Secondary battery and electronic device including the same

Abstract

The application provides a secondary battery and an electronic device comprising the same. The secondary battery comprises a negative electrode sheet and an electrolyte, the electrolyte comprises a compound represented by Formula I, the mass percentage of the compound represented by Formula I in the total mass of the electrolyte is W I %, W I is 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 the single-sided negative electrode material layer 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 I <D, 0.005≤W I / d≤5. In the secondary battery of the application, the electrolyte comprises a compound represented by Formula I, the surface of the negative electrode material layer is provided with a plurality of recesses, and the values of W I / d are regulated within the range of the application, which is beneficial to simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, in particular to a secondary battery and an electronic device comprising the same. BACKGROUND

[0002] 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, small self-discharge, no memory effect and long cycle life. With the continuous expansion of the use of lithium ion batteries, their use scenarios are more diverse, and the market has higher requirements for the electrochemical performance of lithium ion batteries. SUMMARY

[0003] The purpose of the present 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 solutions are as follows:

[0004] The first aspect of the present application provides a secondary battery comprising a negative electrode sheet and an electrolyte, wherein the electrolyte comprises a compound represented by Formula I:

[0005]

[0006] wherein R is selected from C2 to C6 alkyl unsubstituted or substituted with Ra, C6 to C12 aryl unsubstituted or substituted with Ra, C5 to C12 nitrogen-containing heteroaryl unsubstituted or substituted with Ra; each Ra is independently selected from halogen or halogen-substituted C1 to C3 alkyl, and each halogen is independently selected from fluorine, chlorine or bromine; the mass percentage content of the compound represented by Formula I in the electrolyte is W I %, W I is 0.05 to 50, preferably 1 to 35; 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 the negative electrode material layer on a single surface is D μm, the surface of the negative electrode material layer is provided with a plurality of recesses, the depth of each recess is d μm, d < D, and 0.005 ≤ W I / d ≤ 5. In the secondary battery of the present application, the electrolyte comprises a compound represented by Formula I, the surface of the negative electrode material layer is provided with a plurality of recesses, and the values of W I and W I / d are controlled within the above range, which is beneficial to simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0007] In an embodiment of the present application, 0.1 ≤ d / D ≤ 0.5. By controlling the value of d / D within the above range, the present application can better play the role of the recesses and simultaneously improve the lithium precipitation phenomenon, so that the secondary battery has better high-temperature cycle performance and low-temperature discharge performance.

[0008] In an embodiment of the present application, the minimum distance between the outer contours of the projections of two adjacent recesses along the thickness direction of the negative electrode tab is L μm, and 50≤L≤300. Controlling the value of L within the range of the present application can make the recesses have a suitable distribution density, facilitate the processing technology of the secondary battery, and better play the role of the recesses, thereby further improving the high-temperature cycle performance of the secondary battery while taking into account the low-temperature discharge performance of the secondary battery.

[0009] In an embodiment of the present application, 0.005≤W I / L≤1. Controlling the value of W I / L within the range of the present application can make the compound of formula I better play a role, while avoiding the compound of formula I from reacting more in the non-recess region and 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 an embodiment of the present application, 100≤D≤400. Controlling the value of D within the above range is beneficial to increasing the volumetric energy density of the secondary battery and also taking into account the kinetic performance of the secondary battery, thereby ensuring that the secondary battery has good low-temperature discharge performance.

[0011] In an embodiment of the present application, the plurality of recesses are distributed in a stripe shape, and along the thickness direction of the negative electrode tab, the shape of the projection of a single recess includes a strip shape, and the width D1 of the projection of a single recess is 0.02 mm to 0.5 mm. Controlling the value of D1 within the above range can make the secondary battery have better high-temperature cycle performance and low-temperature discharge performance at the same time.

[0012] In an embodiment of the present application, along the thickness direction of the negative electrode tab, the total area of the projections of the plurality of recesses is S1, the area of a single negative electrode material layer is S2, and 0.1≤S1 / S2≤0.8. Controlling the value of S1 / S2 within the above range can make the secondary battery have better high-temperature cycle performance and low-temperature discharge performance at the same time.

[0013] In an embodiment of the present application, the compound of formula I includes at least one of the following compounds:

[0014]

[0015]

[0016] The electrolyte includes the compound shown in formula I within the above range, which can better play a synergistic effect with the concave part of the negative electrode sheet, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0017] In an embodiment of the present application, the electrolyte further includes a fluorine-containing lithium salt additive, the fluorine-containing lithium salt additive includes at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, and the mass percentage content of the fluorine-containing lithium salt additive is W L % and W L is 0.01 to 1, preferably 0.1 to 0.7. The electrolyte includes the fluorine-containing lithium salt additive and regulates the value of W L within the above range, which can synergistically participate in the film formation reaction to form a more stable SEI film, thereby further improving the cycle stability of the secondary battery, improving the high-temperature cycle performance of the secondary battery, and at the same time, taking into account the low-temperature discharge performance of the secondary battery.

[0018] In an embodiment of the present application, 0.5≤W I / W L ≤300. By regulating the value of W I / W L within the above range, the electrolyte can better play a synergistic effect of the compound shown in formula I, the fluorine-containing lithium salt additive, and the concave part of the negative electrode sheet, further improve the high-temperature cycle performance of the secondary battery, and at the same time, take into account the low-temperature discharge performance of the secondary battery.

