Secondary battery and electronic device comprising same

Abstract

The invention provides a secondary battery and an electronic device comprising the same, the secondary battery comprises a negative pole piece and an electrolyte, and the electrolyte comprises a compound as shown in formula I; based on the total mass of the electrolyte, the mass percentage content of the compound shown in the formula I is WI%, and WI is 0.05-50; the negative electrode piece 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-sided negative electrode material layer is D [mu] m, a plurality of concave parts are arranged on the surface of the negative electrode material layer, the depth of each concave part is d [mu] m, d is less than D, and WI / d is more than or equal to 0.005 and less than or equal to 5. In the secondary battery, the electrolyte comprises the compound as shown in the formula I, the surface of the negative electrode material layer is provided with the plurality of concave parts, and the values of WI and WI / d are regulated and controlled within the application range, so that the high-temperature cycle performance and the low-temperature discharge performance of the secondary battery can be improved at the same time.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device comprising the same. Background Art

[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, low self-discharge, no memory effect and long cycle life. As the scope of use of lithium-ion batteries continues to expand and their use scenarios become more diverse, the market has put forward higher requirements on the electrochemical performance of lithium-ion batteries. Summary of the invention

[0003] The purpose of this application is to provide a secondary battery and an electronic device containing the same, so as to improve the high temperature cycle performance and low temperature discharge performance of the secondary battery. The specific technical solution is as follows:

[0004] The first aspect of the present application provides a secondary battery, which includes a negative electrode plate and an electrolyte, wherein the electrolyte includes a compound represented by formula I:

[0005]

[0006] Wherein, R is selected from C2 to C6 alkyl which is unsubstituted or substituted by Ra, C6 to C12 aryl which is unsubstituted or substituted by Ra, C5 to C12 nitrogen-containing heteroaryl which is unsubstituted or substituted by Ra; the Ra are each independently selected from halogen or halogen-substituted C1 to C3 alkyl, and the halogen is 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 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 a single side is D μm, a plurality of recesses are disposed on the surface of the negative electrode material layer, and 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 arranged 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.

[0007] In one embodiment of the present application, 0.1≤d / D≤0.5. The present application can better play the role of the concave part and improve the lithium precipitation phenomenon by adjusting the value of d / D within the above range, so that the secondary battery has better high temperature cycle performance and low temperature discharge performance.

[0008] In one embodiment of the present application, along the thickness direction of the negative electrode sheet, the minimum distance between the outer contours of the positive projections of two adjacent recesses is Lμm, 50≤L≤300. By adjusting the value of L within the scope of the present application, the recesses can have a suitable distribution density, which is convenient for the processing of the secondary battery, and at the same time, the role of the recesses can be better played, 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 one embodiment of the present application, 0.005≤W I / L≤1. Regulate W I The value of / L is within the scope of the present application, which can enable the compound represented by Formula I to play a better role, and at the same time can avoid the compound represented by Formula I from reacting more in the non-recessed area 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 one embodiment of the present application, 100≤D≤400. The present application adjusts the value of D within the above range, which is beneficial to increase the volume energy density of the secondary battery, and can also take into account the dynamic performance of the secondary battery, ensuring that the secondary battery has good low-temperature discharge performance.

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

[0012] In one embodiment of the present application, along the thickness direction of the negative electrode sheet, the total area of ​​the positive projections of the plurality of recesses is S1, the area of ​​the negative electrode material layer on one side is S2, and 0.1≤S1 / S2≤0.8. The present application can make the secondary battery have better high temperature cycle performance and low temperature discharge performance at the same time by adjusting the value of S1 / S2 within the above range.

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

[0014]

[0015]

[0016] The electrolyte includes the compound represented by Formula I within the above range, which can better exert the synergistic effect with the concave portion of the negative electrode plate, thereby further improving the high temperature cycle performance and low temperature discharge performance of the secondary battery.

