Battery cell, battery and electric equipment

Abstract

The invention discloses a battery cell, a battery and electric equipment, the battery cell comprises an electrode assembly and a shell, the electrode assembly is packaged in the shell, and the ratio of the residual space in the shell to the volume of the battery cell is the battery cell residual space; the electrode assembly comprises a positive electrode, a diaphragm and a negative electrode; the negative electrode comprises an active substance, and the active substance comprises graphite and silicon; the diaphragm comprises a base membrane and a coating coated on the surface of the base membrane; the battery cell corresponds to a battery cell safety factor x, and the relational expression is as follows: R represents the residual space of the battery cell; the d coating represents the coating thickness of the surface of the base film; wSi represents the mass percentage of the silicon element content in the negative electrode coating; and the range of the safety factor x of the battery cell is 10-20. The safety factor of the battery cell is controlled to be 10-20 by cooperatively controlling the three parameters, namely the residual space of the battery cell, the thickness of the coating on the surface of the base film and the mass percent of the content of silicon in the negative electrode coating, and the probability of severe thermal runaway and shell explosion during needling can be remarkably reduced while the high energy density can be kept in the range.

Description

Technical Field

[0001] This application belongs to the field of battery safety technology, specifically relating to a battery cell, battery, and electrical device. Background Technology

[0002] With the global energy structure transformation and the rapid development of the electric vehicle industry, the market is placing increasingly urgent demands on battery energy density. As a key component determining battery energy density, breakthroughs in the performance of anode materials are crucial. Traditional graphite anodes, due to their relatively low theoretical specific capacity (approximately 372 mAh / g), are no longer sufficient to meet the needs of next-generation high-energy-density batteries. Against this backdrop, silicon materials, with their extremely high theoretical specific capacity (up to 4200 mAh / g, more than ten times that of graphite), have attracted considerable attention and are considered the most promising next-generation anode material. Currently, the industry generally adopts a technical route of mixing silicon and graphite to form silicon-carbon composite anodes, aiming to significantly improve the driving range of power batteries while maintaining cycle stability.

[0003] While silicon-based composite anodes significantly improve battery energy density, they also present serious safety challenges. Current solutions address battery safety issues through structural optimization and interface modification of silicon-based anodes. However, these technologies have not fundamentally solved the problem of decreased thermal stability caused by battery volume expansion, leading to thermal runaway and casing explosion in silicon-based anode battery systems, thus affecting battery safety performance. Summary of the Invention

[0004] This application aims to provide a battery cell, battery, and electrical device to solve the problem of decreased thermal stability of silicon-based anodes, thereby improving the safety performance of batteries.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows: In a first aspect, embodiments of this application propose a battery cell, including an electrode assembly and a housing, wherein the electrode assembly is encapsulated within the housing, and the ratio of the remaining space within the housing to the volume of the battery cell is the residual space of the battery cell. The electrode assembly includes a positive electrode, a separator, and a negative electrode; the negative electrode includes an active material, which includes graphite and silicon; the separator includes a base film and a coating disposed on the surface of the base film. The battery cell has a corresponding battery cell safety factor x. The relationship between the battery cell safety factor and the residual space of the battery cell, the coating thickness on the surface of the base film, and the mass percentage of silicon in the negative electrode coating is as follows:

[0006] Where R represents the residual space of the battery cell; the relationship of the residual space of the battery cell is:

[0007] Among them, V 电极组件 represents the volume of the electrode assembly in the battery cell; V 壳体 represents the volume of the housing in the battery cell; the residual space of the battery cell is 5% - 15%; d 涂层 represents the coating thickness on the surface of the base film; the coating thickness on the surface of the base film is 2 μm - 4 μm; W Si represents the mass percentage of silicon element in the negative electrode coating; the mass percentage of silicon element in the negative electrode coating is 2.5% - 6%; The range of the battery cell safety factor x is 10 - 20.

[0008] Optionally, the graphite includes at least one of natural graphite and artificial graphite; and / or the silicon includes at least one of silicon-carbon particles, pure silicon particles, SiO x (0 < x < 2) particles; and / or, the average particle size range of the graphite is 2 μm - 30 μm; and / or, the average particle size range of the silicon is 2 μm - 10 μm.

[0009] Optionally, the negative electrode further contains a conductive agent and a binder; the conductive agent includes at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; and / or, the binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, and polyvinylidene fluoride.

[0010] Optionally, the base film includes at least one of polypropylene, polyethylene, and polypropylene and polyethylene; and / or, the thickness of the base film is 5 μm - 20 μm.

[0011] Optionally, the coating includes an aramid coating, and the aramid coating includes inorganic fillers.

[0012] Optionally, the inorganic fillers include one or more of alumina, boehmite, calcium carbonate, barium sulfate, barium titanate, hydrotalcite, montmorillonite, spinel, titanium dioxide, silicon dioxide, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, calcium hydroxide, and silicon carbide.

[0013] Optionally, the double-sided surface density of the negative electrode is 200 - 280 g / m 2 , and / or, the double-sided surface density of the positive electrode is 400 - 500 g / m 2 .

[0014] Optionally, the volumetric energy density of the battery cell is greater than or equal to 630 Wh / L.

[0015] Optionally, the active material in the positive electrode includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based materials.

[0016] Optionally, the positive electrode further includes a conductive agent and a binder. The conductive agent includes at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; and / or, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene.

[0017] Secondly, embodiments of this application propose a battery comprising at least one of the aforementioned cells.

[0018] Thirdly, embodiments of this application propose an electrical device including the battery described above.