[0019] In an embodiment of the present application, the electrolyte further includes at least one of a polycyan compound or a sulfur-oxygen double bond-containing compound; the polycyan compound includes at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, sebonitrile, 1,3,5-pentane trinitrile, 1,3,6-hexane trinitrile; the sulfur-oxygen double bond-containing compound includes at least one of 1,3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, ethylene sulfate, 1,3-propanediol sulfate; the sum of the mass percentage contents of the polycyan compound and the sulfur-oxygen double bond-containing compound is W CNSO % and W CNSO is 0.1 to 15, preferably 1 to 10; 0.1≤W I / W CNSO ≤40. The electrolyte includes the polycyan compound and / or the sulfur-oxygen double bond-containing compound of the above kind and regulates the values of W CNSO and W I / W CNSOThe value of is within the above range, which can inhibit the side reactions of the positive electrode sheet, thereby further improving the high-temperature cycle stability of the secondary battery, and is conducive to better synergistic effect with the compound represented by formula I in the electrolyte and the concave portion of the negative electrode sheet, further improving the high-temperature cycle performance of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0020] The second aspect of the present application provides an electronic device, which comprises the secondary battery according to any one of the aforementioned embodiments. Thus, the electronic device provided by the present application has good performance.

[0021] The present application provides a secondary battery and an electronic device comprising the same. The secondary battery comprises a negative electrode and an electrolyte. The electrolyte comprises 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 0.05 to 50; the negative electrode plate includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, the thickness of the single-sided negative electrode material layer 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 the present application, the electrolyte includes the compound shown in Formula I, a plurality of recesses are provided on the surface of the negative electrode material layer, and W is regulated. I and W I The value of / d being within the above range is beneficial to improving both the high-temperature cycle performance and the low-temperature discharge performance of the secondary battery.

[0022] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0024] Figure 1 Schematic diagram of the cross-sectional structure of the negative electrode sheet along the thickness direction in one embodiment of the present application;

[0025] Figure 2 This is a schematic structural diagram of a single-sided negative electrode material layer according to an embodiment of the present application;

[0026] Figure 3 This is a schematic structural diagram of a single-sided negative electrode material layer according to another embodiment of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0028] It should be noted that the specific embodiments of the present application explain the present application by taking lithium ion batteries as examples of secondary batteries, but the secondary batteries of the present application are not limited to lithium ion batteries. The specific technical solutions are as follows:

[0029] The first aspect of the present application provides a secondary battery, which comprises a negative electrode sheet and an electrolyte, the electrolyte comprising a compound represented by Formula I:

[0030]

[0031] wherein R is selected from C2 to C6 alkyl unsubstituted or substituted with Ra, C6 to C12 aryl unsubstituted or substituted with Ra, C5 to C12 nitrogen-containing heteroaryl unsubstituted or substituted with Ra; each Ra is independently selected from halogen or halogen-substituted C1 to C3 alkyl, and each halogen is independently selected from fluorine, chlorine or bromine; the mass percentage content of the compound represented by Formula I in the electrolyte is W I %, W I is 0.05 to 50, preferably 1 to 35, for example, W I The value of W I may 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 between any two of them; 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 the single-sided negative electrode material layer 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 IThe value of W / 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 between any two of the above values. The "negative material layer is arranged on at least one surface of the negative current collector" means that the negative material layer can be arranged on one surface of the negative current collector along the thickness direction of the negative current collector, or arranged on two surfaces of the negative current collector along the thickness direction of the negative current collector. It should be noted that the "surface" can be the entire area of the surface of the negative current collector, or a partial area of the surface of the negative current collector, and the present application does not have a specific limitation as long as the purpose of the present application can be achieved. For example, as shown in FIG. 2, the negative electrode sheet 210 includes a negative current collector 211 and a negative material layer 212 arranged on two surfaces of the negative current collector, the thickness of the single-sided negative material layer 212 is D μm, and the surface of the negative material layer 212 is provided with a plurality of recesses 214, the depth of a single recess 214 is d μm, and d < D. Figure 1

[0032] The inventors found that the electrolyte of the secondary battery is consumed quickly during the cycle at high temperature, and arranging a plurality of recesses on the surface of the negative material layer can accelerate the flow, infiltration and diffusion of the electrolyte in the negative electrode sheet, enhance the cycle stability of the secondary battery in the liquid-lean state, and thus improve the high-temperature cycle performance of the secondary battery. However, the arrangement of the plurality of recesses on the negative electrode sheet can cause the electrolyte to be locally enriched in the negative electrode sheet, and during the formation process, the electrolyte reacts more in the local area, resulting in a larger local impedance and blocked ion transmission, which leads to a decrease in the low-temperature discharge capacity of the secondary battery and affects the low-temperature discharge performance of the secondary battery. Adding the compound represented by Formula I to the electrolyte can form a thin interface layer with high ion conductivity at the interface of the recesses of the negative electrode sheet, which is highly enriched in lithium, sulfur, fluorine and other elements, and accelerates the conduction of ions, thereby improving the low-temperature discharge capacity and low-temperature discharge performance of the secondary battery. When W I is too small, for example, less than 0.05, the content of the compound represented by Formula I is too low to improve the low-temperature discharge performance of the secondary battery; when W I is too large, for example, greater than 50, the content of the compound represented by Formula I is too high, and the thickness of the solid electrolyte interface (SEI) film formed increases too much, which is not conducive to ion transmission, and thus is not conducive to improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. When W I is too small, for example, less than 0.005, the compound represented by Formula I cannot play a role, and it is difficult to improve the low-temperature discharge performance of the secondary battery; when W I ​When the value of d / D is too large, for example, greater than 5, the compound shown in formula I reacts excessively, resulting in the SEI film formed on the surface of the negative electrode plate being too thick, which is not conducive to improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. In the secondary battery of the present application, the electrolyte comprises the compound shown in formula I, the surface of the negative electrode material layer is provided with a plurality of recesses, and the value of W I and W I When the value of d / D is within the above range, it is conducive to simultaneously improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery. In the present 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.