[0017] In one 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 difluorooxalate borate, lithium difluorophosphate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate. Based on the total mass of the electrolyte, the mass percentage of the fluorine-containing lithium salt additive is W L %W L The electrolyte includes a fluorine-containing lithium salt additive and regulates W L When the value of 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, improving the high-temperature cycle performance of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0018] In one embodiment of the present application, 0.5≤W I / W L ≤300. This application is regulated by W I / W L When the value is within the above range, the synergistic effect of the compound represented by formula I in the electrolyte, the fluorine-containing lithium salt additive, and the concave portion of the negative electrode sheet can be better exerted, 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.

[0019] In one embodiment of the present application, 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 total mass percentage of the polycyano compound and the sulfur-oxygen double bond compound is W CNSO %W CNSO 0.1 to 15, preferably 1 to 10; 0.1≤W I / W CNSO ≤40. The electrolyte includes the above-mentioned polycyano compounds and / or sulfur-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 plate can be suppressed, thereby further improving the high-temperature cycle stability of the secondary battery, which is beneficial to better exert a synergistic effect with the compound represented by formula I in the electrolyte and the concave portion of the negative electrode plate, 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 in any of the above embodiments. Therefore, 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 plate 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 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 Dμm, a plurality of recesses are disposed on the surface of the negative electrode material layer, and the depth of a single recess is dμm, 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 arranged 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, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

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

[0025] Figure 2 A schematic diagram of the structure 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 following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions 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 in the specific implementation of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, 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 includes a negative electrode plate and an electrolyte, wherein the electrolyte includes a compound shown in Formula I:

[0030]

[0031] Wherein, R is selected from C2 to C6 alkyl which is unsubstituted or substituted by Ra, C6 to C12 aryl which is unsubstituted or substituted by Ra, C5 to C12 nitrogen-containing heteroaryl which is unsubstituted or substituted by Ra; Ra are each independently selected from halogen or halogen-substituted C1 to C3 alkyl, and halogen is 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 is 0.05 to 50, preferably 1 to 35, for example, W I The value of 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 consisting of any two of the values; the negative electrode plate includes 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 Dμm, a plurality of recesses are arranged on the surface of the negative electrode material layer, and the depth of a single recess is dμm, 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 consisting of any two of these values. The above-mentioned “negative electrode material layer is arranged on at least one surface of the negative electrode current collector” means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of itself, or on two surfaces of the negative electrode current collector along the thickness direction of itself. It should be noted that the “surface” here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a partial area of ​​the surface of the negative electrode current collector. The present application has no special restrictions, as long as the purpose of the present application can be achieved. For example, such as Figure 1 As shown, the negative electrode plate 210 includes a negative electrode current collector 211 and a negative electrode material layer 212 arranged on both surfaces of the negative electrode current collector. The thickness of the single-sided negative electrode material layer 212 is Dμm, and a plurality of recesses 214 are arranged on the surface of the negative electrode material layer 212. The depth of a single recess 214 is dμm, and d<D.

[0032] The inventors found that the electrolyte of the secondary battery is consumed quickly during the cycle at high temperature. The surface of the negative electrode material layer is provided with multiple recesses, which can accelerate the flow, infiltration and diffusion of the electrolyte in the negative electrode plate, enhance the cycle stability of the secondary battery in the lean state, and thus improve the high temperature cycle performance of the secondary battery. However, the negative electrode plate is provided with multiple recesses, which will cause the electrolyte to be locally enriched in the negative electrode plate. During the formation process, the electrolyte reacts more locally, resulting in a larger local impedance and hindered ion transmission, resulting in a reduction in the low-temperature discharge capacity of the secondary battery, affecting the low-temperature discharge performance of the secondary battery. Adding the compound shown in Formula I to the electrolyte can form a thin interface layer with high ion conductivity that is highly rich in elements such as lithium, sulfur, and fluorine at the interface of the recess of the negative electrode plate, accelerate the conduction of ions, thereby improving the low-temperature discharge capacity of the secondary battery and improving the low-temperature discharge performance. When W I When the value of is too small, for example, less than 0.05, the content of the compound represented by Formula I is small, which is not enough to improve the low-temperature discharge performance of the secondary battery; I When the value of is too large, for example, greater than 50, the content of the compound shown in Formula I is relatively large, and the thickness of the solid electrolyte interface (SEI) film formed increases greatly, which is not conducive to ion transport, and is 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 function properly and it is difficult to improve the low-temperature discharge performance of the secondary battery. IWhen the value of / d is too large, for example, greater than 5, the compound represented by Formula I reacts too much, resulting in an excessively thick SEI film formed on the surface of the negative electrode, 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 includes the compound represented by 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 within the above range is conducive to improving both the high temperature cycle performance and the 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.

