Secondary battery and electric device

Abstract

The invention provides a secondary battery and an electric device. The secondary battery comprises a negative electrode piece, the negative electrode piece comprises a current collector and a negative electrode film layer located on at least one surface of the current collector, the negative electrode film layer comprises a negative electrode material, and the negative electrode material comprises a negative electrode active material and a lithium dendrite consuming material; the negative electrode active material comprises at least one of graphite, hard carbon, soft carbon, a silicon-based material, a tin-based material and lithium titanate, the lithium dendrite consuming material is located on at least one part of the surface of the negative electrode active material, and the oxidation potential of the lithium dendrite consuming material is greater than or equal to 1V. In the negative electrode material, through the introduction of the lithium dendrite consuming material, the lithium dendrite consuming material can react with the lithium dendrite when the lithium dendrite is generated, and further growth of the lithium dendrite is avoided, so that the lithium precipitation phenomenon can be effectively avoided, and the cycle performance of the secondary battery is improved.

Description

[0001] Related Applications

[0002] This application is a divisional application of the Chinese Patent Application No. 2023100741737, filed on January 19, 2023, with the title of “Negative Electrode Material, Negative Electrode Sheet, Secondary Battery and Electric Device”, in the name of the applicant. TECHNICAL FIELD

[0003] The present application relates to the technical field of secondary batteries, in particular to a secondary battery and an electric device. BACKGROUND

[0004] In the use process of lithium ion batteries, lithium ions are deintercalated from the positive electrode and then intercalated into the negative electrode. When lithium ions are intercalated into the negative electrode, the problem of lithium dendrite formation on the surface of the negative electrode may occur, i.e. lithium precipitation problem. The occurrence of lithium precipitation problem will adversely affect the cycle performance of the battery, and even the lithium dendrites may pierce the separator to cause the positive electrode and the negative electrode to contact each other, resulting in safety accidents such as combustion and explosion. Therefore, how to avoid the occurrence of lithium precipitation phenomenon in the battery is of great significance to maintain the cycle performance of the battery. SUMMARY

[0005] The present application provides a secondary battery, comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode film layer located on at least one surface of the current collector, the negative electrode film layer comprising a negative electrode material, the negative electrode material comprising at least one of graphite, hard carbon, soft carbon, silicon-based material, tin-based material and lithium titanate, the lithium dendrite consumption material being located on at least a part of the surface of the negative electrode active material, and the oxidation potential of the lithium dendrite consumption material being ≥1V.

[0006] In the above-mentioned secondary battery, by introducing the lithium dendrite consumption material, when lithium dendrites are generated, the lithium dendrite consumption material can react with the lithium dendrites to avoid the further growth of the lithium dendrites, which can effectively avoid the occurrence of lithium precipitation phenomenon and improve the cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0008] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of the present application. Figure 1 is an exploded view of the secondary battery according to an embodiment of the present application.

[0009] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0010] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0011] Figure 5 is Figure 4 exploded view of a battery pack according to an embodiment of the present application.

[0012] Figure 6 is a schematic view of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0013] Figure 7 is a schematic view of a negative electrode material according to an embodiment of the present application.

[0014] Explanation of Reference Numerals:

[0015] 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: secondary battery; 51: case; 52: electrode assembly; 53: top cap assembly; 6: negative electrode active material; 7: lithium dendrite consuming material; 8: polymer coating layer. DETAILED DESCRIPTION

[0016] Hereinafter, embodiments of a secondary battery and an electric device according to the present application are specifically disclosed while appropriately referring to the accompanying drawings. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters that are already well known, repeated explanations of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0017] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all 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.

[0018] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] If not specifically stated, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true or present, and B is false or not present; A is false or not present, and B is true or present; or both A and B are true, or both A and B are present.

[0023] If not specifically stated, the terms "positive electrode sheet", "positive electrode tab" have the same meaning and can be used interchangeably in this application. The terms "negative electrode sheet", "negative electrode tab" have the same meaning and can be used interchangeably in this application. The terms "separator", "isolation film" have the same meaning and can be used interchangeably.

[0024] An embodiment of the present application provides a negative electrode material, comprising a negative electrode active material and a lithium dendrite consuming material, the lithium dendrite consuming material is located on at least a part of the surface of the negative electrode active material, and the oxidation potential of the lithium dendrite consuming material is ≥1V. In the negative electrode material of the present embodiment, by introducing the lithium dendrite consuming material, when lithium dendrites are generated, the lithium dendrite consuming material can react with the lithium dendrites to avoid the further growth of the lithium dendrites, so that the occurrence of lithium precipitation can be effectively avoided. It can be understood that the lithium dendrite consuming material refers to a material that can react with lithium dendrites to consume lithium dendrites.

