Secondary battery, preparation method thereof and electric device

Abstract

The invention provides a secondary battery, a preparation method thereof and a power utilization device. The secondary battery comprises a positive pole piece, an isolating membrane, a negative pole piece and an electrolyte, the isolating membrane is arranged between the positive pole piece and the negative pole piece; the electrolyte comprises electrolyte and a first gel electrolyte membrane, the first gel electrolyte membrane is arranged between the negative pole piece and the isolating membrane, the curing ratio of the electrolyte is 60%-95%, the thickness of the first gel electrolyte membrane is a [mu] m, the surface capacity of the negative pole piece is bmAh cm <-2 >, and a / b is 0.1-1.5. The secondary battery provided by the invention not only has relatively good cycle performance, but also has relatively high volume energy density.

Description

Secondary battery and preparation method thereof, and power-using device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery, a preparation method thereof, and an electrical device. Background Art

[0002] In recent years, as the application scope of secondary batteries has become increasingly wider, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace and other fields.

[0003] As secondary batteries have made significant progress, higher performance requirements have been placed on them. Cycling performance and energy density are two very important performance indicators of secondary batteries. Therefore, the search for secondary batteries with even better cycling performance and energy density is one of the key areas of focus for those skilled in the art.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and one of its purposes is to provide a secondary battery having good cycle performance and high energy density.

[0006] In order to achieve the above-mentioned object, the first aspect of the present application provides a secondary battery, comprising a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte;

[0007] The separator is provided between the positive electrode sheet and the negative electrode sheet;

[0008] The electrolyte includes an electrolyte solution and a first gel electrolyte membrane. The first gel electrolyte membrane is provided between the negative electrode plate and the separator. The solidification ratio of the electrolyte is 60% to 95%. The thickness of the first gel electrolyte membrane is a μm. The surface capacity of the negative electrode plate is b mAh cm. - 2 , and a / b is 0.1~1.5.

[0009] This application disposes a first gel electrolyte membrane between the negative electrode plate and the separator, and controls the electrolyte solidification ratio to 60% to 95%. The first gel electrolyte membrane's liquid absorption allows a relatively large amount of electrolyte to be retained between the negative electrode plate and the separator, ensuring sufficient electrolyte enters the negative electrode plate during expansion and contraction, thereby improving the secondary battery's cycle performance. Furthermore, the ratio (a / b) of the thickness of the first gel electrolyte membrane to the areal capacity of the negative electrode plate is controlled within a range of 0.1 to 1.5. This not only ensures sufficient electrolyte enters the negative electrode plate during expansion and contraction, thus ensuring the secondary battery's cycle performance, but also reduces the thickness of the first gel electrolyte membrane to a level that significantly impacts the secondary battery's rate performance, and allows the secondary battery to have a higher volumetric energy density.

[0010] In any embodiment, the ratio (a / b) of the thickness of the first gel electrolyte membrane to the areal capacity of the negative electrode plate is 0.15 to 1.2. This ensures that sufficient electrolyte enters the negative electrode plate during expansion and contraction, thereby ensuring the cycle performance of the secondary battery and further improving the volumetric energy density of the secondary battery.

[0011] In any embodiment, the ratio a / b of the thickness of the first gel electrolyte membrane to the surface capacity of the negative electrode sheet is 0.28 to 0.95, thereby further improving the cycle performance and volume energy density of the secondary battery.

[0012] In any embodiment, the solidification ratio of the electrolyte is 70% to 90%, which can further ensure that sufficient electrolyte can enter the negative electrode during the expansion and contraction of the negative electrode, thereby improving the cycle performance of the secondary battery.

[0013] In any embodiment, a is 1 to 10. In this way, the secondary battery can have better cycle performance and higher volume energy density.

[0014] In any embodiment, a is 2 to 4, which is more conducive to improving the cycle performance and volume energy density of the secondary battery.

[0015] In any embodiment, b is 3 to 10. The secondary battery has a high battery capacity.

[0016] In any embodiment, b is 4.2-7.

[0017] In any embodiment, the electrolyte further includes a second gel electrolyte membrane disposed between the positive electrode plate and the separator. The second gel electrolyte membrane can absorb liquid to retain a portion of the electrolyte between the positive electrode plate and the separator, ensuring that sufficient electrolyte enters the positive electrode plate during expansion and contraction, further improving the cycle performance of the secondary battery.

[0018] In any embodiment, the thickness of the second gel electrolyte membrane is less than that of the first gel electrolyte membrane. In this way, the thickness of the second gel electrolyte membrane can be reduced to a minimum while improving the cycle performance of the secondary battery, thereby further improving the volumetric energy density of the secondary battery.

[0019] In any embodiment, the thickness of the second gel electrolyte membrane is c μm, and c is 0.1 to 2. In this way, the cycle performance and volume energy density of the secondary battery can be further improved.

[0020] In any embodiment, the electrolyte further comprises a gel electrolyte filled in the internal pores of the positive electrode sheet and / or the negative electrode sheet. This can effectively buffer the volume expansion of the electrode sheet during charge and discharge, further increasing the electrolyte retention within the electrode sheet, thereby further improving the cycle performance of the secondary battery.

[0021] In any embodiment, the active material of the negative electrode plate contains a silicon-based material, which can improve the energy density of the secondary battery.

[0022] In any embodiment, the mass ratio of the silicon-based material in the active material of the negative electrode plate is ≥10%.