[0033] In one 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 consisting of any two of the values. The present application can better play the role of the concave portion by regulating the value of d / D within the above range, while ensuring the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area of ​​the secondary battery (CB value), improving the lithium precipitation phenomenon, so that the secondary battery has better high temperature cycle performance and low temperature discharge performance.

[0034] In one embodiment of the present application, along the thickness direction of the negative electrode sheet, the minimum distance between the outer contours of the positive projections of two adjacent recesses is Lμm, 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 consisting of any two values ​​therein. In the present application, the minimum distance L between the outer contours of the positive projections of two adjacent recesses can be the same or different, as long as the purpose of the present application can be achieved. By regulating the value of L within the scope of the present application, the recesses can have a suitable distribution density, which is convenient for the processing technology of the secondary battery, and at the same time, the role of the recesses can be better exerted, and the high temperature cycle performance of the secondary battery can be further improved, while taking into account the low temperature discharge performance of the secondary battery.

[0035] In one embodiment of the present application, 0.005≤W I / L≤1, for example, W IThe value of W 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 consisting of any two of the values. I The value of / L is within the scope of the present application, which can enable the compound represented by Formula I to play a better role, and at the same time can avoid the compound represented by Formula I from reacting more in the non-recessed area 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.

[0036] In one 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 consisting of any two of the values. The present application is beneficial to increase the volume energy density of the secondary battery by regulating the value of D within the above range, and can also take into account the dynamic performance of the secondary battery, ensuring that the secondary battery has good low-temperature discharge performance.

[0037] In one embodiment of the present application, a plurality of recesses are distributed in stripes, and along the thickness direction of the negative electrode sheet, the shape of the positive projection of a single recess includes a strip, and the width D1 mm of the positive projection of a single recess is 0.02 mm to 0.5 mm, 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 consisting of any two of the numerical values. The present application can obtain good processability by regulating the value of D1 within the above range, while promoting the formula I molecule to act more fully on the recess area, so that the secondary battery has better high temperature cycle performance and low temperature discharge performance at the same time.

[0038] In the present application, multiple recesses are distributed in stripes, and multiple recesses can be set along the width direction of the negative electrode sheet, multiple recesses can be set along the length direction of the negative electrode sheet, and multiple recesses can be set simultaneously along the width direction and the length direction of the negative electrode sheet. 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 multiple recesses are distributed in stripes, the width D1 of the strips of the orthographic projections of two adjacent recesses can be the same or different, and the lengths of the strips can be the same or different, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the length of the strip, and it can be designed according to the size of the negative electrode sheet, as long as the purpose of the present application can be achieved.

[0039] Specifically, Figure 2 As shown, the surface of the negative electrode material layer 212 is provided with a plurality of recesses 214, and the plurality of recesses 214 are distributed in stripes, and one side of the positive projection of a single recess 214 is parallel to one side of the negative electrode plate 210, and the positive projection of a single recess 214 is in the shape of a narrow and long rectangle, the width of the rectangle is D1, and the minimum spacing between adjacent rectangles is L. It can be understood that, as Figure 3 As shown, multiple recesses 214 are distributed in stripes, and there is an angle between one side of the positive projection of a single recess 214 and one side of the negative electrode plate 210. The positive projection of a single recess 214 is in the shape of a narrow and long rectangle, the width of the rectangle is D1, the minimum spacing between adjacent rectangles is L, and the lengths of adjacent rectangles are different. The present application has no particular limitation on the size of the above-mentioned angle, as long as the purpose of the present application can be achieved. For example, the angle is 25° to 65°. Figure 2 and Figure 3 The sizes, numbers and shapes of the recesses are only examples and do not limit the scope of protection of the present application.

