Secondary battery and electronic device

Abstract

The present invention belongs to the technical field of batteries, and provides a secondary battery and an electronic device. The secondary battery comprises a negative electrode sheet and an electrolyte, wherein the negative electrode sheet comprises a negative electrode active material layer, the negative electrode active material layer comprises silicon-containing active particles, and the spherization degree of the silicon-containing active particles is A; and the electrolyte contains fluoroethylene carbonate, and based on the mass of the electrolyte, the mass percentage content of fluoroethylene carbonate is B%, with A and B satisfying: 1.6≤(B / A)≤29.4. In this way, the synergistic effect between the spheroidization degree of the silicon material particles and the content of fluoroethylene carbonate can be fully exerted, and the crushing of the silicon particles and side reactions with the electrolyte are reduced, thereby improving the initial coulombic efficiency and cycle performance of the secondary battery and enhancing the over-discharge gas production resistance.

Description

Secondary battery and electronic device Technical Field

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery and an electronic device. Background Art

[0002] Silicon, a resource-rich material with a high theoretical specific capacity, holds enormous potential for use in secondary battery anodes. However, silicon-containing anodes experience volume expansion and contraction during the insertion and precipitation of active materials, which can lead to stress concentration in the electrode material and fracture of silicon nanoparticles. These fractured silicon nanoparticles react with the electrolyte to form a solid electrolyte membrane, resulting in capacity loss and a rapid decrease in cycle performance.

[0003] Prior art proposes adding additives to the electrolyte to improve the performance of the solid electrolyte membrane and reduce side reactions between the electrolyte and silicon nanoparticles. However, the use of additives can lead to reduced active ion concentration in the electrolyte, increased electrolyte viscosity, and increased secondary battery impedance, which can still affect the initial efficiency and cycle performance of the secondary battery to a certain extent.

[0004] Summary of the Invention

[0005] In view of this, the present application provides a secondary battery that aims to address the problem of fragile silicon particles and the side reactions that occur in the prior art, thereby improving the coulombic efficiency, capacity retention, and over-discharge tolerance of the secondary battery. Furthermore, the present application provides an electronic device including the aforementioned secondary battery.

[0006] In a first aspect, the present application provides a secondary battery comprising a negative electrode plate and an electrolyte, the negative electrode plate comprising a negative electrode active material layer, the negative electrode active material layer comprising silicon-containing active particles; the silicon-containing active particles having a sphericity A; the electrolyte containing fluoroethylene carbonate (FEC); the mass percentage of fluoroethylene carbonate based on the mass of the electrolyte being B%, wherein A and B satisfy the following: 1.6≤(B / A)≤29.4. The present application adds fluoroethylene carbonate to the electrolyte, closely matching the sphericity of the silicon-containing active particles with the mass percentage of fluoroethylene carbonate in the electrolyte. This allows a solid electrolyte (SEI) film formed by decomposition of the fluoroethylene carbonate to effectively cover the fresh silicon-containing interface exposed after the silicon-containing active particles are broken, thereby reducing side reactions between the exposed active silicon and the electrolyte. The secondary battery has a lower internal resistance, thereby improving the coulombic efficiency and cycle capacity retention of the secondary battery, and providing the secondary battery with better over-discharge resistance.

[0007] In some embodiments, 0.65 ≤ A ≤ 1. When the sphericity of the silicon-containing active particles is within this range, the surface has fewer sharp corners. Combined with the aforementioned relationship between the sphericity and the fluoroethylene carbonate content, this can further reduce side reactions between the active silicon and the electrolyte, further improving the coulombic efficiency of the secondary battery and enhancing its over-discharge tolerance. In some embodiments, 0.71 ≤ A ≤ 1.

[0008] In some embodiments, 1.1≤B≤20. When the mass percentage of fluoroethylene carbonate is within this range, the SEI film that increases the internal resistance of the secondary battery can be reduced or avoided, further improving the initial coulombic efficiency of the secondary battery and enhancing its over-discharge resistance.

[0009] In some embodiments, 2≤B≤7. This can maximize the quality of the SEI film and further enhance the over-discharge resistance of the secondary battery.

[0010] In some embodiments, the minimum angle of the cross-sectional profile of the silicon-containing active particles with a diameter greater than 10 μm is C°, and 96 ≤ C ≤ 180. When the minimum angle of the cross-sectional profile of the silicon-containing active particles with a diameter greater than 10 μm meets the above range, it indicates that the silicon-containing active particles have gentle edges and corners, which can reduce the breakage of the silicon-containing active particles, further improve the coulombic efficiency of the secondary battery, and enhance its cycle performance and over-discharge tolerance.

[0011] In some embodiments, the sphericity A of the silicon-containing active particles, the minimum cross-sectional profile angle C° of the silicon-containing active particles with a diameter greater than 10 μm, and the mass percentage of the fluoroethylene carbonate additive B% satisfy the following: 45.28 ≤ (A × CB) ≤ 176.0. By controlling the sphericity, the shape characteristics of the minimum cross-sectional profile angle of the silicon-containing active particles, and the mass percentage of the fluoroethylene carbonate to satisfy the above relationship, the SEI film formed by the fluoroethylene carbonate can be further ensured to cover the broken surfaces of the silicon-containing active particles, thereby optimizing the cycle performance and over-discharge tolerance of the secondary battery, and improving its initial coulombic efficiency and cycle capacity retention.

