Battery, electrochemical apparatus, and electrical apparatus

Abstract

The present application discloses a battery, an electrochemical apparatus, and an electrical apparatus. The battery comprises a battery cell, the battery cell comprising an electrode sheet and a tab provided on the electrode sheet. A negative electrode active material layer of the electrode sheet contains silicon, and the percentage content of silicon in the negative electrode active material layer is b, the unit being %. The longest distance between the tab and an end portion of the electrode sheet in the length direction is d, the width of the connection position between the tab and the electrode sheet is m, and the units of d and m are the same; and b, d, and m satisfy the following relational expression (I). In the present application, by means of comprehensively controlling the values of formula (II), a battery having higher energy density can be obtained, and it can also be ensured that the battery has better battery fast charging performance.

Description

A battery, an electrochemical device, and an electrical device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411807291.5, filed on December 10, 2024, entitled “A Battery, Electrochemical Device and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, specifically to a battery, an electrochemical device, and an electrical device. Background Technology

[0004] A battery cell includes tabs, which can be classified as either top-mounted tabs or side-mounted tabs based on their location. Side-mounted tabs extend from the short side of the electrode along its long side, while top-mounted tabs extend from the long side of the electrode along its short side. Conventional battery cells typically have the tabs located on or near the short side, and are manufactured through stacking or winding.

[0005] The tabs are used to transmit the current in the battery cell to the external circuit. Currently, in order to improve the energy density of the battery, the length of the battery tabs is usually made longer and longer. This results in an uneven distribution of current density along the length of the tabs, especially on the tabs far from the tabs, where the current density is lower. This increases the impedance of the tabs, which is not conducive to improving the fast charging performance of the battery. Summary of the Invention

[0006] Therefore, the technical problem to be solved by this application is that batteries in the prior art have poor fast charging performance, thereby providing a battery, electrochemical device and electrical device to improve the above-mentioned problem.

[0007] To achieve the above objectives, this application provides a battery, including a cell, wherein the cell includes a negative electrode sheet and a tab disposed on the negative electrode sheet; the negative electrode sheet contains silicon in its negative electrode active material layer, and the mass percentage of silicon in the negative electrode active material layer is b (in %); the longest distance between the tab and the end of the negative electrode sheet, parallel to the long side direction of the negative electrode sheet, is d (in mm); the lead-out direction of the tab is a first direction, and the dimension of the connection between the tab and the negative electrode sheet perpendicular to the first direction is the width m of the tab (in mm); the b, d, and m satisfy the following relationship:

[0008] This application provides an electrochemical device comprising the battery described above.

[0009] This application provides an electrical device comprising the aforementioned electrochemical device.

[0010] The beneficial effects of this application are as follows:

[0011] This application discloses a battery including a cell. By controlling the mass percentage b of silicon in the negative electrode active material layer, the longest distance d between the tabs and the two ends along the long side of the negative electrode sheet, and the width m of the tabs, b, d, and m are made to satisfy... The relationship between the parameters is as follows: By controlling the above parameters, this application can effectively improve the current-carrying capacity of the electrode and improve the fast-charging performance of the battery while ensuring the battery energy density. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0013] Figure 1 is a schematic diagram of the structure in which the tab leads out in the top direction in an embodiment of this application;

[0014] Figure 2 is a schematic diagram of the structure in which the tab leads out to the side in an embodiment of this application. Detailed Implementation

[0015] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application. Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in the art. Reagents or instruments used, where the manufacturer is not specified, are all conventional reagent products that can be obtained commercially. The "scope" disclosed in this application is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular scope. The scope defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope. For example, if a scope of 50%-90% and 60%-80% is listed for a specific parameter, it is expected that the scopes are 50% to 80% and 60% to 90%. Furthermore, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are listed, then the following ranges can all be expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range “a–b” represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range “0.5–4” indicates that all real numbers between “1–4” have been listed herein, such as: 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, etc.; “0.5–4” is simply a shortened representation of these numerical combinations.

