Battery cells, batteries and power consuming devices

Abstract

The present application relates to a battery cell, a battery and a power consuming device, the battery cell comprising an electrolyte, a positive electrode plate, a negative electrode plate and a separator, the electrolyte comprising a lithium salt, the lithium salt comprising lithium hexafluorophosphate, the mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte being 15% to 20%, the positive electrode plate comprising a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector and containing a positive electrode active material, the negative electrode plate comprising a negative electrode collector and a negative electrode film layer disposed on at least one side of the negative electrode collector and containing a negative electrode active material, the negative electrode active material further comprising a carbon-based material and a silicon-carbon composite, the mass content of silicon element in the silicon-carbon composite relative to the total mass of the negative electrode active material being 0.3% or more and 10.0% or less, and the separator is disposed between the positive electrode plate and the negative electrode plate. The discharge power of the battery cell described in the present application can be improved in the later stages of discharge.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Chinese Patent Application No. 202311421105.X, entitled "Battery Cell, Battery and Power Consumption Device," proposed on October 30, 2023, the entire contents of which are incorporated herein by reference.

[0002] This application claims priority to PCT patent application PCT / CN2024 / 084136, entitled "Battery Cell, Battery and Power Consumption Device," filed March 27, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present application relates to the field of rechargeable batteries, and in particular to battery cells, batteries and power consuming devices. [Background technology]

[0004] Due to their characteristics of high capacity and long life, battery cells are widely used in electronic devices, such as mobile phones, laptops, battery cars, electric vehicles, electric airplanes, electric steamships, electric toy cars, electric toy steamships, electric toy airplanes, and power tools. As the battery field has progressed significantly, the requirements for the performance of battery cells have also increased.

[0005] However, current battery cells have relatively poor discharge power in the later stages of discharge. Summary of the Invention

[0006] The present application provides a battery cell, a battery and a power consuming device, which can improve the discharge power of the battery cell described in the present application in the later stage of discharge.

[0007] According to a first aspect, an embodiment of the present application provides a battery cell, the battery cell including: an electrolyte; a positive electrode plate; a negative electrode plate; and a separator; the electrolyte includes a lithium salt, the lithium salt including lithium hexafluorophosphate, and the mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte is 15% to 20%; the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material; the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector and containing a negative electrode active material; the negative electrode active material further includes a carbon-based material and a silicon-carbon composite, and the mass content of silicon in the silicon-carbon composite relative to the total mass of the negative electrode active material is 0.3% or more and 10.0% or less; and a separator is disposed between the positive electrode plate and the negative electrode plate.

[0008] Therefore, in the embodiment of the present application, by adjusting the mass content of the silicon-carbon composite in the negative electrode active material (the mass content of silicon element in the silicon-carbon composite is 0.3% or more and 10.0% or less) and combining it with an appropriate electrolyte system (the mass content of lithium hexafluorophosphate is 15% to 20%), it is possible to reduce the internal resistance of the battery at the end of discharge and improve the discharge power performance.

[0009] In some embodiments, the mass content of silicon in the silicon-carbon composite is 4.0% or more and 7.0% or less relative to the total mass of the negative electrode active material. By setting the mass content of silicon in the silicon-carbon composite within this range, the energy density of the battery cell can be further increased, and the carbon in the silicon-carbon composite can act to mitigate the expansion of the silicon, preventing excessive expansion of the silicon-carbon composite. By combining this with the above-mentioned electrolyte system, the internal resistance of the battery at the end of discharge can be significantly reduced, and discharge power performance can be improved.

[0010] In some embodiments, the mass content of the silicon-carbon composite is 0.4% to 14.5% based on the total mass of the negative electrode active material. When the mass content of silicon in the negative electrode active material satisfies the above range, the discharge power at low SOC of the battery can be further improved.

[0011] In some embodiments, the mass content of the silicon-carbon composite is 5.75% to 10% based on the total mass of the negative electrode active material. When the mass content of silicon element is within this range, the discharge power at low SOC can be further improved.

[0012] In some embodiments, the carbon-based material comprises at least one of artificial graphite and natural graphite.

[0013] In some embodiments, the carbon-based material comprises synthetic graphite.

[0014] In some embodiments, the electrolyte further comprises a cyclic carbonate, and the ratio of the mass content of the cyclic carbonate to the mass content of lithium hexafluorophosphate, based on the total mass of the electrolyte, is (0.60 to 2.50):1, and optionally (1.00 to 1.65):1. The presumable beneficial effect is as follows: when the ratio of the mass content of the cyclic carbonate to the mass content of lithium hexafluorophosphate is within the above range, it is advantageous for sufficient dissociation of more lithium ions from lithium hexafluorophosphate, thereby allowing more lithium ions to be contained in the electrolyte system even at the end of discharge at a low SOC, and lithium ions are continuously dissociated as the battery reaction progresses, thereby improving the power performance of the battery.

[0015] In some embodiments, the mass content of the cyclic carbonate is 10% to 41%, and optionally 20% to 30%. The cyclic carbonate has a high dielectric constant and high ionic conductivity, and can form a stable SEI film on the surface of the negative electrode active material, which is advantageous for the power performance of the battery at the end of discharge.

[0016] In some embodiments, the cyclic carbonate comprises at least one of ethylene carbonate EC, propylene carbonate PC, and butylene carbonate BC.

[0017] In some embodiments, the electrolyte further comprises a chain carbonate, and the ratio of the mass content of the chain carbonate to the mass content of the cyclic carbonate, based on the total mass of the electrolyte, is (0.9 to 6):1, and optionally (1.5 to 2.65):1. When the mass content ratio of the chain carbonate to the cyclic carbonate satisfies the above range, the viscosity and ionic conductivity of the electrolyte can be improved at the same time, thereby enhancing the kinetic performance of lithium ions.

[0018] In some embodiments, the mass content of the chain carbonate is 35% to 65%, and / or the chain carbonate includes at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). The relatively low viscosity of the chain carbonate contributes to sufficient dissolution of a high content of lithium hexafluorophosphate, which is advantageous for rapid migration of lithium ions ionized from the lithium hexafluorophosphate between the positive and negative electrodes. The combined use of the chain carbonate and the cyclic carbonate also contributes to increasing the electrochemical stability of the electrolyte system and effectively reducing side reactions in the electrolyte.

[0019] In some embodiments, the electrolyte further comprises a fluorinated cyclic carbonate. The fluorinated cyclic carbonate is involved in the formation of an SEI film on the surface of the negative electrode active material, improving the film's components and properties and effectively protecting the negative electrode active material. In particular, when the negative electrode contains silicon, the film composition for the SEI film must be further optimized due to the characteristics of silicon expansion. The film composition can be optimized by adjusting the relative proportions of the film-forming additives in the electrolyte. The film formed with the fluorinated cyclic carbonate can improve the flexibility of the SEI film and prevent structural collapse caused by the release of a large amount of lithium ions within a short period of time at the end of discharge. The fluorinated cyclic carbonate also has a certain desolvation ability, which is favorable for lithium ion migration, improving DCR at low SOC and increasing discharge power.

[0020] In some embodiments, the fluorinated cyclic carbonate comprises at least one of monofluoroethylene carbonate FEC, bisfluoroethylene carbonate DFEC, and trifluoropropylene carbonate TFPC, and optionally the fluorinated cyclic carbonate comprises monofluoroethylene carbonate FEC.

[0021] In some embodiments, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of elemental silicon relative to the total mass of the electrolyte is (0.01 to 9.5): 1, and optionally (0.01 to 0.15): 1. Combining a fluorinated cyclic carbonate with the above content in a negative electrode plate can significantly improve the power performance of the battery cell.

[0022] In some embodiments, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt, based on the total mass of the electrolyte, is (0.005 to 0.30): 1, and optionally (0.005 to 0.03): 1. When the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt is within the above range, not only can the flexibility of the SEI film and improvements in ionic conductivity and electronic conductivity be simultaneously achieved, but also the DCR can be reduced, thereby increasing the discharge power of the battery.

[0023] In some embodiments, the mass content of the fluorinated cyclic carbonate is 0.05% to 5.80%, and optionally 0.1% to 1.0%, based on the total mass of the electrolyte solution. Because the carbon element in the silicon-carbon composite can effectively mitigate the expansion of the silicon element, a relatively low content of the fluorinated cyclic carbonate can significantly improve the discharge power performance of the battery cell.

[0024] In some embodiments, the lithium salt further comprises at least one of a fluorine-containing inorganic phosphate and a fluorine-containing inorganic borate, which can participate in the formation of inorganic components in the SEI film, which is beneficial to improving the ionic and electronic conductivity of the SEI film, and which can provide the SEI film with a relatively low interfacial ionic impedance, which is beneficial to lithium ion transport, and can improve the DCR at low SOC.

[0025] In some embodiments, the mass content of the fluorine-containing inorganic phosphate is 0.05% to 0.50%, and optionally 0.10% to 0.30%, based on the total mass of the electrolyte solution. By combining the fluorine-containing inorganic phosphate with the above content in the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0026] In some embodiments, the mass content of the fluorine-containing inorganic borate is 0.05% to 0.50%, and optionally 0.10% to 0.30%, based on the total mass of the electrolyte solution. By combining the above-mentioned content of the fluorine-containing inorganic borate with a negative electrode plate, the power performance of the battery cell can be significantly improved.

[0027] In some embodiments, the fluorine-containing inorganic phosphate comprises lithium difluorophosphate LiPO2F2 and / or the fluorine-containing inorganic borate comprises at least one of lithium tetrafluoroborate LiBF4 and lithium difluoro(oxalato)borate LiDFOB.

[0028] In some embodiments, the electrolyte further comprises an additive, the additive comprising at least one of 1,3-propane sultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F, wherein the mass ratio of the 1,3-propane sultone PS, the vinylene carbonate VC, and the lithium fluorosulfonate LiSO3F, based on the total mass of the electrolyte, is (0.050-0.300):(0.100-0.500):(0.001-0.300). When the mass ratio of the 1,3-propane sultone PS, the vinylene carbonate VC, and the lithium fluorosulfonate LiSO3F is within the above range, the components essentially participate in the formation of an SEI film on the surface of the negative electrode active material, and the SEI film can effectively mitigate the expansion of the silicon-carbon composite.

[0029] In some embodiments, the mass content of 1,3-propane sultone PS is 0.1% to 1.0%, and / or the mass content of vinylene carbonate VC is 0.1% to 1.0%, and / or the mass content of lithium fluorosulfonate LiSO3F is 0.1% to 1.0%.

[0030] In some embodiments, the battery cell has a retention coefficient between 1 g / Ah and 2.5 g / Ah, optionally between 1.0 g / Ah and 1.5 g / Ah.

[0031] The liquid retention coefficient of a battery cell can reflect the liquid retention capacity of the electrolyte. When the liquid retention coefficient of a battery cell is within the above range, the electrolyte can have a relatively good infiltration effect into the positive electrode plate and the negative electrode plate, and there is a certain gap between the negative electrode plate and the separator, which provides an expansion space for the volume expansion of the silicon-carbon composite, thereby reducing the risk of the entire battery swelling.

[0032] In some embodiments, the porosity of the separator is 30% to 40%. In the battery cell of the present application, the addition amount of lithium hexafluorophosphate is relatively high, so the viscosity of the entire electrolyte is relatively high, and the porosity of the separator is relatively high, which is advantageous for the relatively viscous electrolyte to pass through the separator, allowing for smooth movement of lithium ions.

[0033] In some embodiments, the separator includes an organic substrate and a coating disposed on at least one side of the organic substrate, the coating including a heat-resistant layer and an organic layer, the heat-resistant layer being disposed on a surface of the organic substrate, and the organic layer being disposed on a surface of the heat-resistant layer facing away from the organic substrate. Combining the separator with the electrolyte and a negative electrode plate can significantly improve the power performance of a battery cell.