[0033] In an embodiment of the present 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 formed by any two of them. By adjusting the value of d / D within the above range, the present application can better play the role of the recesses, while ensuring the ratio of the unit area negative electrode capacity to the unit area positive electrode capacity (CB value) of the secondary battery, improving the lithium precipitation phenomenon, so that the secondary battery has better high-temperature cycle performance and low-temperature discharge performance at the same time.

[0034] In an embodiment of the present application, along the thickness direction of the negative electrode plate, the minimum distance between the outer contours of the orthographic projections of two adjacent recesses is L μm, 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 formed by any two of them. In the present 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 the present application can be achieved. By adjusting the value of L within the range of the present application, the recesses can have a suitable distribution density, which is conducive to the processing process of the secondary battery, and at the same time, the recesses can better play their role, further improving the high-temperature cycle performance of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0035] In an embodiment of the present 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 between any two of them. The value of W is controlled in the range to make the compound of formula I better play a role, and to avoid the compound of formula I reacting more in the non-recess area, 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. I The value of L in the present application can make the compound of formula I better play a role, while avoiding the compound of formula I reacting more in the non-recess area, 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.

[0036] In an embodiment of the present 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 between any two of them. By controlling the value of D in the above range, the present application is beneficial to increasing the volumetric energy density of the secondary battery, and also takes into account the kinetic performance of the secondary battery, ensuring that the secondary battery has good low-temperature discharge performance.

[0037] In an embodiment of the present application, the plurality of recesses are distributed in a stripe shape, the shape of the orthographic projection of a single recess along the thickness direction of the negative electrode sheet includes a strip shape, and the width D1 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 between any two of them. By controlling the value of D1 in the above range, the present application can obtain good processability, while promoting the formula I molecule to act more fully on the recess area, thereby making the secondary battery have better high-temperature cycle performance and low-temperature discharge performance at the same time.

[0038] In the present application, the plurality of recesses are distributed in a stripe shape. The plurality of recesses can be arranged along the width direction of the negative electrode tab, or along the length direction of the negative electrode tab, or along both the width direction and the length direction of the negative electrode tab. In the present application, the width D1 of the orthographic projection of a single recess is the maximum value of the orthographic projection width. When the plurality of recesses are distributed in a stripe shape, the width D1 of the stripe-shaped orthographic projection of the two adjacent recesses can be the same or different, and the length of the stripe can be the same or different, as long as the purpose of the present application can be achieved. The present application does not particularly limit the length of the stripe, which can be designed according to the size of the negative electrode tab, as long as the purpose of the present application can be achieved.

[0039] Specifically, as shown in FIG. 2A, the surface of the negative material layer 212 is provided with a plurality of recesses 214, the plurality of recesses 214 are distributed in a stripe shape, and one side of the orthographic projection of a single recess 214 is parallel to one side of the negative electrode tab 210. The orthographic projection of a single recess 214 is a narrow and long rectangle, the width of the rectangle is D1, and the minimum distance between adjacent rectangles is L. Figure 2 As shown in FIG. 2B, the plurality of recesses 214 are distributed in a stripe shape, and there is an included angle between one side of the orthographic projection of a single recess 214 and one side of the negative electrode tab 210. The orthographic projection of a single recess 214 is a narrow and long rectangle, the width of the rectangle is D1, the minimum distance between adjacent rectangles is L, and the lengths of adjacent rectangles are different. The present application does not particularly limit the size of the above-mentioned included angle, as long as the purpose of the present application can be achieved. For example, the included angle is 25° to 65°. Figure 3 As shown in FIG. 2B, the plurality of recesses 214 are distributed in a stripe shape, and there is an included angle between one side of the orthographic projection of a single recess 214 and one side of the negative electrode tab 210. The orthographic projection of a single recess 214 is a narrow and long rectangle, the width of the rectangle is D1, the minimum distance between adjacent rectangles is L, and the lengths of adjacent rectangles are different. The present application does not particularly limit the size of the above-mentioned included angle, as long as the purpose of the present application can be achieved. For example, the included angle is 25° to 65°. Figure 2 Figure 3 The size, number and shape of the recesses in FIGS. 2A and 2B are only examples and do not limit the protection scope of the present application.

[0040] In an embodiment of the present application, along the thickness direction of the negative electrode tab, the total area of the orthographic projection of the plurality of recesses is S1, the area of the single-sided negative material layer is S2, and 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 composed of any two of the above values. By adjusting the value of S1 / S2 within the above range, the present application can adjust the proportion of the recesses within a reasonable range, so that the recesses can fully play their functions, thereby enabling the secondary battery to have better high-temperature cycle performance and low-temperature discharge performance at the same time.

[0041] ​The preparation method of the negative electrode sheet is not particularly limited in the present application, as long as the purpose of the present application can be achieved. Illustratively, the preparation method of the negative electrode sheet can include, but is not limited to, the following steps: arranging a negative material layer on one surface of the negative current collector, then repeatedly arranging a negative material layer on the other surface of the negative current collector, and then etching a recess on the surface of the double-sided negative material layer by a laser process to obtain the negative electrode sheet.

[0042] The present application does not have a particular restriction on the way of regulating d, L, D1, S1, as long as the purpose of the present application can be achieved. Illustratively, the size of d, L, D1, S1 can be regulated by a laser process.