[0025] Further, when the lithium dendrite consuming material is applied to a lithium ion battery, the oxidation potential of the lithium dendrite consuming material is ≥1V, which can effectively consume metal lithium dendrites, reduce the accumulation of dead lithium, reduce the polarization of the battery, improve the cycle capacity of the battery, and further improve the cycle performance of the battery.

[0026] Further, when the lithium dendrite consuming material reacts with the lithium dendrites, the lithium dendrites can be converted into lithium ions, which can be recycled in the battery to improve the cycle performance of the battery, and on the other hand, the generated lithium ions can participate in the construction of the SEI film, which is beneficial to maintaining the stability of the battery.

[0027] Further, when the negative electrode material of the present embodiment is applied to a lithium ion battery, the lithium precipitation phenomenon is well avoided, which can effectively improve the cycle performance of the battery.

[0028] Optionally, the oxidation potential of the lithium dendrite consuming material is ≥1.5V. Optionally, the oxidation potential of the lithium dendrite consuming material is ≥2V. Optionally, the oxidation potential of the lithium dendrite consuming material is ≥2.5V. Optionally, the oxidation potential of the lithium dendrite consuming material is 1V-3V.

[0029] It can be understood that the oxidation potential of the lithium dendrite consuming material can be obtained by consulting the oxidation-reduction potential table.

[0030] In this application, oxidation potential is a well-known concept in the art. Specifically, oxidation potential is tested by the following method.

[0031] Oxidation potential test method for lithium dendrite consumable materials:

[0032] 1. Select a single-sided electrode with no creases or scratches on the surface, punch out a small disc with a diameter of 14 mm, and use it as the negative electrode to assemble a button half-cell. The electrolyte is a 1 M LiPF6 ethylene carbonate (EC) / diethyl carbonate (DEC) (volume ratio 3:7) electrolyte with the addition of the lithium dendrite consumption material to be tested. The amount of additive is 0.05 mol / L. The positive electrode shell is an aluminum-plated shell. The electrode includes a current collector and a film layer. The current collector is a 6 μm copper foil. The film layer includes the negative electrode active material artificial graphite, the conductive agent carbon black, and the binder styrene-butadiene rubber and CMC-Na in a mass ratio of 96:1.0:1.5:1.5.

[0033] 2. Assemble the electrochemical workstation with a buckle battery, connect the voltage line and current line of the working electrode together as the positive electrode, and connect the voltage line, current line and white reference line of the counter electrode together as the negative electrode; then connect them to the positive and negative electrodes of the buckle battery respectively.

[0034] 3. The test process is as follows: let it rest for 2 hours, then charge it to 1 V at a constant current. Then scan it at a rate of 0.5 mV / s over a range of 1-5 V. According to the current-voltage curve analysis, the voltage at which the slope begins to rise is the oxidation potential of the lithium dendrite-consuming material.

[0035] In some embodiments, the mass ratio of the lithium dendrite-consuming material to the negative electrode active material is 0.01:1 to 0.1:1. Alternatively, the mass ratio of the lithium dendrite-consuming material to the negative electrode active material is 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, etc. If the amount of the lithium dendrite-consuming material is too small, it will be difficult to effectively inhibit the formation of lithium dendrites. If the amount of the lithium dendrite-consuming material is too large, the proportion of the negative electrode active material may be reduced, which is not conducive to improving the energy density of the negative electrode material.

[0036] Optionally, the Dv50 of the lithium dendrite consuming material is 10 nm to 1000 nm. For example, the Dv50 of the lithium dendrite consuming material is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc. Further optionally, the Dv50 of the lithium dendrite consuming material is 50 nm to 500 nm.

[0037] It can be understood that, in the present application, the Dv50 refers to the particle size corresponding to the cumulative particle size distribution number of 50% in the volume cumulative distribution curve, and its physical meaning is that the particles with a particle size smaller (or larger) than it account for 50%. As an example, the Dv50 can be conveniently determined by referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, using a laser particle size analyzer, such as a Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.

[0038] As some optional examples of the lithium dendrite consuming material, the lithium dendrite consuming material includes at least one of phosphorus pentoxide, lithium polysulfide, iron oxide, iodine and its compounds, titanium disulfide, metallocene, phenothiazine, phenoxazine, thioxanthene, triphenylamine, triphenylphosphine, metalloporphyrin, piperidine oxide, and tetrathiafulvalene. Optionally, the lithium dendrite consuming material includes at least one of phosphorus pentoxide, lithium polysulfide, iron sesquioxide, iron tetraoxide, iodine, tin iodide, titanium disulfide, ferrocene, 10-methylphenothiazine, 5,10-dimethylphenoxazine, thioxanthene, tri[(diethylamino)phenyl]amine, bis(4-methoxyphenyl)phenylphosphine, tetraphenylporphyrin cobalt, 2,2,6,6-tetramethylpiperidine oxide (tempo), and tetrathiafulvalene. Optionally, the lithium polysulfide includes at least one of Li2S8, Li2S6, Li2S4.