[0012] In some embodiments, A, B, and C satisfy: 60≤(A×CB)≤120, further improving and optimizing the cycle performance and over-discharge resistance of the secondary battery.

[0013] In some embodiments, the silicon-containing active particles include a porous carbon matrix and nano-silicon; the nano-silicon is distributed inside and on the surface of the porous carbon matrix.

[0014] In some embodiments, the mass fraction of Si element is 42% to 55% based on the mass of the silicon-containing active particles.

[0015] In some embodiments, the mass fraction of Si element is 2.1% to 22% based on the mass of the negative electrode active material layer. In some embodiments, the mass fraction of silicon-containing active particles is 5% to 40% based on the mass of the negative electrode active material layer.

[0016] In some embodiments, the specific surface area of ​​the silicon-containing active particles is 0.5 m 2 / g~5m 2 When the specific surface area of ​​the silicon-containing active particles is within the above range, the initial coulombic efficiency of the secondary battery can be further improved.

[0017] In some embodiments, the conductivity of the electrolyte is 6.5 mS / cm to 11 mS / cm. By controlling the conductivity within the above range, the transport of active ions can be promoted, so that the secondary battery has improved cycle performance and over-discharge resistance.

[0018] In some embodiments, the hydrofluoric acid content in the electrolyte is ≤83 μg / g, which can further improve the kinetic performance of the secondary battery.

[0019] In a second aspect, the present application further provides an electronic device comprising any one of the above-mentioned secondary batteries.

[0020] The secondary battery based on the present application has the following beneficial effects: the present application produces a synergistic effect by controlling the sphericity of the silicon-containing active particles and the content of fluoroethylene carbonate in the electrolyte. The fluoroethylene carbonate can form a low-impedance SEI film, which can effectively cover the active surface generated by the crushing of the silicon-containing active particles, thereby reducing or avoiding side reactions between the silicon-containing active particles and the electrolyte, reducing the consumption of electrolyte and silicon-containing active particles caused by side reactions, improving the initial efficiency and cycle performance of the secondary battery, and at the same time reducing the gas generated by the side reactions, thereby improving the over-discharge resistance of the secondary battery. Furthermore, the present application defines the synergistic cooperation between the sphericity of the silicon-containing active particles, the minimum angle of the particle cross-section profile, and the fluoroethylene carbonate in the electrolyte, which can further optimize the initial efficiency and cycle performance of the secondary battery, and the secondary battery produces less gas during over-discharge and has a strong over-discharge resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a backscattered SEM image of a cross section of a negative electrode sheet in a secondary battery according to Example 1 of the present application along the thickness direction;

[0022] FIG2 is a schematic diagram of determining the minimum angle of the cross-section profile of silicon-containing active particles with a diameter greater than 10 μm, provided in a specific embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0024] For the sake of clarity, this application only specifically discloses certain numerical ranges. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0025] In the description of the present application, unless otherwise specified, “above” and “below” include the number.

[0026] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0027] In the present application, the term "silicon-containing active particles" refers to a negative electrode material containing silicon elements in a solid particle state, for example, it can be a silicon-carbon composite material in a solid particle state. In some exemplary embodiments, the silicon-containing active particles include porous carbon particles having pores, and silicon formed inside the porous carbon particles and / or on the surface of the porous carbon particles. In the embodiments of the present application, the silicon-containing active particles can better cooperate with the fluoroethylene carbonate in the electrolyte through shape characteristics such as sphericity, thereby helping the secondary battery to achieve higher initial efficiency, cycle performance and improved over-discharge resistance.

[0028] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0029] In order to solve the problem of side reactions between silicon nanoparticles and electrolyte, the present applicant found that when adding FEC to the electrolyte to protect the fresh silicon interface produced by crushing, excessive FEC additives will lead to problems such as reduced active ion concentration in the electrolyte, increased electrolyte viscosity and increased electrode impedance, thereby affecting the coulombic efficiency and capacity retention rate of the secondary battery.

[0030] In view of this, the present application provides a secondary battery comprising a negative electrode plate and an electrolyte, wherein the negative electrode plate comprises a negative electrode active material layer, and the negative electrode active material layer comprises silicon-containing active particles; the sphericity of the silicon-containing active particles is A, and the electrolyte comprises fluoroethylene carbonate; based on the mass of the electrolyte, the mass percentage of fluoroethylene carbonate is B%; wherein A and B satisfy: 1.6≤(B / A)≤29.4. The present application limits the sphericity of the negative electrode silicon material particles and the fluoroethylene carbonate content in the electrolyte to meet the above-mentioned relationship, thereby giving full play to the synergistic effect between the sphericity of the material particles and the fluoroethylene carbonate content, reducing or avoiding the problem of the secondary battery being crushed due to the sharp corners of the silicon material particles during the negative electrode rolling process or the charging and discharging process, and enabling the fluoroethylene carbonate to form an SEI film to effectively cover the fresh silicon-containing interface exposed after the silicon-containing active particles are crushed, reducing the side reaction between the exposed active silicon and the electrolyte, and at the same time ensuring that the SEI film on the surface of the silicon-containing active particles has a low impedance, the secondary battery has a low internal resistance, and the capacity utilization and coulombic efficiency of the secondary battery are improved, as well as the over-discharge resistance of the secondary battery.