[0043] In an embodiment of the present application, the compound represented by formula I includes at least one of the following compounds:

[0044]

[0045] The electrolyte includes the compound represented by formula I within the above range, which can better play a synergistic effect with the recess of the negative electrode sheet, thereby further improving the high-temperature cycle performance and low-temperature discharge performance of the secondary battery.

[0046] In an embodiment of the present application, the electrolyte further includes a fluorine-containing lithium salt additive, and the fluorine-containing lithium salt additive includes at least one of lithium tetrafluoroborate (LiBF4), lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium difluoro-bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate; the mass percentage content of the fluorine-containing lithium salt additive is W L % based on the total mass of the electrolyte, W L is 0.01 to 1, preferably 0.1 to 0.7, for example, the value of W L may 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 formed by any two of them. The electrolyte includes the fluorine-containing lithium salt additive and regulates the value of W L within the above range, which can synergistically participate in the film formation reaction to form a more stable SEI film, thereby further improving the cycle stability of the secondary battery, improving the high-temperature cycle performance of the secondary battery, and at the same time, taking into account the low-temperature discharge performance of the secondary battery.

[0047] In an embodiment of the present application, 0.5≤W I / W L ≤300, for example, W I / W LW 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 between any two of the aforementioned values. 0.1≤W I / W L The value of W is within the above range, which can better play the synergistic effect of the compound represented by formula I in the electrolyte, the fluorine-containing lithium salt additive, and the recess of the negative electrode tab, further improve the high-temperature cycle performance of the secondary battery, and also take into account the low-temperature discharge performance of the secondary battery.

[0048] In an embodiment of the present application, the electrolyte further comprises at least one of a polycyan compound or a sulfur-oxygen double bond-containing compound; the polycyan compound comprises at least one of the following compounds: butanedinitrile, pentanedinitrile, methyl pentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile, 1,3,5-pentane trinitrile, 1,3,6-hexane trinitrile; the sulfur-oxygen double bond-containing compound comprises at least one of the following compounds: 1,3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, ethylene sulfate, 1,3-propanediol sulfate; the total mass percentage content of the polycyan compound and the sulfur-oxygen double bond-containing compound is W CNSO %, W CNSO is 0.1 to 15, preferably 1 to 10, for example W CNSO W 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 between any two of the aforementioned values. 0.1≤W I / W CNSO ≤40, for example W I / W CNSO W 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 between any two of the aforementioned values. The electrolyte comprises the polycyan compound and / or the sulfur-oxygen double bond-containing compound of the aforementioned kind and regulates W CNSO and W I / W CNSOThe value of the compound of formula I is within the above range, the side reaction of the positive electrode sheet can be inhibited, thereby further improving the high-temperature cycle stability of the secondary battery, and the compound of formula I in the electrolyte and the concave part of the negative electrode sheet can better play a synergistic effect, further improving the high-temperature cycle performance of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0049] In an embodiment of the present application, the electrolyte further comprises a polycyanogen compound, and the mass percentage of the polycyanogen compound is 0.1% to 15%, preferably 1% to 10%, based on the total mass of the electrolyte. In an embodiment of the present application, the electrolyte further comprises a compound containing a sulfur-oxygen double bond, and the mass percentage of the compound containing a sulfur-oxygen double bond is 0.1% to 15%, preferably 1% to 10%, based on the total mass of the electrolyte. In an embodiment of the present application, the electrolyte further comprises a polycyanogen compound and a compound containing a sulfur-oxygen double bond, and the mass ratio of the polycyanogen compound to the compound containing a sulfur-oxygen double bond is 1:(0.5 to 1.5).

[0050] In the present application, the electrolyte further comprises an electrolyte salt and a non-aqueous solvent. The electrolyte salt in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the electrolyte salt can 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. The content of the electrolyte salt in the electrolyte in the present application is not particularly limited as long as the purpose of the present application can be achieved. For example, the mass percentage of the electrolyte salt is 8% to 15%, based on the mass of the electrolyte.

[0051] The non-aqueous solvent is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the non-aqueous solvent can include, but is not limited to, at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound, or other organic solvents. The carbonate compound can include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluoro-carbonate compound. The chain carbonate compound can include, but is 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 cyclic carbonate can include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). The fluoro-carbonate compound can include, but is not limited to, at least one of fluoro-ethylene carbonate (FEC), 1,2-difluoro-ethylene carbonate, 1,1-difluoro-ethylene carbonate, 1,1,2-trifluoro-ethylene carbonate, 1,1,2,2-tetrafluoro-ethylene carbonate, 1-fluoro-2-methyl-ethylene carbonate, 1-fluoro-1-methyl-ethylene carbonate, 1,2-difluoro-1-methyl-ethylene carbonate, 1,1,2-trifluoro-2-methyl-ethylene carbonate, or trifluoromethyl-ethylene carbonate. The carboxylic acid ester compound can include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, or caprolactone. The ether compound can include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents can include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The content of the non-aqueous solvent in the electrolyte is not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the mass percentage of the non-aqueous solvent can be 19% to 91% based on the total mass of the electrolyte.

[0052] In one embodiment of the present application, the electrolyte includes the compound of Formula I, an electrolyte salt, and a non-aqueous solvent. Herein, the mass percentages of the compound of Formula I and the electrolyte salt are as described above, and the mass percentage of the non-aqueous solvent is 35% to 91% based on the total mass of the electrolyte. The electrolyte includes the compound of Formula I, and the secondary battery using the electrolyte of the present application has improved high-temperature cycle performance and low-temperature discharge performance.