[0039] As some optional examples of the negative electrode active material, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon-based material, tin-based material, and lithium titanate. Optionally, the negative electrode active material includes at least one of graphite, silicon powder, and silicon oxide. It can be understood that the graphite can be divided into artificial graphite and natural graphite according to the crystal formation mode.

[0040] Optionally, the Dv50 of the negative electrode active material is 3 μm to 25 μm. For example, the Dv50 of the negative electrode active material is 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, etc.

[0041] In some embodiments, the negative electrode material further comprises a polymer coating layer; the polymer coating layer coats at least a part of the surface of the lithium dendrite consumption material. The introduction of the polymer coating layer in the negative electrode material, on the one hand, can fix the position of the lithium dendrite consumption material in the negative electrode active material through the coating of the polymer coating layer, which is conducive to maintaining a relatively stable positional relationship between the lithium dendrite consumption material and the negative electrode active material, and thus is conducive to the stable effect of the lithium dendrite consumption material. On the other hand, the coating of the polymer coating layer can play a good protection effect on the lithium dendrite consumption material, avoiding unnecessary consumption of the lithium dendrite consumption material by entering the electrolyte and reacting with the electrolyte, and thus restricting the effect of the lithium dendrite consumption material. For example, when the electrolyte in the battery is electrolyte, the polymer coating layer can effectively prevent the lithium dendrite consumption material from entering the electrolyte, so that the lithium dendrite consumption material can maintain a relatively stable content in the negative electrode material, and thus maintain a good inhibition effect on lithium precipitation.

[0042] It can be understood that the polymer coating layer can allow lithium ions to pass through. Alternatively, when the electrolyte in the battery is electrolyte, the polymer coating layer can allow electrolyte to pass through.

[0043] In some embodiments, the polymer coating layer extends to the surface of the negative electrode active material. Alternatively, the polymer coating layer coats the lithium dendrite consumption material as a whole and extends to the surface of the negative electrode active material. Further alternatively, the polymer coating layer coats the lithium dendrite consumption material and the negative electrode active material as a whole. At this time, the negative electrode active material and the lithium dendrite consumption material can be maintained in a more stable structure.

[0044] It can be understood that the extension of the polymer coating layer to the surface of the negative electrode active material means that the polymer coating layer extends from the surface of the lithium dendrite consumption material to the surface of the negative electrode active material, which is conducive to further improving the combination effect between the lithium dendrite consumption material and the negative electrode active material.

[0045] Please refer to Figure 7, which shows the structure of the negative electrode material in one embodiment of the present application. In the negative electrode material, the negative electrode material includes a negative electrode active material 6, a lithium dendrite consumable material 7 and a polymer coating layer 8. The lithium dendrite consumable material 7 is located on the surface of the negative electrode active material 6, and the polymer coating layer 8 covers the lithium dendrite consumable material 7 and the negative electrode active material 6 as a whole. In the negative electrode material, the negative electrode active material 6 and the lithium dendrite consumable material 7 have a stable structure, and the lithium dendrite consumable material 7 can stably exist on the surface of the negative electrode active material 6. When the negative electrode material is used in a lithium-ion battery, the electrode liquid infiltrates the polymer coating layer and contacts the lithium dendrite consumable material 7. When no lithium dendrites appear, the lithium dendrite consumable material 7 remains unchanged. When lithium dendrites are generated, the lithium dendrite consumable material 7 can react with the lithium dendrites to convert the lithium dendrites into lithium ions. The lithium ions formed by the transformation of lithium dendrites can continue to circulate in the battery on the one hand, and on the other hand, can participate in the construction of the SEI film to further improve the performance of the battery. It can be understood that Figure 7 The main purpose is to show the structure of the negative electrode material, and it does not limit the content of the negative electrode active material, lithium dendrite consumption material, and the thickness of the polymer coating layer in the negative electrode material.

[0046] In some embodiments, the thickness of the polymer coating layer is 0.1 μm to 10 μm. Alternatively, the thickness of the polymer coating layer is 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Further optionally, the thickness of the polymer coating layer is 1 μm to 10 μm.

[0047] In some embodiments, the polymer coating has a swelling degree of ≥110%. Optionally, the polymer coating has a swelling degree of 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 250%, etc. Further optionally, the polymer coating has a swelling degree of 110% to 200%.

[0048] It can be understood that the swelling degree of the polymer coating layer refers to the ratio of the volume after swelling to the volume before swelling when the polymer of the polymer coating layer adsorbs solvent molecules in the solvent to reach swelling equilibrium.