[0034] In some embodiments, the organic layer comprises a non-fluorinated polymer.The separator, in combination with the electrolyte and negative electrode plate, can significantly improve the power performance of the battery cell.

[0035] In some embodiments, the non-fluorinated polymer comprises a polyacrylate layer. The separator, in combination with the electrolyte and negative electrode plate, can significantly improve the power performance of the battery cell.

[0036] In some embodiments, the separator comprises an organic substrate and a coating disposed on at least one side of the organic substrate, the coating comprising a ceramic layer and / or a polyacrylate layer, optionally the coating comprising a ceramic layer and a polyacrylate layer, optionally the ceramic layer being disposed on a surface of the organic substrate and the polyacrylate layer being disposed on a surface of the ceramic layer facing away from the organic substrate. By disposing the polyacrylate layer on the outer surface of the separator, the outer surface of the separator has a certain flexibility, which can effectively mitigate the volumetric expansion or contraction of the silicon-carbon composite and improve the structural stability of the entire electrode assembly.

[0037] In some embodiments, the thickness of the organic substrate is 6.6 μm to 7.6 μm. When the thickness of the organic substrate is in this range, the lithium ion transfer rate in the negative electrode plate and the transfer rate in the separator can be basically matched, reducing the risk of deterioration of concentration polarization, which is advantageous for improving discharge performance.

[0038] In some embodiments, the coating thickness is 1.5 μm to 2.5 μm. When the coating thickness is in this range, the lithium ion transfer rate in the negative electrode plate and the transfer rate in the separator can be basically matched, reducing the risk of deterioration of concentration polarization, which is advantageous for improving discharge performance.

[0039] In some embodiments, the positive electrode active material has the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) Y zcomprises a compound, where 0 < d ≤ 2.1, 0.6 < a < 1, 0 < b < 1, 0 < c < 1, and 0.6 < a + b + c < 1, 1.8 ≤ z ≤ 3.5, the M element comprises at least one element among B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and the Y element comprises at least one element among O and F. By combining the above positive electrode active material system with the above electrolyte and the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0040] In some embodiments, 0.85 ≤ a ≤ 0.95. By combining the above positive electrode active material system with the above electrolyte and the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0041] In some embodiments, the positive electrode active material comprises at least one of single crystal particles and polycrystalline particles. By combining the above positive electrode active material system with the above electrolyte and the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0042] In some embodiments, the positive electrode active material comprises single crystal particles and polycrystalline particles. By combining the above positive electrode active material system with the above electrolyte and the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0043] According to a second aspect, the present application further proposes a battery, and the battery includes a battery cell described in any one of the embodiments of the first aspect of the present application.

[0044] According to a third aspect, the present application further proposes a power consumption device, and this power consumption device includes a battery described in any one of the embodiments of the second aspect of the present application.

Brief Description of the Drawings

[0045] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without exerting any creative efforts. [Figure 1] 1 is a schematic diagram of one embodiment of a battery cell of the present application. [Figure 2] FIG. 2 is an exploded schematic view of an embodiment of the battery cell of FIG. 1. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of a power consuming device that includes a battery cell of the present application as a power source.The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the battery cell, battery, and power consumption device of the present application will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0047] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values ​​and are combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are already listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0051] Lithium-ion battery discharge is a process in which lithium ions are released from the negative electrode active material and embedded in the positive electrode active material via the electrolyte. In the battery industry, the term "state of charge (abbreviated as SOC)" is often used to reflect the remaining capacity of a battery after discharge. This value is defined as the percentage of the remaining capacity of the battery, and ranges from 0 to 100%. When "SOC = 0", the battery is completely discharged, and when "SOC = 100%", the battery is fully charged.

[0052] The discharge process of lithium-ion batteries suffers from a lack of "discharge power" in the latter stages of discharge. For example, when discharging a battery to a state of charge (SOC) of 10% or less and then continuing to discharge to 0%, the power performance of the discharge is lower than that of the earlier discharge, resulting in a decrease in the power performance of the entire discharge process.

[0053] In view of the above problems, the present application proposes a battery cell that includes a negative electrode plate advantageous for improving the battery's later discharge power, and based on this negative electrode plate, combines an electrolyte advantageous for improving the battery's later discharge power, and may further include a suitable separator and positive electrode plate, thereby significantly improving the power performance of the battery during later discharge (particularly during the discharge process from 10% to 0% SOC).

[0054] Battery cell A first aspect of the present application provides a battery cell, the battery cell including a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material. The electrolyte includes a lithium salt, the lithium salt including lithium hexafluorophosphate, the mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte being 15% to 20%. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector and containing a negative electrode active material. The negative electrode active material further includes a carbon-based material and a silicon-carbon composite, the mass content of silicon in the silicon-carbon composite being 0.3% to 10.0% relative to the total mass of the negative electrode active material.

[0055] The negative electrode active material of the battery cell includes a carbon-based material that provides elemental carbon and a silicon-carbon composite that provides elemental silicon.

[0056] The carbon-based material providing the carbon element may be primarily composed of carbon and may simultaneously contain silicon, or may contain only carbon; the silicon-carbon composite providing the silicon element may simultaneously contain silicon, or may simultaneously contain carbon, or may contain only silicon. The negative electrode active material simultaneously contains a carbon-based material and a silicon-carbon composite, and the mass content of the silicon in the silicon-carbon composite relative to the total mass of the negative electrode active material is 0.3% or more, taking into account the following factors: Compared to carbon-based materials, the silicon-carbon composite contains silicon and has a relatively high lithium absorption / desorption voltage plateau. This allows the silicon-carbon composite to continue discharging even at low SOC (e.g., SOC ≦ 10%), making up for the difficulty / impossibility of carbon-based materials to continue discharging at low SOC. This improves the direct current internal resistance (DCR) during the battery discharge process and further improves the power performance during the battery discharge process.

[0057] In the battery cell of the present application, the negative electrode active material is mainly made of a carbon-based material and a small amount of a silicon-carbon composite is added as a blend, that is, the mass content of silicon element in the negative electrode active material is smaller than the mass content of carbon element, and the mass content of silicon element in the silicon-carbon composite relative to the total mass of the negative electrode active material is 10.0% or less, taking into consideration the following factors:

[0058] Although the lithium absorption / release potential of silicon-carbon composites is higher than that of carbon-based materials, their volume expansion and contraction during charging and discharging is relatively large, which can lead to defects such as structural collapse, bursting, and pulverization of the negative electrode active material, potentially causing undesirable side reactions within the battery. However, because silicon-carbon composites contain carbon, which can effectively mitigate the volume expansion of silicon, in this application, the upper limit of the mass content of silicon in silicon-carbon composites may be slightly higher than the mass content of silicon in silicon oxides, even reaching 10%. Because an excessively high content may be detrimental to improving DCR, when other conditions are met, the power performance of batteries corresponding to negative electrode active materials containing more than 10.0% silicon-carbon composites is not as good as that of batteries with lower silicon contents.

[0059] To further improve the problem of the silicon-carbon composite breaking down into powder, the battery cell of the present application is combined with an electrolyte containing a high amount of lithium hexafluorophosphate (LiPF), and the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 15% or more.

[0060] A relatively high content of lithium hexafluorophosphate (LiPF6) in the electrolyte can effectively alleviate the problem of silicon-carbon composites bursting and pulverizing. A possible cause: lithium hexafluorophosphate is involved in the formation of a solid electrolyte interphase (SEI) film component on the surface of the negative electrode active material. A high fluorine atom content of lithium hexafluorophosphate can optimize the SEI film component, and a high mass content of lithium hexafluorophosphate has a more significant effect on improving the SEI film component, increasing the proportion of fluorine lithium (e.g., lithium fluoride) in the SEI film. Such an SEI film with a relatively high fluorine lithium content can alleviate the problem of silicon-carbon composites bursting and pulverizing, improve the overall structural stability of the negative electrode active material, and delay side reactions between the electrolyte and the surface of the negative electrode active material, thereby improving the discharge stability of the silicon-carbon composite in the later stages of discharge and further enhancing the power performance of the battery.

[0061] In addition, at the end of discharge when the battery cell has a low SOC, the lithium ion concentration in the negative electrode active material is relatively low, making it difficult for the lithium ions to leave the negative electrode active material, reducing the lithium salt concentration difference in the electrolyte system, improving the internal resistance of the battery cell, and further reducing discharge power. Meanwhile, the electrolyte in the embodiment of the present application contains a high content of lithium hexafluorophosphate, which contributes more lithium ions to the battery system, increasing the lithium ion concentration in the electrolyte, effectively reducing the concentration polarization of the lithium salt, and promoting the migration of lithium ions from the negative electrode plate to the positive electrode plate, thereby further improving the power performance of the battery cell.

[0062] However, if the mass content of lithium hexafluorophosphate in the electrolyte is greater than 20%, the viscosity of the electrolyte will be significantly increased, which is unfavorable for the migration of lithium ions from the bulk of the negative electrode active material to the surface, and the migration rate of lithium ions from the negative electrode surface to the positive electrode surface will be slowed, which is unfavorable for the migration of lithium ions from the surface of the negative electrode active material into the bulk of the negative electrode active material. Therefore, even if the negative electrode active material contains a silicon material with a relatively high lithium absorption / desorption voltage plateau, without an appropriate electrolyte system, the internal resistance at the end of discharge of the battery will increase, which will be unfavorable for the discharge power performance.

[0063] To summarize the above, in the battery cell of the embodiment of the present application, the mass content of lithium hexafluorophosphate in the electrolyte is 15% to 20%, and by combining this with 0.3% to 10.0% of silicon element in the negative electrode active material, the synergistic effect between the electrolyte and the negative electrode is utilized to improve the power performance at the end of battery discharge.

[0064] For example, the mass content of silicon element in the silicon-carbon composite relative to the total mass of the negative electrode active material is 0.3% to 10.0%, and optionally 4.0% to 7.0%. For example, the range is 0.3%, 0.4%, 0.5%, 0.6%, 0.64%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.27%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.91%, 2.0%, 2.1%, 2.2%, 2.23%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.86%, 2.9%, 3%, 3.1%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two of the above values.

[0065] In some embodiments, the mass content of the silicon element in the silicon-carbon composite with respect to the total mass of the anode active material is 4.0% or more and 7.0% or less. By setting the mass content of the silicon-carbon composite within the above range, the energy density of the battery cell can be further increased, and the carbon element in the silicon-carbon composite can play a role in alleviating the expansion of the silicon element. Therefore, the expansion of the silicon-carbon composite does not become excessive, and by combining it with the above electrolyte system, the internal resistance at the end of discharge of the battery can be significantly reduced, and the discharge power performance can be improved.

[0066] Exemplarily, the mass content of lithium hexafluorophosphate in the electrolyte with respect to the total mass of the electrolyte may be 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 17.8%, 18%, 18.2%, 18.5%, 19%, 19.5%, 20% or a range consisting of any two of the above numerical values. Correspondingly, the mass content of the silicon-carbon composite in the anode active material to be combined is 0.5% - 10%.

[0067] As described above, the silicon element may be derived from the silicon-carbon composite. Here, the silicon-carbon composite may refer to the form of the silicon element in the anode plate in the battery after formation. The silicon-carbon composite may be a silicon-carbon composite formed by the silicon element and the carbon element through several chemical reactions in the battery cell, or the silicon-carbon composite may be formed by physically mixing the silicon single substance and the carbon single substance. For example, the carbon single substance includes a porous skeleton, and the silicon single substance may be located in the holes of the porous skeleton or on the surface of the porous skeleton. The silicon-carbon composite may be one with a carbon layer or the like coated on the surface of the silicon single substance.