[0016] This application provides a battery, including a cell, the cell comprising a negative electrode and a tab disposed on the negative electrode; the negative electrode active material layer of the negative electrode contains silicon, the mass percentage of silicon in the negative electrode active material layer is b, in %; the longest distance between the tab and the end of the electrode, parallel to the long side direction of the negative electrode, is d, in mm; the lead-out direction of the tab is a first direction, and the dimension of the connection between the tab and the electrode in the first direction is the width m of the tab, in mm; the b, d, and m satisfy the following relationship: In this application The value can be any value between -3.1 and -0.11, such as: -3.1, -3.0, -2.5, -2, -1.5, -1, -0.5, -0.13, -0.11, etc.

[0017] In this application, b represents the mass percentage of silicon in the negative electrode active material layer. Adding silicon to the negative electrode active material layer can improve the overall energy density of the battery. However, the addition of silicon also affects the impedance of the electrode. A higher silicon content will increase the electrode impedance, affecting fast charging performance. d represents the distance between the tab and the electrode end. The tab is used for current carrying, and the distance between the tab and the electrode end affects the current transmission distance. Positions further away from the tab have increased current transmission impedance, resulting in lower current density at the end of the electrode furthest from the tab, thus affecting the battery's fast charging performance. m represents the connection width between the tab and the electrode body. The connection width affects the current magnitude; a larger connection width results in a larger current carrying capacity, less resistance and energy loss due to resistance, and a larger current.

[0018] This application improves the problem of increased electrode impedance caused by long electron transport paths by comprehensively controlling the relationship between silicon content b, distance d between the tab and the end of the negative electrode, and connection width m between the tab and the electrode body, while also taking into account the battery energy density. Specifically, when the b content is too low, the energy density is low; when the b and d contents are too high, the electrode impedance will be large; when the m value is too small, the overcurrent capacity will be poor. Therefore, if the value of m / (d×b) is too small, it will cause the electron transport path to be too long, the electrode end impedance to be large, and thus the DCR to be large, resulting in poor fast charging performance. If the value of m / (d×b) is too large, the DCR will be small, the fast charging performance will be good, but the battery energy density will be low. Research has found that the value of m / (d×b) is not linearly related to fast charging performance and energy density, and it is not possible to simply screen out batteries with good fast charging performance and energy density based on the value of m / (d×b). This application uses an lg function to process the value of m / (d×b), and the processed value can achieve reasonable data analysis and application. Through the processed data, batteries with good fast charging performance and energy density can be effectively obtained. That is, by controlling A value between -3.1 and -0.11 can achieve the goal of improving the fast charging performance of the battery while meeting the energy density requirements.

[0019] Furthermore, by When the value is controlled within a more preferred range of -1.8 to -0.7, the overall performance of the energy density and fast charging performance of the battery in this application is better.

[0020] In one of the alternative approaches, this application optimizes the percentage content b of silicon in the negative electrode active material layer, in %; specifically, the b value cannot be too small, as a small b value will affect the battery energy density; the b value cannot be too large either, as a large b value and a large silicon content will easily cause the electrode to have greater impedance, thereby affecting the fast charging performance of the electrode. The reasons why excessive silicon content leads to greater electrode impedance are as follows: 1) Silicon itself has poor conductivity. Compared with carbon materials, pure silicon has much lower conductivity. When the silicon content increases, the overall conductivity of the composite material decreases, resulting in increased internal resistance and affecting fast charging performance; 2) Silicon has large volume changes. During charging and discharging, silicon undergoes significant volume expansion and contraction, up to about 300%. This large volume change can lead to poor contact between material particles, or even breakage, forming "dead silicon," which obstructs electron transport paths, increases resistance to electrochemical reactions, and thus increases the battery's internal resistance; 3) During the first charge-discharge cycle, a solid electrolyte interphase (SEI) film forms on the silicon surface. Due to the large volume change of silicon, the SEI film continuously breaks and reforms during charging and discharging. This not only consumes lithium ions in the electrolyte but also increases interfacial impedance, further increasing the battery's internal resistance; 4) With the increase of silicon content, the structural stability of the composite material deteriorates, making it prone to pulverization and detachment, reducing the effective contact area and increasing the battery's contact resistance. Therefore, the range of the b value in this application is 1.25 to 16, preferably 2.5 to 7.5. For example, the b% can be controlled to be 1.25%, 1.5%, 2%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, etc.