[0049] Optionally, the method for testing the swelling degree of the polymer coating layer is as follows: the polymer of the polymer coating layer is scraped on a glass plate to form a film, a polymer film piece with a size of 1 cm x 1 cm is taken, the thickness of the polymer film piece is measured by using a vernier caliper or a screw micrometer, and the volume of the polymer film piece is calculated as V1. The polymer film piece is soaked in pure solvent dimethyl carbonate for 12 hours, and after being taken out, the length, width and height of the polymer film piece are measured, and the volume of the polymer film piece is calculated as V2. The swelling degree C = (V2 / V1) x 100%.

[0050] In some embodiments, the polymer of the polymer coating layer comprises at least one of polyacrylic acid, poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyacetylene, poly(p-phenylene), polypyrrole, polythiophene, polyaniline and polyphenylacetylene. Optionally, the polymer coating layer is formed by using the conductive polymer, which can further improve the electrical performance of the battery.

[0051] Optionally, the weight average molecular weight of the polymer of the polymer coating layer is 10,000-150,000.

[0052] The application also provides a preparation method of the negative electrode material. The preparation method of the negative electrode material comprises the following steps: mixing the negative electrode active material and the lithium dendrite consumption material. By mixing, the lithium dendrite consumption material can be adsorbed on at least part of the surface of the negative electrode active material to form the negative electrode material comprising the negative electrode active material and the lithium dendrite consumption material. It can be understood that the selection and amount of the negative electrode active material and the lithium dendrite consumption material can be selected correspondingly in the above content of the negative electrode material, which will not be described here.

[0053] In some embodiments, after the negative electrode active material and the lithium dendrite consumption material are mixed, the method further comprises: forming a polymer coating layer on at least part of the surface of the lithium dendrite consumption material.

[0054] Optionally, forming the polymer coating layer on at least part of the surface of the lithium dendrite consumption material comprises: mixing the mixture obtained by mixing the negative electrode active material and the lithium dendrite consumption material with a polymer slurry to obtain a mixed solution; and removing the solvent in the mixed solution. Further optionally, the solvent in the polymer slurry is removed by drying.

[0055] It can be understood that the polymer slurry comprises a polymer and a solvent, and the polymer can be selected in the above content of the negative electrode material, which will not be described here.

[0056] In some embodiments, the mass ratio of polymer to solvent in the polymer slurry is 1:10 to 1:100. Alternatively, the mass ratio of polymer to solvent is 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc. Further optionally, the solvent in the polymer slurry includes at least one of acetonitrile, acetone, ethylene glycol, and N-methylpyrrolidone.

[0057] Another embodiment of the present application provides a negative electrode slurry, which includes the negative electrode material or the negative electrode material prepared by the method for preparing the negative electrode material, and a solvent.

[0058] Another embodiment of the present application provides a method for preparing a negative electrode slurry, which comprises mixing the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned method for preparing the negative electrode material with a solvent.

[0059] Optionally, the negative electrode slurry further includes at least one of a binder, a conductive agent and a thickener.

[0060] Another embodiment of the present application provides a negative electrode plate, which includes a current collector and a negative electrode film layer located on at least one surface of the current collector, wherein the negative electrode film layer includes the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned method for preparing the negative electrode material.

[0061] Another embodiment of the present application provides a method for preparing a negative electrode sheet. The method comprises the following steps: transferring a slurry containing the aforementioned negative electrode material or a negative electrode material prepared using the aforementioned method to at least one surface of a current collector and curing the slurry to form a negative electrode film layer on the corresponding surface of the current collector. Optionally, the transfer is performed by coating.

[0062] Another embodiment of the present application provides a method for preparing a negative electrode sheet. The method comprises the following steps: transferring the negative electrode slurry to at least one surface of a current collector and curing the slurry to form a negative electrode film layer on the corresponding surface of the current collector. Optionally, the transfer is performed by coating.

[0063] The application further provides a preparation method of the negative electrode sheet. The preparation method of the negative electrode sheet comprises the following steps: transferring a slurry comprising a negative electrode active material and a lithium dendrite consuming material to at least one surface of a current collector and solidifying to form an intermediate layer on the corresponding surface of the current collector, and transferring a polymer slurry to the surface of the intermediate layer and solidifying to form a negative electrode film layer on the corresponding surface of the current collector. Optionally, the transferring is coating. In the preparation method, when the slurry comprising the negative electrode active material and the lithium dendrite consuming material is transferred to at least one surface of the current collector and solidified, the interaction between the negative electrode active material and the lithium dendrite consuming material forms a structure in which the lithium dendrite consuming material is located on the surface of the negative electrode active material. After the polymer slurry is transferred to the surface of the intermediate layer, the polymer penetrates into the pores of the intermediate layer to form a polymer coating layer. After the obtained negative electrode sheet is applied in a battery, the occurrence of lithium precipitation can be effectively avoided. It can be understood that the negative electrode active material, the lithium dendrite consuming material and the polymer can be selected correspondingly in the content of the negative electrode material described above, which will not be repeated here.