[0053] In an embodiment of the present application, the electrolyte includes the compound represented by Formula I, a lithium salt containing fluorine additive, an electrolyte salt, and a nonaqueous solvent. Among them, the mass percentage content of the compound represented by Formula I, the lithium salt containing fluorine additive, and the electrolyte salt is as shown above, and the mass percentage content of the nonaqueous solvent is 34% to 91% based on the total mass of the electrolyte. The electrolyte includes the compound represented by Formula I and the lithium salt containing fluorine additive, and the secondary battery using the electrolyte of the present application has further improved high-temperature cycle performance and low-temperature discharge performance.

[0054] In an embodiment of the present application, the electrolyte includes the compound represented by Formula I, at least one of a polycyanide compound or a compound containing a sulfur-oxygen double bond, an electrolyte salt, and a nonaqueous solvent. Among them, the sum of the mass percentage content of the compound represented by Formula I, the polycyanide compound, and the compound containing a sulfur-oxygen double bond, and the mass percentage content of the electrolyte salt is as shown above, and the mass percentage content of the nonaqueous solvent is 20% to 91% based on the total mass of the electrolyte. The electrolyte includes the compound represented by Formula I and at least one of the polycyanide compound or the compound containing a sulfur-oxygen double bond, and the secondary battery using the electrolyte of the present application has further improved high-temperature cycle performance and low-temperature discharge performance.

[0055] In an embodiment of the present application, the electrolyte includes the compound represented by Formula I, at least one of a polycyanide compound or a compound containing a sulfur-oxygen double bond, an electrolyte salt, and a nonaqueous solvent. Among them, the sum of the mass percentage content of the compound represented by Formula I, the polycyanide compound, and the compound containing a sulfur-oxygen double bond, and the mass percentage content of the electrolyte salt is as shown above, and the mass percentage content of the nonaqueous solvent is 20% to 91% based on the total mass of the electrolyte. The electrolyte includes the compound represented by Formula I and at least one of the polycyanide compound or the compound containing a sulfur-oxygen double bond, and the secondary battery using the electrolyte of the present application has further improved high-temperature cycle performance and low-temperature discharge performance.

[0056] In the present application, the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, it can include a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a foamed nickel, a foamed copper, or a composite current collector, and exemplarily, 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. The thickness of the negative electrode current collector is not particularly limited in the present application as long as the object of the present application can be achieved, for example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0057] The negative electrode material layer includes a negative electrode active material, which is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the negative electrode active material can include, but is not limited to, at least one of natural graphite, artificial graphite, meso-carbon microbead, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-type lithium titanate Li4Ti5O12, or Li-Al alloy. 12 or Li-Al alloy.

[0058] In some embodiments of the present application, the negative electrode material layer can further include a conductive agent and a binder, which are not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the conductive agent can include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotube (CNT), carbon fiber, flake graphite, graphene, metal material, or conductive polymer, and the conductive carbon black can include, but is not limited to, at least one of acetylene black or Ketjen black. The above-described carbon nanotube can include, but is not limited to, single-walled carbon nanotube and / or multi-walled carbon nanotube. The above-described carbon fiber can include, but is not limited to, vapor-grown carbon fiber (VGCF) and / or nano-carbon fiber. The above-described metal material can include, but is not limited to, metal powder and / or metal fiber, and specifically, the metal can include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The above-described conductive polymer can include, but is not limited to, at least one of polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. For example, the binder can 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. The mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer is not particularly limited in the present application, and can be selected by a person skilled in the art as needed as long as the purpose of the present application can be achieved.

[0059] In some embodiments of the present application, a conductive agent, a binder, and a thickening agent can be further included, which are not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the conductive agent and the binder can be at least one of the above-described conductive agent and the above-described binder. The thickening agent can include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. The mass ratio of the negative electrode active material, the conductive agent, the binder, and the thickening agent in the negative electrode material layer is not particularly limited in the present application, and can be selected by a person skilled in the art as needed as long as the purpose of the present application can be achieved.

[0060] Optionally, the negative electrode sheet can further include a conductive layer between the negative current collector and the negative material layer. The composition of the conductive layer is not particularly limited in the present application and can be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application and can be at least one of the above-mentioned conductive agent and the above-mentioned binder.

[0061] In the present application, the secondary battery further includes a positive electrode sheet including a positive current collector and a positive material layer disposed on at least one surface of the positive current collector. The above-mentioned "positive material layer disposed on at least one surface of the positive current collector" means that the positive material layer can be disposed on one surface of the positive current collector in the thickness direction of the positive current collector, or can be disposed on both surfaces of the positive current collector in the thickness direction of the positive current collector. It should be noted that the "surface" here can be the entire area of the surface of the positive current collector, or can be a partial area of the surface of the positive current collector, which is not particularly limited in the present application as long as the purpose of the present application can be achieved.

[0062] The positive current collector is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, can include an aluminum foil, an aluminum alloy foil, or a composite current collector (for example, an aluminum-carbon composite current collector), etc.

[0063] The positive material layer includes a positive active material, which is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, the positive active material can include but is not limited to at least one of nickel-cobalt-manganese lithium phosphate (for example, NCM811, NCM622, NCM523, NCM111), nickel-cobalt-aluminum lithium phosphate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate (LiCoO2), lithium manganate, lithium manganese iron phosphate, or lithium titanate.

[0064] The positive material layer can further include a conductive agent and a binder, which are not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, can be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the positive active material, the conductive agent, and the binder in the positive material layer is not particularly limited in the present application, which can be selected by a person skilled in the art according to actual needs as long as the purpose of the present application can be achieved.