[0021] In one alternative embodiment, this application optimizes the longest distance d between the tab and the ends of the negative electrode sheet along the long side extension direction. When the tab extends from the long side extension direction of the negative electrode sheet, the longest distance from the tab to the end of the electrode sheet is the length of the electrode sheet; when the tab is extended perpendicular to the long side extension direction of the electrode sheet, the longest distance from the tab to the end of the electrode sheet is the distance between the tab and the end of the electrode sheet located away from the tab. In this application, the d-value cannot be too large. If the d-value is too large, the electron transport path will be too long, resulting in uneven current density distribution and high electrode impedance, which in turn affects fast charging performance. Therefore, for electrodes of the same length, the smaller the d-value, the better. However, for electrodes of different lengths, the d-value cannot be too small, as this usually requires shortening the electrode length, which in turn affects the energy density of the battery. Therefore, in this application, the d-value is preferably 42 to 1000, preferably 250 to 450, with units of mm. For example, the d-value can be controlled to be 42, 45, 50, 60, 80, 100, 150, 200, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 960, 1000, etc.

[0022] In one of the alternative methods, the lead-out direction of the tab is a first direction. Perpendicular to this first direction, the dimension of the connection between the tab and the negative electrode is the width m of the tab. This application optimizes the width m of the connection position between the tab and the negative electrode. The value of m cannot be too small; if m is too small, the current-carrying cross-section is small, the current-carrying capacity is low, the current-carrying capacity of the electrode is poor, and the internal resistance increases. Furthermore, the value of m cannot be too high either. If m is too high, it may lead to problems such as increased impedance, low energy density, and increased packaging difficulty. This is because the space in a battery is limited, and an excessively large tab may prevent the battery from fitting into this space, affecting battery integration and increasing the packaging difficulty. Moreover, increasing the size of the tab will increase the overall weight of the battery, thereby reducing the energy density (WH / KG). Therefore, in this application, the value of m is 9 to 960, preferably 50 to 180; for example, the value of m is controlled to be 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 80, 100, 150, 200, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 960, etc.

[0023] This application further optimizes the areal density of the negative electrode active material layer. Areal density also affects the battery's fast-charging performance. A lower areal density results in a thinner electrode, lower battery impedance, and a shorter lithium-ion transport distance, which is beneficial for improving fast-charging performance. However, the areal density cannot be too low, as this leads to less coated active material and a lower battery energy density. Conversely, a higher areal density results in a longer lithium-ion transport path, higher battery internal resistance, and potential congestion along the lithium-ion migration path. This can prevent complete lithium-ion insertion and extraction in a short time, increasing polarization and consequently reducing charging efficiency during both regular and fast charging, thus hindering the improvement of fast-charging capabilities. The preferred areal density in this application is 90-300 g / m³. 2 For example: controlling the areal density to be 90 g / m³. 2 100g / m 2 150g / m 2 200g / m 2 250g / m 2 300g / m 2 wait.