[0064] The application further provides a secondary battery. The secondary battery comprises the negative electrode sheet or the negative electrode sheet prepared by the preparation method of the negative electrode sheet.

[0065] Optionally, the secondary battery further comprises an electrolyte, and the concentration of the lithium dendrite consuming material in the electrolyte is ≤100 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤90 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤80 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤60 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤40 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤20 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is ≤10 mmol / L. Optionally, the concentration of the lithium dendrite consuming material in the electrolyte is 0.

[0066] The application further provides a secondary battery. The secondary battery comprises the negative electrode sheet or the negative electrode sheet prepared by the preparation method of the negative electrode sheet.

[0067] The application further provides a battery module. The battery module comprises the secondary battery.

[0068] The application further provides a battery pack. The battery pack comprises the secondary battery or the battery module.

[0069] The application further provides an electric device. The electric device comprises at least one of the secondary battery, the battery module and the battery pack.

[0070] Hereinafter, the secondary battery will be described with reference to the relevant drawings.

[0071] 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.

[0072] [Positive electrode]

[0073] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0074] 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.

[0075] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate. Optionally, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Optionally, the polymer substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0076] In some embodiments, when the secondary battery is a lithium ion battery, the positive electrode active material can employ a positive electrode active material for a lithium ion battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and a modified compound thereof, etc. Optionally, the lithium cobalt oxide includes LiCoO2. The lithium nickel oxide includes LiNiO2. The lithium manganese oxide includes at least one of LiMnO2and LiMn2O4. The lithium nickel cobalt manganese oxide includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 ), and LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ). The lithium nickel cobalt aluminum oxide includes LiNi 0.85 Co 0.15 Al 0.05 O2. Examples of the lithium-containing phosphate of an olivine structure can include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. Optionally, the lithium iron phosphate includes LiFePO4(LFP). The lithium manganese phosphate includes LiMnPO4.

[0077] In some embodiments, when the secondary battery is a sodium ion battery, the positive electrode active material may adopt the positive electrode active material for sodium ion batteries known in the art. As an example, the positive electrode active material may be used alone or in combination of two or more. Among them, the positive electrode active material may be selected from sodium iron composite oxide, sodium cobalt composite oxide, sodium chromium composite oxide, sodium manganese composite oxide, sodium nickel composite oxide, sodium nickel titanium composite oxide, sodium nickel manganese composite oxide, sodium iron manganese composite oxide, sodium nickel cobalt manganese composite oxide, sodium iron phosphate compound, sodium manganese phosphate compound, sodium cobalt phosphate compound, Prussian blue material, polyanion material, etc., but the present application is not limited to these materials, and the present application may also use other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries. Optionally, sodium iron composite oxide includes NaFeO2. Sodium cobalt composite oxide includes NaCoO2. Sodium chromium composite oxide includes NaCrO2. Sodium manganese composite oxide includes NaMnO2. Sodium nickel composite oxide includes NaNiO2. Sodium nickel titanium composite oxide includes NaNi 1 / 2 Ti 1 / 2 O2. Sodium nickel manganese composite oxide includes NaNi 1 / 2 Mn 1 / 2 O2. Sodium iron manganese composite oxide includes Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. Sodium nickel cobalt manganese composite oxides include NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. Sodium iron phosphate includes NaFePO4. Sodium manganese phosphate includes NaMnPO4. Sodium cobalt phosphate includes NaCoPO4. The polyanion material includes at least one of phosphate, fluorophosphate, pyrophosphate and sulfate.

[0078] In some embodiments, the positive electrode film layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0079] In some embodiments, the positive electrode film layer may further 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.

[0080] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and subjecting the positive electrode current collector to drying, cold pressing, and the like to obtain the positive electrode sheet. Optionally, the solvent includes N-methylpyrrolidone.

[0081] [the negative electrode sheet]

[0082] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0083] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two surfaces of the negative electrode current collector.

[0084] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material on a polymer material base layer. Optionally, the metal material includes at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0085] In some embodiments, the negative electrode active material can employ a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0086] In some embodiments, the negative film layer further optionally comprises a binder. The binder can 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), carboxymethyl chitosan (CMCS), polyamide-imide (PAI), polyethylenimine (PEI), polyimide (PI), and t-butyl acrylate- triethoxy vinyl silane (TBATEVS).

[0087] In some embodiments, the negative film layer further optionally comprises a conductive agent. The conductive agent can be selected from at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative film layer further optionally comprises other auxiliary agents, such as a thickening agent. Optionally, the thickening agent comprises sodium carboxymethyl cellulose (CMC-Na).