[0019] Compared with the prior art, this application has at least the following advantages: In the embodiments of this application, the battery includes an electrode assembly and a housing. The electrode assembly is encapsulated within the housing, and the ratio of the remaining space within the housing to the volume of the battery cell is called the residual space of the battery cell. The electrode assembly includes a positive electrode, a separator, and a negative electrode. The negative electrode includes an active material, which includes graphite and silicon. The separator includes a base film and a coating disposed on the surface of the base film. The battery cell has a corresponding battery cell safety factor x. The relationship between the battery cell safety factor and the residual space of the battery cell, the thickness of the coating on the base film surface, and the percentage of silicon content in the negative electrode coating by mass is as follows:

[0020] Where R represents the residual space of the battery cell; the relationship of the residual space of the battery cell is:

[0021] V 电极组件 V represents the volume of the electrode assembly in the battery cell; 壳体 d represents the volume of the casing within the battery cell; 涂层 Indicates the coating thickness on the base film surface; W Si This indicates the percentage of silicon in the negative electrode coating by mass; the cell safety factor x ranges from 10 to 20.

[0022] By synergistically controlling the above three parameters—a residual space of 5%–15% in the battery cell, a coating thickness of 2–4 micrometers on the base film surface, and a silicon content of 2.5%–6% of the mass percentage of the negative electrode coating—the safety factor of the battery cell can be controlled at 10–20. Maintaining a safety factor of 10–20 significantly reduces the probability of severe thermal runaway and casing explosion during needle penetration while preserving high energy density.

[0023] In summary, the cell safety factor provided in this application can solve the problem of decreased thermal stability of silicon-based anodes, thereby improving the safety performance of batteries.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0025] The embodiments of this application will now be described in detail, with examples of these embodiments, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The following embodiments are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0026] Studies have shown that silicon-based anode batteries exhibit significantly worse thermal runaway behavior compared to mature pure graphite anode systems. Under abusive conditions such as nail penetration, silicon-based anode batteries with the same state of charge (SOC) experience far more severe thermal runaway. Specifically, the maximum thermal runaway temperature can reach over 1500°C, the fireball ejected from inside the battery lasts longer, and the probability of the encapsulation casing (especially the aluminum-plastic film of pouch batteries) melting and rupturing (i.e., "shell explosion") increases significantly. These phenomena indicate that the incorporation of silicon significantly reduces the overall thermal stability of the battery, posing a serious threat to the safety performance of the battery system.

[0027] A deeper investigation reveals that the root cause of the deterioration in the safety performance of silicon-based anodes lies in their inherently large volume effect during charging and discharging. Silicon undergoes volume expansion and contraction exceeding 300% during alloying / dealloying reactions. This drastic volume change triggers multiple negative impacts: firstly, it causes electrode material particles to pulverize and detach from the current collector, resulting in structural failure; secondly, it leads to repeated rupture and regeneration of the solid electrolyte interphase (SEI) film on the electrode surface, continuously consuming the limited active lithium and electrolyte within the battery; and thirdly, it exposes new, unstable solid-liquid interfaces, exacerbating interfacial side reactions. These factors combined not only accelerate battery performance degradation but, more importantly, result in higher reactivity of silicon-based anodes under thermal abuse conditions, lowering the thermal runaway initiation temperature. Once triggered, the internal chemical reactions are more intense, the exothermic rate is faster, ultimately leading to more violent and dangerous fires, explosions, and a high probability of casing failure. Therefore, fundamentally improving the thermal stability of silicon-based anodes and suppressing their violent reactions under abuse conditions has become a critical technical challenge urgently needing to be addressed in this field.

[0028] This application aims to address the problem of decreased thermal stability of silicon-based anodes, leading to thermal runaway and casing explosion in silicon-based anode battery systems, thereby affecting battery safety performance. In a first aspect, embodiments of this application provide a battery cell, including an electrode assembly and a casing. The electrode assembly is encapsulated within the casing, and the ratio of the remaining space within the casing to the volume of the battery cell is called the residual space of the battery cell. The electrode assembly includes a positive electrode, a separator, and a negative electrode; the negative electrode includes an active material, which includes graphite and silicon; the separator includes a base film and a coating disposed on the surface of the base film; Each battery cell has a corresponding safety factor x. The relationship between the safety factor and the residual space of the battery cell, the coating thickness on the base film surface, and the percentage of silicon content in the negative electrode coating is as follows:

[0029] Where R represents the residual space of the battery cell; the relationship of the residual space of the battery cell is:

[0030] Among them, V 电极组件 V represents the volume of the electrode assembly in the battery cell; 壳体 This indicates the volume of the battery cell casing; the residual space within the battery cell is 5%~15%. d 涂层 This indicates the coating thickness on the base film surface; the coating thickness on the base film surface is 2 micrometers to 4 micrometers. W Si This indicates the percentage of silicon content in the negative electrode coating by mass; the percentage of silicon content in the negative electrode coating by mass is 2.5% to 6%.

[0031] The range of the battery cell safety factor x is 10 to 20.

[0032] It should be noted that the range of the battery cell safety factor x is 10 to 20. For example, the range of the battery cell safety factor x can be one of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or the range value of any two of them.

[0033] It should be noted that the electrode assembly refers to the whole formed by winding or laminating the negative electrode, the separator, and the positive electrode.

[0034] It should be noted that the negative electrode includes a negative current collector and a negative active material layer provided on the surface of the negative current collector. The negative active material layer includes negative active substances, and the negative active substances include graphite and silicon. In one embodiment, the negative current collector can be selected from one of copper foil, carbon-coated copper foil, and composite copper foil. In one embodiment, the graphite includes at least one of natural graphite and artificial graphite. In one embodiment, the silicon includes at least one of silicon-carbon particles, pure silicon particles, and SiO x (0 < x < 2) particles.