[0068] In some embodiments, the anode active material may further include other active materials containing silicon elements. For example, the silicon element exists in the anode film layer in at least one form of silicon single substance, silicon oxide SiO x (0 < x ≦ 2). Here, the silicon single substance, the silicon-carbon composite, and the silicon oxide SiOx (0 < x ≤ 2) may refer to a silicone-based material or the form of silicon element in the negative electrode plate of the battery after formation. Here, silicon oxide SiO x , 0 < x ≤ 2 because the bonding mode between silicon atoms and oxygen atoms in the negative electrode film layer is diverse, and it may be at least one of SiO, SiO 1.2 , or SiO2 and other possible silicon oxides.

[0069] Carbon element is mainly a constituent element of carbon-based materials. In some embodiments, the carbon-based materials may include at least one of artificial graphite and natural graphite.

[0070] Optionally, the carbon-based material may include artificial graphite. The combination of artificial graphite and the above electrolyte system, and the combination with the silicon-carbon composite can reduce DCR and improve power.

[0071] In some embodiments, based on the total mass of the negative electrode active material, the ratio of the mass content of the silicon-carbon composite to the mass content of the artificial graphite is (0.4:99.6) to (14.5:85.5).

[0072] When the content ratio of the silicon-carbon composite and artificial graphite in the negative electrode active material meets the requirements, the discharge power of the battery at low SOC can be further improved.

[0073] Exemplarily, the ratio of the mass content of the silicon-carbon composite to the mass content of the artificial graphite may be 0.4:99.6, 0.5:99.5, 1:99, 1.5:98.5, 2:98, 2.5:97.5, 3:97, 3.5:96.5, 4:96, 4.5:95.5, 5:95, 6.5:93.5, 7:93, 7.5:92.5, 8:92, 8.5:91.5, 9:91, 9.5:90.5, 10:90, 11:89, 12:88, 13:87, 14:86, 14.5:85.5 or a range consisting of any two of the above numerical values.

[0074] In some embodiments, the mass content of the silicon-carbon composite is 0.4% to 14.5%, optionally 5.75% to 10%, such as 0.4%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 5.5%, 5.75%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 14.5%, or a range consisting of any two of the foregoing values. When the mass content of the silicon-carbon composite satisfies the above content range, the cycle performance of the battery can be improved.

[0075] In some embodiments, the mass content of the artificial graphite may be 85.5% to 99.6%, and optionally 90% to 94.25%, such as 85.5%, 90%, 91%, 92%, 93%, 94%, 95%, 95.1%, 95.2%, 95.3%, 95.4%, 95.5%, 95.6%, 95.7%, 95.8%, 95.9%, 96%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5% , 96.6%, 96.7%, 96.8%, 96.9%, 97%, 97.1%, 97.2%, 97.3%, 97.4%, 97.5%, 97.6%, 97.7%, 97.8%, 97.9%, 98%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 98.9%, 99%, 99.5%, 99.6%, or a range consisting of any two of the above values. When the mass content of the artificial graphite satisfies the above content range, the cycle performance of the battery can be improved.

[0076] Alternatively, the carbon-based material may include natural graphite, which generally has a smaller particle size and can absorb and release lithium ions faster. The surface of natural graphite generally contains amorphous carbon, and the presence of amorphous carbon can reduce DCR and improve power.

[0077] The qualitative and quantitative analysis of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. Relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And from the perspective of detection accuracy, those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. to obtain more accurate detection results. It is possible to perform qualitative or quantitative measurement using one detection method, or it is also possible to perform qualitative or quantitative measurement by combining multiple detection methods.

[0078] For example, taking the detection of silicon element in the negative electrode active material as an example, qualitative and quantitative analysis can be carried out by referring to JY / T015 - 1996 "General Rules for Inductively Coupled Plasma Atomic Emission Spectrometry", and further referring to the GB - T17359 - 2012 standard, analysis can also be carried out on the surface elements of the negative electrode plate or the cross - section elements after ion polishing.

[0079] For example, the graphite material in this application can be qualitatively analyzed by performing an X - ray powder diffraction test on the negative electrode plate or the negative electrode active material in combination with JIS / K0131 - 1996 General Rules for X - ray Diffraction Analysis. The silicon - carbon composite and silicon oxide SiO x (0 < x ≤ 2) in this application can also be tested and qualitatively analyzed using the above X - ray powder diffraction.

[0080] In some embodiments, based on the total mass of the negative electrode film layer, the mass content of the negative electrode active material is 85% or more and less than 100%. For example, the mass content of the negative electrode active material may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or a range consisting of any two of the above numerical values.

[0081] In some embodiments, the thickness of the single-sided negative electrode film layer is 65 μm to 90 μm. The thickness of the negative electrode film layer refers to the thickness of the single-sided negative electrode film layer. For example, when a negative electrode film layer is provided on both sides of the negative electrode current collector, the thickness of the negative electrode film layer on one side of the negative electrode current collector is the thickness of one side of the negative electrode film layer. Alternatively, when a negative electrode film layer is provided on one side of the negative electrode current collector, the thickness of the negative electrode film layer on that side is the thickness of the single-sided negative electrode film layer. When the thickness of the negative electrode film layer is in this range, the lithium ion transfer rate in the negative electrode plate and the transfer rate in the separator can be basically matched, reducing the risk of deterioration of concentration polarization and advantageously improving discharge performance.

[0082] For example, the thickness of the negative electrode film layer may be 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 83 μm, 84 μm, 85 μm, 86 μm, 87 μm, 88 μm, 89 μm, 90 μm, or a range consisting of any two of the above values.

[0083] In the embodiments of the present application, the thickness of the negative electrode film layer has a meaning known in the art and can be detected using instruments and methods known in the art. Relevant detection methods can be found in domestic and international detection standards, domestic and international corporate standards, etc., and those skilled in the art can adaptively change some detection steps / instrument parameters, etc., to achieve more accurate detection results. A single detection method can be used for qualitative or quantitative measurement, or multiple detection methods can be used in combination for qualitative or quantitative measurement. For example, in accordance with GB / T 17359-2012 "Quantitative Analysis by Microbeam Analysis Spectroscopy," a negative electrode plate containing no electrolyte can be used as a sample for ion-polished cross-sectional elemental analysis to determine the thickness of the negative electrode film layer. For example, measurements can be taken multiple times using a micrometer and the average values ​​calculated: take a negative electrode plate (a negative electrode plate with a negative electrode film layer applied to both sides) that does not contain electrolyte, first test the thickness of any five parts of the negative electrode plate with a micrometer to obtain an average value H1, wipe off the negative electrode film layer, and then test the thickness of any five parts of the remaining current collector to obtain an average value H2. The thickness of a single layer of negative electrode film layer is (H2-H1) / 2.

[0084] In some embodiments, the packed density PD of the negative electrode membrane layer is 1.3 g / cm 3 ~1.7g / cm 3 When the compaction density of the negative electrode film layer is within this range, the negative electrode plate has good dynamic performance and cycle performance.

[0085] For example, the compaction density PD of the negative electrode film layer is 1.3 g / cm 3 , 1.35g / cm 3 , 1.4g / cm 3 , 1.45g / cm 3 , 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 Alternatively, it may be a range consisting of any two of the above values.

[0086] Areal density = weight of one-sided negative electrode film layer / area of ​​one-sided negative electrode film layer, where since there is a negative electrode film layer on both sides of the negative electrode current collector, weight of one-sided negative electrode film layer = (average weight of electrode plate - average weight of current collector) / 2. Compaction density = areal density / average thickness of negative electrode film layer, where since there is a negative electrode film layer on both sides of the negative electrode current collector, average thickness of negative electrode film layer = (average thickness of electrode plate - average thickness of current collector) / 2.

[0087] The "average" here may be the average value obtained after five parallel tests.

[0088] In some embodiments, the negative electrode film layer optionally further includes a negative electrode conductive agent. The embodiments of the present application are not particularly limited to the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≦5% based on the total mass of the negative electrode film layer.

[0089] In some embodiments, the negative electrode film layer optionally further includes a negative electrode adhesive. The embodiments of the present application are not particularly limited to the type of negative electrode adhesive. For example, the negative electrode adhesive may include styrene butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), or water-based acrylic acid-based resin (e.g., at least one of polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS)). In some embodiments, the mass content of the negative electrode adhesive is ≦5% based on the total mass of the negative electrode film layer.

[0090] In some embodiments, the negative electrode membrane layer further optionally contains other additives. For example, the other additives may include a thickener, such as carboxymethylcellulose sodium CMC-Na, a PTC thermistor material, etc. In some embodiments, the mass content of the other additives is ≦2% based on the total mass of the negative electrode membrane layer.

[0091] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is copper foil. The composite current collector may include a polymer base layer and a metal material layer formed on at least one surface of the polymer base layer. For example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0092] In some embodiments, the thickness of the negative electrode current collector is 6 μm or less, and optionally a thin current collector of 4.5 μm to 6 μm, for example, a thin metal current collector is employed.

[0093] The negative electrode current collector of the battery cell of the present application is optionally a thin current collector with a thickness of 4.5 μm to 6 μm, which weakens the heat dissipation path of the battery cell and can reserve some heat within the battery under low SOC discharge conditions. The combination of a low-silicon negative electrode plate and a high-content lithium hexafluorophosphate electrolyte system further enhances the beneficial effect of reducing DCR growth at the end of discharge (low SOC), thereby improving discharge power at low SOC.

[0094] For example, the thickness of the negative electrode current collector may be 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, or a range consisting of any two of the above numerical values.

[0095] The negative electrode film layer is typically obtained by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliary agents in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0096] The negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some examples, the negative electrode plate of the present application further includes a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In addition, in some examples, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0097] In some embodiments, the electrolyte further comprises an organic solvent.

[0098] In some embodiments, the organic solvent may include a cyclic carbonate, and the ratio of the mass content of the cyclic carbonate to the mass content of the lithium hexafluorophosphate, based on the total mass of the electrolyte, is (0.60-2.50):1, and optionally (1.00-1.65):1.

[0099] The presumable beneficial effects are as follows: when the ratio of the mass content of the cyclic carbonate to the mass content of lithium hexafluorophosphate is within the above range, it is advantageous for sufficiently dissociating more lithium ions from the lithium hexafluorophosphate, so that even at the end of discharge with a low SOC, more lithium ions can be contained in the electrolyte system, and the lithium ions can be continuously dissociated as the battery reaction progresses, thereby improving the power performance of the battery.

[0100] For example, the ratio of the mass content of the cyclic carbonate to the mass content of lithium hexafluorophosphate may be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.15:1, 1.2:1, 1.3:1, 1.35:1, 1.37:1, 1.4:1, 1.5:1, 1.6:1, 1.65:1, 1.67:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, or a range consisting of any two of the above values.

[0101] In some embodiments, the mass content of the cyclic carbonate in the electrolyte is 10% to 45%, and more preferably 20% to 30%. Cyclic carbonate has a high dielectric constant and high ionic conductivity, and can form a stable SEI film on the surface of the negative electrode active material, which is advantageous for the power performance of the battery at the end of discharge.

[0102] For example, the mass content of the cyclic carbonate may be 10%, 10.92%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 20.93%, 21%, 22%, 23%, 23.66%, 24%, 25%, 26%, 27%, 28%, 29%, 29.12%, 30%, 30.03%, 31%, 32%, 33%, 34%, 35%, 36%, 36.4%, 37%, 38%, 39%, 40%, 40.4%, 41%, 42%, 43%, 44%, 45%, or a range consisting of any two of the above values.

[0103] In some embodiments, the cyclic carbonate may include at least one of ethylene carbonate EC, propylene carbonate PC, and butylene carbonate BC.