[0023] The second aspect of the present application provides a method for preparing the secondary battery of the first aspect of the present application, comprising:

[0024] Providing a negative electrode plate, and forming a metallic lithium layer on the surface of the negative electrode plate;

[0025] The negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence to form a bare battery cell, with the metallic lithium layer being located between the negative electrode sheet and the separator;

[0026] Placing the bare battery cell in a housing, injecting electrolyte raw materials and dissolving the metallic lithium layer, wherein the electrolyte raw materials include electrolyte salt, solvent, polymer monomer and initiator;

[0027] The electrolyte raw material is partially solidified in the bare cell to form an electrolyte, and a first gel electrolyte membrane is formed at a position before the metal lithium layer is dissolved.

[0028] The preparation method of the present application can regulate the thickness of the first gel electrolyte membrane by controlling the thickness of the preset metal lithium layer on the surface of the negative electrode plate, thereby preparing the secondary battery of the present application having a first gel electrolyte membrane of a certain thickness between the negative electrode plate and the isolation membrane, and the preparation process is simple.

[0029] In any embodiment, the solidification ratio of the electrolyte is 60% to 95%, the thickness of the first gel electrolyte membrane is a μm, and the surface capacity of the negative electrode plate is b mAh cm -2 , and a / b is 0.1~1.5.

[0030] In any embodiment, the polymer monomers include one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether segment-containing oligomers, and siloxanes.

[0031] In any embodiment, the initiator includes one or more of an azo initiator, a peroxide initiator, an anionic and cationic initiator, an organometallic compound initiator, an amine catalyst initiator, and an organophosphorus initiator. The above-mentioned polymer monomers and initiators are in situ polymerized and cured within the bare battery cell to form a gel electrolyte, thereby obtaining an electrolyte having both a gel electrolyte and an electrolyte solution.

[0032] In a third aspect of the present application, an electrical device is provided, which includes the secondary battery according to the first aspect of the present application.

[0033] The secondary battery of the present application provides a first gel electrolyte membrane between the negative electrode plate and the separator, controls the solidification ratio of the electrolyte to be 60% to 95%, and controls the ratio a / b of the thickness of the first gel electrolyte membrane to the surface capacity of the negative electrode plate to be 0.1 to 1.5; thus, the secondary battery has not only good cycle performance but also high volume energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to better describe and illustrate the embodiments and / or examples of the present application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the presently described embodiments and / or examples, and any of the best modes currently understood for these applications.

[0035] FIG1 is a schematic structural diagram of a bare cell of a secondary battery according to an embodiment of the present application;

[0036] FIG2 is a scanning electron microscope image of a negative electrode sheet and a first gel electrolyte membrane in a secondary battery according to an embodiment of the present application;

[0037] 3 is a scanning electron microscope image of a positive electrode sheet and a second gel electrolyte membrane in a secondary battery according to an embodiment of the present application;

[0038] FIG4 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0039] FIG5 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG4 ;

[0040] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0041] Description of reference numerals:

[0042] 1. Secondary battery; 11. Negative electrode plate; 12. First gel electrolyte membrane; 13. Separator; 14. Second gel electrolyte membrane; 15. Positive electrode plate; 16. Housing; 17. Electrode assembly; 18. Cover plate; 111. Negative current collector; 112. Negative active material layer; 151. Positive current collector; 152. Positive active material layer; 2. Electrical device. DETAILED DESCRIPTION

[0043] Below, the secondary battery and its preparation method, and the embodiment of the electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0049] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] The weights described in this specification may be weight units known in the chemical industry, such as μg, mg, g, and kg.

[0051] At present, due to the great development of secondary batteries, higher requirements are also being placed on the cycle performance and energy density of secondary batteries. The cycle performance and energy density of traditional secondary batteries need to be further improved. In response to this, the present application provides a secondary battery that uses an electrolyte containing a gel electrolyte membrane and controls the solidification ratio of the electrolyte, the thickness of the gel electrolyte membrane, and the ratio of the negative electrode surface capacity, so that the secondary battery not only has good cycle performance but also has a high volume energy density.

[0052] Referring to FIG. 1 , a first aspect of the present application provides a secondary battery 1 comprising a negative electrode sheet 11, a separator 13, a positive electrode sheet 15, and an electrolyte; the separator 13 is disposed between the positive electrode sheet 14 and the negative electrode sheet 11; the electrolyte comprises an electrolyte solution and a first gel electrolyte membrane 12, the first gel electrolyte membrane 12 being disposed between the negative electrode sheet 11 and the separator 13; the solidification ratio of the electrolyte is 60% to 95%, the thickness of the first gel electrolyte membrane 12 is a μm, and the surface capacity of the negative electrode sheet 11 is b mAh cm -2 , and a / b is 0.1~1.5.

[0053] In traditional secondary batteries, due to the fluidity of the electrolyte, the expansion and contraction of the electrode during the battery charging and discharging process will cause the electrolyte in the electrode to be squeezed out, making it difficult for the electrolyte to enter the interior of the electrode well, resulting in deterioration of the cycle performance of the secondary battery.