[0035] It should be noted that the test method for the mass percentage of silicon element in the negative electrode coating is as follows: Scrape off the coating on the surface of the negative electrode of the battery cell and weigh its mass m 涂层 , and then dissolve it by the method of hydrofluoric acid and microwave digestion, and test the content of silicon element m Si in the mixture through inductively coupled plasma (ICP). The mass percentage W si of the silicon element in the negative electrode coating is Si = (m 涂层 / m

[0036] It should be noted that the test method for the residual space R of the battery cell is as follows: Measure the volume V 壳体 of the battery cell housing and the volume V 电极组件 of the internal electrode assembly (a whole formed by winding or laminating the positive electrode sheet, the separator, and the negative electrode sheet) of the battery cell respectively, and obtain the residual space of the battery cell through the residual space relationship formula of the battery cell:

[0037] In this embodiment, the battery cell includes an electrode assembly and a housing. The electrode assembly is encapsulated within the housing, and the ratio of the remaining space within the housing to the volume of the battery cell is called the residual space of the battery cell. The electrode assembly includes a positive electrode, a separator, and a negative electrode. The negative electrode includes an active material, which includes graphite and silicon. The separator includes a base film and a coating covering the surface of the base film. The battery cell has a corresponding safety factor x, and the relationship between the safety factor and the residual space of the battery cell, the thickness of the coating on the base film surface, and the percentage of silicon content in the negative electrode coating is as follows:

[0038] Where R represents the residual space in the battery cell; d 涂层 Indicates the coating thickness on the base film surface; W Si This indicates the percentage of silicon in the negative electrode coating by mass; the cell safety factor x ranges from 10 to 20.

[0039] By synergistically controlling the above three parameters—a residual space of 5%–15% in the battery cell, a coating thickness of 2–4 micrometers on the base film surface, and a silicon content of 2.5%–6% of the mass percentage of the negative electrode coating—the safety factor of the battery cell can be controlled at 10–20. Maintaining a safety factor of 10–20 significantly reduces the probability of severe thermal runaway and casing explosion during needle penetration while preserving high energy density.

[0040] In summary, the cell safety factor provided in this application can solve the problem of decreased thermal stability of silicon-based anodes, which leads to thermal runaway and casing explosion in silicon-based anode battery systems, thereby improving the safety performance of the battery.

[0041] It should be noted that the coating thickness on the base film surface is 2 micrometers to 4 micrometers. For example, the coating thickness on the base film surface can be any one or a combination of 2 micrometers, 2.2 micrometers, 2.5 micrometers, 2.8 micrometers, 3.0 micrometers, 3.2 micrometers, 3.5 micrometers, 3.6 micrometers, 3.8 micrometers, and 4 micrometers. A coating that is too thin (less than 2 micrometers) provides insufficient protection; a coating that is too thick (greater than 4 micrometers) significantly increases ion transport resistance and reduces battery rate performance.

[0042] It should be noted that the coating on the base film surface can be applied to one or both sides of the base film. The coating material is a thermally stable material with high temperature resistance and good mechanical strength, such as aramid (poly(p-phenylene terephthalamide)) and polyimide (PI).

[0043] In this embodiment, the coating thickness on the base film surface is controlled between 2 and 4 micrometers. The coating exhibits excellent thermal stability (high melting point, high decomposition temperature), mechanical strength (needle penetration resistance), and flame retardancy. During needle penetration abuse, a thicker coating can more effectively prevent metal needles from directly piercing the positive and negative electrodes and causing large-area short circuits, or slow down the needle penetration speed. The coating's ability to maintain integrity at high temperatures is superior to traditional polyolefin separators, delaying separator thermal shrinkage and reducing instantaneous Joule heating. Even in the event of a localized short circuit, the coating's insulation and heat resistance help limit the expansion of the short circuit point, preventing the instantaneous release of energy from the entire battery.

[0044] It should be noted that the silicon content accounts for 2.5% to 6% of the mass of the negative electrode coating. For example, the silicon content accounts for one or any two of the following ranges: 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.7%, 3.9%, 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, 5.5%, 5.7%, and 6%.

[0045] In this embodiment, the silicon content is controlled at 2.5% to 6% of the mass percentage of the negative electrode coating. On the one hand, this avoids the problem that too low a silicon content will not significantly improve the battery energy density; on the other hand, it avoids that too high a silicon content will exacerbate the volume expansion effect and interface instability, causing the SEI film to rupture repeatedly, exacerbating the side reactions of the electrolyte at the negative electrode interface, and causing excessive heat released during the needle puncture, which could lead to severe thermal runaway and shell explosion.

[0046] It should be noted that an electrode assembly refers to the entire assembly formed by the negative electrode, separator, and positive electrode through a winding or stacking process. Therefore, electrode assemblies include wound electrode assemblies (cylindrical / flat round) and stacked electrode assemblies (square / soft pack), etc.

[0047] The volume of the casing in the battery cell is calculated based on the external dimensions of the battery cell (including the complete structure such as the tabs, but excluding the external protection plate and connecting wires).

[0048] Therefore, the formulas for calculating the volume of the electrode assembly in the battery cell and the volume of the casing in the battery cell are as follows: Cylindrical: Volume is πr 2 h (r is the radius, h is the height, in cm); Square / soft package: Volume is length × width × height (unit: cm).

[0049] If the electrode assembly has an irregular shape or requires the highest precision, the water displacement method can be used for actual measurement. Step 1: Fill a measuring cup with a known volume of liquid (such as dimethyl carbonate, to avoid electrolyte residue reaction) and record the initial volume V1; Step 2: Completely immerse the electrode assembly in the liquid and record the final volume V2; Step 3: The volume of the electrode assembly is V2-V1. The displacement method can avoid errors in geometric calculations (such as winding eccentricity, uneven stacking) and directly obtain the actual occupied volume.