[0089] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after processes such as drying, cold pressing, etc., a negative electrode sheet is obtained. Optionally, the solvent comprises deionized water.

[0090] [Electrolyte]

[0091] The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0092] In some embodiments, the electrolyte adopts an electrolyte solution. Further, the electrolyte solution comprises an electrolyte salt and a solvent.

[0093] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0094] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0095] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0096] [Separator]

[0097] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0098] 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, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0099] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0100] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-described electrode assembly and the electrolyte solution.

[0101] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0102] The shape of the secondary battery is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 1 is a square structure secondary battery 5 as an example.

[0103] In some embodiments, with reference to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0104] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0105] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of secondary batteries 5 may further be fixed by fasteners.

[0106] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0107] 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.

[0108] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0109] In addition, the application also provides a power utilization device, which comprises at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. For example, the mobile device includes a mobile phone, a notebook computer, etc. The electric vehicle includes a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.

[0110] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0111] Figure 6 The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of the power utilization device for high power and high energy density of the secondary battery, the battery pack or the battery module can be used.

[0112] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the secondary battery can be used as a power supply.

[0113] Embodiment

[0114] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0115] In Table 1, tempo represents 2,2,6,6-tetramethylpiperidine oxide. X represents the mass ratio of lithium dendrite consumption material to active material. PVDF-HFP represents poly(vinylidene fluoride-co-hexafluoropropylene).

[0116] Embodiments 1-4

[0117] Preparation of the negative electrode sheet.

[0118] (1) The negative electrode active material and the lithium dendrite consumption material are stirred and mixed to obtain a mixture.

[0119] (2) The mixture, the conductive agent, the binder, and the deionized water are mixed to obtain a negative electrode slurry, wherein the conductive agent is superp, and the binder is a mixture of CMC and SBR in a mass ratio of 1:1.

[0120] (3) The negative electrode slurry is coated and dried on the negative electrode current collector to obtain a negative electrode sheet.

[0121] The selection of the negative electrode active material and the lithium dendrite consumption material and the Dv50 in Examples 1-4 are shown in Table 1.

[0122] Example 5

[0123] Preparation of the negative electrode sheet.

[0124] (1) The negative electrode active material and the lithium dendrite consumption material are stirred and mixed to obtain a mixture.

[0125] (2) The mixture, the conductive agent, the binder, and deionized water are mixed to obtain a negative electrode slurry, wherein the conductive agent is super P, and the binder is a mixture of CMC and SBR in a mass ratio of 1:1.

[0126] (3) The negative electrode slurry is coated and dried on the negative electrode current collector to form an intermediate layer on the surface of the negative electrode current collector.

[0127] (4) The polymer and the acetone solvent are mixed in a mass ratio of 1:10 to obtain a polymer slurry. The polymer slurry is blade-coated onto the surface of the intermediate layer, and the solvent in the slurry is dried and removed to obtain a negative electrode sheet.

[0128] The selection of the negative electrode active material and the lithium dendrite consumption material and the Dv50 in the present example and the polymer are shown in Table 1.

[0129] Example 6

[0130] Preparation of the negative electrode sheet.

[0131] (1) The negative electrode active material and the lithium dendrite consumption material are stirred and mixed to obtain a mixture.

[0132] (2) The mixture, the conductive agent, the binder, and deionized water are mixed to obtain a negative electrode slurry, wherein the conductive agent is super P, and the binder is a mixture of CMC and SBR in a mass ratio of 1:1.

[0133] (3) The negative electrode slurry is coated and dried on the negative electrode current collector to form an intermediate layer on the surface of the negative electrode current collector.

[0134] (4) The polymer and the N-methyl pyrrolidone solvent are mixed in a mass ratio of 1:10 to obtain a polymer slurry. The polymer slurry is blade-coated onto the surface of the intermediate layer, and the solvent in the slurry is dried and removed to obtain a negative electrode sheet.

[0135] The selection of the negative electrode active material and the lithium dendrite consumption material and the Dv50 in the present example and the polymer are shown in Table 1.

[0136] Example 7

[0137] Preparation of the negative electrode sheet.

[0138] (1) The negative electrode active material and the lithium dendrite consumption material were stirred and mixed to obtain a mixture.

[0139] (2) The mixture, the conductive agent, the binder, and deionized water were mixed to obtain a negative electrode slurry, wherein the conductive agent was super P, and the binder was a mixture of CMC and SBR in a mass ratio of 1:1.

[0140] (3) The negative electrode slurry was coated and dried on the negative electrode current collector to form an intermediate layer on the surface of the negative electrode current collector.