[0024] This application further optimizes the compaction density of the negative electrode active material layer. Excessive compaction density reduces the interparticle distance, resulting in tighter contact and enhanced electronic conductivity. However, it also reduces or blocks ion movement channels, hindering the rapid movement of a large number of ions. The migration speed of lithium ions cannot keep up with the charging speed, leading to significant internal polarization of the battery. During fast charging, the battery easily reaches its voltage limit, causing it to easily switch to a lower charging rate, resulting in a lower charging rate to achieve the required SOC for fast charging, thus reducing fast charging capability and increasing charging time. Conversely, insufficient compaction density increases the interparticle distance, increasing ion channels and electrolyte absorption, which is beneficial for rapid ion movement. However, the excessive interparticle spacing leads to longer migration paths for lithium ions within the electrode. This increases the diffusion time and difficulty of lithium ions within the electrode. During fast charging, lithium ions need to rapidly migrate from the electrolyte into the electrode material for intercalation. If the migration path of lithium ions is too long, it will slow down the charging speed and affect fast charging efficiency. Therefore, this application controls the compaction density to be 1.2–2.3 g / m³. 3 When the compaction density is relatively low, for example, 1.2–1.6 g / m³, the compaction density is lower. 3 At that time, control formula A value within the range of -1.8 to -0.7 can enable the battery to have better fast charging performance; when the compaction density is relatively high, for example, 1.6 to 2.3 g / m³, the compaction density is also higher. 3 When the formula m can be controlled within the range of 50 to 960, the battery can achieve superior fast-charging performance. The aforementioned compaction density can be 1.2 g / m³. 3 1.4g / m 3 1.5g / m 3 1.6g / m 3 1.7g / m 3 1.8g / m 3 1.9g / m 3 2.0g / m 3 2.3g / m 3 wait.

[0025] As an optional configuration, the tab is a side-out tab, that is, the tab extends from the long side of the negative electrode plate and is perpendicular to the tab leading direction. The ratio of the tab width to the width of the negative electrode plate is greater than or equal to 0.5 and less than or equal to 1. This configuration can better increase the current carrying capacity, thereby reducing the internal resistance and improving the fast charging performance of the battery cell.

[0026] As an optional configuration, in order to ensure a high energy density, the long side length of the negative electrode sheet is ≥300mm; the long side length of the negative electrode sheet can be 300-1100mm; specifically, it can be 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm, or 1100mm.

[0027] And / or, the battery cell is a laminated battery cell, which refers to a battery cell formed by laminating a positive electrode, a negative electrode, and a separator through a lamination process.

[0028] The following appropriately discloses embodiments of an electrochemical device and an electrical device according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0029] [Electrochemical device]

[0030] The electrochemical device in this application is a secondary battery, also known as a rechargeable battery or storage battery, which refers to a battery that can be used again after being discharged by recharging to activate the active materials.

[0031] Typically, a secondary battery consists of a battery cell, an electrolyte, and an outer casing. The battery cell includes electrodes (positive and negative), tabs on the electrodes, and a separator between the positive and negative electrodes. The tabs are usually integrally formed with the current collectors on the electrodes. The battery cell and electrolyte are assembled inside the outer casing. During charging and discharging, active ions (such as lithium ions) move back and forth between the positive and negative electrodes, inserting and releasing. The separator, located between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, located between the positive and negative electrodes, mainly serves to conduct active ions.

[0032] As an example, the preparation process of a secondary battery is as follows: Positive and negative electrode sheets are prepared separately; tabs are formed during the electrode sheet forming process. Specifically, during electrode sheet processing, a slurry is first coated onto the current collector, forming a coated area and a blank area on the current collector; after drying, it is rolled and then cut, with tabs cut out from the blank area; the material of the tabs is the same as the material of the current collector in the electrode sheet. For example, if the current collector material in the negative electrode sheet is copper, the material of the tabs on the negative electrode sheet is also copper. The electrode sheets with tabs and the separator are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, they are wound, placed in an outer packaging shell, dried, and injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a secondary battery is obtained.

[0033] [Positive electrode tablets]

[0034] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which can be any existing publicly disclosed positive electrode active material or a positive electrode active material optimized based on existing materials.

[0035] This application does not impose any particular limitation on the type of positive electrode active material for the positive electrode sheet. As an example, the positive electrode active material in this application includes lithium-containing transition metal oxides (e.g., LiCoO2), phosphides (e.g., LiFePO4), or lithium intercalation compounds (e.g., positive electrode materials for binary lithium batteries such as lithium cobalt oxide and lithium nickel oxide, or positive electrode materials for ternary lithium batteries such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide). As one possible arrangement, the positive electrode active material in this application is preferably LiNi. x Co y Mn z O2 material, where 1>x≥0.5, x+y+z=1.

