porous polyethylene film with a thickness of 7μm (provided by Celgard) was used as the separator.

[0094] <Preparation of Lithium-ion Batteries>

[0095] The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag and dehydrated at 80°C. The electrolyte prepared above is then injected, and the battery undergoes vacuum sealing, settling, formation, degassing, and edge trimming to obtain a lithium-ion battery. The formation upper limit voltage is 4.15V, the formation temperature is 70°C, and the formation settling time is 2 hours.

[0096] Examples 1-2 to 1-25

[0097] Except for adjusting the mass percentage W of the compound shown in Formula I as shown in Table 1 in the <Preparation of Electrolyte>. IThe percentage of non-aqueous solvents and the percentage of electrolyte salts remain unchanged. Except for adjusting the relevant preparation parameters of the negative electrode sheet as shown in Table 1 in the <Preparation of Negative Electrode Sheet>, the rest are the same as in Example 1-1.

[0098] Examples 1-26 to Examples 1-29

[0099] Except for adjusting the types of compounds shown in Formula I as shown in Table 1 in the <Preparation of Electrolyte> section, the rest is the same as in Examples 1-4.

[0100] Examples 2-1 to 2-22

[0101] In addition to adding fluorinated lithium salt additives, polycyanate compounds, and sulfur-containing oxygen double bond compounds as shown in Table 2 in the <Preparation of Electrolyte>, the mass percentage W of the compounds shown in Formula I is adjusted according to Table 2. I %, mass percentage of fluorinated lithium salt additives W L %, types and mass percentages of polycyano compounds, types and mass percentages of sulfur-containing oxygen double bond compounds, and the total mass percentage of polycyano compounds and sulfur-containing oxygen double bond compounds (W) CNSO Except for the percentage of non-aqueous solvents and the percentage of electrolyte salts, which remain unchanged, the contents are the same as in Examples 1-4.

[0102] Comparative Example 1-1

[0103] Except that laser processing is not performed in the <Preparation of Negative Electrode Sheet> to obtain a negative electrode sheet without recesses in the negative electrode material layer, and the compound shown in Formula I is not added in the <Preparation of Electrolyte>, the mass percentage of the non-aqueous solvent is changed accordingly, and the mass percentage of the electrolyte salt remains unchanged, the rest is the same as in Examples 1-4.

[0104] Comparative Examples 1-2

[0105] Except that the compound shown in Formula I is not added in the <Preparation of Electrolyte>, the mass percentage of the non-aqueous solvent is changed accordingly, and the mass percentage of the electrolyte salt remains unchanged, the rest is the same as in Examples 1-4.

[0106] Comparative Examples 1-3

[0107] Except for adjusting the mass percentage W of the compound shown in Formula I as shown in Table 1 in the <Preparation of Electrolyte>. I Except for the percentage of non-aqueous solvents and the percentage of electrolyte salts, which remain unchanged, the contents are the same as in Examples 1-4.

[0108] Comparative Examples 1-4

[0109] Except for the fact that no laser processing is performed in the <Preparation of Negative Electrode Sheet> to obtain a negative electrode sheet without recesses in the negative electrode material layer, the rest is the same as in Examples 1-4.

[0110] As can be seen from Examples 1-1 to 1-29 and Comparative Examples 1-1 to 1-4, when the electrolyte includes the compound represented by Formula I and its content W is adjusted... I The value is within the range of this application; the negative electrode has multiple recesses; and W is adjusted. I Within the scope of this application, lithium-ion batteries can simultaneously exhibit high high-temperature cycle capacity retention and high low-temperature discharge capacity retention, indicating that lithium-ion batteries possess both excellent high-temperature cycle performance and low-temperature discharge performance.

[0111] d / D, L, W I The values ​​of / L, D, D1, and S1 / S2 typically affect the high-temperature cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 1-1 to 1-25, adjusting d / D, L, and W... I When the values ​​of / L, D, D1, and S1 / S2 are within the range of this application, the lithium-ion battery can simultaneously have a higher high-temperature cycle capacity retention rate and a higher low-temperature discharge capacity retention rate, indicating that the lithium-ion battery has better high-temperature cycle performance and low-temperature discharge performance.

[0112] The type of compound shown in Formula I typically affects the high-temperature cycling performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 1-4, 1-26 to 1-29, lithium-ion batteries using the type of compound shown in Formula I within the scope of this application can simultaneously exhibit high high-temperature cycling capacity retention and low-temperature discharge capacity retention, indicating that the lithium-ion battery has both good high-temperature cycling performance and low-temperature discharge performance.

[0113] The type and content of fluorinated lithium salt additives, polycyanate compounds, and sulfur-containing oxygen double bond compounds typically affect the high-temperature cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 1-3 to 1-4 and Examples 2-1 to 2-22, when the electrolyte includes at least one of the fluorinated lithium salt additives, polycyanate compounds, and sulfur-containing oxygen double bond compounds within the range of types and contents specified in this application, the lithium-ion battery can achieve a higher high-temperature cycle capacity retention rate while also maintaining a relatively high low-temperature discharge capacity retention rate. This indicates that the lithium-ion battery possesses better high-temperature cycle performance and also exhibits good low-temperature discharge performance.