[0031] In some embodiments, the ratio B / A of the mass percentage B% of the fluoroethylene carbonate additive to the sphericity A of the silicon-containing active particles can be 1.6, 2.9, 4, 4.4, 4.9, 5.1, 5.9, 6.2, 7.3, 8.8, 9.8, 10.1, 10.3, 16.2, 18.3, 22.0, 23.5, 24.4, 29.4, or a value within a range consisting of any two of these values. When B / A < 1.6, the SEI film formed by the fluoroethylene carbonate will not be able to effectively cover the fresh silicon-containing interface generated by particle crushing, and ultimately the exposed active silicon will continue to consume electrolyte, resulting in a decrease in the coulombic efficiency of the secondary battery. When B / A > 29.4, the excessive content of the fluoroethylene carbonate additive will increase the impedance of the formed SEI film, thereby increasing the internal resistance of the secondary battery and reducing the initial coulombic efficiency performance of the secondary battery.

[0032] In some embodiments, when the B / A value satisfies 6.2≤(B / A)≤16.2, the combination of fluoroethylene carbonate and the spherical degree of silicon-containing active particles can enable the secondary battery to exhibit higher first coulombic efficiency and capacity retention rate, as well as better over-discharge resistance.

[0033] In some embodiments, the conductivity of the electrolyte is 6.5 mS / cm to 11 mS / cm. By controlling the conductivity within the above range, the transport of active ions can be promoted, so that the secondary battery has improved cycle performance and over-discharge resistance.

[0034] In some embodiments, the hydrofluoric acid content in the electrolyte is ≤83 μg / g, which can further improve the kinetic performance of the secondary battery.

[0035] In some embodiments, 0.65≤A≤1. For example, the sphericity A of the silicon-containing active particles can be 0.65, 0.68, 0.71, 0.79, 0.82, 0.91, 1, or a value within a range consisting of any two of these values. The silicon-containing active particles with a sphericity within this range have fewer sharp corners on the surface, which can reduce or avoid the silicon-containing active particles from being crushed during the cold pressing process of the electrode, reduce the exposure of active silicon, and, combined with the above-mentioned relationship between the sphericity and the content of fluoroethylene carbonate, can further reduce the side reaction between active silicon and the electrolyte, further improve the coulombic efficiency of the secondary battery and enhance its over-discharge resistance. In some embodiments, 0.71≤A≤1 can further improve the coulombic efficiency of the secondary battery and enhance its over-discharge resistance.

[0036] In some embodiments, 1.1≤B≤20. For example, B can be 1.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a value within a range consisting of any two of these values. Based on the relationship between the degree of sphericity of the silicon-containing active particles and the content of fluoroethylene carbonate, further regulating the mass percentage of fluoroethylene carbonate can reduce or avoid the SEI film produced from increasing the internal resistance of the secondary battery, further improving the initial coulombic efficiency of the secondary battery. In some embodiments, 2≤B≤7, by further controlling the mass percentage of fluoroethylene carbonate, the quality of the SEI film can be maximized, while protecting the silicon-containing active particles, improving the dynamic performance of the secondary battery and enhancing its over-discharge resistance.

[0037] In some embodiments, the minimum angle of the cross-sectional profile of the silicon-containing active particles with a diameter greater than 10 μm is C°, 96≤C≤180. For example, C can be a value within the range of 96, 100, 110, 120, 129, 135, 140, 150, 160, 170, 180, or any two of these values. When the minimum angle of the cross-sectional profile of the silicon-containing active particles with a diameter greater than 10 μm meets the above range, it indicates that the edges and corners of the silicon-containing active particles are gentle, which is beneficial for uniform force on the silicon-containing active particles in the negative electrode active material layer, reduces the breakage of the silicon-containing active particles, improves the active ion transport, further improves the coulombic efficiency of the secondary battery, and enhances its cycle performance and over-discharge resistance. In the present application, the diameter of the silicon-containing active particle is the longest distance between any two points on the cross-sectional profile of the silicon-containing active particle.

[0038] In some embodiments, the sphericity A of the silicon-containing active particles, the minimum cross-sectional profile angle C° of the silicon-containing active particles with a diameter greater than 10 μm, and the mass percentage B% of the fluoroethylene carbonate additive satisfy the following conditions: 45.3 ≤ (A×CB) ≤ 176.0. For example, A×CB may be 45.28, 45.3, 67.72, 63.4, 69.8, 70.59, 71.72, 76.72, 79.85, 80.72, 83.72, 85.72, 86.62, 86.72, 89.8, 90.8, 97.8, 97.91, 98.8, 101.78, 113.39, 151.5, 176.0, or a range consisting of any two of these values. By controlling the aforementioned relationship between the sphericity of the silicon-containing active particles, the shape characteristics of the minimum angle of the cross-section profile, and the mass percentage of fluoroethylene carbonate, the SEI film formed by fluoroethylene carbonate can be further ensured to cover the broken surfaces of the silicon-containing active particles, thereby reducing the internal impedance of the secondary battery, optimizing the secondary battery's cycling performance and over-discharge tolerance, and improving its initial coulombic efficiency and cycle capacity retention. In some embodiments, A, B, and C satisfy the following: 60 ≤ (A × CB) ≤ 120, further improving the cycling performance and over-discharge tolerance of the secondary battery.

[0039] In some embodiments, the specific surface area of ​​the silicon-containing active particles is 0.5 m 2 / g~5m 2 In some embodiments, the specific surface area of ​​the silicon-containing active particles is 0.5 m 2 / g~2.8m 2 When the specific surface area of ​​the silicon-containing active particles is within the above range, the active ion transmission and diffusion rate can be guaranteed, while the side reaction with the electrolyte is reduced, further improving the initial coulombic efficiency of the secondary battery.