[0036] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, rolling, cutting and other processes.

[0037] In this application, the binder is used to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. This application does not impose any particular limitation on the type of binder for the positive electrode sheet; the binder can be any conventional choice in the battery industry. Specifically, the binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethyl cellulose (CMC), or sodium alginate.

[0038] This application does not impose any particular restrictions on the positive electrode current collector, as long as it is conductive and will not cause adverse chemical changes in the battery, and can be made of, for example: stainless steel, aluminum, nickel, titanium, sintered carbon; or aluminum or stainless steel that has been surface treated with one of carbon, nickel, titanium, silver, etc.

[0039] [Negative electrode plate]

[0040] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer contains silicon; that is, the negative electrode active material included in the negative electrode active material layer includes at least a silicon-based material. This application does not specifically limit the type of silicon-based material. As an example, the silicon-based material can be one or more of silicon-oxygen materials and silicon-carbon materials. In some embodiments, the negative electrode active material in the negative electrode active material layer may also optionally include one or more of artificial graphite, natural graphite, and hard carbon.

[0041] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and after drying, rolling, cutting and other processes, a negative electrode sheet with tabs can be obtained.

[0042] This application does not specifically limit the type of negative electrode conductive agent. In some embodiments, as an example, the negative electrode conductive agent can be one or more of conventional negative electrode conductive agents such as acetylene black and carbon nanotubes.

[0043] This application does not specifically limit the type of negative electrode binder. In some embodiments, as an example, the binder can be one or more of conventional negative electrode binders such as styrene-butadiene rubber latex (SBR) and polyvinylidene fluoride (PVDF).

[0044] This application does not impose specific limitations on the type of negative electrode current collector. In some embodiments, as an example, the negative electrode current collector can be one of the conventional negative electrode current collectors such as copper foil.

[0045] Electrolyte

[0046] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. As an example, the electrolyte in this application can be any electrolyte suitable for electrochemical energy storage devices in the art. The electrolyte includes an electrolyte and a solvent; the electrolyte typically includes a lithium salt, and additives may also be added to the electrolyte.

[0047] Specifically, the lithium salt includes at least one selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte solution can be 0.5–5 mol / L.

[0048] Specifically, the solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0049] In some implementations, as an example, the additive may be a conventional electrolyte additive such as fluoroethylene carbonate (FEC), chloroethylene carbonate (CEC), or vinylene carbonate (VC).

[0050] [Septum]

[0051] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0052] In some embodiments, as an example, the separator is one of PP, PE, and PP / PF, and the surface of the separator may be coated with an inorganic coating and / or an organic coating. The inorganic coating may be selected from alumina ceramic layers, osmium silicate, etc.; the organic coating may be selected from PVDF, etc.

[0053] Example

[0054] An electrochemical device, such as a secondary battery, includes a positive electrode, a negative electrode with tabs, a separator, an electrolyte, and an outer casing.

[0055] 1. Preparation of positive electrode sheet

[0056] The specific preparation process of the positive electrode is as follows: obtaining the positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 O2 is used to mix the positive electrode active material, conductive agent acetylene black, and binder PVDF at a mass ratio of 92:4:4. NMP solvent is added and the mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of an aluminum foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet is obtained.

[0057] 2. Preparation of negative electrode sheet

[0058] The specific preparation process is as follows: A mixture of silicon carbon and graphite, the negative electrode active materials, is obtained according to the mass ratio shown in Table 1. The mixture, conductive agent SWCNT, conductive agent SP, thickener CMC, binder SBR, and binder PAA are mixed in a mass ratio of 96:0.05:0.95:0.2:1.5:1.3. Deionized water is added, and the mixture is stirred under vacuum until the system is homogeneous, resulting in a negative electrode slurry. This negative electrode slurry is coated onto two surfaces of a copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, a negative electrode sheet with tabs is obtained. The tabs have two lead-out directions: one is top-out as shown in Figure 1, and the other is side-out as shown in Figure 2. In this application, the width of the negative electrode sheet is 200 mm. The parameters of the tab lead-out direction, the compaction density of the negative electrode sheet, the areal density of the negative electrode sheet, the length L of the slit negative electrode sheet, the longest distance d from the tab to the end of the negative electrode sheet, and the width of the tab are shown in Table 1.