[0050] In this embodiment, the internal space of the battery cell is adjusted by controlling the volume of the battery cell casing or the volume of the electrode assembly, so as to avoid the battery cell explosion caused by excessive gas pressure increase, thereby improving the safety performance of the battery.

[0051] It should be noted that the residual space of the battery cell is 5% to 15%. For example, the residual space of the battery cell can be one or any two of the following values: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%.

[0052] In this embodiment, the residual space of the battery cell is controlled at 5% to 15%. The residual space of the battery cell represents the remaining space inside the battery cell excluding the electrode assembly. A higher residual space provides a buffer space for the high-temperature gas generated during thermal runaway, avoiding the battery cell explosion caused by excessive gas pressure increase; however, it is not conducive to improving the volumetric energy density of the battery cell. On the other hand, if the residual space is too low, it will cause the gas to expand rapidly and the internal pressure to increase sharply during thermal runaway, increasing the risk of casing explosion.

[0053] Alternatively, in one embodiment, the average particle size of the graphite ranges from 2 micrometers to 30 micrometers.

[0054] It should be noted that the average particle size of graphite ranges from 2 micrometers to 30 micrometers. For example, the average particle size of graphite ranges from one or any two of the following: 2 micrometers, 5 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 15 micrometers, 18 micrometers, 20 micrometers, 23 micrometers, 25 micrometers, 27 micrometers, 29 micrometers, and 30 micrometers.

[0055] In this embodiment, the average particle size of graphite is controlled within the range of 2 micrometers to 30 micrometers. On the one hand, this can increase the electrode compaction density, reduce ineffective space, and indirectly increase the volumetric energy density of the battery cell. On the other hand, it can reduce the ion transport distance and improve the rate performance of the battery.

[0056] Alternatively, in one embodiment, the average particle size of silicon ranges from 2 micrometers to 10 micrometers.

[0057] It should be noted that the average particle size of silicon ranges from 2 micrometers to 10 micrometers. For example, the average particle size of silicon ranges from one or any two of the following: 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, and 10 micrometers.

[0058] In this embodiment, the average particle size of silicon ranges from 2 micrometers to 10 micrometers. By combining silicon with graphite, the overall capacity of the negative electrode can be significantly improved, directly driving the improvement of the cell's energy density. It can also shorten the diffusion path of lithium ions inside the silicon particles, reduce transmission resistance, and improve rate performance. Silicon particles with a size of 2 to 10 micrometers have relatively good mechanical strength, and the stress generated when the volume expands (>300%) is more easily buffered by the graphite framework, delaying the triggering and propagation of thermal runaway.

[0059] Alternatively, in one embodiment, the negative electrode further comprises a conductive agent and a binder; The conductive agent includes at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; the binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, and polyvinylidene fluoride.

[0060] In this embodiment, the conductive agent and binder of the negative electrode optimize the conductive network and stabilize the electrode structure, thereby reducing the risks of local overheating and internal short circuits from the source, and providing key guarantees for the safety and stability of silicon-based negative electrodes (with high volume expansion characteristics).

[0061] Alternatively, in one embodiment, the base film includes polypropylene, polyethylene, or at least one of polypropylene and polyethylene.

[0062] It should be noted that polyethylene (PE) has a melting point of approximately 130°C, and polypropylene (PP) has a melting point of approximately 167°C, both of which are below the critical temperature for thermal runaway of the battery cell (typically >200°C). When the battery cell experiences localized overheating (such as a short circuit or abnormal fast charging), the base film will melt and shrink first, blocking the pores on the film, cutting off the lithium-ion transport channels, terminating the electrochemical reaction, preventing the continuous accumulation of heat, and preventing the initiation of thermal runaway from the source.

[0063] In this embodiment, the base membrane of the separator (polypropylene / polyethylene / the blend thereof) is a physical barrier for the safety of the battery cell. Through melting, mechanical isolation, and electrolyte stability, it prevents direct contact between the positive and negative electrodes from the source, thereby suppressing internal short circuits, delaying thermal runaway, and thus improving the safety performance of the battery cell.

[0064] Optionally, in one embodiment, the thickness of the base film is 5 micrometers to 20 micrometers.

[0065] It should be noted that the thickness of the base film is 5 micrometers to 20 micrometers. For example, the thickness of the base film can be one or any two of the following values: 5 micrometers, 6 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 15 micrometers, 17 micrometers, 19 micrometers, and 20 micrometers. In this application, a base film thickness of 10 micrometers is preferred.

[0066] In this embodiment, the thickness of the base film is controlled between 5 micrometers and 20 micrometers, which is the key to balancing cell safety protection, energy density and ion transport efficiency. It can ensure the mechanical isolation and thermal runaway prevention effect, while avoiding excessive thickness from dragging down battery performance.

[0067] Alternatively, in one embodiment, the coating comprises an aramid coating, which includes inorganic fillers.

[0068] In this embodiment, the aramid coating (polyaramid) exhibits excellent thermal stability (high melting point, high decomposition temperature), mechanical strength (needle penetration resistance), and flame retardancy. During needle penetration abuse, a thicker aramid coating can more effectively prevent metal needles from directly piercing the positive and negative electrodes and causing large-area short circuits, or slow down the needle penetration speed. The aramid coating maintains its integrity at high temperatures better than traditional polyolefin separators, delaying separator thermal shrinkage and reducing instantaneous Joule heating. Even in the event of a localized short circuit, the insulation and heat resistance of the aramid help limit the expansion of the short circuit point, preventing the instantaneous release of energy from the entire battery.