[0040] In some embodiments, the gram capacity of the silicon-containing active particles is 1621 mAh / g to 1796 mAh / g, and the first coulombic efficiency of the silicon-containing active particles is 75.3% to 83.5%.

[0041] In some embodiments, the silicon-containing active particles provided herein are prepared using a method comprising the following steps: Step S100, subjecting a mixture of a carbon source and an alkali to a gradient temperature increase and heat preservation treatment to obtain a porous carbon material; Step S200, introducing silane gas into the porous carbon material under an inert gas atmosphere for reaction to obtain the silicon-containing active particles. This method facilitates obtaining silicon-containing active particles comprising porous carbon particles and silicon formed within and / or on the surface of the porous carbon particles, thereby better cooperating with fluoroethylene carbonate in the electrolyte through their shape characteristics.

[0042] In some embodiments, the gradient temperature rise and insulation treatment comprises: heating the mixture of the carbon source and the alkali to 350° C. to 550° C. and insulation treatment for 15 min to 45 min, and then heating to 600° C. to 900° C. and insulation treatment for 0.5 h to 2 h.

[0043] In some embodiments, the carbon source is selected from at least one of phenolic resin, coal, biomass material, and petroleum coke.

[0044] In some embodiments, the carbon source has a sphericity of 0.68 to 1, for example, 0.68, 0.70, 0.74, 0.78, 0.82, 0.92, 0.93, 0.96, 1, or a value within a range of any two of these values. The sphericity of the silicon-containing active particles in this application can be controlled by controlling the sphericity of the carbon source. Using a carbon source with such a sphericity in combination with a gradient temperature increase and insulation treatment can produce silicon-containing active particles with a higher sphericity. When combined with FEC, these particles can further improve the kinetic performance and over-discharge tolerance of secondary batteries.

[0045] In some embodiments, the minimum angle of the cross-sectional profile of the carbon source is 105° to 180°, for example, 105°, 113°, 121°, 130°, 136°, 146°, 152°, 167°, 172°, 175°, 180°, or a value within the range of any two of these values. In the present application, the minimum angle of the cross-sectional profile of the silicon-containing active particles can be regulated by controlling the minimum angle of the cross-sectional profile of the carbon source. By using the carbon source with the above-mentioned minimum cross-sectional profile angle in combination with a gradient temperature increase and insulation treatment, silicon-containing active particles with a higher minimum cross-sectional profile angle can be obtained. When combined with the sphericity and FEC in the electrolyte, it is beneficial to further optimize the cycle performance and over-discharge resistance of the secondary battery, and improve its first coulombic efficiency and cycle capacity retention rate.

[0046] In some embodiments, after the reaction of introducing silane gas in step S200 is completed, the step further includes introducing acetylene gas into the porous carbon material to ensure the purity of silicon particles deposited in the porous carbon.

[0047] In some specific embodiments, the method for preparing silicon-containing active particles comprises the following steps:

[0048] Step S100: Phenolic resin microspheres and potassium hydroxide are mixed in an alkali-to-carbon ratio of (1-4):(1-2). The mixture is first heated in a rotary kiln at 300°C to 400°C for 20-40 minutes. The temperature of the rotary kiln is then raised to 600°C to 800°C and held for 20-50 minutes. The resulting product is then acid-washed, washed with water, and dried to obtain a porous carbon material.

[0049] Step S200: Take the above-mentioned porous carbon material and add it to a fluidized bed reactor, heat it to 400°C to 550°C under a nitrogen atmosphere of 7L / min to 14L / min and keep it warm for 1h to 3h, then introduce 1.5L / min to 3.5L / min of silane gas for 200min to 400min. After stopping the introduction of silane, heat the fluidized bed reactor to 400°C to 550°C and keep it warm for 0.5h to 2.5h, then introduce 3.5L / min to 6L / min of acetylene gas for 250min to 350min. After the reaction is completed, silicon-containing active particles can be obtained. In some embodiments, the negative electrode active material layer also includes a binder and a conductive agent. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated or acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0050] In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0051] The secondary battery of the present application further includes a positive electrode, which includes a positive electrode current collector and a positive electrode active material layer, which includes a positive electrode active material, a binder, and a conductive agent.

[0052] According to some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0053] According to some embodiments of the present application, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminum oxide, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel lithium manganese oxide, spinel lithium nickel manganese oxide and lithium titanate. In some embodiments, the binder includes a binder polymer such as polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber or polyurethane. In some embodiments, the polyolefin binder includes at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol or polyacrylic acid. In some embodiments, the conductive agent includes a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black or carbon fiber; a metal-based material such as metal powder or metal fiber of copper, nickel, aluminum, silver, etc.; a conductive polymer such as a polyphenylene derivative; or a mixture thereof.

[0054] The secondary battery of the present application also includes an isolation membrane. The material and shape of the isolation membrane used in the secondary battery of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the isolation membrane includes a polymer or inorganic substance formed from a material that is stable to the electrolyte of the present application. For example, the isolation membrane may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, polypropylene porous membrane, polyethylene porous membrane, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite membrane can be selected.

[0055] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material is selected from at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0056] The secondary battery of the present application also includes an electrolyte. The electrolyte in the present application includes an organic solvent, a lithium salt and optional additives. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate. In some embodiments, the organic solvent includes an ether solvent, for example, including at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalatoborate) LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB). The additives may be electrolyte additives known in the art.