[0054] To address the aforementioned issues, the electrolyte employed in the secondary battery 1 of the present application includes an electrolyte and a first gel electrolyte membrane 12. The first gel electrolyte membrane 12 is disposed between the negative electrode plate 11 and the separator 13. The electrolyte solidification ratio is controlled between 60% and 95%, and the ratio (a / b) of the thickness of the first gel electrolyte membrane 12 to the surface capacity of the negative electrode plate 11 is controlled within a range of 0.1 to 1.5. Since the expansion and contraction of the secondary battery 1 during charge and discharge primarily occurs in the negative electrode plate 11, by disposing the first gel electrolyte membrane 12 between the negative electrode plate 11 and the separator 13 and controlling the electrolyte solidification ratio to 60% to 95%, an appropriate amount of electrolyte is maintained in the electrolyte. The absorption of the first gel electrolyte membrane 12 allows a relatively large amount of electrolyte to be retained between the negative electrode plate 11 and the separator 13. This ensures that sufficient electrolyte enters the negative electrode plate 11 during its expansion and contraction, thereby improving the cycle performance of the secondary battery 1.

[0055] Furthermore, the amount of electrolyte required in the negative electrode sheet 11 is proportional to the surface capacity of the negative electrode sheet 11, and the thickness of the first gel electrolyte membrane 12 is positively correlated with the amount of electrolyte it absorbs. In this application, the ratio a / b of the thickness of the first gel electrolyte membrane 12 to the surface capacity of the negative electrode sheet 11 is controlled within the range of 0.1 to 1.5. On the one hand, this ensures that sufficient electrolyte enters the negative electrode sheet 11 during the expansion and contraction process of the negative electrode sheet 11, thereby ensuring the cycle performance of the secondary battery 1. On the other hand, the thickness of the first gel electrolyte membrane 12 is not too thick, thereby enabling the secondary battery 1 to have higher rate performance and volume energy density. Since the ionic conductivity of the gel electrolyte membrane is lower than that of the electrolyte, if the thickness of the first gel electrolyte membrane 12 is too thick, not only the rate performance of the secondary battery 1 will be reduced, but also the volume energy density of the secondary battery 1 will be reduced.

[0056] Referring to Figure 1 , the negative electrode sheet 11 in the secondary battery 1 includes a negative electrode current collector 111 and a negative electrode active material layer 112 disposed on the negative electrode current collector 111, wherein the negative electrode active material layer 112 is disposed between the negative electrode current collector 111 and the separator 13. The positive electrode sheet 15 includes a positive electrode current collector 151 and a positive electrode active material layer 152 disposed on the positive electrode current collector 151, wherein the positive electrode active material layer 152 is disposed between the positive electrode current collector 151 and the separator 13. FIG. 2 is a scanning electron microscope image of the negative electrode sheet 11 and the first gel electrolyte membrane 12 in the secondary battery 1 according to one embodiment of the present application. In FIG. 2 , the upper layer is the negative electrode sheet 11, and the lower layer is the first gel electrolyte membrane 12.

[0057] It should be noted that electrolyte refers to the liquid electrolyte that can flow within a bare battery cell. The electrolyte solidification ratio refers to the ratio of the mass of the gel-state electrolyte to the total mass of the electrolyte. Areal capacity refers to the discharge capacity per unit electrode area.

[0058] It can be understood that the solidification ratio of the electrolyte in the secondary battery 1 of the present application can be, but is not limited to, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, or 95%; and the ratio a / b of the thickness of the first gel electrolyte membrane 12 to the areal capacity of the negative electrode sheet 11 can be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0059] In some embodiments, the ratio a / b of the thickness of the first gel electrolyte membrane 12 to the areal capacity of the negative electrode plate 11 is 0.15 to 1.2. This ensures that sufficient electrolyte enters the negative electrode plate 11 during expansion and contraction, thereby ensuring the cycle performance of the secondary battery 1. It also prevents the first gel electrolyte membrane 12 from being too thick, thereby enabling the secondary battery 1 to have a higher volumetric energy density.

[0060] In some embodiments, the ratio a / b of the thickness of the first gel electrolyte membrane 12 to the areal capacity of the negative electrode plate 11 is 0.28 to 0.95. This ensures that sufficient electrolyte enters the negative electrode plate 11 during expansion and contraction, thereby ensuring the cycle performance of the secondary battery 1. It also prevents the first gel electrolyte membrane 12 from being too thick, further enhancing the volumetric energy density of the secondary battery 1.

[0061] In some embodiments, the solidification ratio of the electrolyte is 70% to 90%. Controlling the solidification ratio of the electrolyte within the range of 70% to 90% can further ensure that the electrolyte has an appropriate amount of electrolyte, better ensuring that sufficient electrolyte is retained between the negative electrode plate 11 and the separator 13, thereby ensuring that sufficient electrolyte can enter the negative electrode plate 11 during the expansion and contraction process of the negative electrode plate 11, which is beneficial to improving the cycle performance of the secondary battery 1.

[0062] In some embodiments, the thickness of the first gel electrolyte membrane 12 is 1 μm to 10 μm, i.e., a is 1 to 10. It is understood that the thickness of the first gel electrolyte membrane 12 can be appropriately adjusted within the scope of this application based on the areal capacity of the negative electrode plate 11. Generally, controlling the thickness of the first gel electrolyte membrane 12 within the range of 1 μm to 10 μm can enable the secondary battery 1 to have better cycle performance and higher volumetric energy density.

[0063] It is understood that the thickness of the first gel electrolyte membrane 12 can be, but is not limited to, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or 10 μm.

[0064] In some embodiments, the thickness of the first gel electrolyte membrane 12 is 2 μm to 4 μm, that is, a is 2 to 4. This is more conducive to improving the cycle performance and volume energy density of the secondary battery 1.

[0065] In some embodiments, the surface capacity of the negative electrode plate 11 is 3 mAh cm -2 ~10mAh cm -2 , that is, b is 3 to 10. The surface capacity of the negative electrode sheet 11 is positively correlated with the battery capacity. The technical solution of the present application is applicable to secondary batteries 1 with higher capacity.

