Lithium-ion batteries, batteries and power consumption devices

Abstract

The present application relates to a lithium ion battery, a battery and a power consuming device, the lithium ion battery comprising an electrolyte and a positive electrode plate, the electrolyte comprising a lithium salt, the lithium salt comprising lithium hexafluorophosphate, the mass content of the lithium hexafluorophosphate being 15% to 20% relative to the total mass of the electrolyte, the positive electrode plate comprising 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 positive electrode active material having a molecular formula of Li d Ni a Co b Mn c M (1-a-b-c) Q z Compounds in which:

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to Chinese patent application 202311422403.0, filed on October 30, 2023, entitled “Lithium-ion battery, battery and power consumption device,” the entirety of which is incorporated herein by reference.

[0002] This application claims priority to PCT patent application PCT / CN2024 / 075983, filed on February 5, 2024, entitled “Lithium-ion battery, battery and power consumption device,” the entirety of which is incorporated herein by reference.

[0003] This application relates to lithium-ion batteries, batteries, and power consumption devices. [Background technology]

[0004] Lithium-ion batteries have characteristics such as high capacity and long lifespan, and are therefore 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. Because lithium-ion batteries have made significant progress, higher demands are being placed on their performance.

[0005] However, the cycle performance of lithium-ion batteries remains low at present. [Overview of the project]

[0006] This application provides a lithium-ion battery, a battery and a power consumption device, and the cycle performance of the lithium-ion battery of this application is relatively low.

[0007] According to a first aspect, an embodiment of the present application provides a lithium-ion battery. The lithium-ion battery includes an electrolyte and a positive electrode plate. The electrolyte contains a lithium salt, the lithium salt contains lithium hexafluorophosphate, and the mass content of lithium hexafluorophosphate in the total mass of the electrolyte is 15% to 20%. The positive electrode plate contains a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector and containing a positive electrode active material. The positive electrode active material contains a compound with the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) Q z 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 contains at least one element selected from 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. The Q element contains at least one element selected from O, F.

[0008] As a result, the nickel element content of the positive electrode active material in the embodiments of this application is relatively high, and in order to improve the stability of the positive electrode active material structure, the positive electrode active material in the embodiments of this application further contains element M, and the introduction of element M can improve the stability of the crystal structure of the positive electrode active material and improve the cycle performance of the lithium-ion battery. However, as the cycle progresses, there is a risk that both metallic and nonmetallic elements in the positive electrode active material will dissolve, and the dissolved metallic and nonmetallic elements can migrate to the surface of the negative electrode plate via the electrolyte, and to the solid electrolyte interface (Solid Electrolyte) on the surface of the negative electrode plate. Interphase (SEI) film may be destroyed and deposited as individual metals on the surface of the negative electrode plate, thereby degrading cycle performance. Embodiments of this application further combine lithium hexafluorophosphate with a high content, where the mass content of lithium hexafluorophosphate (LiPF6) relative to the total mass of the electrolyte is 15% to 20%. The high content of lithium hexafluorophosphate can form a protective layer on the surface of the positive electrode active material, with lithium fluoride (LiF) as the main film component, thereby mitigating the leaching of metallic and nonmetallic elements to some extent and further improving the cycle performance of the lithium-ion battery.

[0009] In some embodiments, element M includes at least one element from Ti and Zr. By combining a positive electrode active material containing the above elements with an electrolyte, the cycle performance of a lithium-ion battery can be effectively improved.

[0010] In some embodiments, the element M includes the element Zr. By combining a positive electrode active material containing the above elements with an electrolyte, the cycle performance of a lithium-ion battery can be effectively improved.

[0011] In some embodiments, the M element comprises at least one of Ti and Zr, and the electrolyte comprises a first additive, the first additive comprising at least one of lithium difluoro(oxalato)borate LiDFOB and lithium tetrafluoroborate LiBF4.

[0012] As a result, in the later stages of the lithium-ion battery cycle, metal ions such as Ti and Zr ions in the positive electrode active material have the risk of dissolving into the electrolyte and migrating to the surface of the negative electrode plate. The first additive contains fluoride ions and boron ions, which have a relatively strong binding ability with the above metal ions, thereby reducing the risk of metal ions migrating to the surface of the negative electrode plate and improving the cycle performance of the lithium-ion battery. Furthermore, while Ti and Zr ions can improve the structural stability of the material, they can adversely affect the conduction of lithium ions within the crystal lattice, potentially causing power degradation. The first additive can further compensate for the power degradation caused by Ti and Zr ions.