[0057] According to some embodiments of the present application, the secondary battery of the present application includes, but is not limited to: a lithium-ion battery or a sodium-ion battery. In some embodiments, the secondary battery includes a lithium-ion battery.

[0058] The present application further provides an electronic device, which includes the secondary battery according to the first aspect of the present application.

[0059] The electronic devices or devices of the present application are not particularly limited. In some embodiments, the electronic devices of the present application include, but are not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0060] The present invention is described below using lithium-ion batteries as an example and in conjunction with the following specific examples and comparative examples. In the following examples and comparative examples, all reagents, materials, and instruments used are commercially available unless otherwise specified.

[0061] Example 1

[0062] The lithium-ion battery of this embodiment includes a negative electrode plate and an electrolyte. The negative electrode plate includes a negative electrode active material layer, and the negative electrode active material layer includes silicon-containing active particles. The sphericity A of the silicon-containing active particles is 0.68. The electrolyte contains FEC, and the mass percentage B% of FEC based on the mass of the electrolyte is 1.1%. Wherein, A and B satisfy: B / A = 1.6.

[0063] The minimum angle C° of the cross-section profile of silicon-containing active particles with a diameter greater than 10 μm is 129°; (A×CB)=86.62.

[0064] The lithium-ion battery of this embodiment is prepared by a method comprising the following steps:

[0065] <Preparation of Porous Carbon>

[0066] 1000g of thermoplastic linear phenolic resin and 120g of hexamethylenetetramine curing agent were dissolved in 2.5L of methanol at 50°C for 1 hour. The methanol solvent was then removed by vacuum distillation to obtain a uniform mixture of the phenolic resin and hexamethylenetetramine.

[0067] A 0.15 mol / L aqueous sodium dodecyl sulfate solution was prepared in an autoclave, and a uniform mixture of the phenolic resin and hexamethylenetetramine was dissolved therein. The autoclave temperature was raised to 130°C and maintained for 30 minutes. After the autoclave was cooled, phenolic resin microspheres were obtained. The phenolic resin microspheres had a sphericity of 0.72 and a minimum cross-sectional profile angle of 136°.

[0068] Phenolic resin microspheres and potassium hydroxide were mixed in an alkali-to-carbon ratio of 3:1. The mixture was first heated in a rotary kiln at 400°C for 30 minutes, then raised to 750°C and held there for 45 minutes. The resulting product was then acid-washed, washed with water, and dried to obtain a porous carbon material.

[0069] <Preparation of Silicon-Containing Active Particles>

[0070] 1000g of the porous carbon was added to a fluidized bed reactor and heated to 480°C under a 10L / min nitrogen atmosphere for 2 hours. Monosilane gas was then introduced at 2.5L / min for 300 minutes. After stopping the silane introduction, the fluidized bed was heated to 500°C and maintained for 1 hour. Acetylene gas was then introduced at 5L / min for 300 minutes. Upon completion of the reaction, silicon-containing active particles were obtained.

[0071] The specific surface area of ​​silicon-containing active particles is 2.80m 2 / g, based on the mass of the silicon-containing active particles, the mass fraction of Si element is 46.2%.

[0072] <Preparation of negative electrode sheet>

[0073] The negative electrode active material (silicon-containing active particles and graphite mixed in a mass ratio of 1:9), carbon nanotubes, lithium carboxymethyl cellulose, and lithium polyacrylate were mixed in a mass ratio of 97.4:0.2:0.4:2, and deionized water was added as a solvent. A negative electrode slurry was obtained under the action of a vacuum mixer. The solid content of the negative electrode slurry was 45wt% and the viscosity was 6000mPa.s. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm. The copper foil was dried at 80°C to obtain a coating weight of 100.1mg / 1540.25mm 2 The negative electrode sheet is coated on one side with a negative electrode material layer. The above steps are then repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode material layer. After cold pressing, cutting, and slitting, a negative electrode sheet with a size of 661mm x 78mm is obtained.

[0074] FIG1 is a backscattered SEM image of a cross section of a negative electrode sheet in a lithium-ion battery according to Example 1 of the present application along the thickness direction, wherein the mass fraction of Si element is 4.5% based on the mass of the negative electrode active material layer.

[0075] <Preparation of positive electrode sheet>

[0076] The positive electrode active material LiCoO2, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride were mixed in a mass ratio of 96.7:1.7:1.6, and N-methylpyrrolidone (NMP) was added to obtain a positive electrode slurry under the action of a vacuum mixer. The positive electrode slurry had a solid content of 76 wt %. The positive electrode slurry was evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9 μm. The aluminum foil was dried at 120°C to obtain a coating weight of 260 mg / 1540.25 mm 2 The positive electrode sheet is coated on one side with a positive electrode material layer. The above steps are then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated on both sides with a positive electrode material layer. After cold pressing, cutting, and slitting, a positive electrode sheet with a size of 661 mm x 76.5 mm is obtained.

[0077] <Preparation of Electrolyte>

[0078] In an argon atmosphere glove box with a water content of less than 10 ppm, EC, PC, EP, and PP were mixed in a mass ratio of 17:25:40:18 to obtain an organic solvent. Lithium salts LiPF6 and FEC were then added to the organic solvent to produce an electrolyte. The mass percentage of the lithium salt LiPF6 was 12.5%, and the mass percentage of FEC was 1.1%, based on the mass of the electrolyte. The electrolyte had a conductivity of 7.83 mS / cm and a hydrofluoric acid content of 28.2 μg / g.