[0069] Optionally, in one embodiment, the inorganic filler includes one or more of the following: alumina, boehmite, calcium carbonate, barium sulfate, barium titanate, hydrotalcite, montmorillonite, spinel, titanium dioxide, silicon dioxide, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, calcium hydroxide, and silicon carbide.

[0070] It should be noted that inorganic fillers such as alumina, boehmite, and silicon carbide have high hardness and excellent mechanical strength, which can significantly enhance the overall rigidity of the coating, resist the compression of the silicon-based negative electrode volume expansion and the puncture of electrode particles, and prevent the positive and negative electrodes from directly contacting due to the diaphragm rupture.

[0071] Inorganic fillers such as alumina, silicon dioxide, and magnesium oxide have extremely high melting points (usually >1500℃), which can maintain the coating structure in high-temperature environments (such as after the base film melts), preventing the diaphragm from completely collapsing and causing the positive and negative electrodes to conduct, thus buying time for thermal runaway suppression.

[0072] Fillers such as titanium dioxide and zirconium dioxide have stable surface properties and can form a benign interface with the electrolyte, avoiding excessive growth and shedding of the SEI film on the negative electrode (especially silicon-based negative electrodes), reducing electrolyte consumption and gas generation, and lowering the risk of battery swelling and increased internal pressure.

[0073] In this embodiment, the inorganic filler in the aramid coating enhances mechanical protection, optimizes thermal stability, and suppresses side reactions, forming a synergistic effect with the aramid matrix, significantly improving the safety redundancy of the separator, and ensuring the safety of the battery cell from three aspects: physical isolation, thermal runaway prevention, and interface stability.

[0074] Optionally, in one embodiment, the areal density of the negative electrode bifacial layer is 200~280 g / m³. 2 .

[0075] It should be noted that the areal density of the negative electrode is 200~280 g / m³. 2 For example, the areal density of the negative electrode bifacial layer can be 200 g / m³. 2 210 g / m 2 220 g / m 2 230 g / m 2 240 g / m 2 250 g / m 2 260 g / m 2 270 g / m 2 280 g / m 2 The range of one or any two of them.

[0076] In this embodiment, the areal density of the negative electrode double-sided surface is controlled at 200~280 g / m². 2 By increasing the loading of negative electrode active material, the energy density of the cell can be improved, while avoiding the drag on battery performance due to excessive areal density.

[0077] Optionally, in one embodiment, the areal density of the positive electrode bifacial layer is 400~500 g / m³. 2 .

[0078] It should be noted that the areal density of the positive electrode is 400~500 g / m³. 2 For example, the areal density of the positive electrode bifacial layer can be 400 g / m³. 2 410 g / m 2 420 g / m 2 430 g / m 2 440 g / m 2 450 g / m 2 460 g / m 2 470 g / m 2 480 g / m 2 490 g / m 2 500 g / m 2 The range of one or any two of them.

[0079] In this embodiment, the double-sided areal density of the positive electrode is controlled at 400~500 g / m². 2 By maximizing the loading of positive electrode active material, the energy density of the battery cell can be directly improved.

[0080] Optionally, in one embodiment, the volumetric energy density of the battery cell is greater than or equal to 630Wh / L.

[0081] It should be noted that the volumetric energy density (VED) of a battery cell is the ratio of the cell's rated capacity to its volume.

[0082] In this embodiment, a volumetric energy density (VED) of 630 Wh / L or greater is the core threshold for high-energy-density batteries. The aim is to maximize energy storage within a limited volume, directly driving a leap forward in the range, space utilization, and portability of end products, while also adapting to technological upgrades for high-demand scenarios. The VED directly reflects the cost-effectiveness of volume versus energy storage; a higher VED value means the battery can store more energy in the same volume, or a smaller battery volume for storing the same amount of energy.

[0083] Optionally, in one embodiment, the active material in the positive electrode includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based materials.

[0084] It should be noted that the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, which includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), and lithium-rich manganese-based materials. The positive electrode current collector is selected from aluminum foil, carbon-coated aluminum foil, and composite aluminum foil.

[0085] It should be noted that nickel-cobalt-manganese / nickel-cobalt-aluminum ternary materials include type 333 (LiNi). 0.3 Co 0.3 Mn 0.3 O2), 442 type (LiNi) 0.4 Co 0.4 Mn 0.2 O2), Type 523 (LiNi) 0.5 Co 0.2 Mn 0.3 O2), 622 type (LiNi) 0.6 Co 0.2 Mn 0.2 O2), 811 type (LiNi) 0.8 Co 0.1 Mn 0.1 O2), LiNi 0.9 Co 0.5 Al 0.5 O2, etc.

[0086] In this embodiment, the thermally stable material (LFP / LMFP) can reduce the design pressure of the cell on the cooling system and pressure relief structure. Even if the safety protection device has a slight delay in response, it can buy time to suppress thermal runaway, thereby improving the safety performance of the battery.

[0087] High-energy-density materials (such as nickel-cobalt-manganese / nickel-cobalt-aluminum ternary materials) are beneficial for improving the energy density of batteries.

[0088] Optionally, in one embodiment, the positive electrode further includes a conductive agent and a binder. Conductive agents include at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; and / or, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene.

[0089] In this embodiment, the positive electrode uses a conductive agent and a binder to reduce local heat generation through a conductive network and prevent particle shedding through structural fixation, thus providing dual protection for electrode stability and reducing safety risks such as internal short circuits and heat accumulation from the source, thereby improving the safety performance of the battery.

[0090] Alternatively, in one embodiment, the battery cell further includes an electrolyte comprising lithium salt, solvent, and additives.