[0065] The thickness of the positive current collector and the positive material layer is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, and the thickness of the positive material layer is 30 μm to 120 μm.

[0066] Optionally, the positive electrode tab can further include an electrically conductive layer between the positive current collector and the positive electrode material layer. The composition of the electrically conductive layer is not particularly limited and can be an electrically conductive layer commonly used in the art. The electrically conductive layer includes an electrically conductive agent and a binder. The electrically conductive agent and the binder in the electrically conductive layer are not particularly limited in the present application and, for example, can be at least one of the above-described electrically conductive agents and the above-described binders.

[0067] In the present application, the secondary battery further includes a separator. The separator is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the material of the separator can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the separator can include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a calendered film, or a spunlaid film.

[0068] In some embodiments of the present application, the separator can include a base layer and a surface treatment layer. The base layer can be a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the base layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0069] Optionally, at least one surface of the base layer is provided with a surface treatment layer, which can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited in the present application and, for example, can include at least one of aluminum oxide, 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. The binder is not particularly limited in the present application and, for example, can be at least one of the above-described binders. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0070] In the present application, the thickness of the separator is not particularly limited as long as the object of the present application can be achieved, and, for example, the thickness of the separator can be 3 µm to 30 µm.

[0071] In the present application, the secondary battery further comprises a shell for accommodating the positive electrode sheet, the separator, the negative electrode sheet, the electrolyte, and other components known in the art of secondary batteries, and the present application does not limit the above-mentioned other components. The shell is not particularly limited in the present application and can be a shell known in the art as long as the purpose of the present application can be achieved. For example, the shell can be a hard shell or a flexible shell. The material of the hard shell can be metal, and the type of metal is not limited in the present application, and a metal hard shell known in the art can be used as long as the purpose of the present application can be achieved. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0072] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and the present application is not particularly limited, for example, the preparation process of the secondary battery can include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding, etc. according to the need to obtain the electrode assembly with a winding structure, placing the electrode assembly into the shell, injecting the electrolyte into the shell and sealing, to obtain the secondary battery. Alternatively, the positive electrode sheet, the separator and the negative electrode sheet are stacked in order, and then the four corners of the entire stack structure are fixed with adhesive tape to obtain the electrode assembly with a stack structure, the electrode assembly is placed into the shell, the electrolyte is injected into the shell and sealed, to obtain the secondary battery. In addition, the overcurrent prevention element, the guide plate, etc. can also be placed in the shell according to the need, so as to prevent the pressure rise in the secondary battery and overcharge and discharge.

[0073] The type of secondary battery is not particularly limited in the present application, which can include any device that undergoes an electrochemical reaction. For example, the secondary battery can include but is not limited to: lithium metal secondary battery, lithium ion battery, sodium ion battery, lithium polymer secondary battery, lithium ion polymer secondary battery.

[0074] The second aspect of the present application provides an electronic device comprising the secondary battery of any one of the preceding embodiments. The secondary battery provided in the present application has good high-temperature cycle performance and low-temperature discharge performance, so that the electronic device of the present application has a longer service life.

[0075] The kind of the electronic device is not particularly limited in the present application, and it can be any electronic device known in the art. In some embodiments of the present application, the electronic device can include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio player, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large storage battery, a lithium ion capacitor, and the like.

[0076] Embodiment

[0077] Hereinafter, the embodiments of the present application are more specifically described by citing examples and comparative examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are on a mass basis.

[0078] Test methods and equipment:

[0079] Measurement of size:

[0080] d, D: The cross section of the negative electrode sheet in the thickness direction is subjected to ion polishing to obtain the cross section of the negative electrode sheet, and the cross section is observed under a scanning electron microscope to measure the depth d of a single recess and the thickness D of a single negative electrode material layer.

[0081] D1, L, S1: The negative electrode material layer of the negative electrode sheet is placed with the negative electrode material layer surface facing up under a VHX5000 microscope, and the magnification is set to 50 to 200 times. A photograph of the negative electrode material layer surface is taken, and the width D1 of the orthographic projection of a single recess, the minimum distance L between the orthographic projections of two adjacent recesses, and the integral and accumulated area S1 of the orthographic projection of the recesses in the image are measured using the microscope software.

[0082] Each of the above sizes is measured at 10 points, and the average value is taken as the final result.

[0083] High-temperature cycle performance test:

[0084] The lithium ion battery is placed in a 45°C constant temperature oven, charged at a constant current of 4.5C to 4.48V, charged at a constant voltage of 4.48V to 0.05C, and discharged at a constant current of 1C to 3.0V. This is one charge and discharge cycle process, and the first discharge capacity is recorded as C1. The above process is repeated 800 times, and the discharge capacity after the 800th cycle is recorded as C800.

[0085] 45°C capacity retention rate = (C800 / C1) x 100%.

[0086] Low temperature discharge performance test:

[0087] Place the lithium-ion battery in a high and low temperature box, 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 that has reached a constant temperature 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 a constant voltage with the charging voltage until the current is equal to 0.05C. Also at a temperature of 25°C, discharge it to 3.0V at a current of 0.5C, and record the discharge capacity as the initial discharge capacity. At a temperature of 25°C, charge it to 4.5V at a current of 0.5C, and then charge it at a constant voltage with the charging voltage until the current is equal to 0.05C. Afterwards, place the lithium-ion battery at a temperature of -10°C and let it stand for 30 minutes to keep the temperature of the lithium-ion battery consistent with the external temperature. At -10°C, discharge it to 3.0V at a current of 0.5C, and record the discharge capacity as the low-temperature discharge capacity.