[0013] In some embodiments, element M includes elements Ti and Zr. When M includes both Ti and Zr, the two elements can be used together to further stabilize the material structure and improve cycle performance.

[0014] In some embodiments, the mass content of Ti element is between 100 ppm and 600 ppm, based on the total mass of the positive electrode active material.

[0015] In some embodiments, the mass content of element Zr is between 500 ppm and 5000 ppm, based on the total mass of the positive electrode active material. By combining the positive electrode active material containing the above element with the electrolyte, the cycle performance of the lithium-ion battery can be effectively improved.

[0016] In some embodiments, the mass content of Ti is 100 ppm to 600 ppm and the mass content of Zr is 500 ppm to 5000 ppm relative to the total mass of the positive electrode active material, and the mass content of the first additive is 30 ppm to 1200 ppm, and selectively 100 ppm to 400 ppm, relative to the total mass of the electrolyte.

[0017] In some embodiments, the positive electrode active material includes one or more single-crystal particles and polycrystalline particles. By combining the positive electrode active material with the electrolyte having the above structure, the cycle performance of the lithium-ion battery can be effectively improved.

[0018] In some embodiments, the positive electrode active material includes single-crystal particles and polycrystalline particles. By combining the positive electrode active material with the electrolyte having the above structure, the cycle performance of the lithium-ion battery can be effectively improved.

[0019] In some embodiments, the positive electrode active material comprises single crystal particles, each comprising an inner region and an outer region, the outer region being a region extending 500 nm directly into the interior of the single crystal particle from any point on the outer surface of the single crystal particle, and the M element comprising the Al element, the Al element being distributed at least in the outer region. The distribution of the aluminum Al element at least in the outer region helps to form aluminum oxide Al2O3 in the positive electrode active material, passivating side reactions between the positive electrode active material and the electrolyte, further improving the stability of the positive electrode active material structure, and improving the cycle performance of the lithium-ion battery.

[0020] In some embodiments, the electrolyte includes a second additive, the second additive being lithium difluorophosphate. Lithium difluorophosphate (LiPO2F2), when combined with the element Al in the positive electrode active material, can improve the DCR of the surface of the positive electrode active material and enhance the interfacial power.

[0021] In some embodiments, the mass content of Al is 500 ppm to 3000 ppm relative to the total mass of the positive electrode active material, and the mass content of the second additive is 100 ppm to 3000 ppm relative to the total mass of the electrolyte.

[0022] In some embodiments, element M further comprises at least one element from among P, S, and B, where at least one of P, S, and B is distributed in the outer region, and the electrolyte comprises a third additive, the third additive comprising lithium fluorosulfonate. The elements phosphorus (P), sulfur (S), and boron (B) are absorbed into the oxygen layer and play a role in stabilizing lithium, thereby improving the stability of the positive electrode active material structure and improving the cycle performance of the lithium-ion battery.

[0023] In some embodiments, the total mass content of elements P, S, and B is 10 ppm to 800 ppm relative to the total mass of the positive electrode active material, and the mass content of the third additive is 50 ppm to 200 ppm relative to the total mass of the electrolyte. The third additive, in combination with elements phosphorus (P), sulfur (S), and boron (B) in the positive electrode active material, can reduce the DCR on the surface of the positive electrode active material and improve the interfacial power.

[0024] In some embodiments, the electrolyte contains 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 selectively (1.00 to 1.65):1. 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 to sufficiently dissociate more lithium ions from lithium hexafluorophosphate, thereby allowing the electrolyte system to contain more lithium ions even at the end of low SOC discharge, and enabling continuous dissociation of lithium ions as the battery reaction progresses, thereby improving the power performance of the battery.

[0025] In some embodiments, the mass content of the cyclic carbonate is 20 to 30% of the total mass of the electrolyte, and / or the cyclic carbonate includes at least one of ethylene carbonate EC, propylene carbonate PC, and butylene carbonate BC. 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.

[0026] In some embodiments, the lithium-ion battery further includes a negative electrode plate, the negative electrode plate containing a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector and containing a negative electrode active material, the negative electrode active material containing carbon and silicon, and the mass content of silicon is 0.30% to 10.00% based on the total mass of the negative electrode active material. By combining the above negative electrode active material, positive electrode active material and electrolyte, the cycle performance of the lithium-ion battery can be effectively improved.