[0104] In some embodiments, the organic solvent may contain a chain carbonate, and the ratio of the mass content of the chain carbonate to the mass content of the cyclic carbonate, based on the total mass of the electrolyte, is (0.9 to 6): 1, and optionally (1.5 to 2.65): 1. When the mass content ratio of the chain carbonate to the cyclic carbonate satisfies the above range, the viscosity and ionic conductivity of the electrolyte can be improved at the same time, and the kinetic performance of the lithium ion can be enhanced.

[0105] Exemplary ratios of the mass content of the linear carbonate to the mass content of the cyclic carbonate are 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.37:1, 1.4:1, 1.5:1, 1.6:1, 1.65:1, 1.67:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 3.1:1, 3.2 :1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4.0:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1, 5.0:1, 5.1:1, 5.2:1, 5.3:1, 5.4:1, 5.5:1, 5.6:1, 5.7:1, 5.8:1, 5.9:1, 5.95:1, 6:1, or a range consisting of any two of the above values.

[0106] In some embodiments, the mass content of the chain carbonate is 35% to 65%, and more preferably 50% to 60%. The relatively low viscosity of the chain carbonate contributes to sufficient dissolution of lithium hexafluorophosphate at a high content, which is advantageous for the rapid migration of lithium ions ionized from lithium hexafluorophosphate between the positive and negative electrodes. The combined use of the chain carbonate and the cyclic carbonate also contributes to increasing the electrochemical stability of the electrolyte system and effectively reducing side reactions in the electrolyte.

[0107] For example, the mass content of the chain carbonate may be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 50.4%, 51%, 52%, 52.5%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, or a range consisting of any two of the above values.

[0108] In some embodiments, the linear carbonate comprises at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC).

[0109] In some embodiments, the electrolyte may further include an additive.

[0110] In some embodiments, the additive may include a fluorinated cyclic carbonate.

[0111] In some embodiments, the fluorinated cyclic carbonate includes at least one of monofluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), and trifluoropropylene carbonate (TFPC), and optionally the fluorinated cyclic carbonate includes monofluoroethylene carbonate (FEC). FEC has a relatively small number of fluorine atoms and is more polar, which makes it easier for the fluorine atoms to leave and participate in the film-forming reaction of the SEI film.

[0112] In some embodiments, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of elemental silicon relative to the total mass of the electrolyte is (0.01-9.5):1, and optionally (0.01-0.15):1.

[0113] Illustratively, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the silicon element relative to the total mass of the electrolyte may be 0.01:1, 0.02:1, 0.03:1, 0.035:1, 0.04:1, 0.05:1, 0.055:1, 0.06:1, 0.07:1, 0.08:1, 0.1:1, 0.15:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.05:1, 1.1:1, 1.2:1, 1.3:1, 1.35:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 1.1:1, 1.2:1, 1.3 ...1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1 The ratio may be 5:1, 1.57:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.36:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 4.7:1, 4.71:1, 4.8:1, 5:1, 5.5:1, 5.8:1, 6:1, 6.5:1, 7:1, 7.5:1, 7.8:1, 8:1, 8.5:1, 9:1, 9.1:1, 9.2:1, 9.3:1, 9.4:1, 9.43:1, 9.5:1, or a range consisting of any two of the above values.

[0114] Fluorinated cyclic carbonates are involved in the formation of an SEI film on the surface of the negative electrode active material, improving the film's composition and properties and effectively protecting the negative electrode active material. In particular, for silicon-containing negative electrodes, the expansion characteristics of silicon necessitate further optimization of the film composition. This is achieved by adjusting the relative proportions of film-forming additives in the electrolyte. The film formed with fluorinated cyclic carbonates can improve the flexibility of the SEI film and prevent structural collapse caused by the rapid release of large amounts of lithium ions at the end of discharge. Furthermore, fluorinated cyclic carbonates have a certain desolvation ability, which favors lithium ion migration, improving DCR at low SOC and increasing discharge power. Research has shown that when the ratio of silicon content in the negative electrode active material to FEC content in the electrolyte is (0.01-9.5):1, the battery's power dissipation performance at the end of discharge is significantly improved. Since the carbon element in the silicon-carbon composite can effectively mitigate the volume change of the silicon element, a relatively low content of the fluorinated cyclic carbonate can also significantly improve the discharge power performance of the battery cell. Optionally, the ratio of the silicon content in the negative electrode active material to the FEC content in the electrolyte satisfies (0.01-0.15):1.

[0115] In some embodiments, the mass content of the fluorinated cyclic carbonate relative to the total mass of the electrolyte solution may be 0.05% to 5.8%, and optionally 0.1% to 1.0%.

[0116] For example, the mass content of fluorinated cyclic carbonate relative to the total mass of the electrolyte is 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9 ... The value may be 8%, 1.9%, 1.91%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.82%, 3.9%, 4%, 4.1%, 4.5%, 5%, 5.2%, 5.5%, 5.7%, 5.73%, 5.8%, or a range consisting of any two of the above values.

[0117] In some embodiments, the additive may further include at least one of 1,3-propane sultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F.

[0118] In some embodiments, the ratio of the mass contents of 1,3-propane sultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F, based on the total mass of the electrolyte, is (0.050-0.300):(0.100-0.500):(0.001-0.300). When the ratio of the mass contents of 1,3-propane sultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F is within the above range, these components can essentially participate in the formation of an SEI film on the surface of the negative electrode active material, and the SEI film can effectively mitigate the expansion of the silicon-carbon composite.

[0119] In some embodiments, the mass content of 1,3-propane sultone PS is 0.1% to 1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or a range consisting of any two of the foregoing values.

[0120] In some embodiments, the mass content of vinylene carbonate (VC) is 0.1% to 1%, e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or a range consisting of any two of the foregoing values.

[0121] In some embodiments, the mass content of lithium fluorosulfonate LiSO3F is between 0.1% and 1%, e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or a range consisting of any two of the foregoing values.

[0122] After dissolving in an organic solvent, lithium salts can release a large amount of active lithium ions and participate in the charge and discharge cycles. Some lithium salts can also optimize the structure of the SEI film, improve the electrolyte reaction activity, reduce side reactions, and even improve the discharge power of the battery.

[0123] In some embodiments, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt, based on the total mass of the electrolyte, is (0.005-0.30):1, and optionally (0.005-0.03):1.

[0124] The fluorinated cyclic carbonate forms an organic substance on the surface of the silicon-carbon composite, improving the flexibility of the SEI film. The lithium salt is involved in the formation of the SEI film, allowing the SEI film to contain inorganic components, which is advantageous for increasing the ionic and electronic conductivity of the SEI film and improving the ionic and electronic conductivity of the entire negative electrode plate. When the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt is within the above range, not only can the flexibility of the SEI film, but also improvements in ionic and electronic conductivity can be achieved, but the DCR can also be reduced, thereby increasing the discharge power of the battery.

[0125] Illustratively, the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt may be 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.010:1, 0.012:1, 0.014:1, 0.016:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0. The ratio may be 10:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, 0.20:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1, 0.30:1, or a range consisting of any two of the above values.

[0126] In some embodiments, the lithium salt further comprises at least one of a fluorine-containing inorganic phosphate and a fluorine-containing inorganic borate, which can participate in the formation of inorganic components in the SEI film, which is beneficial to improving the ionic and electronic conductivity of the SEI film, and which can provide the SEI film with a relatively low interfacial ionic impedance, which is beneficial to lithium ion transport, and can improve the DCR at low SOC.

[0127] In some embodiments, the fluorine-containing inorganic phosphate comprises at least one of lithium monofluorophosphate Li2PO3F and lithium difluorophosphate LiPO2F2, and optionally, the fluorine-containing inorganic phosphate comprises lithium difluorophosphate LiPO2F2.

[0128] In some embodiments, the fluorine-containing inorganic borate comprises at least one of lithium tetrafluoroborate LiBF4 and lithium difluoro(oxalato)borate LiDFOB, and optionally, the fluorine-containing inorganic borate comprises lithium tetrafluoroborate LiBF4.

[0129] In some embodiments, the mass content of the fluorine-containing inorganic phosphate or fluorine-containing inorganic borate is 0.05% to 0.50%, and optionally 0.10% to 0.30%, based on the total mass of the electrolyte.

[0130] For example, the mass content of the fluorine-containing inorganic phosphate or fluorine-containing inorganic borate may be 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, or a range consisting of any two of the above values.

[0131] Exemplary lithium salts include lithium difluorophosphate LiPO2F2 and lithium tetrafluoroborate LiBF4.

[0132] Optionally, based on the total mass of the electrolyte, the mass content of lithium difluorophosphate LiPO2F2 may be 0.05% to 0.5%, and optionally 0.10% to 0.30%, for example, the mass content of lithium difluorophosphate LiPO2F2 may be 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or a range consisting of any two of the above values.

[0133] Alternatively, the mass content of lithium tetrafluoroborate LiBF4 may be 0.1% to 0.3% based on the total mass of the electrolyte, for example, the mass content of lithium tetrafluoroborate LiBF4 may be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or a range consisting of any two of the above values.

[0134] Optionally, based on the total mass of the electrolyte, the mass content of lithium difluoro(oxalato)borate LiDFOB may be 0.01% to 0.1%, for example, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, or a range consisting of any two of the above values.

[0135] The qualitative and quantitative determination of each substance or element in this application can be performed using appropriate devices and methods known to those skilled in the art. For relevant detection methods, reference can be made to domestic and international detection standards, domestic and international corporate standards, etc. Those skilled in the art can adaptively change some detection steps / instrument parameters, etc., from the perspective of detection accuracy to obtain more accurate detection results. A single detection method may be used for qualitative or quantitative measurement, or multiple detection methods may be used in combination for qualitative or quantitative measurement.

[0136] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte have meanings known in the art and can be detected using instruments and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be analyzed qualitatively or quantitatively by ion chromatography analysis with reference to standard JY / T020-1996 "General Principles for Ion Chromatography Analysis Methods." In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or a battery that has already been discharged (discharged to a lower cutoff voltage to bring the battery's charge state to about 0% SOC) can be reverse disassembled and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis.

[0137] In the embodiments of the present application, the type and content of organic components in the electrolyte are defined as those known in the art and can be detected using instruments and methods known in the art, for example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography in accordance with GB / T9722-2006 "General Principles of Gas Chromatography Methods for Chemical Reagents." In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or a battery that has already been discharged (discharged to a lower cutoff voltage to bring the battery's charge state to about 0% SOC) can be reverse disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis.

[0138] For example, to test for the presence of an additive in an electrolyte by liquid nuclear magnetic chromatography (NMR) to detect lithium difluorophosphate and lithium hexafluorophosphate, a 7ml glass vial is prepared in a nitrogen gas glove box, 5ml of nuclear magnetic reagent premix is ​​added to the vial, and the vial is left in the nitrogen gas glove box at room temperature (20-25°C) for 24 hours to allow the electrolyte in the electrode plate and separator to diffuse into the nuclear magnetic reagent premix, thereby obtaining a nuclear magnetic test sample. The nuclear magnetic reagent premix is ​​composed of 100ml of deuterated acetonitrile and 3ml of trifluoromethylbenzene (C7H5F3). The nuclear magnetic reagent premix is ​​then pre-dried over 4A molecular sieves (15g of unlocked 4A molecular sieves is added to 100ml of the nuclear magnetic reagent premix and dried for 30 days in a nitrogen gas glove box at room temperature (20-25°C)). Measurement is carried out using 19F NMR (nuclear magnetic (NMR): Bruker Avance 400HD).

[0139] To identify and quantify each species, the following settings for the reversal angle and scan time were used:

[0140] Fluorine spectrum test pulse sequence: 2gfhigqn.2, Extension time: 1 second, Number of scans: 16.