[0079] <Isolation Film>

[0080] A porous polyethylene film with a thickness of 10 μm (supplied by Celgard) was used.

[0081] <Preparation of lithium-ion batteries>

[0082] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide insulation, and then wound to form an electrode assembly. The electrode assembly is then placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. The lithium-ion battery is then produced through vacuum packaging, resting, formation, degassing, and trimming.

[0083] Example 2

[0084] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 2% based on the mass of the electrolyte; wherein B / A=2.9.

[0085] Example 3

[0086] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 4% based on the mass of the electrolyte; wherein B / A=5.9.

[0087] Example 4

[0088] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 7% based on the mass of the electrolyte; wherein B / A=10.3.

[0089] Example 5

[0090] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 11% based on the mass of the electrolyte; wherein B / A=16.2.

[0091] Example 6

[0092] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 16% based on the mass of the electrolyte; wherein B / A=23.5.

[0093] Example 7

[0094] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the mass percentage of FEC is 20% based on the mass of the electrolyte; wherein B / A=29.4.

[0095] Example 8

[0096] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the sphericity A of the silicon-containing active particles is 0.79, and the mass percentage of FEC based on the mass of the electrolyte is 4%; wherein B / A=5.1.

[0097] Example 9

[0098] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the sphericity A of the silicon-containing active particles is 0.82, and the mass percentage of FEC based on the mass of the electrolyte is 4%; wherein B / A=4.9.

[0099] Example 10

[0100] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the sphericity A of the silicon-containing active particles is 0.91, and the mass percentage of FEC based on the mass of the electrolyte is 4%; wherein B / A=4.4.

[0101] Example 11

[0102] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the sphericity A of the silicon-containing active particles is 0.65, and the mass percentage of FEC based on the mass of the electrolyte is 4%; wherein B / A=6.2.

[0103] Example 12

[0104] The lithium-ion battery of this embodiment differs from that of Example 1 only in that the sphericity A of the silicon-containing active particles is 0.68, the mass percentage B% of FEC based on the mass of the electrolyte is 20%, B / A = 29.4, the minimum angle C° of the cross-section profile of the silicon-containing active particles with a diameter greater than 10 μm is 96°, and (A×CB) = 45.28.

[0105] Example 13

[0106] The lithium-ion battery of this embodiment differs from that of Example 1 only in that the sphericity A of the silicon-containing active particles is 1, the mass percentage B% of FEC based on the mass of the electrolyte is 4%, where B / A = 4, the minimum angle C° of the cross-section profile of the silicon-containing active particles with a diameter greater than 10 μm is 180°, and (A×CB) = 176.0.

[0107] Comparative Example 1

[0108] The lithium-ion battery of this comparative example differs from that of Example 1 only in that the sphericity A of the silicon-containing active particles is 0.68, and the mass percentage of FEC based on the mass of the electrolyte is 1%; wherein B / A=1.5.

[0109] Comparative Example 2

[0110] The lithium-ion battery of this comparative example differs from that of Example 1 only in that the sphericity A of the silicon-containing active particles is 0.71, and the mass percentage of FEC based on the mass of the electrolyte is 21%; wherein B / A=29.6.

[0111] Test example

[0112] The following test methods were used to test various parameters or performances of the lithium-ion batteries provided in the examples and comparative examples of this application:

[0113] 1. Sphericity test

[0114] The sphericity of the silicon-containing active particles was tested using the equivalent diameter method. The test method was to use a ZEISS-SEM (sigma-02-33) scanning electron microscope to observe the silicon-containing active particle powder or the silicon-containing active particles in the negative electrode sheet, remove incomplete particles, and calculate the equivalent diameter of the circumference of the complete particles and the equivalent diameter of the particle area.

[0115] Sphericity = circumference equivalent diameter / area equivalent diameter.

[0116] 2. Minimum angle of cross-section profile of particles with diameter greater than 10 μm

[0117] 0.47g of silicon-containing active particles and 0.396g of polyacrylic acid were dispersed in water, mixed thoroughly in a homogenizer, and then applied to a copper foil surface with a spatula. After drying, the mixture was sectioned using a JEOL ion polisher (Model: IB-09010CP). Cross-sectional micrographs of the silicon-containing active particles were captured using a ZEIS-SEM (Sigma-02-33). The cross-sectional profiles of silicon-containing active particles with a diameter greater than 10μm were selected for analysis. Figure 2 shows a schematic diagram of determining the minimum angle of the cross-sectional profile of silicon-containing active particles with a diameter greater than 10μm. As shown in Figure 2, the outline of the silicon-containing active particle was outlined, and then tangent lines were drawn along the edges of the sharp corners, and the angle between the two tangent lines was measured. The values ​​of the measured angles were compared, and the minimum value was taken as the minimum angle value of the cross-sectional profile of the particle (for example, in the schematic diagram of Figure 2, Angle 1 is 115°, Angle 2 is 105°, Angle 3 is 142°, and Angle 4 is 140°, then Angle 2 is recorded as the minimum angle of the cross-sectional profile of the silicon-containing active particle, that is, the minimum angle of the cross-sectional profile of the silicon-containing active particle is 105°). The degrees of the minimum angles in the cross-sectional profiles of at least 20 silicon-containing active particles were counted and averaged to obtain the minimum angle of the cross-sectional profile of the silicon-containing active particles in the batch with a diameter greater than 10 μm.