[0066] It is understood that the surface capacity of the negative electrode plate 11 can be but is not limited to 3 mAh cm -2 、3.5mAh cm -2 , 4mAh cm -2 、4.5mAh cm -2 , 5mAh cm -2 、5.5mAh cm -2 、6mAh cm -2 、6.5mAh cm -2 , 7mAh cm -2 、7.5mAh cm -2 、8mAh cm -2 、8.5mAh cm -2 , 9mAh cm -2 、9.5mAh cm -2 、10mAh cm -2 .

[0067] In some embodiments, the surface capacity of the negative electrode plate 11 is 4.2 mAh cm -2 ~7mAh cm -2 , that is, b is 4.2~7.

[0068] In some embodiments, the electrolyte further includes a second gel electrolyte membrane 14, which is disposed between the positive electrode plate 15 and the separator 13. During the charge and discharge process of the secondary battery 1, although the expansion and contraction of the electrode plates mainly occur on the negative electrode plate 11, there will also be a certain expansion and contraction process in the positive electrode plate 15. There is also a possibility that the electrolyte in the positive electrode plate 15 is extruded, which affects the cycle performance of the secondary battery 1. In this application, by providing a second gel electrolyte membrane 14 between the positive electrode plate 15 and the separator 13, a part of the electrolyte in the electrolyte can be retained between the positive electrode plate 15 and the separator 13 through the liquid absorption effect of the second gel electrolyte membrane 14, ensuring that there is enough electrolyte entering the positive electrode plate 15 during the expansion and contraction process of the positive electrode plate 15, and further improving the cycle performance of the secondary battery 1.

[0069] Figure 3 is a scanning electron microscope image of the positive electrode plate 15 and the second gel electrolyte membrane 14 in the secondary battery 1 according to an embodiment of the present application. In Figure 3, the upper layer is the second gel electrolyte membrane 14, and the lower layer is the positive electrode plate 15.

[0070] In some embodiments, the thickness of the second gel electrolyte membrane 14 is c μm, and the thickness of the second gel electrolyte membrane 14 is less than the thickness of the first gel electrolyte membrane 12, that is, c < a. Since the expansion and contraction of the electrode plates mainly occur on the negative electrode plate 11 during the charge and discharge process of the secondary battery 1, the expansion and contraction of the positive electrode plate 15 is relatively small; by setting the thickness of the second gel electrolyte membrane 14 to be less than the thickness of the first gel electrolyte membrane 12, the thickness of the second gel electrolyte membrane 14 can be prevented from being too thick while improving the cycle performance of the secondary battery 1, thereby better improving the volume energy density of the secondary battery 1.

[0071] In some embodiments, the thickness of the second gel electrolyte membrane 14 is 0.1 μm to 2 μm, that is, c is 0.1 to 2. In this way, it can be ensured that there is enough electrolyte entering the positive electrode plate 15 during the expansion and contraction process of the positive electrode plate 15, further improving the cycle performance of the secondary battery 1 while further improving the volume energy density of the secondary battery 1.

[0072] It can be understood that the thickness of the second gel electrolyte membrane 14 can be, but is not limited to, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm.

[0073] In some embodiments, the electrolyte further includes a gel electrolyte filled in the internal pores of the positive electrode plate 15 and / or the negative electrode plate 11. The gel electrolyte in the internal pores of the positive electrode plate 15 and the negative electrode plate 11 can be a gel electrolyte formed by injecting electrolyte raw materials into the battery cell, and polymer monomers entering the pores between the active material layers of the electrode plates and the pores of the materials themselves, and then undergoing in-situ polymerization. By filling the internal pores of the positive electrode plate 15 and the negative electrode plate 11 with gel electrolyte, the volume expansion of the electrode plates during charging and discharging can be effectively buffered, and the electrolyte retention capacity inside the electrode plates can be further increased, thereby further improving the cycle performance of the secondary battery 1.

[0074] In some embodiments, the active material of the negative electrode plate 11 contains a silicon-based material. The technical solution of the present application can be applied to a secondary battery 1 whose negative electrode does not contain a silicon-based material, or to a secondary battery 1 whose negative electrode contains a silicon-based material. Using a secondary battery 1 containing a silicon-based material in the negative electrode can improve the energy density of the secondary battery 1. It is understood that since the content of the silicon-based material in the negative electrode is positively correlated with the surface capacity of the negative electrode, the thickness of the first gel electrolyte membrane 12 can be appropriately adjusted within the scope of the present application based on the content of the silicon-based material in the negative electrode.

[0075] In some embodiments, the mass ratio of the silicon-based material in the active material of the negative electrode plate 11 is ≥ 10%. It is understood that the mass ratio of the silicon-based material in the active material can be, but is not limited to, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. This can increase the energy density of the secondary battery 1.

[0076] In some embodiments, the silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.

[0077] The second aspect of the present application provides a method for preparing the secondary battery 1 of the first aspect of the present application, comprising:

[0078] Providing a negative electrode plate 11, and forming a metallic lithium layer on the surface of the negative electrode plate 11;

[0079] The negative electrode sheet 11, the separator 13, and the positive electrode sheet 15 are stacked in sequence to form a bare cell, with the metallic lithium layer located between the negative electrode sheet 11 and the separator 13;

[0080] Placing the bare battery cell in a housing, injecting electrolyte raw materials and dissolving the metallic lithium layer, wherein the electrolyte raw materials include electrolyte salt, solvent, polymer monomer and initiator;

[0081] The electrolyte raw material is partially solidified in the bare cell to form an electrolyte, and a first gel electrolyte membrane 12 is formed at a position before the metal lithium layer is dissolved.