[0141] The relative content of trifluoromethylbenzene and LiPF6 was calculated based on the integrated intensity of the signal peaks of both substances in F-NMR. The calculation method is as follows: PF6 - Relative content = (I PF6 - ×M PF6 - / 6) / (I CF3ph ×M CF3ph / 3), where I is the corresponding nuclear magnetic peak area, M is the corresponding relative molecular weight, and the content of lithium hexafluorophosphate in the electrolyte solution is calculated based on the molar ratio relationship between hexafluorophosphate radicals and lithium ions.

[0142] Trifluoromethylbenzene and PO2F2 in F-NMR - Calculate the relative content of both substances based on the integrated intensity of their signal peaks. The calculation method is: PO2F2 - Relative content = (I PO2F2- ×M PO2F2- / 2) / (I CF3ph ×M CF3ph / 3), where I is the corresponding nuclear magnetic peak area, M is the corresponding relative molecular weight, and the content of lithium difluorophosphate in the electrolyte is calculated based on the molar ratio relationship between difluorophosphate radicals and lithium ions.

[0143] In some embodiments, the various solutes or solvents in the electrolyte solutions referred to in this application include substances that are added spontaneously when the electrolyte solution is manufactured, and also include substances derived from substances that are / are already present in some electrolyte solutions during the manufacture of the electrolyte solution, during the manufacture of a battery with said electrolyte solution, or during storage or use of a battery containing said electrolyte solution.

[0144] In some embodiments, the battery cell has a retention coefficient between 1.0 g / Ah and 2.5 g / Ah, optionally between 1.0 g / Ah and 1.5 g / Ah.

[0145] The liquid retention coefficient of a battery cell can reflect the liquid retention capacity of the electrolyte. When the liquid retention coefficient of a battery cell is within the above range, the electrolyte can have a relatively good infiltration effect into the positive electrode plate and the negative electrode plate, and there is a certain gap between the negative electrode plate and the separator, which provides an expansion space for the volume expansion of the silicon-carbon composite, thereby reducing the risk of the entire battery swelling.

[0146] For example, the electrolyte retention coefficient of the battery may be 1.0 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, 1.5 g / Ah, 1.6 g / Ah, 1.7 g / Ah, 1.8 g / Ah, 1.9 g / Ah, 2.0 g / Ah, 2.1 g / Ah, 2.2 g / Ah, 2.3 g / Ah, 2.4 g / Ah, 2.5 g / Ah, or a range consisting of any two of the above values.

[0147] In the embodiments of the present application, the liquid retention coefficient of a battery cell has a meaning known in the art and can be determined using equipment and methods known in the art, for example, in accordance with GB / T 31486-2015 "Electrical Performance Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," where a lithium ion battery is charged at 1C to 4.35V and discharged at 1C to 2.8V at 25°C, the resulting discharge capacity C is used as the denominator, and the lithium ion battery is weighed as M0. The positive electrode plate, negative electrode plate, separator, and electrolyte are disassembled, with the released electrolyte stored in a housing / bag. The entire solid assembly is placed in an oven at 60°C and baked for more than 4 hours (including, but not limited to, the positive electrode plate, negative electrode plate, separator, and other mechanical parts that contribute to the M0 of the disassembled battery cell), and the entire battery cell assembly is weighed as M1, where the weight difference between M0 and M1 is used as the numerator. The liquid retention coefficient is equal to the volume C divided by the weight difference between M0 and M1.

[0148] In some embodiments, the battery cell may further include a separator, and the porosity of the separator is between 30% and 40%.

[0149] In the battery cell of the present application, the amount of lithium hexafluorophosphate added is relatively high, and therefore the viscosity of the entire electrolyte is relatively high, and the porosity of the separator is relatively high, which is advantageous for the relatively viscous electrolyte to pass through the separator, allowing for smooth movement of lithium ions.

[0150] For example, the porosity of the separator may be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or a range consisting of any two of the above values.

[0151] In the present application, the porosity is the percentage of the volume of the holes in the separator relative to the total volume of the separator. The porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries."

[0152] In some embodiments, the separator includes an organic substrate and a coating disposed on at least one side of the organic substrate, the coating including a heat-resistant layer and an organic layer, the heat-resistant layer being located on a surface of the organic substrate and the organic layer being disposed on a surface of the heat-resistant layer facing away from the organic substrate. Combining the separator with the electrolyte and a negative electrode plate can significantly improve the power performance of a battery cell.

[0153] Optionally, the heat-resistant layer contains inorganic particles.The combination of the separator with the electrolyte and the negative electrode plate can significantly improve the power performance of the battery cell.

[0154] Optionally, the organic layer includes one of a non-fluorine-based polymer and a fluorine-containing polymer, and optionally the organic layer includes a non-fluorine-based polymer, for example, the non-fluorine-based polymer includes polyacrylate, in which case the organic layer is a polyacrylate layer. Combining the separator with the electrolyte and a negative electrode plate can significantly improve the power performance of the battery cell.

[0155] Illustratively, the coating may include a ceramic layer and / or a polyacrylate layer, a ceramic layer alone, a polyacrylate layer alone, or a ceramic layer and a polyacrylate layer.

[0156] Alternatively, when the coating comprises a ceramic layer and a polyacrylate layer, the polyacrylate layer may be disposed on at least one surface of the organic substrate and the ceramic layer may be disposed on a surface of the polyacrylate layer facing away from the organic substrate, or the ceramic layer may be disposed on at least one surface of the organic substrate and the polyacrylate layer may be disposed on a surface of the ceramic layer facing away from the organic substrate.

[0157] By installing a polyacrylate layer on the outer surface of the separator, the outer surface of the separator has a certain degree of flexibility, which can effectively mitigate the volume expansion or contraction of the silicon-carbon composite, and improve the structural stability of the entire electrode assembly.

[0158] The material of the organic substrate is not particularly limited, and any known substrate having good chemical and mechanical stability can be selected. For example, the organic substrate may include at least one of a porous polyolefin resin film (e.g., at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The organic substrate may be selected from a single-layer film or a multilayer composite film. When the organic substrate is a multilayer composite film, the materials of each layer may be the same or different.

[0159] In some embodiments, the thickness of the organic substrate is between 6.6 μm and 7.6 μm.

[0160] When the thickness of the organic base material is within the above range, the lithium ion transmission rate in the negative electrode plate and the transmission rate in the separator can be basically matched, reducing the risk of deterioration of concentration polarization, which is advantageous for improving discharge performance.

[0161] For example, the thickness of the organic substrate may be 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, or a range consisting of any two of the above values.

[0162] In some embodiments, the polyacrylate in the polyacrylate layer may be formed by polymerization of a polymeric monomer, where the polymeric monomer includes at least one of a first polymeric monomer, a second polymeric monomer, and a third polymeric monomer. Optionally, the polymeric monomer includes the first polymeric monomer, the second polymeric monomer, and the third polymeric monomer. By forming the polyacrylate by polymerization of the three polymeric monomers, the separator can have adequate adhesion to the electrode plates, improving the dynamic performance of the battery.

[0163] The first polymer monomer has at least one ester linkage and is optionally one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, glycidyl methacrylate, or trimethylolpropane triacrylate, more optionally one or more of methyl methacrylate, lauryl acrylate, lauryl methacrylate, or trimethylolpropane triacrylate.

[0164] The second polymer monomer has at least one cyano bond and is optionally one or more of acrylonitrile, methacrylonitrile, ethacrylonitrile, more optionally one or more of acrylonitrile, methacrylonitrile.

[0165] The third polymer monomer has at least one amide bond and is optionally one or more of acrylamide, N-methylolacrylamide, N-butoxymethacrylamide, more preferably one or more of acrylamide, N-methylolacrylamide.

[0166] In some embodiments, the weight ratio of the first polymeric monomer to the second polymeric monomer to the third polymeric monomer in the polyacrylate formed above is (45-70):(10-25):(10-35), for example, (50-70):(10-25):(10-35), (55-70):(10-25):(10-35), (60-70):(10-25):(10-35), (65-70):(10-25):(10-35). ), (45~70):(15~25):(10~35), (45~70):(20~25):(10~35), (45~70):(22~25):(10~35), (45~70):(10~25):(15~35), (45~70):(10~25):(20~35), (45~70):(10~25):(25~35), (45~70):(10~25):(30~35), (45~70):(10~25):(32~35), etc.

[0167] In some embodiments, the ceramic layer includes inorganic particles having heat resistance properties, and the inorganic particles may include at least one of inorganic particles having a dielectric constant of 5 or higher, inorganic particles having active ion transport capabilities, and inorganic particles capable of generating electrochemical oxidation and reduction.

[0168] In some embodiments, the inorganic particles having a dielectric constant of 5 or higher include boehmite (γ-AlOOH), aluminum oxide (AlO), barium sulfate (BaSO), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)), silicon oxide (SiO). x(0 < x ≤ 2), tin dioxide (SnO2), titanium dioxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium dioxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), magnesium fluoride (MgF2), Pb(Zr,Ti)O3 (abbreviation: PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviation: PLZT, 0 < m < 1, 0 < n < 1) and Pb(Mg3Nb 2 / 3 )O3 - PbTiO3 (abbreviation: PMN - PT) may include at least one of them.

[0169] In some embodiments, the inorganic particles having the ability to transmit active ions are lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y - based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 - based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 - based glass (Li x P y S zIt may include at least one of (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0170] In some embodiments, the inorganic particles capable of generating electrochemical oxidation and reduction may include at least one of lithium-containing transition metal oxides, olivine-structured lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0171] In some embodiments, the ceramic layer may further include an adhesive. Optionally, the adhesive includes one or more of polyacrylate, acrylic acid, carboxymethyl cellulose, polyvinylidene fluoride-co-trichloroethylene copolymer, polymethyl methacrylate, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, and cyanoethyl pullulan.

[0172] In some embodiments, the thickness of the coating is 1.5 μm to 2.5 μm.

[0173] The thickness of the coating is the thickness of the coating on one side. Specifically, it includes the total thickness of the ceramic layer and the polyacrylate layer. For example, when coatings are installed on both sides of the organic substrate, the thickness of the coating on one side of the organic substrate is the thickness of the coating on one side, or when a coating is installed on one side of the two sides of the organic substrate, the thickness of this side coating is the thickness of the coating on one side. When the thickness of the coating is within the above range, the transmission rate of lithium ions in the negative electrode plate and the transmission rate in the separator can be basically made to coincide, reducing the risk of deterioration of concentration polarization, which is advantageous for improving the discharge performance.

[0174] Illustratively, the coating thickness may be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, or a range consisting of any two of the foregoing values.

[0175] In some embodiments, the ratio of the thickness of the ceramic layer to the thickness of the polyacrylate layer can be (0.5-2.0):1, e.g., 0.5:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, or a range consisting of any two of the foregoing values.

[0176] In the embodiments of the present application, the organic substrate and coating thickness are defined as those known in the art and can be detected using equipment and methods known in the art, such as a combination of an ion cross-section polishing device and a scanning electron microscope. For example, the following steps can be performed: First, cut the separator into a sample of a certain size (e.g., 6 mm x 6 mm), sandwich the sample between two electrically and thermally conductive sheets (e.g., copper foil), and bond the sample to the sheets with adhesive (e.g., double-sided adhesive). Press an iron block with a certain mass (e.g., about 400 g) for a certain period of time (e.g., 1 hour) to minimize the gap between the sample and the copper foil. Then, align the edges with scissors and attach the sample to a sample holder with conductive adhesive, allowing the sample to slightly protrude beyond the edge of the holder. Then, the sample stage is locked and fixed to the sample shelf, the power of the argon ion cross-section polishing device is turned on, and the vacuum (e.g., 10 Pa-4 Pa), argon gas flow rate (e.g., 0.15 MPa), voltage (e.g., 8 KV), and polishing time (e.g., 2 hours) are set. The sample stage is then adjusted to oscillation mode and polishing begins. After polishing is completed, a scanning electron microscope (e.g., ZEISS Sigma 300) is used to obtain an ion-polished cross-section topography (CP) image of the sample to be measured, and the thickness of the coating and the organic substrate are measured.