[0059] The aforementioned silicon-carbon anode active material is prepared by CVD deposition. The preparation process of this silicon-carbon is as follows: through the adsorption force of porous carbon, silane (~450℃, silane decomposes to produce elemental silicon) is gradually permeated into the carbon skeleton at different temperatures; acetylene carbon coating (~550℃) forms a stable coated carbon layer / a-Si@a-PC structure on the surface of silicon-carbon; this application can control the number of silicon grains deposited in porous carbon by controlling parameters such as silane flow rate and deposition time, thereby adjusting the percentage content of silicon in the anode active material layer.

[0060] 3. Acquisition of the diaphragm

[0061] In this embodiment, the diaphragm is selected as a diaphragm with a coating on a base membrane. The base membrane is selected as polyethylene (PE), and the coating is an alumina ceramic layer.

[0062] 4. Preparation of electrolyte

[0063] The preparation process is as follows: In an argon-filled glove box, fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and propylene carbonate (PC) are mixed in a mass ratio of 15:20:60:5 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent. Next, 0.5% of 1,3-propanesulfonyl lactone, 0.5% of tris(trimethylsilyl)phosphate, and 1% of vinyl sulfate are added to the electrolyte solution. The mixture is stirred until completely dissolved to prepare an electrolyte solution with a lithium salt concentration of 1.3M.

[0064] 5. Assembly of secondary batteries

[0065] The specific process is as follows: the positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. Then, the electrode assembly is obtained through a stacking process. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After conventional vacuum sealing, settling, formation, and shaping processes, a lithium-ion secondary battery is obtained.

[0066] Table 1

[0067] In Table 1 above, the test methods for parameters b, areal density, and compacted density are as follows:

[0068] 1. Test of the percentage content b of silicon element in the negative electrode active material layer:

[0069] The silicon content in the negative electrode was determined using the alkaline dissolution-ICP method. Specifically, the battery was discharged at 0.33C, cleaned with DMC solvent, soaked for 48 hours, dried at 60℃, and the powder of the negative electrode active material layer was scraped off. A sample of the powder was weighed and placed in a nickel crucible pre-filled with potassium hydroxide. A small amount of potassium hydroxide was added to cover the sample surface, and two drops of ethanol were added. The mixture was heated on an electric furnace until the potassium hydroxide melted and dehydrated. Then, it was transferred to a muffle furnace at 1100℃ and kept at this molten temperature for 8 hours. The nickel crucible was removed and allowed to cool slightly. The sample was placed in a 300mL plastic beaker, and hot water was added for extraction. After the reaction, the crucible was washed out. HCl was added to the extract for acidification, and hydrogen peroxide and hydrochloric acid were added to form a mixed acid to further convert the silicon compounds to silicon ions. After cooling, the extract was washed out with water and transferred to a 100mL volumetric flask. The volume was adjusted and the solution was shaken well. After standing, the solution was transferred to another 100mL volumetric flask, adjusted to volume, shaken well, and allowed to stand until clear to obtain the test solution. At the same time, a blank solution is prepared as a control. No sample is added to the blank solution. The blank sample control is prepared according to the operation procedure, which can eliminate the possible influence of the operation.

[0070] ICP testing was performed on the solution to be tested. The element detection spectral wavelength was selected, and the experimental conditions were set: Based on the characteristics of the sample and the ICP testing of the solution to be tested, the element detection spectral wavelength of Si was selected as 288.158 nm, and the Si content of the element was determined by ICP testing.

[0071] 2. Measurement of the longest distance d between the tab and the end of the electrode along its length, and the width m at the connection point between the tab and the electrode:

[0072] The longest distance d from the tab to the end of the electrode along the length direction is shown in Figure 1, where L is the length of the electrode.