[0091] The lithium salt is selected from one or more of LiPF6, LiFSI, LiTFSI, LiOTf, LiBF4, LiAsF6, and LiClO4.

[0092] The solvent can be selected from one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and propylene carbonate (PC).

[0093] The additives may be selected from one or more of the following: vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfate (DTD), methane disulfonate (MMDS), siloxane additives, lithium bis(oxalate)borate, lithium difluorophosphate, lithium difluorooxalateborate, and lithium nitrate.

[0094] Secondly, embodiments of this application provide a battery, which includes at least one of the above-described cells.

[0095] In this application, the battery form can be one of the following: prismatic battery, cylindrical battery, blade battery, and pouch battery, and at least one of the above-mentioned cells is connected in parallel or series to form a battery.

[0096] Thirdly, embodiments of this application provide an electrical device including the battery described above.

[0097] The above-described electrical equipment embodiments include the aforementioned battery and achieve the same technical effect. To avoid repetition, they will not be described again here. For relevant details, please refer to the description of the battery embodiments.

[0098] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the application is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0099] The present application will be described in detail below through embodiments.

[0100] Test method: (1) Silicon content test: The coating on the surface of the negative electrode of the battery cell is scraped off and its mass m is weighed. 涂层 The mixture was then dissolved using hydrofluoric acid and microwave digestion, and the silicon content (m) in the mixture was determined by inductively coupled plasma (ICP). Si The silicon content as a percentage of the mass of the negative electrode coating is W. si = (m Si / m 涂层 )*100%.

[0101] (2) Cell residual space test: Measure the volume V of the battery cell casing respectively 壳体 The volume V of the internal electrode assembly (a whole formed by winding or stacking positive electrode, separator, and negative electrode) of the battery cell. 电极组件 The residual space of the battery cell is obtained through the formula for residual space of the battery cell:

[0102] (3) Cell volumetric energy density test: A constant current charge-discharge test is performed at a current density of 1C within a voltage range (e.g., for ternary cathodes, a voltage range of 3.0~4.2 V). The battery discharge capacity is recorded based on the test results. The volumetric energy density of the cell is obtained by calculating the ratio of cell capacity to cell volume.

[0103] (4) Needle prick test: Each group was tested with 10 battery cells. A steel needle with a diameter of 3mm was used to pierce the battery cell at a speed of 10mm / s, and the test was conducted for 1 minute. The phenomenon was observed and recorded.

[0104] Example 1 (1) Preparation of negative electrode: Graphite, SiO x(0 < x < 2), carbon black as the conductive agent, and the binder are mixed in a mass ratio of 91.7:3.3:2.5:2.5 to form a mixture. Among them, the binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2. An appropriate amount of water is added to the above mixture as a solvent, and it is stirred evenly to form a negative electrode paste. The negative electrode paste is evenly coated on the surface of an 8-micron-thick negative electrode current collector copper foil with a scraper, and both sides are coated, and the thickness of each layer is controlled at 84 microns, and it is dried in an oven at 80 °C for 24 h to obtain a negative electrode sheet.

[0105] (2) Preparation of the positive electrode sheet: Using LiNi 0.9 Co 0.5 Al 0.5 O2 as the positive electrode active material, the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride as the binder are mixed in a mass ratio of 93:5:2, and an appropriate amount of N-methylpyrrolidone is added as a solvent, and it is stirred evenly to form a positive electrode paste. The positive electrode paste is evenly coated on the surface of a 16-micron-thick positive electrode current collector aluminum foil with a scraper, and both sides are coated. The coating surface density is controlled so that the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet N / P = 1.1. The obtained electrode sheet is dried in an oven at 80 °C for 24 h to obtain a positive electrode sheet.

[0106] (3) Preparation of the separator: Using a 10-micron-thick polyethylene as the base film, a 2-micron aramid coating is coated on one side of the base film surface. The aramid coating contains 25 wt% aluminum oxide inorganic filler, and a separator is obtained after drying.

[0107] (4) Preparation of the battery cell The positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to obtain an electrode assembly, and the volume V of the electrode assembly is measured 电极组件 , the volume V of the battery cell housing is measured 壳体 , and the residual space R of the battery cell is calculated to be 15% according to the battery cell residual space relational formula. A soft package bag with the required volume is obtained by pre-stamping and forming. The electrode assembly is placed in the soft package bag, and an appropriate amount of electrolyte (the electrolyte is 1 M LiPF6-EC / DEC (1:1 vol%)) is injected and then heat-sealed to obtain the battery cell to be tested.

[0108] In Example 1, the battery cell safety factor x is 12.

[0109] Example 2 The difference between Example 2 and Example 1 is: In the preparation of the separator in step (3), the thickness of the aramid coating is adjusted to 4 microns; in the preparation of the battery cell in step (4), the residual space of the battery cell is adjusted to 10%.

[0110] The remaining steps and dosages are the same as those in Example 1, and the battery cell to be tested is obtained.

[0111] In Example 2, the cell safety factor x is 16.

[0112] Example 3 The difference between Example 3 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The addition amount was adjusted to 3.9%.

[0113] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0114] In Example 3, the cell safety factor x is 10.

[0115] Example 4 The difference between Example 4 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 3.9%, and the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers; and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 10%.

[0116] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0117] In Example 4, the cell safety factor x is 13.3.

[0118] Example 5 The difference between Example 5 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 3.9%, and the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers.

[0119] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0120] In Example 5, the cell safety factor x is 20.

[0121] Example 6 The difference between Example 6 and Example 1 is: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 6.6%, and the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers.

[0122] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0123] In Example 6, the cell safety factor x is 12.

[0124] Example 7 The difference between Example 7 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 7.9%, and the thickness of the aramid coating in step (3) of the membrane preparation was adjusted to 4 micrometers.