[0141] (4) The polymer and the acetone solvent were mixed in a mass ratio of 1:50 to obtain a polymer slurry. The polymer slurry was blade-coated onto the surface of the intermediate layer, and the solvent in the slurry was dried to remove to obtain a negative electrode sheet.

[0142] In this embodiment, the negative electrode active material, the lithium dendrite consumption material, the selection of the materials, Dv50, and the polymer are as shown in Table 1.

[0143] Example 8

[0144] Preparation of the negative electrode sheet.

[0145] (1) The negative electrode active material and the lithium dendrite consumption material were stirred and mixed to obtain a mixture.

[0146] (2) The mixture, the conductive agent, the binder, and deionized water were mixed to obtain a negative electrode slurry, wherein the conductive agent was super P, and the binder was a mixture of CMC and SBR in a mass ratio of 1:1.

[0147] (3) The negative electrode slurry was coated and dried on the negative electrode current collector to form an intermediate layer on the surface of the negative electrode current collector.

[0148] (4) The polymer and the acetone solvent were mixed in a mass ratio of 1:100 to obtain a polymer slurry. The polymer slurry was blade-coated onto the surface of the intermediate layer, and the solvent in the slurry was dried to remove to obtain a negative electrode sheet.

[0149] In this embodiment, the negative electrode active material, the lithium dendrite consumption material, the selection of the materials, Dv50, and the polymer are as shown in Table 1. In this embodiment, the mass ratio of silicon oxide and graphite in the negative electrode active material was 1:1.

[0150] Examples 9-30

[0151] Compared with Example 5, the differences between Examples 9 to 30 are that the selection of lithium dendrite consumable materials and / or Dv50 and / or the mass ratio of lithium dendrite consumable materials to negative electrode active materials and / or the polymer coating layer are different, as shown in Table 1.

[0152] Example 31

[0153] Preparation of negative electrode sheet.

[0154] (1) The negative electrode active material and the lithium dendrite consumption material are stirred and mixed to obtain a mixture.

[0155] (2) The polymer and acetone solvent are mixed in a mass ratio of 1:10 to obtain a polymer slurry. The polymer slurry is mixed with the mixture obtained in (1), and the solvent in the slurry is removed by drying to obtain a negative electrode material.

[0156] (3) The negative electrode material, conductive agent, binder and deionized water obtained in (2) are mixed to obtain a negative electrode slurry, wherein the conductive agent is super p and the binder is CMC and SBR mixed in a mass ratio of 1:1.

[0157] (4) The negative electrode slurry is coated on the negative electrode current collector and dried to obtain a negative electrode sheet.

[0158] Among them, the characteristics of the negative electrode active material, lithium dendrite consumption material, Dv50 and polymer in this embodiment are shown in Table 1.

[0159] Comparative Example 1~Comparative Example 2

[0160] Preparation of negative electrode sheet.

[0161] (1) The negative electrode active material, the conductive agent, the binder and the deionized water are mixed to obtain the negative electrode slurry, wherein the conductive agent is super p, and the binder is CMC and SBR mixed in a mass ratio of 1:1.

[0162] (2) The negative electrode slurry is coated on the negative electrode current collector and dried to form an intermediate layer on the surface of the negative electrode current collector.

[0163] (4) The polymer and acetone solvent are mixed in a mass ratio of 1:10 to obtain a polymer slurry. The polymer slurry is scraped onto the surface of the intermediate layer and dried to remove the solvent in the slurry to obtain a negative electrode sheet.

[0164] The characteristics of the negative electrode active materials and polymers in Comparative Examples 1 and 2 are shown in Table 1.

[0165] Comparative Example 3

[0166] Preparation of negative electrode sheet.

[0167] (1) The negative active material, conductive agent, binder and deionized water are mixed to obtain a negative slurry, wherein the conductive agent is super p, and the binder is a mixture of CMC and SBR in a mass ratio of 1:1.

[0168] (2) The negative slurry is coated on the negative current collector and dried to obtain a negative electrode sheet.

[0169] In the present example, the negative active material is as shown in Table 1.

[0170] Preparation of the positive electrode sheet.

[0171] The positive active material, PVDF and conductive carbon are mixed in a mass ratio of 8:1:1, and N-methyl pyrrolidone is added for stirring to obtain a positive slurry. The positive slurry is coated on the surface of the positive current collector and dried to obtain a positive electrode sheet. The positive active material in each example and comparative example is as shown in Table 1.

[0172] Electrolyte.

[0173] The fluorinated ethylene carbonate (FEC) with a mass percentage of 2%, 1 mol / L lithium hexafluorophosphate (LiPF6), and the solvent ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed uniformly in a volume ratio of 3:7.

[0174] Separator film.

[0175] A polyethylene separator film is used.

[0176] Secondary battery.