[0073] 3. Measurement of the areal density and compaction density of the negative electrode active material layer;

[0074] The battery under test was charged to 0% SOC and disassembled in a closed environment at around 25°C. The negative electrode sheet was obtained after disassembly and immersed in DMC for 48 hours. The DMC was replaced every 24 hours. The cleaned negative electrode sheet was placed in an oven at 70°C and baked for 2 hours to remove the residual DMC solvent and obtain the electrode sheet to be tested.

[0075] A sampler is used to take samples from the electrode to be tested, obtaining circular pieces with a fixed area, denoted as S0. To ensure testing accuracy, the middle position of the electrode is selected for sampling, and three or more circular pieces are taken as parallel samples. The weight m1 of each circular piece is weighed using an electronic balance, and the thickness h1 of the circular piece is measured using a micrometer. During the process of measuring the thickness of the negative electrode with a micrometer, the micrometer screw needs to be gradually brought closer to the anvil, and the electrode needs to be clamped in it. After each measurement point, the graphite powder adhering to the cross section is cleaned, and the zeroing is repeated. Finally, an appropriate amount of deionized water is dropped onto each of the three circular pieces, and the coating on the circular pieces is gently wiped off with lint-free paper to expose the copper foil. The pieces are left to stand (dry) at room temperature for 10 minutes. After the copper foil is dry, the mass of the three copper foil pieces is weighed and recorded as m0. The thickness h0 of the circular piece is measured using a micrometer.

[0076] The thickness measurement process requires testing the thickness of 5 points along the longitudinal direction of the disc. Three discs need to be tested for each battery, and then the average value of all test results is taken.

[0077] Areal density measurement: The areal density A obtained by the sampler is calculated by (m1-m0) / S0. The value of A is the areal density of the negative electrode active material layer. The units of m1 and m0 are mg, and the unit of S0 is cm. 2 When, the unit of A is mg / cm³ 2 Converted to g / m 2 At that time, the value of A needs to be multiplied by 0.1.

[0078] Measurement of compaction density: The coating thickness is obtained according to h2 = h1 - h0, and the compaction density of the negative electrode active material layer is obtained according to A / h2.

[0079] Performance tests were conducted on the batteries of the embodiments and comparative examples under the above parameter conditions. The test methods are as follows:

[0080] 1. Trial fabrication of three electrodes and lithium plating.

[0081] Prepare several enameled copper wires with a diameter of 40 μm, immerse them in 98% concentrated sulfuric acid for 3 hours, then rinse with anhydrous ethanol for 5 minutes, followed by immersion in 20% dilute hydrochloric acid for 20 minutes, and then rinse with deionized water for 5 minutes. Finally, place the treated copper wires in a 50°C drying oven until the surface of the copper wires is dry. This treated copper wire will be used as the reference electrode of the battery.

[0082] Assemble the battery in the following order: positive electrode, separator, reference electrode, separator, negative electrode, and lead out the tab of the reference electrode from the top of the battery.

[0083] Using Blue Electric button cell charging and discharging equipment, lithium plating of the reference electrode was carried out in the following manner: (1) Forward lithium plating: the electrode connection method is positive electrode + reference electrode, current 0.1mA, time 5h; (2) Reverse lithium plating: the electrode connection method is negative electrode + reference electrode, current 0.1mA, time 5h.

[0084] 2. Fast charging performance test.

[0085] The testing method is as follows:

[0086] a. Charge the battery at a constant current of 0.33C to the upper limit voltage of 4.25V, then charge it at a constant voltage until the cutoff current is less than or equal to 0.05C, and then discharge it;

[0087] Repeat the above steps 3 times, and use the discharge capacity of the third discharge as the discharge capacity of the battery.