[0125] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0126] In Example 7, the cell safety factor x is 10.

[0127] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The addition amount was adjusted to 2.6%.

[0128] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0129] In Comparative Example 1, the cell safety factor x is 15.

[0130] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is as follows: In step (4) of cell preparation, the residual space of the cell is adjusted to 5%.

[0131] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0132] In Comparative Example 2, the cell safety factor x is 4.

[0133] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is as follows: In step (4) of cell preparation, the residual space of the cell is adjusted to 10%.

[0134] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0135] In Comparative Example 3, the cell safety factor x is 8.

[0136] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is as follows: In step (4) of cell preparation, the residual space of the cell is adjusted to 19%.

[0137] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0138] In Comparative Example 4, the cell safety factor x is 15.2.

[0139] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is as follows: In step (3), the thickness of the aramid coating in the preparation of the diaphragm is adjusted to 1 micrometer.

[0140] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0141] In Comparative Example 5, the cell safety factor x is 6.

[0142] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is as follows: In step (4) of cell preparation, the residual space of the cell is adjusted to 5%.

[0143] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0144] In Comparative Example 6, the cell safety factor x is 8.

[0145] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is as follows: In step (3), the thickness of the aramid coating in the preparation of the diaphragm is adjusted to 4 micrometers.

[0146] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0147] In Comparative Example 7, the cell safety factor x is 24.

[0148] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is as follows: In step (3) of the preparation of the diaphragm, the thickness of the aramid coating is adjusted to 5 micrometers. In step (4) of the preparation of the battery cell, the residual space of the battery cell is adjusted to 5%.

[0149] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0150] In Comparative Example 8, the cell safety factor x is 10.

[0151] Comparative Example 9 The difference between Comparative Example 9 and Example 1 is as follows: In step (3) of the preparation of the diaphragm, the thickness of the aramid coating is adjusted to 5 micrometers. In step (4) of the preparation of the battery cell, the residual space of the battery cell is adjusted to 10%.

[0152] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0153] In Comparative Example 9, the cell safety factor x is 20.

[0154] Comparative Example 10 The difference between Comparative Example 10 and Example 1 is as follows: In step (3) of the preparation of the diaphragm, the thickness of the aramid coating is adjusted to 5 micrometers. In step (4) of the preparation of the battery cell, the residual space of the battery cell is adjusted to 15%.

[0155] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0156] In Comparative Example 10, the cell safety factor x is 30.

[0157] Comparative Example 11 The difference between Comparative Example 11 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of added is adjusted to 3.9%, and the residual space of the cell in step (4) is adjusted to 5%.

[0158] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0159] In Comparative Example 11, the cell safety factor x is 3.3.

[0160] Comparative Example 12 The difference between Comparative Example 12 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of added is adjusted to 3.9%, and the residual space of the cell in step (4) is adjusted to 10%.

[0161] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0162] In Comparative Example 12, the cell safety factor x is 6.7.

[0163] Comparative Example 13 The difference between Comparative Example 13 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 3.9%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 5%.

[0164] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0165] In Comparative Example 13, the cell safety factor x is 6.7.

[0166] Comparative Example 14 The difference between Comparative Example 14 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiOx The amount of added is adjusted to 6.6%, and the residual space of the cell in step (4) is adjusted to 5%.

[0167] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0168] In Comparative Example 14, the cell safety factor x is 2.

[0169] Comparative Example 15 The difference between Comparative Example 15 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of added is adjusted to 6.6%, and the residual space of the cell in step (4) is adjusted to 10%.

[0170] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0171] In Comparative Example 15, the cell safety factor x is 4.

[0172] Comparative Example 16 The difference between Comparative Example 16 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The addition amount has been adjusted to 6.6%.

[0173] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0174] In Comparative Example 16, the cell safety factor x is 6.

[0175] Comparative Example 17 The difference between Comparative Example 17 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 6.6%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 5%.

[0176] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0177] In Comparative Example 17, the cell safety factor x is 4.

[0178] Comparative Example 18 The difference between Comparative Example 18 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO xThe amount of aramid added was adjusted to 6.6%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 10%.

[0179] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0180] In Comparative Example 18, the cell safety factor x is 8.

[0181] Comparative Example 19 The difference between Comparative Example 19 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of added is adjusted to 7.9%, and the residual space of the cell in step (4) is adjusted to 4%.

[0182] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0183] In Comparative Example 19, the cell safety factor x is 1.3.

[0184] Comparative Example 20 The difference between Comparative Example 20 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of added is adjusted to 7.9%, and the residual space of the cell in step (4) is adjusted to 9%.

[0185] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0186] In Comparative Example 20, the cell safety factor x is 3.0.

[0187] Comparative Example 21 The difference between Comparative Example 21 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 7.9%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 4%.

[0188] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0189] In Comparative Example 21, the cell safety factor x is 2.7.

[0190] Comparative Example 22 The difference between Comparative Example 22 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO xThe amount of aramid added was adjusted to 7.9%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 10%.

[0191] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0192] In Comparative Example 22, the cell safety factor x is 6.7.

[0193] Comparative Example 23 The difference between Comparative Example 23 and Example 1 is as follows: In the preparation of the negative electrode in step (1), SiO x The amount of aramid added was adjusted to 9.2%, the thickness of the aramid coating in the preparation of the diaphragm in step (3) was adjusted to 4 micrometers, and the residual space of the battery cell in the preparation of the battery cell in step (4) was adjusted to 14%.

[0194] The remaining steps and dosages are the same as in Example 1, and the battery cell to be tested is obtained.

[0195] In Comparative Example 23, the cell safety factor x is 8.0.