[0082] The aforementioned method for preparing the secondary battery 1 forms a metallic lithium layer on the surface of the negative electrode plate 11. When assembled into a bare cell, the metallic lithium layer is positioned between the negative electrode plate 11 and the separator 13. After injecting the electrolyte raw material, the metallic lithium layer dissolves and spontaneously embeds into the negative electrode active material. After the electrolyte raw material is partially solidified, a first gel electrolyte membrane 12 is formed at the location where the metallic lithium layer was previously dissolved. The aforementioned method can control the thickness of the first gel electrolyte membrane 12 by controlling the thickness of the predetermined metallic lithium layer on the surface of the negative electrode plate 11, thereby producing the secondary battery 1 of the present application having a first gel electrolyte membrane 12 of a predetermined thickness between the negative electrode plate 11 and the separator 13.

[0083] In the above-described preparation method, the thickness of the metallic lithium layer on the surface of the negative electrode sheet 11 can be controlled by calculating the loading of the negative electrode sheet 11 and controlling the pressure at which the metallic lithium layer is laminated onto the negative electrode sheet 11. Furthermore, the thickness of the metallic lithium layer can be used to control the thickness of the first gel electrolyte membrane 12.

[0084] In addition, while forming the first gel electrolyte membrane 12, a second gel electrolyte membrane 14 is also formed in the gap between the positive electrode plate and the separator. The thickness of the second gel electrolyte membrane 14 can be determined by the polyvinylidene fluoride microspheres on the separator. By controlling the coating amount of the polyvinylidene fluoride microspheres on the separator surface, the distance between the positive electrode plate and the separator can be 0.1 μm to 2 μm.

[0085] μm, so that the second gel electrolyte membrane 14 is formed within this interval.

[0086] In some embodiments, metallic lithium is first melted, and the molten metallic lithium is coated on the surface of the negative electrode plate 11. After the metallic lithium cools and solidifies, a metallic lithium layer is formed on the surface of the negative electrode plate 11. It will be understood that the present application is not limited to the above specific method, and other conventional methods in the art may also be used to form the metallic lithium layer on the surface of the negative electrode plate 11.

[0087] In some embodiments, the polymer monomers in the electrolyte raw material include one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether-containing segment oligomers and siloxanes.

[0088] In some embodiments, the initiator in the electrolyte raw material includes one or more of an azo initiator, a peroxide initiator, an anionic and cationic initiator, an organometallic compound initiator, an amine catalyst initiator, and an organophosphorus initiator.

[0089] By adopting the above-mentioned polymer monomers and initiators, a gel electrolyte can be formed by in-situ polymerization and curing inside the bare battery cell. The gel electrolyte includes a first gel electrolyte membrane 12, a second gel electrolyte membrane 14, and a gel electrolyte filled in the pores inside the positive electrode sheet 15 and the negative electrode sheet 11.

[0090] In some embodiments, the electrolyte salt in the electrolyte raw material includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorophosphate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0091] In some embodiments, the solvent in the electrolyte raw material includes one or more of fluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0092] It can be understood that by regulating the ratio of electrolyte salt, solvent, polymer monomer and initiator in the electrolyte raw materials, the relative content of gel electrolyte and electrolyte in the electrolyte can be controlled, thereby adjusting the solidification ratio of the electrolyte.

[0093] In a third aspect of the present application, an electrical device is provided, which includes the secondary battery according to the first aspect of the present application.

[0094] The secondary battery and the electric device of the present application will be described below with reference to FIG. 4 to FIG. 6 as appropriate.

[0095] Unless otherwise specified, the components, material types, or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.

[0096] In one embodiment of the present application, a secondary battery is provided.

[0097] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0098]

Positive electrode

[0099] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0100] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0101] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material on a polymer material substrate. Among them, the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc. Polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.)

[0102] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0103] As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0104] As an example, the positive electrode active material of a sodium ion secondary battery may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0105] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0106] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n- valence.

[0107] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds consisting of anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0108] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0109] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0110] Prussian blue compounds can be composed of sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0111] The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight percent based on the total weight of the positive electrode film layer.

[0112] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20 weight%, based on the total weight of the positive electrode film layer.

[0113] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.

[0114] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40% by mass (wt%) to 80% by weight, and the viscosity at room temperature is adjusted to 5000 mPa·s to 25000 mPa·s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, the positive electrode sheet is formed by cold rolling; the positive electrode powder coating unit area density is 150 mg / m2 (mg / m 2 )~350mg / m 2 The compacted density of the positive electrode is 3.0 g / cm3 (g / cm 3 )~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0115] The calculation formula of the compacted density is:

[0116] Compaction density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0117] The mass M of the positive electrode active material per unit area of ​​the positive electrode membrane can be obtained by weighing using a standard balance.

[0118] The thickness T of the positive electrode film can be measured using a micrometer, for example, a Mitutoyo 293-100 with an accuracy of 0.1 μm. It should be noted that the thickness of the positive electrode film described in this application refers to the thickness of the positive electrode film in the positive electrode sheet after cold pressing and used in battery assembly.

[0119]

Negative electrode

[0120] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0121] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0122] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate. Among them, the metal material includes but is not limited to copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc., and the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates.