[0118] 3. Specific surface area test

[0119] 2.0g of silicon-containing active particles were weighed and placed in a sample tube. The sample tube was then installed in a degassing station and heated to 200°C for 120 minutes. Nitrogen was then introduced into the sample tube. The equilibrium pressure in the sample tube was controlled to directly measure the adsorption partial pressure, and the adsorption capacity at that partial pressure point was determined from the gas equation of state. During the measurement, the adsorbate gas was gradually added to increase the adsorption equilibrium pressure, ultimately yielding an adsorption isotherm. The adsorption equilibrium pressure was then gradually reduced by removing the adsorbate gas, resulting in a desorption isotherm. Finally, the specific surface area of ​​the silicon-containing active particles was calculated using the Barrett-Joyner-Halenda (BJH) theory.

[0120] 4. Test of hydrofluoric acid content in electrolyte

[0121] Place 100g of ice-water mixture in a plastic beaker and add 10 drops of 1g / L bromothymol blue indicator. Stir thoroughly. Titrate with 0.01mol / L NaOH standard solution until the ice-water mixture turns blue. Record the volume (V0) of NaOH standard solution consumed at the endpoint.

[0122] Prepare an ice-water mixture and a bromothymol blue indicator solution using the same method as above. Add 20 g of the electrolyte to be tested, recording the mass of electrolyte added (m (g)). Titrate with a 0.01 mol / L NaOH standard solution until the ice-water mixture displays a blue color. Record the standard volume (V1 (ml) of NaOH standard solution consumed at the titration endpoint.

[0123] Finally, the content of hydrofluoric acid in the electrolyte to be tested is calculated using the following formula: HF (μg / g) = (V1-V0) × 200 / m.

[0124] 5. Electrolyte conductivity test

[0125] The test was carried out with reference to HG / T 4067-2015, Determination of conductivity in lithium hexafluorophosphate electrolyte, and the electrode selected was a DJS-1C platinum black electrode.

[0126] 6. Gram capacity test of silicon-containing active particles

[0127] Silicon-containing active particles, a conductive agent (SP), a binder (PAA-Li), carbon nanotubes (CNTs), and a dispersant (CMC) were mixed in a mass ratio of 84:10:5:0.4:0.6, and deionized water was added to produce a negative electrode slurry with a solid content of 48%. The negative electrode slurry was mixed evenly and then coated onto copper foil. After drying, cold pressing, and punching, the negative electrode sheet was obtained.

[0128] In a glove box with a water and oxygen content of less than 10 ppm, ethyl methyl carbonate (EMC), ethylene carbonate (EC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to create a mixed solvent. FEC was then added at a 10% volume fraction of the mixed solvent, and finally, lithium PF6 was added to create an electrolyte solution. The concentration of the lithium PF6 was 1 mol / L.

[0129] In a glove box with a water and oxygen content of less than 10 ppm, the above-mentioned negative electrode plate, the counter electrode metal lithium plate, the polypropylene (PP) separator and the above-mentioned electrolyte were assembled into a button battery.

[0130] Silicon-containing active particles gram capacity test: After standing for 6 hours at 25°C, the button cell was discharged at 0.05C to 5mV. Then, it was discharged at 50μA to 5mV. After standing for 5 minutes, it was discharged again at 10μA to 5mV. After standing for 5 minutes, it was charged at 0.05C to 0.8V. The discharge capacity is recorded as G0, and the charge capacity is recorded as G1.

[0131] Gram capacity of silicon-containing active particles = G1; first coulombic efficiency of silicon-containing active particles = G1 / G0×100%.

[0132] 7. First discharge capacity and first coulombic efficiency test of lithium-ion battery

[0133] Under normal pressure at 25°C, the newly prepared lithium-ion battery was charged at a constant current of 0.5C to 4.53V, and then charged at a constant voltage of 0.05C, and allowed to stand for 5 minutes. The charging capacity of this step was recorded as C1; the battery was discharged at a constant current of 0.2C to 3.0V, and the discharge capacity of this step was recorded as C2. C2 is the first discharge capacity of the lithium-ion battery.

[0134] The first coulombic efficiency of lithium-ion battery = C2 / C1×100%.

[0135] 8. Lithium-ion battery cycle performance test

[0136] Place the lithium-ion battery in a 25°C constant temperature test chamber and let it rest for 30 minutes to allow the lithium-ion battery to reach a constant temperature of 25°C. Charge it at a constant current of 1C to 4.53V, then charge it at a constant voltage to a current of 0.025C. Let it rest for 5 minutes, then discharge it at a constant current of 0.5C to 3.0V. Record the initial discharge capacity as C0. Repeat this cycle for 400 cycles, and record the discharge capacity after 400 cycles as C1.

[0137] After 400 cycles, the capacity retention rate = C1 / C0×100%.

[0138] 9. Over-discharge resistance test

[0139] The test temperature is 25°C, and the battery is charged and discharged at a constant current of 0.2C to 3.0V. After standing for 5 minutes, the battery is discharged at a constant current of 10mA to 0.1V. After standing for 30 minutes, the battery is discharged at a constant current of 1mA to 0.1V. The thickness of the lithium-ion battery is tested using online thickness measurement equipment. The measurement weight is 300g, and the sampling interval is 10s. The initial thickness of the lithium-ion battery is recorded as T1, and the thickness after discharge is recorded as T2. The lithium-ion battery voltage is also recorded.