[0177] In some embodiments, the battery cell further includes a positive electrode plate.

[0178] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on one or both of the two opposing surfaces of the positive electrode current collector.

[0179] The positive electrode film layer contains a positive electrode active material, and the positive electrode active material can employ a positive electrode active material known in the art for batteries. As an example, the positive electrode active material may include at least one material of a layered structure positive electrode active material (such as lithium nickel cobalt manganese oxide, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium / sodium-rich layered and rock salt phase layered materials), an olivine-type phosphate active material, a spinel structure positive electrode active material (such as spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide and lithium nickel manganese oxide).

[0180] In some embodiments, the positive electrode active material has the chemical formula Li d Ni a Co b Mn c M (1-a-b-c) Y z of a compound, where 0 < d ≤ 2.1, 0.6 < a < 1, 0 < b < 1, 0 < c < 1, and 0.6 < a + b + c < 1, 1.8 ≤ z ≤ 3.5, the M element includes at least one element of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and the Y element includes at least one element of O, F. By combining the above positive electrode active material system with the above electrolyte and the negative electrode plate, the power performance of the battery cell can be significantly improved.

[0181] In addition to containing lithium, the positive electrode active material further contains nickel, cobalt, manganese and M, where nickel can increase the gram capacity of the positive electrode active material, cobalt can stabilize the crystal structure of the positive electrode active material, manganese can increase the structural stability of the entire positive electrode active material, and M can improve the crystalline structural stability of the positive electrode active material.

[0182] In some embodiments, d is 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 3, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or a range consisting of any two of the above numerical values.

[0183] In some embodiments, 0.85≦a≦0.95.

[0184] a may be 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the above values. By combining the above positive electrode active material system with the above electrolyte and negative electrode plate, the power performance of the battery cell can be significantly improved.

[0185] In some embodiments, b is 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the above values.

[0186] In some embodiments, c is 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the above values.

[0187] In some embodiments, a+b+c can be 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or a range consisting of any two of the foregoing values.

[0188] In some embodiments, z can be 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, or a range consisting of any two of the foregoing values.

[0189] During the charge and discharge process, a battery absorbs, releases, and consumes active ions, such as Li, and the molar content of Li varies when the battery is discharged to different states. In the embodiments of the present application, the molar content of Li in the list of positive electrode active materials refers to the initial state of the material, i.e., the state before the material is added. When the positive electrode active material is used in a battery system and goes through charge and discharge cycles, the molar content of Li may change.

[0190] In the enumeration of positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is merely a theoretical value, and the molar content of oxygen O changes due to oxygen release from the lattice, and in reality, fluctuations occur in the molar content of oxygen O.

[0191] In some embodiments, the M element includes at least one of titanium (Ti) and zirconium (Zr), and optionally, M includes Ti and Zr, both of which can enhance cycle performance.

[0192] In some embodiments, the total mass content of Ti and Zr is 1600 ppm to 3150 ppm, based on the total mass of the positive electrode active material. When the amount of Ti and Zr added is within this range, the crystalline structure of the positive electrode active material can be further improved, and the cycle performance can be improved.

[0193] The total mass content of Ti and Zr elements is the ratio of the total mass of Ti and Zr elements to the total mass of the positive electrode active material.

[0194] For example, the total mass content of Ti and Zr elements may be 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3100 ppm, 3150 ppm, or a range consisting of any two of the above values.

[0195] In some embodiments, the mass content of the Ti element, based on the total mass of the positive electrode active material, may be 100 ppm to 600 ppm, for example, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 450 ppm, 500 ppm, 600 ppm, or a range consisting of any two of the above values.

[0196] In some embodiments, the mass content of Zr element, based on the total mass of the positive electrode active material, is 500 ppm to 2550 ppm, and optionally 1500 ppm to 2550 ppm, such as 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2550 ppm, or a range consisting of any two of the foregoing values.

[0197] In some embodiments, at least one of lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4) in the electrolyte can provide fluorine ions and boron ions. During the later stages of battery cycling, metal ions in the positive electrode active material, such as Ti and Zr ions, may leach into the electrolyte and migrate to the surface of the negative electrode plate. However, the fluorine ions and boron ions have a relatively strong bonding ability with the metal ions, reducing the risk of the metal ions migrating to the surface of the negative electrode plate. This can improve the cycle performance of the battery and compensate for the power degradation caused by the Ti and Zr ions.

[0198] In some embodiments, the active cathode material comprises at least one of single-crystalline particles and polycrystalline particles. The active cathode material system, combined with the electrolyte and the anode plate, can significantly improve the power performance of the battery cell.

[0199] In some embodiments, the cathode active material comprises a single crystal particle, the single crystal particle comprising an inner region and an outer region, the outer region extending 500 nm from any point on the outer surface of the single crystal particle directly into the single crystal material, and the M element comprises aluminum Al, which is distributed in at least the outer region.

[0200] The inner region of the single crystal particle may be understood as the core of the single crystal particle, the outer region is coated on the outside of the inner region, and there may be no clear boundary between the outer region and the inner region, and the outer region and the inner region may be considered as two artificially defined regions, the outer region is a region extending 500 nm from any one point on the outer surface of the single crystal particle toward the inside of the single crystal particle, and the extension path is a straight path, and the outer region may be understood as a ring structure, and the radial pitch of the ring structure is 500 nm or less.

[0201] In some embodiments, the active cathode material includes both single-crystalline particles and polycrystalline particles. Combining the active cathode material system with the electrolyte and anode plate can significantly improve the power performance of a battery cell.

[0202] The aluminum (Al) element is distributed in at least the outer region, and contributes to the formation of aluminum oxide (Al2O3) in the positive electrode active material, thereby passivating side reactions between the positive electrode active material and the electrolyte, thereby further enhancing the structural stability of the positive electrode active material and improving the cycle performance of the battery. Of course, the aluminum element may be distributed not only in the outer region but also in the inner region.

[0203] In some embodiments, the mass content of Al element is 500 ppm to 3000 ppm, and optionally 1000 ppm to 2000 ppm, based on the total mass of the positive electrode active material.

[0204] For example, the mass content of Al element may be 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, or a range consisting of any two of the above values.

[0205] In some embodiments, the combination of lithium difluorophosphate LiPO2F2 in the electrolyte and elemental Al in the active cathode material can improve the DCR on the surface of the active cathode material and increase the interfacial power.

[0206] In some embodiments, the M element includes at least one of phosphorus (P), sulfur (S), and boron (B), and optionally, the M element includes phosphorus (P), sulfur (S), and boron (B). The phosphorus (P), sulfur (S), and boron (B) elements can enhance the structural stability of the positive electrode active material and improve the cycle performance of the battery.

[0207] In some embodiments, the total mass content of P, S, and B, based on the total mass of the positive electrode active material, is 0 to 800 ppm, and optionally 10 ppm to 500 ppm, for example, 0, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, or a range consisting of any two of the foregoing. A total mass content of P, S, and B of 0 indicates that such elements are not added.

[0208] In some embodiments, the total mass content of the P element, based on the total mass of the positive electrode active material, is 10 ppm to 500 ppm, for example, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, or a range consisting of any two of the foregoing values.

[0209] In some embodiments, the total mass content of the S element, based on the total mass of the positive electrode active material, is 10 ppm to 500 ppm, for example, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, or a range consisting of any two of the foregoing values.

[0210] In some embodiments, the total mass content of the B element, based on the total mass of the positive electrode active material, is 10 ppm to 500 ppm, for example, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, or a range consisting of any two of the foregoing values.

[0211] In some embodiments, the electrolyte additive may further include lithium fluorosulfonate, which can form a low-impedance film component on the surface of the positive electrode active material. The combination of lithium fluorosulfonate with the phosphorus (P), sulfur (S), and boron (B) elements in the positive electrode active material can reduce the DCR and increase the interfacial power on the surface of the positive electrode active material.

[0212] In the embodiments of the present application, the element content of the positive electrode active material is defined as being known in the art and can be detected using instruments and methods known in the art. For example, in accordance with EPA 6010D-2014, the element content is measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES, instrument model: Thermo ICAP7400). First, 0.4 g of the positive electrode active material is weighed out, and 10 ml (50% concentration) of aqua regia is added. This is then left on a tablet at 180°C for 30 minutes. After digestion on the tablet, the volume is adjusted to 100 mL, and a quantitative test is performed using the calibration curve method.

[0213] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The embodiments of the present application are not particularly limited to the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≦5% based on the total mass of the positive electrode film layer.

[0214] In some embodiments, the positive electrode membrane layer optionally further includes a positive electrode adhesive. The embodiments of the present application are not particularly limited to the type of positive electrode adhesive. For example, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass content of the positive electrode adhesive is ≦5% based on the total mass of the positive electrode membrane layer.

[0215] In some embodiments, the ratio of the compaction density of the positive electrode membrane layer to the compaction density of the negative electrode membrane layer is (2 to 2.5):1, such as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, or a range consisting of any two of the foregoing values.

[0216] In some embodiments, the packed density PD of the positive electrode membrane layer is 3 g / cm 3 ~3.5g / cm 3 For example, 3g / cm 3 , 3.1g / cm 3 , 3.2g / cm 3 , 3.3g / cm 3 , 3.4g / cm 3 , 3.5g / cm 3 Or it is a range consisting of any two of the above values.

[0217] In the present application, the compaction density of the positive electrode active material layer has a meaning known in the art and can be tested using methods known in the art. For example, a positive electrode plate that has been coated on one side and cold-pressed (if the positive electrode plate is coated on both sides, the positive electrode film on one side can be wiped off first) is taken and punched into a small wafer with an area of ​​S1, which is weighed and recorded as M1. Then, the positive electrode film is wiped off from the weighed positive electrode plate, and the weight of the positive electrode current collector is measured and recorded as M0. The areal density of the positive electrode active material layer = (weight of positive electrode plate M1 - weight of positive electrode current collector M0) / S1, and the compaction density of the positive electrode active material layer = areal density of the positive electrode active material layer / thickness of the positive electrode active material layer.

[0218] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material of the metal layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0219] In some embodiments, the thickness of the positive electrode current collector is 13 μm or less, optionally 8 μm to 13 μm, and optionally 10 μm to 13 μm.

[0220] The thickness of the positive electrode current collector is relatively thin, which can weaken the heat dissipation path of the battery and reserve some heat within the battery cell under low SOC discharge conditions, which is beneficial for improving the DCR at low SOC and thereby improving the discharge power at low SOC.

[0221] For example, the thickness of the positive electrode current collector may be 8 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9.0 μm, 9.2 μm, 9.5 μm, 9.6 μm, 9.8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or a range consisting of any two of the above numerical values.

[0222] In the embodiments of the present application, the thickness of the positive electrode current collector has a meaning known in the art and can be detected using an instrument and a method known in the art. For example, a positive electrode plate is used as a sample, and the positive electrode film layer on the surface of the positive electrode plate is washed with an organic solvent such as alcohol, and the thickness of the positive electrode current collector is measured with a multimeter.

[0223] The positive electrode film layer is typically obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other optional components in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0224] In some embodiments, the positive electrode plate, separator, and negative electrode plate can be manufactured into an electrode assembly by a winding process and / or a stacking process, and the electrode assembly may be understood as being a wound electrode assembly or a stacked electrode assembly. Optionally, the electrode assembly is a stacked electrode assembly, which can provide closer contact between the positive electrode plate and the negative electrode plate and further improve the DCR.