[0088] b: Based on the battery capacity in a, charge the battery at 0.33C to 10% SOC; denoted as T0;

[0089] c: Subsequently, the battery was charged at 4C, 3.5C, 3.0C, 2.75C, 2.5C, 2.25C, 2.0C, 1.75C, 1.5C, 1.25C, 1C, 0.75C, 0.5C, and 0.33C. A jump to the negative electrode-reference auxiliary potential of 0V was monitored and set (i.e., for example, during a 4C charge, a jump occurred when the negative electrode-reference auxiliary potential reached 0V, and subsequent charging began at 3.5C). The time taken to charge the battery to 80% SOC was recorded as T1, and T1-T0 was the fast charging time, in minutes. The test temperature was 25±2℃.

[0090] 3. Energy density test.

[0091] The testing method is as follows:

[0092] a: Charge the battery at a constant current of 0.33C to the upper limit voltage of 4.25V, then charge it at a constant voltage until the cutoff current is less than or equal to 0.05C, and then discharge it;

[0093] Repeat the above steps 3 times, and use the discharge energy of the third discharge as the discharge energy E of the battery;

[0094] b: The battery weight M is obtained by weighing using an electronic balance;

[0095] c: Calculation of weight energy density: E / M, unit: Wh / Kg.

[0096] The fast charging time and energy density data of the batteries under various embodiments and comparative conditions are shown in Table 2 below.

[0097] Table 2

[0098] The data results in Tables 1 and 2 show that: by comprehensively controlling b, d, and m, the following conditions are met. While maintaining relatively high energy density, it also ensures fast charging performance of the battery. This is especially true through further optimization. A value within the range of -1.8 to -0.7 allows for batteries with higher energy density and better fast-charging performance. Specifically, for the above-mentioned scheme with a long side length L of 450mm for the negative electrode, the fast-charging time is ≤45min, preferably ≤20min; the energy density is ≥250Wh / KG, preferably ≥270Wh / KG, and more preferably ≥290Wh / KG. For the above-mentioned scheme with a long side length L of 1000-1100mm for the negative electrode, the fast-charging time is ≤50min, preferably ≤30min; the energy density is ≥300Wh / KG, preferably ≥310Wh / KG.

[0099] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A battery, comprising a cell, the cell including a negative electrode and tabs disposed on the negative electrode; characterized in that, The negative electrode active material layer contains silicon, and the mass percentage of silicon in the negative electrode active material layer is b (in %). The longest distance between the tab and the end of the negative electrode, parallel to the long side of the negative electrode, is d (in mm). The lead-out direction of the tab is a first direction, and the dimension perpendicular to the first direction connecting the tab and the negative electrode is the width m of the tab (in mm). b, d, and m satisfy the following relationship:

2. The battery according to claim 1, characterized in that, The value ranges from -1.8 to -0.

7.

3. The battery according to claim 1 or 2, characterized in that, The value of b is 1.25 to 16; And / or, the value of d is 42 to 1000; And / or, the value of m is 9 to 960.

4. The battery according to claim 3, characterized in that, The value of b is 2.5 to 10; And / or, the value of d is 250 to 450; And / or, the value of m is 50 to 180.

5. The battery according to claim 1 or 2, characterized in that, The areal density of the negative electrode active material layer is 90–300 g / m³. 2 .

6. The battery according to claim 1 or 2, characterized in that, The compaction density of the negative electrode active material layer ranges from 1.2 to 2.3 g / cm³. 3 .

7. The battery according to claim 1 or 2, characterized in that, The tab extends from the long side of the negative electrode plate, and perpendicular to the tab extension direction, the ratio of the tab width to the width of the negative electrode plate is greater than or equal to 0.5 and less than or equal to 1. And / or, the length L of the long side of the negative electrode is ≥300mm; And / or, the battery cell is a laminated battery cell.

8. The battery according to claim 1 or 2, characterized in that, The positive electrode material used in the positive electrode sheet of the battery cell is LiNi. x Co y Mn z O2 material, where 1>x≥0.5, x+y+z=1.

9. An electrochemical device, characterized in that, It includes the battery as described in any one of claims 1-8.

10. An electrical device, characterized in that, It includes the electrochemical device as described in claim 9.

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