[0196] The negative electrodes of the cells obtained in each embodiment and comparative example were tested for silicon content, volumetric energy density, and needle penetration. The results are shown in Table 1.

[0197] Table 1

[0198] As can be seen from Table 1, increasing the silicon content in the negative electrode is beneficial to improving the energy density of the battery. However, if the content is too high (Comparative Example 23), it will lead to a decrease in the safety performance of the cell. For example, in Examples 6 and 7, the silicon content in the negative electrode is high, and the VED of Examples 6 and 7 is much higher than 630 Wh / L. The needle penetration results show that one cell exploded. However, compared with the multiple cell explosions in the comparative example, Examples 6 and 7 significantly improve the safety performance of the cell.

[0199] Increasing the thickness of the aramid coating on the diaphragm surface can improve the safety performance of the battery cell, but if it is too thick (comparative examples 8-10), it will greatly affect ion diffusion, thereby affecting the battery cell capacity output and causing a decrease in energy density.

[0200] A larger residual space can improve battery safety performance, but excessive residual space will lead to a decrease in battery VED. The cell safety factor x can comprehensively reflect the battery safety performance. The battery safety performance increases with the increase of x. When x≥10, the cell safety performance is good, but too large x (Comparative Example 7) will also lead to a decrease in battery VED.

[0201] Since the embodiments of this application need to take into account both the volumetric energy density and safety performance (needle penetration results), although the needle penetration results of comparative examples 1, 4, 8, and 9 are comparable to the test results of the embodiments, the volumetric energy density of the above comparative examples (all less than 630 Wh / L) is lower than that of the embodiments (greater than or equal to 630 Wh / L).

[0202] In the embodiments of this application, under higher volumetric energy density levels (greater than or equal to 630 Wh / L), most cells do not explode or only one cell explodes; in contrast, in the comparative examples, under volumetric energy density ranges (greater than or equal to 630 Wh / L), more than five cells explode; this demonstrates that the embodiments can reduce the explosion range of cells. Therefore, the solution of the embodiments of this application can improve the safety performance of cells while taking into account volumetric energy density.

[0203] In summary, when the cell safety factor x is controlled at 10~20, the silicon content as a percentage of the negative electrode coating is controlled at 2.5%~6%, the coating thickness on the base film surface is controlled at 2 micrometers~4 micrometers, and the residual space of the cell is controlled at 5%~15%, the corresponding cell can achieve both high energy density and safety performance.

[0204] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0205] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly and a housing, wherein the electrode assembly is encapsulated within the housing, and the ratio of the remaining space within the housing to the volume of the battery cell is the residual space of the battery cell. The electrode assembly includes a positive electrode, a separator, and a negative electrode; the negative electrode includes an active material, which includes graphite and silicon; the separator includes a base film and a coating disposed on the surface of the base film. The battery cell has a corresponding battery cell safety factor x. The relationship between the battery cell safety factor and the residual space of the battery cell, the coating thickness on the surface of the base film, and the mass percentage of silicon in the negative electrode coating is as follows: Where R represents the residual space of the battery cell, and the relationship of the residual space of the battery cell is as follows: Among them, V 电极组件 V represents the volume of the electrode assembly in the battery cell; 壳体 This indicates the volume of the casing within the battery cell; the residual space within the battery cell is 5% to 15%. d 涂层 This indicates the coating thickness on the surface of the base film, which is 2 micrometers to 4 micrometers. W Si This indicates the percentage of silicon content in the negative electrode coating by mass, where the silicon content is 2.5% to 6% by mass. The cell safety factor x ranges from 10 to 20.

2. The battery cell according to claim 1, characterized in that, The graphite includes at least one of natural graphite and artificial graphite; and / or The silicon includes at least one of silicon carbide particles, pure silicon particles, and SiO x (0 < x < 2) particles; and / or, The average particle size of the graphite ranges from 2 micrometers to 30 micrometers; and / or, The average particle size of the silicon ranges from 2 micrometers to 10 micrometers.

3. The battery cell according to claim 1, characterized in that, The negative electrode also includes a conductive agent and a binder; The conductive agent includes at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; and / or, The adhesive includes at least one of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, and polyvinylidene fluoride.

4. The battery cell according to claim 1, characterized in that, The base film comprises polypropylene, polyethylene, or at least one of polypropylene and polyethylene; and / or, The thickness of the base film is 5 micrometers to 20 micrometers.

5. The battery cell according to claim 1, characterized in that, The coating includes an aramid coating, and the aramid coating includes inorganic fillers.

6. The battery cell according to claim 5, characterized in that, The inorganic filler includes one or more of the following: alumina, boehmite, calcium carbonate, barium sulfate, barium titanate, hydrotalcite, montmorillonite, spinel, titanium dioxide, silicon dioxide, zirconium dioxide, magnesium oxide, calcium oxide, beryllium oxide, magnesium hydroxide, calcium hydroxide, and silicon carbide.

7. The battery cell according to claim 1, characterized in that, The anode double-sided surface density is 200~280 g / m³. 2 , and / or The positive electrode has a double-sided surface density of 400~500 g / m³. 2 .

8. The battery cell according to any one of claims 1-7, characterized in that, The volumetric energy density of the battery cell is greater than or equal to 630 Wh / L.

9. The battery cell according to claim 8, characterized in that, The active material in the positive electrode includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based materials.

10. The battery cell according to claim 9, characterized in that, The positive electrode also includes a conductive agent and a binder. The conductive agent includes at least one of conductive graphite, carbon black, carbon nanotubes, and graphene; and / or, The adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene.

11. A battery, characterized in that, The battery includes at least one cell as described in any one of claims 1-10.

12. An electrical appliance, characterized in that, Includes the battery as described in claim 11.

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