[0088] -10°C low-temperature discharge capacity retention rate = (low-temperature discharge capacity / initial discharge capacity) x 100%.

[0089] Example 1-1

[0090] <Preparation of negative electrode sheet>

[0091] The negative electrode active material, artificial graphite, the binder, styrene-butadiene rubber, and the conductive agent, acetylene black, were mixed in a mass ratio of 97.4:1.4:1.2. Deionized water was added as a solvent to form a slurry with a solid content of 45 wt%. The mixture was stirred evenly in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was evenly coated on one surface of a 6 μm thick negative electrode current collector copper foil and dried at 120°C to obtain a negative electrode sheet coated on one side with a negative electrode material layer. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode material layer. After drying at 120°C, the sheet was cold pressed. Laser processing was then used to etch recessed areas in the negative electrode material layers on both sides. The sheet was then cut and the tabs welded to obtain a negative electrode sheet measuring 78 mm x 875 mm for future use. Here, d = 10 μm, D = 100 μm, L = 100 μm, D1 = 0.1 mm, and S1 / S2 = 0.5.

[0092] <Preparation of positive electrode sheet>

[0093] The positive electrode active material LiCoO2, the conductive agent Super P, and the binder polyvinylidene fluoride were mixed in a mass ratio of 97.9:0.9:1.2, N-methyl pyrrolidone (NMP) was added as a solvent, and a slurry with a solid content of 75 wt% was prepared. After uniform stirring in a vacuum, a positive electrode slurry was obtained. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and was dried at 120°C to obtain a positive electrode tab with a single-sided positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode tab with a double-sided positive electrode material layer. After drying at 120°C and cold pressing, the tab was cut and the tabs were welded to obtain a positive electrode tab with a size of 74 mm x 867 mm. The thickness of the single-sided positive electrode material layer was 90 μm.

[0094] <Preparation of electrolyte>

[0095] In an environment with a water content of less than 10 ppm, dimethyl carbonate, diethyl carbonate, and ethylene carbonate were mixed in a mass ratio of 1:1:1 to obtain a non-aqueous solvent, and then a compound represented by Formula I, Formula I-1, and an electrolyte salt LiPF6 were added to the non-aqueous solvent to obtain an electrolyte. The mass percentage of the compound represented by Formula I was 0.05%, the mass percentage of the electrolyte salt was 12.5%, and the balance was the non-aqueous solvent, based on the mass of the electrolyte. I

[0096] <Separator>

[0097] A porous polyethylene film (provided by Celgard) with a thickness of 7 μm was used as a separator.

[0098] <Preparation of lithium ion battery>

[0099] The positive electrode tab, the separator, and the negative electrode tab prepared above were stacked in order, with the separator between the positive electrode tab and the negative electrode tab to act as a separator, and were wound to obtain an electrode assembly. The electrode assembly was placed in an aluminum-plastic film packaging bag, and was dehydrated at 80°C. The electrolyte prepared above was injected, and the lithium ion battery was obtained after vacuum packaging, standing, formation, degassing, and edge cutting. The upper limit voltage of the formation was 4.15 V, the formation temperature was 70°C, and the standing time of the formation was 2 h.

[0100] Examples 1-2 to 1-25

[0101] In the <Preparation of electrolyte>, the mass percentage W I ​The mass percentage content of the nonaqueous solvent was changed, the mass percentage content of the electrolyte salt was unchanged, and the rest was the same as in Example 1-1, except that the relevant preparation parameters of the negative electrode sheet were adjusted according to Table 1 in <Preparation of a negative electrode sheet>.

[0102] Examples 1-26 to 1-29

[0103] The rest was the same as in Example 1-4, except that the type of the compound represented by Formula I was adjusted according to Table 1 in <Preparation of an electrolyte solution>.

[0104] Examples 2-1 to 2-22

[0105] The rest was the same as in Example 1-4, except that the fluorine-containing lithium salt additive, the polycyano compound, and the sulfur-oxygen double bond-containing compound were added according to Table 2 in <Preparation of an electrolyte solution>, and the mass percentage content W of the compound represented by Formula I was adjusted according to Table 2. I The mass percentage content W of the fluorine-containing lithium salt additive L The type and mass percentage content of the polycyano compound, the type and mass percentage content of the sulfur-oxygen double bond-containing compound, and the total mass percentage content W of the polycyano compound and the sulfur-oxygen double bond-containing compound CNSO The rest was the same as in Example 1-4, except that the mass percentage content of the nonaqueous solvent was changed, the mass percentage content of the electrolyte salt was unchanged.

[0106] Comparative Example 1-1

[0107] The rest was the same as in Example 1-4, except that no laser processing was performed in <Preparation of a negative electrode sheet> to obtain a negative electrode sheet without recesses in the negative electrode material layer, no compound represented by Formula I was added in <Preparation of an electrolyte solution>, the mass percentage content of the nonaqueous solvent was changed, and the mass percentage content of the electrolyte salt was unchanged.

[0108] Comparative Example 1-2

[0109] The rest was the same as in Example 1-4, except that no compound represented by Formula I was added in <Preparation of an electrolyte solution>, the mass percentage content of the nonaqueous solvent was changed, and the mass percentage content of the electrolyte salt was unchanged.

[0110] Comparative Example 1-3

[0111] The rest was the same as in Example 1-4, except that the mass percentage content W of the compound represented by Formula I was adjusted according to Table 1 in <Preparation of an electrolyte solution>. I The rest was the same as in Example 1-4, except that the mass percentage content of the nonaqueous solvent was changed, the mass percentage content of the electrolyte salt was unchanged.