[0040] In one embodiment of the present application, along the thickness direction of the negative electrode sheet, the total area of ​​the positive projection of the plurality of recesses is S1, the area of ​​the single-sided negative electrode material layer is S2, 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 consisting of any two of the 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 give full play to their functions, so that the secondary battery has better high temperature cycle performance and low temperature discharge performance at the same time.

[0041] The present application has no particular restrictions on the method for preparing the negative electrode sheet, as long as the purpose of the present application can be achieved. By way of example, the method for preparing the negative electrode sheet may include but is not limited to the following steps: arranging a negative electrode material layer on one surface of the negative electrode collector, and then repeatedly arranging the negative electrode material layer on the other surface of the negative electrode collector, and then etching a concave portion on the surface of the double-sided negative electrode material layer by a laser process to obtain a negative electrode sheet.

[0042] The present application has no particular limitation on the method of adjusting d, L, D1, and S1, as long as the purpose of the present application can be achieved. For example, the size of d, L, D1, and S1 can be adjusted by laser technology.

[0043] In one 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 exert the synergistic effect with the concave portion of the negative electrode plate, thereby further improving the high temperature cycle performance and low temperature discharge performance of the secondary battery.

[0046] In one 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 (LiBF4), 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 is 0.01 to 1, preferably 0.1 to 0.7, for example, W L The value of 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 consisting of any two of the values. The electrolyte includes a fluorine-containing lithium salt additive and regulates W L When the value of 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, improving the high-temperature cycle performance of the secondary battery, while taking into account the low-temperature discharge performance of the secondary battery.

[0047] In one embodiment of the present application, 0.5≤W I / W L ≤300, e.g. W I / W LThe value of 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 consisting of any two of the values. I / W L When the value is within the above range, the synergistic effect of the compound represented by formula I in the electrolyte, the fluorine-containing lithium salt additive, and the concave portion of the negative electrode sheet can be better exerted, 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.

[0048] In one embodiment of the present application, 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 total mass percentage of the polycyano compound and the sulfur-oxygen double bond compound is W CNSO %W CNSO is 0.1 to 15, preferably 1 to 10, for example, W CNSO The value of 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 consisting of any two of them; 0.1≤W I / W CNSO ≤40, e.g. W I / W CNSO The value of 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 consisting of any two of the values. The electrolyte includes the above-mentioned polycyano compound and / or sulfur-oxygen double bond compound and regulates W CNSO and W I / W CNSOWhen the value is within the above range, the side reactions of the positive electrode plate can be suppressed, thereby further improving the high-temperature cycle stability of the secondary battery, which is beneficial to better exert a synergistic effect with the compound represented by formula I in the electrolyte and the concave portion of the negative electrode plate, 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 one embodiment of the present application, the electrolyte further comprises a polycyano compound; based on the total mass of the electrolyte, the mass percentage of the polycyano compound is 0.1% to 15%, preferably 1% to 10%. In one embodiment of the present application, the electrolyte further comprises a sulfur-oxygen double bond compound; based on the total mass of the electrolyte, the mass percentage of the sulfur-oxygen double bond compound is 0.1% to 15%, preferably 1% to 10%. In one embodiment of the present application, the electrolyte further comprises a polycyano compound and a sulfur-oxygen double bond compound, and the mass ratio of the polycyano compound to the sulfur-oxygen double bond compound is 1:(0.5 to 1.5).

[0050] In the present application, the electrolyte also includes an electrolyte salt and a non-aqueous solvent. The present application has no particular restrictions on the electrolyte salt, as long as the purpose of the present application can be achieved. 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(oxalatoborate) (LiBOB) or lithium difluoroborate. The present application has no particular restrictions on the content of the electrolyte salt in the electrolyte, as long as the purpose of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage of the electrolyte salt is 8% to 15%.