[0114] W I / W LThe value of W typically affects the high-temperature cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 1-3 to 1-4 and Examples 2-1 to 2-7, when W is adjusted... I / W L When the value is within the range of this application, the lithium-ion battery has a higher high-temperature cycle capacity retention rate, while also maintaining a relatively high low-temperature discharge capacity retention rate, indicating that the lithium-ion battery simultaneously achieves good high-temperature cycle performance and low-temperature discharge performance.

[0115] W I / W CNSO The value of W typically affects the high-temperature cycle performance and low-temperature discharge performance of lithium-ion batteries. As can be seen from Examples 1-3 to 1-4 and Examples 2-8 to 2-15, when W is adjusted... I / W CNSO When the value is within the range of this application, the lithium-ion battery has a higher high-temperature cycle capacity retention rate, while also maintaining a relatively high low-temperature discharge capacity retention rate, indicating that the lithium-ion battery has better high-temperature cycle performance and also maintains good low-temperature discharge performance.

[0116] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0117] The element connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms refers to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B. Similarly, "at least one of A, B, or C" means only A, only B, only C, only A and B, only A and C, only B and C, A and B and C.

[0118] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0119] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A secondary battery comprising a negative electrode and an electrolyte, said electrolyte comprising a compound of formula I: in, R is selected from unsubstituted or Ra-substituted C2 to C6 alkyl groups, unsubstituted or Ra-substituted C6 to C12 aryl groups, and unsubstituted or Ra-substituted C5 to C12 nitrogen-containing heteroaryl groups; each Ra is independently selected from halogens or halogen-substituted C1 to C3 alkyl groups, and each halogen is independently selected from fluorine, chlorine, or bromine; based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is W. I %, W I The range is from 0.05 to 50; The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector. The thickness of the negative electrode material layer on one side is D μm, and the surface of the negative electrode material layer is provided with a plurality of recesses, the depth of a single recess being d μm, where d < D and 0.005 ≤ W. I / d≤5.

2. The secondary battery according to claim 1, wherein, 1≤W I ≤35。 3. The secondary battery according to claim 1, wherein, 0.1≤d / D≤0.

5.

4. The secondary battery according to claim 1, wherein, Along the thickness direction of the negative electrode sheet, the minimum distance between the outer contours of the orthogonal projections of two adjacent recesses is Lμm, where 50≤L≤300.

5. The secondary battery according to claim 4, wherein, 0.005≤W I / L≤1。 6. The secondary battery according to any one of claims 1 to 5, wherein, 100≤D≤400。 7. The secondary battery according to any one of claims 1 to 5, wherein, The plurality of recesses are distributed in a stripe pattern along the thickness direction of the negative electrode sheet. The shape of the orthographic projection of a single recess includes a stripe shape, and the width D1 mm of the orthographic projection of a single recess is 0.02 mm to 0.5 mm.

8. The secondary battery according to any one of claims 1 to 5, wherein, Along the thickness direction of the negative electrode sheet, the total area of ​​the orthogonal projection of the plurality of recesses is S1, and the area of ​​the negative electrode material layer on one side is S2, 0.1≤S1 / S2≤0.

8.

9. The secondary battery according to any one of claims 1 to 5, wherein, The compound represented by Formula I includes at least one of the following compounds:

10. The secondary battery according to any one of claims 1 to 5, wherein, The electrolyte further includes a fluorinated lithium salt additive, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate; the mass percentage of the fluorinated lithium salt additive based on the total mass of the electrolyte is W. L %, W L It ranges from 0.01 to 1.

11. The secondary battery according to claim 10, wherein, 0.1≤W L ≤0.7。 12. The secondary battery according to claim 10, wherein, 0.5≤W I / IN L ≤300。 13. The secondary battery according to any one of claims 1 to 5, wherein, The electrolyte further includes at least one of a polycyano compound or a sulfur-containing oxygen double bond compound; the polycyano compound includes at least one of the following compounds: succinic acid, glutaronitrile, methylglutaronitrile, adiponitrile, heptacyanide, octanoic acid, azelaic acid, sebacate, 1,3,5-pentanetrionitrile, 1,3,6-hexanetrionitrile; the sulfur-containing oxygen double bond compound includes at least one of the following compounds: 1,3-propanesulfonate lactone, 2,4-butanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, 1,3-propanediol sulfate. Based on the total mass of the electrolyte, the total mass percentage of the polycyano compound and the sulfur-containing oxygen double bond compound is W. CNSO %, W CNSO The range is from 0.1 to 15; 0.1≤W I / IN CNSO ≤40。 14. An electronic device comprising a secondary battery according to any one of claims 1 to 13.

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