[0112] Comparative Example 1-4

[0113] The rest is the same as Example 1-4.

[0114]

[0115]

[0116] As can be seen from Example 1-1 to Example 1-29 and Comparative Example 1-1 to Comparative Example 1-4, when the electrolyte comprises the compound shown in Formula I and the content W I of the compound shown in Formula I is within the range of the present application, the negative electrode sheet is provided with a plurality of recesses, and the values of W I / d are within the range of the present 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 simultaneously has good high-temperature cycle performance and low-temperature discharge performance.

[0117] The values of d / D, L, W I / L, D, D1, S1 / S2 will generally affect the high-temperature cycle performance and low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-1 to Example 1-25, when the values of d / D, L, W I / L, D, D1, S1 / S2 are within the range of the present 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 simultaneously has better high-temperature cycle performance and low-temperature discharge performance.

[0118] The type of the compound shown in Formula I will generally affect the high-temperature cycle performance and low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-4, Example 1-26 to Example 1-29, when the type of the compound shown in Formula I is selected from the lithium ion battery within the range of the present application, the lithium ion battery can simultaneously have a higher high-temperature cycle capacity retention rate and a low-temperature discharge capacity retention rate, indicating that the lithium ion battery simultaneously has better high-temperature cycle performance and low-temperature discharge performance.

[0119] The type and content of the fluorine-containing lithium salt additive, the type and content of the polycyanide compound, and the type and content of the sulfur-oxygen double bond-containing compound will generally affect the high-temperature cycle performance and low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-3 to Example 1-4, Example 2-1 to Example 2-22, when the electrolyte comprises at least one of the fluorine-containing lithium salt additive, the polycyanide compound, and the sulfur-oxygen double bond-containing compound within the type and content range of the present application, the lithium ion battery can have a higher high-temperature cycle capacity retention rate, while also having a higher low-temperature discharge capacity retention rate, indicating that the lithium ion battery has better high-temperature cycle performance and also has better low-temperature discharge performance.

[0120] W I / W L The value of W generally affects the high-temperature cycle performance and the low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-3 to Example 1-4, Example 2-1 to Example 2-7, when the value of W is regulated within the range of the present application, the lithium ion battery has a higher high-temperature cycle capacity retention rate, while also having 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. I / W L The value of W generally affects the high-temperature cycle performance and the low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-3 to Example 1-4, Example 2-1 to Example 2-7, when the value of W is regulated within the range of the present application, the lithium ion battery has a higher high-temperature cycle capacity retention rate, while also having 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.

[0121] W I / W CNSO The value of W generally affects the high-temperature cycle performance and the low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-3 to Example 1-4, Example 2-1 to Example 2-7, when the value of W is regulated within the range of the present application, the lithium ion battery has a higher high-temperature cycle capacity retention rate, while also having 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. I / W CNSO The value of W generally affects the high-temperature cycle performance and the low-temperature discharge performance of the lithium ion battery. As can be seen from Example 1-3 to Example 1-4, Example 2-1 to Example 2-7, when the value of W is regulated within the range of the present application, the lithium ion battery has a higher high-temperature cycle capacity retention rate, while also having 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.

[0122] It should be noted that in this document, the terms "comprising", "containing", or any other similar term are intended to encompass non-exclusive inclusions, such that a process, method, or article that comprises a list of elements does not only include those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, or article.

[0123] The elements connected by the terms "at least one of", "at least one", "at least one of", or other similar terms refer to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B. For another example, "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.

[0124] Each embodiment in the specification is described in a relevant manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment focuses on the difference from other embodiments.

[0125] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery comprising a negative electrode and an electrolyte, wherein the electrolyte comprises a compound represented by formula I: in, R is selected from C2 to C6 alkyl groups which are unsubstituted or substituted by Ra, C6 to C12 aryl groups which are unsubstituted or substituted by Ra, and C5 to C12 nitrogen-containing heteroaryl groups which are unsubstituted or substituted by Ra; the Ra are each independently selected from halogen or halogen-substituted C1 to C3 alkyl groups, and the halogen are each 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 0.05 to 50; The negative electrode plate includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The thickness of the negative electrode material layer on a single side is D μm. A plurality of recesses are provided on the surface of the negative electrode material layer. The depth of each recess is d μm, d<D, 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 orthographic projections of two adjacent recesses is L μm, and 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 shape. Along the thickness direction of the negative electrode sheet, the orthographic projection of a single recess includes a strip 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 orthographic projections of the plurality of recesses is S1, the area of ​​the negative electrode material layer on a single side is S2, and 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 fluorine-containing lithium salt additive, which includes at least one of lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate; based on the total mass of the electrolyte, the mass percentage of the fluorine-containing lithium salt additive is W L %,W L 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-oxygen double bond compound; the polycyano compound includes at least one of the following compounds: succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile, sebacate, 1,3,5-pentanetrinitrile, 1,3,6-hexanetrinitrile; the sulfur-oxygen double bond compound includes at least one of the following compounds: 1,3-propane sultone, 2,4-butane sultone, 1,4-butane sultone, vinyl sulfate, 1,3-propylene glycol sulfate; Based on the total mass of the electrolyte, the sum of the mass percentages of the polycyano compound and the sulfur-oxygen double bond compound is W CNSO %,W CNSO 0.1 to 15; 0.1≤W I / IN CNSO ≤40。 14 . An electronic device comprising the secondary battery according to claim 1 .

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