[0051] The present application has no particular restrictions on non-aqueous solvents, as long as the purpose of the present application can be achieved, for example, non-aqueous solvents may include but are not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents. The above-mentioned carbonate compounds may include but are not limited to at least one of linear carbonate compounds, cyclic carbonate compounds or fluorinated carbonate compounds. The above-mentioned linear 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 ethyl methyl carbonate (MEC). The above-mentioned cyclic carbonate may include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound may include, but is 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 above-mentioned carboxylate compound may include, but is 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, decalactone, valerolactone, or caprolactone. The above-mentioned ether compound may include but is 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. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. The present application does not particularly limit the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved. For example, based on the total mass of the electrolyte, the mass percentage of the non-aqueous solvent is 19% to 91%.

[0052] In one embodiment of the present application, the electrolyte includes a compound shown in Formula I, an electrolyte salt, and a non-aqueous solvent. Wherein, based on the total mass of the electrolyte, the mass percentage of the compound shown in Formula I and the electrolyte salt is as shown above, and the mass percentage of the non-aqueous solvent is 35% to 91%. The electrolyte includes the compound shown in 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 one embodiment of the present application, the electrolyte includes a compound shown in Formula I, a fluorine-containing lithium salt additive, an electrolyte salt, and a non-aqueous solvent. Wherein, based on the total mass of the electrolyte, the mass percentage of the compound shown in Formula I, the fluorine-containing lithium salt additive, and the electrolyte salt is as shown above, and the mass percentage of the non-aqueous solvent is 34% to 91%. The electrolyte includes a compound shown in Formula I and a fluorine-containing lithium salt 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 one embodiment of the present application, the electrolyte includes at least one of the compound shown in Formula I, a polycyano compound or a sulfur-oxygen double bond compound, an electrolyte salt and a non-aqueous solvent. Wherein, based on the total mass of the electrolyte, the sum of the mass percentages of the compound shown in Formula I, the polycyano compound and the sulfur-oxygen double bond compound, the mass percentage of the electrolyte salt are as shown above, and the mass percentage of the non-aqueous solvent is 20% to 91%. The electrolyte includes at least one of the compound shown in Formula I and a polycyano compound or a sulfur-oxygen double bond compound. The secondary battery using the electrolyte of the present application has further improved high temperature cycle performance and low temperature discharge performance.

[0055] In one embodiment of the present application, the electrolyte includes a compound shown in Formula I, a fluorine-containing lithium salt additive, a polycyano compound or a sulfur-oxygen double bond compound, an electrolyte salt and a non-aqueous solvent. Wherein, based on the total mass of the electrolyte, the sum of the mass percentages of the compound shown in Formula I, the fluorine-containing lithium salt additive, the polycyano compound and the sulfur-oxygen double bond compound, and the mass percentage of the electrolyte salt are as shown above, and the mass percentage of the non-aqueous solvent is 19% to 91%. The electrolyte includes a compound shown in Formula I, a fluorine-containing lithium salt additive, and at least one of a polycyano compound or a sulfur-oxygen double bond compound. 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, there is no particular restriction on the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or composite current collector, illustratively, 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 present application does not have a particular restriction on the thickness of the negative electrode current collector, as long as the purpose 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. The present application has no particular limitation on the negative electrode active material as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include but is not limited to natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 Or at least one of Li-Al alloy.

[0058] In some embodiments of the present application, the negative electrode material layer may also include a conductive agent and a binder. The present application does not particularly limit the types of conductive agents and binders, as long as the purpose of the present application can be achieved. 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, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned 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. The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer, and those skilled in the art may select according to actual needs, 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 thickener may also be included. The present application has no particular restrictions on the types of conductive agents and thickeners, as long as the purpose of the present application can be achieved. For example, the conductive agent and the binder may be at least one of the above conductive agents and the above binders. The thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. The present application has no particular restrictions on the mass ratio of the negative electrode active material, the conductive agent, the binder and the thickener in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0060] Optionally, the negative electrode plate may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, and it may be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, and it may be at least one of the above conductive agent and the above binder.