[0177] The positive electrode sheet, the separator film and the negative electrode sheet are sequentially stacked in the order of the positive electrode sheet, the separator film and the negative electrode sheet to form a cell, and the cell is placed in an outer package, injected with an electrolyte and packaged to obtain a secondary battery.

[0178] Formation treatment: the secondary battery is charged to 30% SOC at 0.04C.

[0179] Test example

[0180] The secondary battery is subjected to a cycle test: charged at 0.33C to 4.0V and discharged at 0.33C to 2.0V. When the capacity retention rate is 80%, the cycle number is recorded. The test results are shown in Table 1.

[0181] Test method of lithium precipitation degree: after the battery is charged to 4.0V, it is disassembled, and the negative electrode sheet is taken out for cutting. A 50mm*50mm electrode sheet is pasted on a conductive adhesive, and an electron microscope is used for analysis. The number of dendritic metal lithium in the selected area is observed to determine the degree of lithium precipitation. In Table 1, the degrees of lithium precipitation "low", "relatively low" and "high" represent gradually increasing degrees of lithium precipitation.

[0182] Table 1

[0183]

[0184] As can be seen from Table 1, when a lithium dendrite-consuming material is introduced into the negative electrode material, the cycle performance of the battery can be improved. When a lithium dendrite-consuming material and a polymer coating layer are introduced into the negative electrode material, the cycle performance of the battery can be further improved.

[0185] 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, characterized in that: It includes a negative electrode plate, which includes a current collector and a negative electrode film layer located on at least one surface of the current collector, the negative electrode film layer includes a negative electrode material, the negative electrode material includes a negative electrode active material and a lithium dendrite consumable material, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon-based material, tin-based material and lithium titanate, the lithium dendrite consumable material is located on at least a portion of the surface of the negative electrode active material, and the oxidation potential of the lithium dendrite consumable material is ≥1V.

2. The secondary battery according to claim 1, wherein The lithium dendrite consumption material satisfies at least one of the following characteristics: (1) The oxidation potential of the lithium dendrite consumable material is 1V~3V; (2) The mass ratio of the lithium dendrite consumable material to the negative electrode active material is 0.01:1 to 0.1:1; (3) The Dv50 of the lithium dendrite consumable material is 10nm~1000nm; Optionally, the Dv50 of the lithium dendrite consumable material is 50nm~500nm.

3. The secondary battery according to any one of claims 1 to 2, characterized in that The lithium dendrite consumption material includes at least one of phosphorus pentoxide, lithium polysulfide, iron oxide, iodine and its compounds, titanium disulfide, metallocene, phenothiazine, phenazine, thianthrene, triphenylamine, triphenylphosphine, metalloporphyrin, piperidine oxide and tetrathiafulvalene.

4. The secondary battery according to any one of claims 1 to 3, characterized in that The lithium dendrite-consuming material includes at least one of tin iodide, ferrocene, 10-methylphenothiazine, 5,10-dimethyldihydrophenazine, tris[(diethylamino)phenyl]amine, bis(4-methoxyphenyl)phenylphosphine, tetraphenylcobalt porphyrin and 2,2,6,6-tetramethylpiperidinium oxide.

5. The secondary battery according to any one of claims 1 to 4, characterized in that The negative electrode active material satisfies at least one of the following characteristics: (1) The silicon-based material includes at least one of silicon powder and silicon oxide; (2) The Dv50 of the negative electrode active material is 3 μm to 25 μm.

6. The secondary battery according to any one of claims 1 to 5, characterized in that The negative electrode material further includes a polymer coating layer; the polymer coating layer is coated on at least a portion of the surface of the lithium dendrite consumable material.

7. The secondary battery according to claim 6, characterized in that The polymer coating layer extends to the surface of the negative electrode active material; Optionally, the polymer coating layer integrally coats the lithium dendrite-consuming material and the negative electrode active material.

8. The secondary battery according to any one of claims 6 to 7, characterized in that The polymer coating layer satisfies at least one of the following characteristics: (1) The thickness of the polymer coating layer is 0.1 μm to 10 μm; Optionally, the thickness of the polymer coating layer is 1 μm to 10 μm; (2) The swelling degree of the polymer coating layer is ≥110%; Optionally, the swelling degree of the polymer coating layer is 110% to 200%; (3) The polymer of the polymer coating layer includes at least one of polyacrylic acid, poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyacetylene, polyparaphenylene, polypyrrole, polythiophene, polyaniline and polyphenylene vinylene; (4) The weight average molecular weight of the polymer in the polymer coating layer is 10,000 to 150,000.

9. The secondary battery according to any one of claims 1 to 8, characterized in that It also includes an electrolyte; optionally, the concentration of the lithium dendrite consumable material in the electrolyte is ≤100 mmol / L.

10. An electrical device, characterized in that: A secondary battery according to any one of claims 1 to 9.

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