[0123] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art.

[0124] As an example, the negative electrode active material of a lithium-ion secondary battery may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0125] As an example, the negative electrode active material of a sodium ion secondary battery is generally a hard carbon material, a two-dimensional metal carbide or a nitride. Preferably, the negative electrode active material of a sodium ion secondary battery is generally a hard carbon material.

[0126] The weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100 weight percent based on the total weight of the negative electrode film layer.

[0127] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0 to 30% by weight, based on the total weight of the negative electrode film layer.

[0128] In some embodiments, the negative electrode film layer may further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight, based on the total weight of the negative electrode film layer.

[0129] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)). The weight ratio of the other additives in the negative electrode film layer is 0 to 15% by weight, based on the total weight of the negative electrode film layer.

[0130] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa·s to 10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing, such as rolling, is performed to obtain the negative electrode sheet. The negative electrode powder coating unit area density is 75mg / m 2 ~220 mg / m 2 The compacted density of the negative electrode is 1.2 g / m3 (g / m 3 )~2.0g / m 3 .

[0131] The mass M of the negative electrode active material per unit area of ​​the negative electrode membrane can be obtained by weighing using a standard balance.

[0132] The thickness T of the negative electrode film can be measured using a micrometer, such as a Mitutoyo 293-100 with an accuracy of 0.1 μm. It should be noted that the thickness of the negative electrode film described in this application refers to the thickness of the negative electrode film after cold pressing and compaction and used in the negative electrode sheet assembled into the battery.

[0133] Electrolytes

[0134] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The electrolyte of the present application includes gel electrolyte and electrolyte solution.

[0135] In some embodiments, the electrolyte raw materials include an electrolyte salt, a solvent, a polymer monomer, and an initiator.

[0136] In some embodiments, the electrolyte salt of the lithium ion secondary battery can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0137] The electrolyte salt of the sodium ion secondary battery can be selected from one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

[0138] In some embodiments, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0139] In some embodiments, the polymer monomers include one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether segment-containing oligomers, and siloxanes.

[0140] In some embodiments, the initiator includes one or more of an azo initiator, a peroxide initiator, an anionic and cationic initiator, an organometallic compound initiator, an amine catalyst initiator, and an organophosphorus initiator.

[0141] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0142]

Isolation film

[0143] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0144] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0145] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0146] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0147] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0148] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0149] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG4 shows a secondary battery 1 with a square structure as an example.

[0150] In some embodiments, referring to Figure 5, the outer packaging may include a shell 16 and a cover plate 18. The shell 16 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 16 has an opening connected to the receiving cavity, and the cover plate 18 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 17 through a winding process or a lamination process. The electrode assembly 17 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 17. The number of electrode assemblies 17 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0151] In some embodiments, the secondary batteries 1 can be assembled into a battery module. The battery module can contain one or more secondary batteries 1. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0152] In the battery module, the plurality of secondary batteries 1 can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 1 can be fixed by fasteners.

[0153] Optionally, the battery module may further include a housing having a receiving space, and the plurality of secondary batteries 1 are received in the receiving space.

[0154] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0155] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0156] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0157] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0158] Figure 6 shows an example of an electric device 2. The electric device 2 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device 2's requirements for high power and high energy density of the secondary battery 1, a battery pack or battery module can be used.

[0159] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0160] The following are some examples.

[0161] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0162] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0163] 1. Implementation

[0164] Example 1:

[0165] 1) Preparation of positive electrode sheet

[0166] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black SP and binder PVDF were dispersed in the solvent NMP in a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained. The coating amount per unit area was 0.3g / 1540.25mm 2 .

[0167] 2) Preparation of negative electrode sheet

[0168] The negative electrode active material graphite, the negative electrode active material silicon oxide, the conductive agent acetylene black, the binder SBR, and the dispersant CMC were dispersed in deionized water at a mass ratio of 77:25:1:1:1 to obtain a negative electrode slurry; the obtained negative electrode slurry was coated on a copper foil, dried, cold pressed, and cut to obtain a negative electrode sheet, and the coating amount per unit area was 0.12g / 1540.25mm 2 The negative electrode surface capacity b is 4.2 mAh / cm 2 .

[0169] 3) Isolation film

[0170] A PE diaphragm is used, both sides of which are coated with an aluminum oxide coating with a thickness of 1 μm and a coating amount of 1 mg / 1540.25 mm 2 polyvinylidene fluoride microspheres.

[0171] 4) Preparation of metallic lithium layer

[0172] A metal lithium layer is coated on the surface of the negative electrode plate, and the thickness of the metal lithium layer is determined according to the thickness of the first gel electrolyte membrane to be prepared.

[0173] 5) Battery assembly

[0174] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to form a bare cell. In the bare cell, the metallic lithium layer is located between the negative electrode sheet and the separator. The bare cell is placed in a casing and the electrolyte raw materials are injected. The electrolyte raw materials are composed of 10 parts by weight of polyethylene glycol acrylate, 10 parts of fluoroethylene carbonate, 0.2 parts of the initiator azobisisobutyronitrile, 35 parts of dimethyl carbonate, and 35 parts of ethylene carbonate. After the above components are mixed evenly, 10 parts of lithium hexafluorophosphate (LiPF6) are added until the lithium salt is fully dissolved. The polymer monomers in the electrolyte raw materials are polymerized and solidified in situ to form an electrolyte containing a gel electrolyte and an electrolyte solution. The electrolyte solidification ratio is 90%. The metallic lithium layer on the negative electrode sheet side dissolves and forms a first gel electrolyte membrane at its corresponding position. A second gel electrolyte membrane forms in the gap between the polyvinylidene fluoride microspheres on the positive electrode sheet side and the separator. The thickness a of the first gel electrolyte membrane is 2 μm, and the thickness c of the second gel electrolyte membrane is 0.5 μm.