[0061] In the present application, the secondary battery also includes a positive electrode plate, which includes a positive electrode collector and a positive electrode material layer disposed on at least one surface of the positive electrode collector. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode collector along its own thickness direction, or on two surfaces of the positive electrode collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode collector, or it can be a partial area of ​​the surface of the positive electrode collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0062] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0063] The positive electrode material layer includes a positive electrode active material. The present application has no particular limitation on the positive electrode active material as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to at least one of lithium nickel cobalt manganese oxide (such as 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 iron manganese phosphate or lithium titanate.

[0064] The positive electrode material layer may also include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, it may be at least one of the above conductive agent and the above binder. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0065] The present application has no particular limitation on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the positive electrode material layer is 30 μm to 120 μm.

[0066] Optionally, the positive electrode sheet may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, for example, it can be at least one of the above conductive agent and the above binder.

[0067] In the present application, the secondary battery also includes a separator. The present application has no particular restrictions on the separator, as long as the purpose of the present application can be achieved. For example, the material of the separator may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of separator may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0068] In some embodiments of the present application, the isolation film may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film or a composite film having 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 film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0069] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on inorganic particles, such as inorganic particles 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 present application has no particular restrictions on binders, such as binders can be at least one of the above-mentioned 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, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

[0070] In the present application, there is no particular limitation on the thickness of the isolation film, as long as the purpose of the present application can be achieved. For example, the thickness of the isolation film may be 3 μm to 30 μm.

[0071] In the present application, the secondary battery also includes a shell for accommodating a positive electrode plate, a separator, a negative electrode plate and an electrolyte, as well as other components known in the field of secondary batteries, and the present application does not limit the above-mentioned other components. The present application has no special restrictions on the shell, and it 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 present application does not limit the type of metal. 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 there is no particular limitation in the present application. For example, the preparation process of the secondary battery may 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 and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery. Alternatively, stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire laminated structure with tape to obtain an electrode assembly of a laminated structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a secondary battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the shell as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0073] The present application does not particularly limit the type of secondary battery, which may include any device that generates an electrochemical reaction. For example, the secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium ion battery, a sodium ion battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery.

[0074] The second aspect of the present application provides an electronic device, which comprises the secondary battery in any of the above 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 long service life.

[0075] The present application does not particularly limit the type of electronic device, and it can be used for any electronic device known in the prior art. In some embodiments of the present application, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0076] Example

[0077] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0078] Test methods and equipment:

[0079] Size Measurements:

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

[0081] 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 photo of the surface of the negative electrode material layer, and use the microscope software to measure the width D1 of the orthographic projection of a single concave and the minimum distance L between the outer contours of the orthographic projections of two adjacent concave portions, and integrate and accumulate the orthographic projection area of ​​the concave in the image to obtain S1.

[0082] The above dimensions were measured at 10 points and the average value was taken as the final result.

[0083] High temperature cycle performance test:

[0084] Place the lithium-ion battery in a 45°C constant temperature box, charge it to 4.48V at a constant current of 4.5C, charge it to 0.05C at a constant voltage of 4.48V, and then discharge it to 3.0V at a constant current of 1C. This is a charge and discharge cycle process. Record the first discharge capacity as C1. Perform 800 charge and discharge cycles in the above manner, and record the discharge capacity after the 800th cycle as C800.