[0225] In some embodiments, the battery may include an outer casing, which may be used to package the electrode assembly and electrolyte.

[0226] In some embodiments, the battery exterior may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The battery exterior may be a pouch, such as a bag-like pouch. The pouch may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0227] The embodiments of the present application are not particularly limited to the shape of the battery, which may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0228] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be wound and / or stacked to form an electrode assembly 52. ​​The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0229] The manufacturing method of the battery according to the embodiment of the present application is well known. In some embodiments, a battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate can be wound and / or stacked to form an electrode assembly. The electrode assembly can then be placed in an outer casing, dried, and then injected with an electrolyte. The battery can then be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0230] In some examples of the embodiments of the present application, the batteries according to the embodiments of the present application may be assembled into a battery module, and the number of batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0231] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of battery cells 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of battery cells 5 may be fixed by fasteners.

[0232] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of battery cells 5 are accommodated in this accommodating space.

[0233] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0234] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0235] power consumption equipment A third aspect of an embodiment of the present application provides a power consuming device, the power consuming device including at least one of the battery, battery module, or battery pack of the embodiment of the present application. The battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0236] A power consuming device can select a battery, a battery module, or a battery pack according to its usage needs.

[0237] 6 is a schematic diagram of an example power consuming device 6, which may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density demands of the power consuming device 6, a battery pack or battery module may be employed.

[0238] Another example of a power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. This power consuming device generally requires a thin design and may employ a battery as a power source.

[0239] Example The following examples more specifically describe the contents disclosed in the embodiments of the present application, and these examples are merely descriptive explanations, since it will be apparent to those skilled in the art that various modifications and variations can be made within the scope of the contents disclosed in the embodiments of the present application. Unless otherwise specified, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or can be synthesized and obtained by conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0240] Example 1 1. Manufacturing of positive electrode plates The positive electrode plate includes a positive electrode current collector and a positive electrode film layer. The positive electrode current collector is an aluminum foil with a thickness of 10 μm. The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (solvent: N-methylpyrrolidone NMP) on the surface of the aluminum foil positive electrode current collector, drying, and cold pressing. The positive electrode film layer includes a positive electrode active material in a weight ratio of 97.5:1.4:1.1, a conductive agent of carbon black, and an adhesive of polyvinylidene fluoride (PVDF).

[0241] The positive electrode active material has a single crystal structure and has the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) O z wherein the nickel cobalt manganese oxide substrate in the positive electrode active material has the molecular formula LiNi 0.70 Co 0.10 Mn 0.20 Contains compounds of O2.

[0242] The M elements include 450 ppm Ti element, 1700 ppm Zr element, 1600 ppm Al element, and 120 ppm (B, S and P) elements.

[0243] 2. Manufacturing of negative electrode plates The negative electrode plate includes a negative electrode current collector and a negative electrode film layer. The negative electrode current collector is a copper foil with a thickness of 4.5 μm. The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (solvent: deionized water) on the surface of the negative electrode current collector copper foil, drying, and cold pressing. The negative electrode film layer includes a negative electrode active material in a weight ratio of 96.2:1.8:1.2:0.8, an adhesive agent: styrene butadiene rubber (SBR), a thickener: sodium carboxymethyl cellulose (CMC-Na), and a conductive agent: carbon black (Super P).

[0244] The negative electrode active material is 97% artificial graphite and 3% silicon oxide SiO x The mass content of silicon relative to the total mass of the negative electrode active material is 1.91%.

[0245] 3. Separator The separator can be purchased directly from Ningde Zhuo High-Tech Materials Technology Co., Ltd. The porosity of the separator is 30% and includes an organic substrate (porous polypropylene PP (7 μm)) and a coating. The coating includes a ceramic layer (1 μm) and a polyacrylate layer (1 μm). The ceramic layer is disposed on two surfaces of the organic substrate. The ceramic layer includes a film layer formed by dissolving an adhesive and inorganic aluminum oxide in N-methylpyrrolidone (NMP) and applying the solution to the organic substrate. The polyacrylate layer is disposed on the surface of the ceramic layer facing away from the organic substrate. The polyacrylate layer is a film layer formed by applying a polyacrylate-containing substance to the surface of the ceramic layer.

[0246] 4. Electrolyte production The electrolyte solution includes an organic solvent, a lithium salt, and an additive. The organic solvent includes a cyclic carbonate (EC, PC, and BC, with a mass ratio of 1:1:1) and a chain carbonate (EMC, DMC, and DEC, with a mass ratio of 1:1:1). The additive includes monofluoroethylene carbonate (FEC). The additive further includes at least one of PS, VC, and LiSO3F, with the total content being ≦2%.

[0247] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate are stacked in this order, with a separator positioned between the positive electrode plate and the negative electrode plate to provide isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an outer case and dried, after which an electrolyte is injected. After vacuum packaging, standing, chemical formation, shaping, and other processes, a lithium ion battery is obtained, and the liquid retention coefficient of the lithium ion battery is 2.0 g / Ah.

[0248] Comparative Example 1 A lithium ion battery was manufactured using a method similar to that of Example 1. The difference from Example 1 is that the negative electrode active material of Comparative Example 1 is different. The negative electrode active material is 94% artificial graphite and 6% silicon oxide SiO x and the mass content of silicon element is 3.82%.

[0249] Comparative Examples 2 and 3 Lithium-ion batteries were manufactured using a method similar to that of Example 1. The difference from Example 1 is that the components of the electrolyte, particularly the content of lithium hexafluorophosphate, were adjusted in Comparative Examples 2 and 3.

[0250] Comparative Example 4 A lithium ion battery was fabricated using a method similar to that of Example 1, except that the negative electrode active material of Comparative Example 4 was different, and the negative electrode active material contained 100% artificial graphite.

[0251] Examples 2-1 to 2-5 Lithium ion batteries were manufactured using a method similar to that of Example 1, and the difference from Example 1 is that in Examples 2-1 to 2-5, at least the composition of the negative electrode active material was adjusted.

[0252] Examples 3-1 to 3-3 Lithium ion batteries were manufactured using a method similar to that of Example 1, and the difference from Example 1 is that in Examples 3-1 to 3-3, at least the composition of the negative electrode active material was adjusted.

[0253] Example 4 to Example 4-2 Lithium ion batteries were manufactured using a method similar to that of Example 1, and the difference from Example 1 is that Examples 4 to 4-2 adjusted at least the composition of the electrolyte, particularly the mass content of lithium hexafluorophosphate.

[0254] Examples 5-1 to 5-7 Lithium ion batteries were manufactured using a method similar to that of Example 1, but the difference from Example 1 is that Examples 5-1 to 5-7 adjusted the composition of at least one of the electrolytes, particularly the mass content of at least one of the cyclic ester and the linear carbonate.

[0255] Examples 6-1 to 6-4 Lithium ion batteries were manufactured using a method similar to that of Example 1, except that Examples 6-1 to 6-4 were different from Example 1 in that the composition of at least the electrolyte, particularly the mass content of the fluorinated cyclic carbonate, was adjusted.

[0256] Example 7 A lithium-ion battery was fabricated using a method similar to that of Example 1. The difference between Example 7 and Example 1 is that the composition of the electrolyte, particularly the type of fluorinated cyclic carbonate, was adjusted to DFEC, which contains two fluorine atoms, has relatively weak polarity, and is more difficult to form a film with compared to FEC.

[0257] Examples 8-1 to 8-4 Lithium ion batteries were manufactured using a method similar to that of Example 1, and differ from Example 1 in that Examples 8-1 to 8-4 adjusted at least the liquid retention coefficient of the electrolyte.

[0258] Examples 9-1 to 9-4 Lithium ion batteries were manufactured using a method similar to that of Example 1, except that Examples 9-1 to 9-4 were different from Example 1 in that at least one of the coating thickness and porosity of the separator was adjusted.

[0259] Examples 9-3 and 9-4 use PP materials with different porosities, and the different porosities can be adjusted by methods known to those skilled in the art.

[0260] The parameters of the examples and comparative examples are as shown in Tables 1 to 3.

[0261] Performance Test 1. Lithium-ion battery DC internal resistance (DCR) test Capacity test flow: In an environment of 25°C, the lithium ion batteries manufactured in the examples and comparative examples were first discharged to 2.8V at 0.33C, then charged to 4.35V at 0.33C, and then charged at 4.35V at a constant voltage until the current value was less than 0.05C. Then, the batteries were discharged to 2.8V at 0.33C. The discharge capacity at this time was recorded as the actual capacity D0 of the battery. 10%SOC adjustment: Charge the lithium-ion battery at 0.1C (where C is determined by the tested D0) for 6 minutes to adjust it to 10% SOC, record the voltage value at this time as U1, and discharge it at 4C for 10 seconds, record the voltage value at this time as U2, DC internal resistance DCR = (U1-U2) / I.

[0262] Test results The test results are shown in Tables 1 to 3.

[0263] [Table 1] JPEG0007801471000002.jpg252170 JPEG0007801471000003.jpg79170

[0264] [Table 2] JPEG0007801471000005.jpg252160JPEG0007801471000006.jpg252156JPEG0007801471000007.jpg25284

[0265] [Table 3] JPEG0007801471000009.jpg252157JPEG0007801471000010.jpg252160

[0266] As can be seen from Tables 1 to 3, Although Comparative Examples 1 and 4 both used appropriate electrolyte systems, the silicon content in Comparative Example 1 was relatively high. Even though the system contained a relatively high amount of lithium hexafluorophosphate, the volume expansion of the silicone-based material could not be effectively alleviated. This increased the risk of structural collapse and pulverization of the silicone-based material, which was unfavorable for improving DCR and resulted in relatively poor battery discharge power. Comparative Example 4 used artificial graphite as the negative electrode active material, but at a low SOC, the artificial graphite was less involved in discharge and prone to insufficient discharge, resulting in relatively poor discharge power.

[0267] Comparative Examples 2 and 3 both used appropriate silicon materials, but Comparative Example 2 used a relatively low content of lithium hexafluorophosphate (12%). The relatively low content of lithium hexafluorophosphate resulted in a relatively small amount of fluorine lithium oxide formed on the surface of the negative electrode active material, and was unable to effectively alleviate the problem of the silicon-based material exploding and pulverizing. Comparative Example 3 used a relatively high content of lithium hexafluorophosphate (23%). The relatively high content of lithium hexafluorophosphate effectively alleviated the volume expansion of the silicon-based material, but the lithium hexafluorophosphate made the viscosity of the electrolyte system too high, which was unfavorable for the migration of lithium ions from the negative electrode surface to the positive electrode surface. This made it difficult to improve the discharge power in the later stages of discharge.

[0268] Compared to Comparative Examples 1 to 4, Example 1 adjusts the silicon content (mass content of silicon element is 0.3% or more and 3.0% or less) in the silicon oxide of the negative electrode active material and combines it with an appropriate electrolyte system (mass content of lithium hexafluorophosphate is 15% to 20%), thereby reducing the internal resistance of the battery at the end of discharge and improving the discharge power performance.

[0269] The change in silicon content has a certain effect on the discharge power of the battery. When the silicon content is low, the negative electrode active material involved in the later discharge is relatively small, which is unfavorable for improving the discharge power of the battery. When the silicon content is high, the unfavorable effect of volume expansion gradually appears. Therefore, selecting an appropriate silicon content is more favorable for improving the discharge power of the battery. For example, when the silicon content by mass in silicon oxide is 0.3% or more and 3.0% or less, the battery discharge power can be significantly improved. The quality of the silicone-based material and carbon-based material also has a certain effect on the discharge power. The composition of the electrolyte also has a certain effect on the discharge power.