[0175] Example 2:

[0176] This embodiment is substantially the same as the embodiment 1, except that the thickness a of the first gel electrolyte membrane is different. In this embodiment, the thickness a of the first gel electrolyte membrane is 4 μm.

[0177] Example 3:

[0178] This embodiment is substantially the same as the embodiment 1, except that the thickness c of the second gel electrolyte membrane is different. In this embodiment, the thickness c of the second gel electrolyte membrane is 0.8 μm.

[0179] Example 4:

[0180] This embodiment is basically the same as embodiment 1, except that the surface capacity b of the negative electrode plate is different. The surface capacity b of the negative electrode plate in this embodiment is 7 mAh / cm 2 .

[0181] Example 5:

[0182] This embodiment is substantially the same as embodiment 4, except that the solidification ratio of the electrolyte is different. In this embodiment, the solidification ratio of the electrolyte is 70%.

[0183] Example 6:

[0184] This embodiment is substantially the same as embodiment 4, except that the solidification ratio of the electrolyte is different. In this embodiment, the solidification ratio of the electrolyte is 62%.

[0185] Example 7:

[0186] This embodiment is substantially the same as embodiment 4, except that the solidification ratio of the electrolyte is different. In this embodiment, the solidification ratio of the electrolyte is 94%.

[0187] Example 8:

[0188] This embodiment is basically the same as embodiment 4, except that: the thickness a of the first gel electrolyte membrane is 1, the surface capacity b of the negative electrode sheet is 7; and the ratio of the thickness a of the first gel electrolyte membrane to the surface capacity b of the negative electrode sheet is 0.14.

[0189] Example 9:

[0190] This embodiment is basically the same as embodiment 4, except that: the thickness a of the first gel electrolyte membrane is 9, the surface capacity b of the negative electrode sheet is 7; and the ratio of the thickness a of the first gel electrolyte membrane to the surface capacity b of the negative electrode sheet is 1.28.

[0191] Comparative Example 1:

[0192] This comparative example is substantially the same as Example 1, except that the solidification ratio of the electrolyte is different. In this comparative example, the solidification ratio of the electrolyte is 98%.

[0193] Comparative Example 2:

[0194] This comparative example is essentially the same as Example 1, except that the thickness a of the first gel electrolyte membrane is different, and accordingly, the ratio of the first gel electrolyte membrane a to the areal capacity b of the negative electrode sheet is different. In this comparative example, the thickness a of the first gel electrolyte membrane is 11 μm, and a / b is 2.62.

[0195] Comparative Example 3:

[0196] This comparative example is essentially the same as Example 1, except that the thickness a of the first gel electrolyte membrane is different, and accordingly, the ratio of the first gel electrolyte membrane a to the areal capacity b of the negative electrode sheet is different. In this comparative example, the thickness a of the first gel electrolyte membrane is 8 μm, and a / b is 1.90.

[0197] 2. Test Method

[0198] 1) Gel electrolyte membrane thickness test:

[0199] The positive and negative electrode sheets were sliced ​​in a direction perpendicular to the active material layer, and the cut surfaces were photographed using a scanning electron microscope to observe the thickness of the gel electrolyte membrane on the surface of the positive and negative electrode active material layers.

[0200] 2) Surface capacity test:

[0201] The negative electrode plate is assembled with metallic lithium into a button battery, which is discharged at a rate of 0.1C to 0.01V at room temperature, and then charged to 1.5V at 0.1C. The charge capacity at this time divided by the area of ​​the negative electrode plate is the surface capacity of the negative electrode plate.

[0202] 3) Discharge capacity retention rate test:

[0203] At room temperature, the secondary battery was charged to the upper limit voltage at a 1 / 3C rate, and then discharged to the lower limit voltage at 0.33C and 2C, respectively. The discharge capacity at the 0.33C rate was used as the nominal capacity reference group, and the capacity retention rate of the secondary battery at the 2C rate was calculated. The discharge capacity retention rate reflects the rate performance of the secondary battery.

[0204] 4) Cycle life test:

[0205] At room temperature, the secondary battery is charged to the upper limit voltage at a rate of 1 / 3C and charged to 0.05C at a constant voltage. After standing for 10 minutes, it is discharged to the lower limit voltage at a rate of 1 / 3C and stood for 10 minutes. The above charge and discharge process is repeated, and the ratio of the discharge capacity of each cycle to the discharge capacity of the first cycle is recorded until the ratio is ≤80%.

[0206] 5) Volume energy density test:

[0207] At room temperature, a secondary battery is charged to its upper voltage limit at a 1 / 3C rate, and then discharged to its lower voltage limit at a 1 / 3C rate. The energy during discharge is calculated as follows: The volumetric energy density (Wh / L) of a secondary battery is calculated as the energy during discharge divided by the volume of the secondary battery.

[0208] 6) Electrolyte solidification ratio test:

[0209] After the electrolyte is heated from room temperature to 100°C at a heating rate of 5°C / min to 20°C / min, the ratio of the residual weight to the initial weight is the solidification ratio.

[0210] The parameters and performance test data of the secondary batteries of the above embodiments and comparative examples are shown in Table 1.