[0085] 45°C capacity retention rate = (C800 / C1) × 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. The lithium-ion battery that has reached a constant temperature is discharged to 3.0V at a current of 0.5C, then charged to 4.5V at a current of 0.5C, and then charged to a current of 0.05C at a constant voltage with the charging voltage. Also at a temperature of 25°C, discharge 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 to 4.5V at a current of 0.5C, and then charge to a current of 0.05C at a constant voltage with the charging voltage. After that, 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 outside temperature. At -10°C, discharge 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 are mixed in a mass ratio of 97.4:1.4:1.2, and deionized water is added as a solvent to prepare a slurry with a solid content of 45wt%. The negative electrode slurry is obtained after being stirred evenly by a vacuum mixer. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 120°C to obtain a negative electrode sheet coated with a negative electrode material layer on one side. Then repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode material layer on both sides. After drying at 120°C, cold pressing is performed, and then a concave portion is etched on the surface of the double-sided negative electrode material layer by laser processing technology, and then the sheet is cut and the pole ear is welded to obtain a negative electrode sheet with a specification of 78mm×875mm for standby use. Among them, d=10μm, D=100μm, L=100μm, D1=0.1mm, 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 are mixed in a mass ratio of 97.9:0.9:1.2, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and the positive electrode slurry is obtained after vacuum stirring. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. Then repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. After drying at 120°C, cold pressing, cutting and welding of the pole ears are performed to obtain a positive electrode sheet with a specification of 74mm×867mm for standby use. Among them, the thickness of the single-sided positive electrode material layer is 90μm.

[0094] <Preparation of Electrolyte>

[0095] 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, and then the compound of formula I-1 and electrolyte salt LiPF6 are added to the non-aqueous solvent and mixed evenly to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage content of the compound of formula I is W I % is 0.05%, the mass percentage of the electrolyte salt is 12.5%, and the balance is the non-aqueous solvent.

[0096] <Isolation film>

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

[0098] <Preparation of lithium-ion batteries>

[0099] The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is wound. The electrode assembly is placed in an aluminum-plastic film packaging bag, and the water is removed at 80°C, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, degassing, trimming and other processes, a lithium-ion battery is obtained. Among them, the formation upper limit voltage is 4.15V, the formation temperature is 70°C, and the formation standing time is 2h.

[0100] Example 1-2 to Example 1-25

[0101] In addition to adjusting the mass percentage W of the compound represented by Formula I in <Preparation of Electrolyte> as shown in Table 1 I%, the mass percentage of the non-aqueous solvent changes accordingly, and the mass percentage of the electrolyte salt remains unchanged. Except for adjusting the relevant preparation parameters of the negative electrode sheet in <Preparation of the Negative Electrode Sheet> as shown in Table 1, the rest is the same as Example 1-1.

[0102] Example 1-26 to Example 1-29

[0103] Except that the type of the compound represented by Formula I is adjusted as shown in Table 1 in <Preparation of Electrolyte>, the rest is the same as Example 1-4.

[0104] Example 2-1 to Example 2-22

[0105] In addition to adding fluorine-containing lithium salt additives, polycyano compounds, and sulfur-oxygen double bond compounds as shown in Table 2 in <Preparation of Electrolyte>, and adjusting the mass percentage content W of the compound shown in Formula I as shown in Table 2 I %, mass percentage of fluorine-containing lithium salt additive W L %, the type and mass percentage of polycyano compounds, the type and mass percentage of sulfur-oxygen double bond compounds, the sum of the mass percentage of polycyano compounds and sulfur-oxygen double bond compounds W CNSO %, the mass percentage of the non-aqueous solvent changes accordingly, and the mass percentage of the electrolyte salt remains unchanged, and the rest is the same as Example 1-4.

[0106] Comparative Example 1-1

[0107] The present invention is the same as Examples 1-4 except that laser processing is not performed in <Preparation of Negative Electrode Plate> to obtain a negative electrode plate without a recessed portion in the negative electrode material layer, and that the compound represented by Formula I is not added in <Preparation of Electrolyte>, the mass percentage of the non-aqueous solvent changes accordingly, and the mass percentage of the electrolyte salt remains unchanged.

[0108] Comparative Example 1-2

[0109] Except that the compound represented by formula I is not added in <Preparation of electrolyte>, the mass percentage of non-aqueous solvent is changed accordingly, and the mass percentage of electrolyte salt remains unchanged, the rest is the same as Example 1-4.

[0110] Comparative Examples 1-3

[0111] In addition to adjusting the mass percentage W of the compound represented by Formula I in <Preparation of Electrolyte> as shown in Table 1 I %, the mass percentage of the non-aqueous solvent changes accordingly, and the mass percentage of the electrolyte salt remains unchanged, and the rest is the same as Example 1-4.