[0140] The voltage value when (T2-T1) / T1×100% equals 10% is recorded as the over-discharge gas production test voltage of the lithium-ion battery. The lower the value of the over-discharge gas production test voltage, the stronger the over-discharge resistance of the lithium-ion battery.

[0141] The parameters and performance characterization results of the lithium-ion batteries of Examples 1 to 13 and Comparative Examples 1 to 2 provided in this application obtained through the above tests are shown in Table 1 below.

[0142] Table 1

[0143] As shown in Table 1, the lithium-ion batteries of Examples 1-13 control the sphericity A of the silicon-containing active particles and the mass percentage B% of FEC in the electrolyte to satisfy 1.6≤(B / A)≤29.4. Their initial coulombic efficiency reaches 86.4% to 90.7%, and the capacity retention rate after 400 cycles reaches 92.0% to 97.2%, showing high initial efficiency and cycling performance. In addition, the over-discharge gas production test voltage of the lithium-ion batteries of Examples 1-13 can reach 1.85V to 2.31V. It can be seen that the lithium-ion batteries of the present application can achieve a lower discharge voltage when producing the same volume of gas, indicating that the lithium-ion batteries of the present application produce less gas during discharge and have strong over-discharge resistance.

[0144] In contrast, when the B / A value of the lithium-ion batteries in Comparative Examples 1 and 2 is outside the specified range, their initial coulombic efficiency is 83.2% to 85.4%, the capacity retention rate after 400 cycles is 88.6% to 89.7%, and the over-discharge gas production test voltage can be 2.47V to 2.58V. The reason may be that the fresh interface generated by the silicon-containing active particles when subjected to force cannot be covered by the dense SEI film, resulting in continuous side reactions between the active silicon and the electrolyte, and the performance of the lithium-ion battery is seriously deteriorated.

[0145] When the sphericity degree A of the silicon-containing active particles is controlled to be 0.65 to 1, the initial efficiency, cycle performance and over-discharge resistance of the lithium-ion battery can be further improved.

[0146] As can be seen from Examples 1-7, FEC can form a dense, low-resistance SEI film on the surface of silicon-containing active particles, preventing side reactions of active silicon and further decomposition of the electrolyte. This allows more active silicon to participate in alloying / de-alloying reactions, improving the initial coulombic efficiency of the lithium-ion battery and the capacity retention after 400 cycles, while reducing the over-discharge gas production test voltage and improving the cycling performance of the lithium-ion battery. Further controlling the FEC mass percentage B% to 2≤B≤7, the lithium-ion battery achieved even higher initial coulombic efficiency and cycle capacity retention. Furthermore, the discharge voltage at which expansion occurred during the over-discharge gas production test was lower, indicating that the lithium-ion battery produces less gas during over-discharge and has stronger over-discharge resistance.

[0147] Compared with Examples 8 to 11, the FEC content is the same, but the sphericity of the silicon-containing active particles changes. Among them, Examples 8 to 10, on the basis of meeting the B / A range, further optimize the shape characteristics of the sphericity, so that the sphericity of the silicon-containing active particles is above 0.79, and have higher first efficiency, cycle performance and over-discharge resistance than Example 11.

[0148] In Examples 1 to 13, by controlling the sphericity A of the silicon-containing active particles, the minimum cross-sectional profile angle C of the silicon-containing active particles with a diameter greater than 10 μm, and the mass percentage B% of FEC in the electrolyte to meet the requirements of 45.28 ≤ (A×CB) ≤ 176.0, the lithium-ion batteries exhibit significantly improved initial efficiency and cycle capacity retention, as well as significantly enhanced cycling performance and over-discharge tolerance. Specifically, when A, B, and C meet the requirements of 60 ≤ (A×CB) ≤ 120, the performance of the secondary battery can be further enhanced, exhibiting even better cycling performance and over-discharge tolerance.

Claims

1. A secondary battery comprising a negative electrode and an electrolyte, characterized in that: The negative electrode plate includes a negative electrode active material layer, and the negative electrode active material layer includes silicon-containing active particles; the sphericity of the silicon-containing active particles is A; The electrolyte comprises fluoroethylene carbonate; based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is B%; Among them, A and B satisfy: 1.6≤(B / A)≤29.

4.

2. The secondary battery according to claim 1, wherein 0.65≤A≤1。 3. The secondary battery according to claim 1 or 2, characterized in that 1.1≤B≤20。 4. The secondary battery according to any one of claims 1 to 3, characterized in that 2≤B≤7。 5. The secondary battery according to any one of claims 1 to 4, characterized in that The minimum angle of the cross-section profile of the silicon-containing active particles with a diameter greater than 10 μm is C°, and 96≤C≤180.

6. The secondary battery according to claim 5, characterized in that A, B and C satisfy: 45.28≤(A×CB)≤176.

0.

7. The secondary battery according to claim 5 or 6, characterized in that: A, B and C satisfy: 60≤(A×CB)≤120.

8. The secondary battery according to any one of claims 1 to 7, characterized in that The silicon-containing active particles include a porous carbon matrix and nano-silicon; the nano-silicon is distributed inside and on the surface of the porous carbon matrix.

9. The secondary battery according to any one of claims 1 to 8, characterized in that The secondary battery satisfies at least one of the following conditions: (1) Based on the mass of the silicon-containing active particles, the mass fraction of Si element is 42% to 55%; (2) The specific surface area of ​​the silicon-containing active particles is 0.5 m 2 / g~5m 2 / g; or (3) The conductivity of the electrolyte is 6.5 mS / cm to 11 mS / cm.

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

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