[0211] Table 1

[0212] As can be seen from Table 1, the secondary batteries of Examples 1 to 9 have good discharge capacity retention and cycle performance, and also have high volume energy density. Compared with Example 1, Comparative Example 1 only has a different electrolyte solidification ratio. In Comparative Example 1, the electrolyte solidification ratio is too large, and the discharge capacity retention, cycle life, and volume energy density of the secondary battery are all reduced. Compared with Example 1, Comparative Example 2 has an excessively large thickness a of the first gel electrolyte membrane, and correspondingly, an excessively large value of a / b. The discharge capacity retention, cycle life, and volume energy density of the secondary battery are all significantly reduced. Compared with Examples 1 and 2, Comparative Example 3 has a different thickness a of the first gel electrolyte membrane, and correspondingly, an excessively large value of a / b. The discharge capacity retention, cycle life, and volume energy density of the secondary battery are also significantly reduced.

[0213] By comparing Example 6 with Example 4, it can be found that when the electrolyte solidification ratio is less than 70%, the cycle life of the secondary battery is significantly reduced. Comparing Example 7 with Example 4, it can be seen that when the electrolyte solidification ratio is higher than 90%, although the cycle life is improved, the discharge capacity retention rate and volume energy density of the secondary battery are reduced. This shows that controlling the electrolyte solidification ratio between 70% and 90% can further achieve a balance between cycle performance and energy density, resulting in better overall performance.

[0214] Comparing Example 8 with Example 4, it can be seen that in Example 8, the thickness a of the first gel electrolyte membrane is less than 2, and the corresponding a / b value is less than 0.28, resulting in a significant decrease in the cycle life of the secondary battery. Comparing Example 9 with Example 4, it can be seen that in Example 9, the thickness a of the first gel electrolyte membrane is greater than 4, and the corresponding a / b value is greater than 0.95, resulting in a decrease in the discharge capacity retention rate, cycle life, and volumetric energy density of the secondary battery. This indicates that controlling the thickness a of the first gel electrolyte membrane to between 2 and 4 and the a / b value to between 0.28 and 0.95 can further improve the overall performance of the secondary battery.

[0215] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte; The isolation film is arranged between the positive electrode sheet and the negative electrode sheet; The electrolyte includes an electrolyte solution and a first gel electrolyte membrane, the first gel electrolyte membrane is disposed between the negative electrode plate and the separator, the solidification ratio of the electrolyte is 60% to 95%, the thickness of the first gel electrolyte membrane is a μm, and the surface capacity of the negative electrode plate is b mAh cm - 2 , and a / b is 0.1~1.

5.

2. The secondary battery according to claim 1, characterized in that: The a / b is 0.15 to 1.2; Optionally, a / b is 0.28 to 0.

95.

3. The secondary battery according to any one of claims 1 to 2, characterized in that: The solidification ratio of the electrolyte is 70% to 90%.

4. The secondary battery according to any one of claims 1 to 3, characterized in that: The a is 1 to 10; Optionally, a is 2-4.

5. The secondary battery according to any one of claims 1 to 4, characterized in that: The b is 3 to 10; Optionally, b is 4.2-7.

6. The secondary battery according to any one of claims 1 to 5, characterized in that: The electrolyte further includes a second gel electrolyte membrane, and the second gel electrolyte membrane is disposed between the positive electrode sheet and the separator.

7. The secondary battery according to claim 6, characterized in that: The thickness of the second gel electrolyte membrane is smaller than the thickness of the first gel electrolyte membrane.

8. The secondary battery according to claim 7, characterized in that: The thickness of the second gel electrolyte membrane is c μm, and c is 0.1-2.

9. The secondary battery according to any one of claims 1 to 8, characterized in that: The electrolyte further includes a gel electrolyte filled in the inner pores of the positive electrode sheet and / or the negative electrode sheet.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The active material of the negative electrode plate contains silicon-based material.

11. The secondary battery according to claim 10, characterized in that: The mass ratio of the silicon-based material in the active material of the negative electrode plate is ≥10%.

12. A method for preparing a secondary battery, comprising: Providing a negative electrode plate, and forming a metal lithium layer on the surface of the negative electrode plate; The negative electrode sheet, the separator and the positive electrode sheet are stacked in sequence to form a bare battery cell, wherein the metal lithium layer is located between the negative electrode sheet and the separator; Placing the bare battery cell in a housing, injecting electrolyte raw materials and dissolving the metal lithium layer, wherein the electrolyte raw materials include electrolyte salt, solvent, polymer monomer and initiator; The electrolyte raw material is partially solidified in the bare battery cell to form an electrolyte, and a first gel electrolyte membrane is formed at a position before the metal lithium layer is dissolved.

13. The method for preparing a secondary battery according to claim 12, characterized in that: The solidification ratio of the electrolyte is 60% to 95%, the thickness of the first gel electrolyte membrane is a μm, and the surface capacity of the negative electrode plate is b mAh cm -2 , and a / b is 0.1~1.

5.

14. The method for preparing a secondary battery according to claim 12 or 13, characterized in that: The polymer monomers include one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether segment-containing oligomers and siloxanes.

15. The method for preparing a secondary battery according to any one of claims 12 to 14, characterized in that: The initiator includes one or more of an azo initiator, a peroxide initiator, an anionic and cationic initiator, an organic metal compound initiator, an amine catalyst initiator and an organic phosphorus initiator.

16. An electrical device comprising the secondary battery according to any one of claims 1 to 11.

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