[0112] Comparative Examples 1-4

[0113] Except that laser processing is not performed in <Preparation of Negative Electrode Plate> to obtain a negative electrode plate without a concave portion in the negative electrode material layer, the rest is the same as Example 1-4.

[0114]

[0115]

[0116] It can be seen from Examples 1-1 to 1-29 and Comparative Examples 1-1 to 1-4 that when the electrolyte includes the compound represented by Formula I and the content thereof is adjusted W I The value of W is within the scope of this application, the negative electrode sheet is provided with multiple recesses, and W is adjusted I / dWhen it is within the scope of this application, the lithium-ion battery can simultaneously have a high high-temperature cycle capacity retention rate and a high low-temperature discharge capacity retention rate, indicating that the lithium-ion battery has both good high-temperature cycle performance and low-temperature discharge performance.

[0117] d / D, L, W I The values ​​of d / D, L, D1, and S1 / S2 usually affect the high temperature cycle performance and low temperature discharge performance of lithium-ion batteries. 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 both better high-temperature cycle performance and low-temperature discharge performance.

[0118] The type of compound represented by Formula I usually affects the high temperature cycle performance and low temperature discharge performance of lithium ion batteries. It can be seen from Examples 1-4, 1-26 to 1-29 that lithium ion batteries using the type of compound represented by Formula I within the scope of the present application can simultaneously have a high high temperature cycle capacity retention rate and a low temperature discharge capacity retention rate, indicating that the lithium ion battery has both good high temperature cycle performance and low temperature discharge performance.

[0119] The type and content of fluorine-containing lithium salt additives, the type and content of polycyano compounds, and the type and content of sulfur-oxygen double bond compounds usually affect the high temperature cycle performance and low temperature discharge performance of lithium ion batteries. It can be seen from Examples 1-3 to 1-4 and Examples 2-1 to 2-22 that when the electrolyte includes at least one of the fluorine-containing lithium salt additives, polycyano compounds, and sulfur-oxygen double bond compounds 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 taking into account a higher low temperature discharge capacity retention rate, indicating that the lithium ion battery has better high temperature cycle performance and takes into account good low temperature discharge performance.

[0120] W I / W L The value of usually affects the high temperature cycle performance and low temperature discharge performance of lithium ion batteries. From Examples 1-3 to 1-4, and Examples 2-1 to 2-7, it can be seen that when W is adjusted I / W L When the value of is within the range of the present application, the lithium-ion battery has a higher high-temperature cycle capacity retention rate, while taking into account a higher low-temperature discharge capacity retention rate, indicating that the lithium-ion battery has both good high-temperature cycle performance and low-temperature discharge performance.

[0121] W I / W CNSO The value of usually affects the high temperature cycle performance and low temperature discharge performance of lithium ion batteries. From Examples 1-3 to 1-4, and Examples 2-8 to 2-15, it can be seen that when W is adjusted I / W CNSO When the value of is within the range of the present application, the lithium-ion battery has a higher high-temperature cycle capacity retention rate, while taking into account a higher low-temperature discharge capacity retention rate, indicating that the lithium-ion battery has better high-temperature cycle performance and takes into account better low-temperature discharge performance.

[0122] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such process, method or article.

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

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

[0125] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles 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 plate 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 groups are each independently selected from halogen or halogen-substituted C1 to C3 alkyl groups, and the halogen groups 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 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 a single surface is D μm, a plurality of recesses are disposed on the surface of the negative electrode material layer, and the depth of a single 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 multiple recesses are distributed in stripes, and along the thickness direction of the negative electrode sheet, the shape of the orthographic projection of a single recess includes a strip, 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 comprises at least one of a polycyano compound or a sulfur-oxygen double bond compound; the polycyano compound comprises at least one of the following compounds: succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile, sebacatenitrile, 1,3,5-pentanetrinitrile, 1,3,6-hexanetrinitrile; the sulfur-oxygen double bond compound comprises 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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