[0270] Example 10-1 1. Manufacturing of positive electrode plates The positive electrode plate includes a positive electrode current collector and a positive electrode film layer. The positive electrode current collector is an aluminum foil with a thickness of 12 μm. The positive electrode film layer is formed by uniformly coating the surface of the aluminum foil positive electrode current collector with a positive electrode slurry (solvent: N-methylpyrrolidone (NMP)), drying, and cold pressing. The positive electrode film layer includes a positive electrode active material in a weight ratio of 97.5:1.4:1.1, a conductive agent: carbon black, and an adhesive: polyvinylidene fluoride (PVDF). The compaction density of the positive electrode film layer is 3.35 g / cm. 3 is.

[0271] The positive electrode active material has a single crystal structure and has the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) O z wherein the nickel cobalt manganese oxide substrate in the positive electrode active material has the molecular formula LiNi0.70 Co 0.10 Mn 0.20 The M element contains 450 ppm Ti, 1700 ppm Zr, 1600 ppm Al, and 120 ppm (B, S, and P) elements.

[0272] 2. Manufacturing of negative electrode plates The negative electrode plate includes a negative electrode current collector and a negative electrode film layer. The negative electrode current collector is a copper foil with a thickness of 4.5 μm. The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (solvent: deionized water) on the surface of the negative electrode current collector copper foil, drying, and cold pressing. The negative electrode film layer includes a negative electrode active material in a weight ratio of 96.2:1.8:1.2:0.8, an adhesive styrene butadiene rubber (SBR), a thickener carboxymethyl cellulose sodium (CMC-Na), and a conductive agent carbon black (Super P).

[0273] The negative electrode active material includes artificial graphite and a silicon-carbon composite.

[0274] 3. Separator The separator can be purchased directly from a separator supplier. The porosity of the separator is 30%. The separator includes an organic substrate (porous polypropylene (PP) (7 μm)) and a coating. The coating includes a ceramic layer (1 μm) and a polyacrylate layer (1 μm). The ceramic layer is attached to two surfaces of the organic substrate. The ceramic layer includes a film layer formed by dissolving an adhesive and inorganic aluminum oxide in N-methylpyrrolidone (NMP) and applying the solution to the organic substrate. The polyacrylate layer is attached to the surface of the ceramic layer facing away from the organic substrate. The polyacrylate layer is a film layer formed by applying a polyacrylate-containing substance to the surface of the ceramic layer.

[0275] 4. Electrolyte production The electrolyte solution contains an organic solvent, a lithium salt, and an additive. The organic solvent contains cyclic carbonate (EC, PC, and BC, the mass ratio of each component is 1:1:1) and linear carbonate (EMC, DMC, and DEC, the mass ratio of each component is 1:1:1). The additive contains 0.25% monofluoroethylene carbonate (FEC). The lithium salt contains 18.2% lithium hexafluorophosphate, 0.2% lithium difluorophosphate, and 0.2% lithium tetrafluoroborate. The total lithium salt content is 18.6%, and the rest is organic solvent.

[0276] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate are stacked in this order, with a separator positioned between the positive electrode plate and the negative electrode plate to provide isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an outer case and dried, after which an electrolyte is injected. After vacuum packaging, standing, chemical formation, shaping, and other processes, a lithium ion battery is obtained, and the liquid retention coefficient of the lithium ion battery is 1.3 g / Ah.

[0277] Examples 10-2 to 10-4 A lithium ion battery was manufactured using a method similar to that of Example 10-1, except that the content of each negative electrode active material in the negative electrode plate was adjusted.

[0278] Example 11 and Example 11-2 A lithium ion battery was fabricated using a method similar to that of Example 10-1, except that the mass content of monofluoroethylene carbonate FEC in the electrolyte was adjusted.

[0279] The detection was carried out using the test methods in Tables 1 to 3, and the test results are shown in Table 4.

[0280] [Table 4]

[0281] As can be seen from Table 4, in Examples 10-1 to 11-2, by adjusting the silicon content (mass content of silicon element in the silicon-carbon composite is 0.3% or more and 10% or less) and combining it with an appropriate electrolyte system (mass content of lithium hexafluorophosphate is 15% to 20%), the internal resistance of the battery at the end of discharge can be significantly reduced and the discharge power performance can be improved.By adjusting the mass content of the fluorinated cyclic carbonate, the internal resistance of the battery at the end of discharge can be adjusted and the discharge power performance can be improved.

[0282] Although illustrative embodiments have been demonstrated and described, it should be understood by those skilled in the art that the above embodiments should not be construed as limitations on the present application, and that the embodiments can be changed, substituted, and modified without departing from the spirit, principles, and scope of the present application. [Explanation of symbols]

[0283] The symbols are explained as follows: 1, battery pack, 2, upper housing, 3, lower housing, 4, battery module, 5, battery cell, 51, case, 52, electrode assembly, 53, cover plate, 6, power consumption equipment.

Claims

1. A battery cell, an electrolyte solution containing a lithium salt, wherein the lithium salt includes lithium hexafluorophosphate, and the mass content of the lithium hexafluorophosphate relative to the total mass of the electrolyte solution is 15% to 20%; a positive electrode plate including a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material; a negative electrode plate including a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector and containing a negative electrode active material, the negative electrode active material further including a carbon-based material and a silicon-carbon composite, and a mass content of silicon in the silicon-carbon composite relative to the total mass of the negative electrode active material is 0.3% or more and 10.0% or less; a separator disposed between the positive electrode plate and the negative electrode plate, The battery cell, wherein the electrolyte further comprises a fluorinated cyclic carbonate.

2. 2. The battery cell according to claim 1, wherein the mass content of silicon element in the silicon-carbon composite relative to the total mass of the negative electrode active material is 4.0% or more and 7.0% or less.

3. 3. The battery cell according to claim 1, wherein the mass content of the silicon-carbon composite is 0.4% to 14.5% based on the total mass of the negative electrode active material.

4. The battery cell of claim 3 , wherein the mass content of the silicon-carbon composite is 5.75% to 10% based on the total mass of the negative electrode active material.

5. The battery cell according to claim 1 or 2, wherein the carbon-based material includes at least one of artificial graphite and natural graphite.

6. The battery cell of claim 5 , wherein the carbon-based material includes artificial graphite.

7. 2. The battery cell according to claim 1, wherein the electrolyte solution further contains a cyclic carbonate, and a ratio of a mass content of the cyclic carbonate to a mass content of the lithium hexafluorophosphate, based on a total mass of the electrolyte solution, is (0.60 to 2.50):

1.

8. 8. The battery cell according to claim 7, wherein the ratio of the mass content of the cyclic carbonate to the mass content of the lithium hexafluorophosphate is (1.00-1.65):

1.

9. the cyclic carbonate content by mass is between 10% and 41%; and / or 9. The battery cell according to claim 7, wherein the cyclic carbonate includes at least one of ethylene carbonate, propylene carbonate, and butylene carbonate.

10. 10. The battery cell according to claim 9, wherein the mass content of the cyclic carbonate is 20% to 30%.

11. 8. The battery cell according to claim 7, wherein the electrolyte solution further contains a chain carbonate, and the ratio of the mass content of the chain carbonate to the mass content of the cyclic carbonate, based on the total mass of the electrolyte solution, is (0.9 to 6):

1.

12. 12. The battery cell according to claim 11, wherein the ratio of the mass content of the chain carbonate to the mass content of the cyclic carbonate is (1.5 to 2.65):

1.

13. the mass content of the linear carbonate is 35% to 65%; and / or 13. The battery cell according to claim 11 or 12, wherein the chain carbonate includes at least one of ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate.

14. 2. The battery cell of claim 1, wherein the fluorinated cyclic carbonate comprises at least one of monofluoroethylene carbonate, bisfluoroethylene carbonate, and trifluoropropylene carbonate.

15. the fluorinated cyclic carbonate comprises monofluoroethylene carbonate; and / or 15. The battery cell according to claim 14, wherein a ratio of a mass content of the fluorinated cyclic carbonate to a mass content of the silicon element relative to a total mass of the electrolyte solution is (0.01-9.5):

1.

16. 16. The battery cell according to claim 15, wherein the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the silicon element relative to the total mass of the electrolyte solution is (0.01-0.15):

1.

17. 2. The battery cell according to claim 1, wherein the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt is (0.005-0.30):1, based on the total mass of the electrolyte solution.

18. 18. The battery cell according to claim 17, wherein the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of the lithium salt is (0.005-0.03):1, based on the total mass of the electrolyte solution.

19. The battery cell according to claim 1 , wherein the mass content of the fluorinated cyclic carbonate is 0.05% to 5.80% based on the total mass of the electrolyte solution.

20. 20. The battery cell of claim 19, wherein the mass content of the fluorinated cyclic carbonate is 0.1% to 1.0%, based on the total mass of the electrolyte solution.

21. 2. The battery cell of claim 1, wherein the lithium salt further comprises at least one of a fluorine-containing inorganic phosphate and a fluorine-containing inorganic borate.

22. The mass content of the fluorine-containing inorganic phosphate is 0.05% to 0.50% based on the total mass of the electrolyte; and / or 22. The battery cell of claim 21, wherein the mass content of the fluorine-containing inorganic borate is 0.05% to 0.50%, based on the total mass of the electrolyte solution.

23. the mass content of the fluorine-containing inorganic phosphate is between 0.10% and 0.30%, and / or 23. The battery cell according to claim 22, wherein the mass content of the fluorine-containing inorganic borate is 0.10% to 0.30%.

24. The fluorine-containing inorganic phosphate is lithium difluorophosphate LiPO ２ F ２ and / or The fluorine-containing inorganic borate is lithium tetrafluoroborate LiBF ４ and lithium difluoro(oxalato)borate LiDFOB.

25. 2. The battery cell according to claim 1, wherein the battery cell has a liquid retention coefficient of 1.0 g / Ah to 2.5 g / Ah.

26. 26. The battery cell according to claim 25, wherein the battery cell has a liquid retention coefficient of 1.0 g / Ah to 1.5 g / Ah.

27. The battery cell according to claim 1 , wherein the porosity of the separator is 30% to 40%.

28. 2. The battery cell of claim 1, wherein the separator includes an organic substrate and a coating disposed on at least one side of the organic substrate, the coating including a heat-resistant layer and an organic layer, the heat-resistant layer being disposed on a surface of the organic substrate, and the organic layer being disposed on a surface of the heat-resistant layer that is away from the organic substrate.

29. 30. The battery cell of claim 28, wherein the organic layer comprises a non-fluorinated polymer.

30. 30. The battery cell of claim 29, wherein the non-fluorinated polymer comprises a polyacrylate layer.

31. the thickness of the organic substrate is between 6.6 μm and 7.6 μm; and / or 31. The battery cell according to any one of claims 28 to 30, wherein the coating has a thickness of 1.5 μm to 2.5 μm.

32. The positive electrode active material has the molecular formula Li ｄ Ni ａ Co ｂ Mn ｃ M （１－ａ－ｂ－ｃ） Y ｚ wherein 0<d≦2.1, 0.6<a<1, 0<b<1, 0<c<1, and 0.6<a+b+c<1, 1.8≦z≦3.5, the M element includes at least one element selected from the group consisting of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and the Y element includes at least one element selected from the group consisting of O and F.

33. 33. The battery cell of claim 32, wherein 0.85≦a≦0.

95.

34. 34. The battery cell of claim 32 or 33, wherein the positive electrode active material includes at least one of single-crystal particles and polycrystalline particles.

35. 35. The battery cell of claim 34, wherein the positive electrode active material comprises single-crystalline particles and polycrystalline particles.

36. A battery comprising the battery cell according to claim 1 or 2.

37. 37. A power consuming device comprising the battery of claim 36.

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