[0027] As a result, the negative electrode active material simultaneously includes a carbon-based material and a silicon-based material. Because the lithium discharge voltage plateau of the silicon-based material is relatively higher than that of the carbon-based material, the silicon-based material can still continue to participate in discharge even at low SOC (e.g., SOC ≤ 10%), compensating for the shortcomings of the carbon-based material, which is that it is difficult to discharge or cannot continue to discharge at low SOC. This improves the DC internal resistance (DCR) during the battery discharge process and further improves the power performance during the battery discharge process. The electrolyte of the embodiment of this application further uses 15% to 20% lithium hexafluorophosphate in combination, and the synergistic action of the electrolyte and the negative electrode improves the power performance at the end of the battery discharge process.

[0028] In some embodiments, the electrolyte contains a fluorinated cyclic carbonate, and the ratio of the mass content of the fluorinated cyclic carbonate to the mass content of silicon relative to the total mass of the electrolyte is (0.01 to 9.5):1, and selectively (0.01 to 0.15):1. This allows the fluorinated cyclic carbonate to participate in the formation of an SEI film on the surface of the negative electrode active material, improving the film composition and properties and effectively protecting the negative electrode active material. In particular, when the negative electrode contains silicon, due to the expansion properties of silicon, it is necessary to further optimize the film composition for SEI film formation. This optimization of the film composition is adjusted by adjusting the relative ratio of film-forming additives in the electrolyte, which can improve the flexibility of the SEI film by participating in the film formed by the fluorinated cyclic carbonate, improving structural collapse caused by the rapid release of a large amount of lithium ions at the end of discharge. Furthermore, the fluorinated cyclic carbonate has a certain desolvation capacity, which is advantageous for lithium ion movement, improving DCR at low SOC and improving discharge power.

[0029] In some embodiments, the mass content of fluorinated cyclic carbonate is 0.05% to 5.80% of the total mass of the electrolyte, and selectively 0.1% to 1.0%. Fluorinated cyclic carbonate in the above mass content can effectively reduce the expansion of the negative electrode active material and reduce surface damage to the positive electrode active material, thereby effectively improving the cycle performance of the lithium-ion battery.

[0030] In some embodiments, the fluorinated cyclic carbonate comprises at least one of monofluoroethylene carbonate FEC, bisfluoroethylene carbonate DFEC, and trifluoropropylene carbonate TFPC, and selectively, the fluorinated cyclic carbonate comprises monofluoroethylene carbonate FEC.

[0031] In some embodiments, the ratio of the compaction density of the positive electrode film layer to the compaction density of the negative electrode film layer is (2 to 2.5):1. Selectively, the compaction density of the positive electrode film layer is 3.0 g / cm³. 3 From 3.5 g / cm³ 3and the consolidation density of the negative electrode film layer is 1.3 g / cm 3 to 1.7 g / cm 3 .

[0032] In some embodiments, the electrolytic solution further contains a fourth additive, and the fourth additive contains at least one of 1,3 - propane sultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F. The above components can basically participate in forming a SEI film on the surface of the negative electrode active material, and the SEI film can effectively relieve the expansion of the silicon - based material.

[0033] In some embodiments, based on the total mass of the electrolytic solution, the mass content of 1,3 - propane sultone PS is from 0.1% to 1%, and / or based on the total mass of the electrolytic solution, the mass content of vinylene carbonate VC is from 0.1% to 1%, and / or based on the total mass of the electrolytic solution, the mass content of lithium fluorosulfonate LiSO3F is from 0.1% to 1%.

[0034] In some embodiments, 0.85 ≦ a ≦ 0.95. By combining the positive electrode active material with the above - described structure and the electrolytic solution, the cycle performance of the lithium - ion battery can be effectively improved.

[0035] According to a second aspect, the present application further provides a battery including the lithium - ion battery of any embodiment of the first aspect of the present application.

[0036] According to a third aspect, the present application further provides a power - consuming device, and this power - consuming device includes the battery of any one embodiment of the second aspect of the present application.

Brief Description of the Drawings

[0037] To more clearly illustrate the technical concept of the embodiments of this application, the following briefly introduces the drawings that may be used in the embodiments of this application. It is obvious that the drawings in the following description are only a few of the embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the lithium-ion battery of this application. [Figure 2] Figure 1 is a schematic diagram of an exploded view of an embodiment of a lithium-ion battery. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment of a power consumption device that uses a lithium-ion battery as a power source according to this application. The drawing is not necessarily drawn to actual scale. [Modes for carrying out the invention]

[0038] The following describes in detail embodiments of the lithium-ion battery, battery and power consumption device of this application, with appropriate reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters and repeated explanations of structures that are actually the same may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the topics described in the claims.

[0039] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the limit value, and any combination is possible, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that the ranges 60 to 110 and 80 to 120 can also be assumed. Furthermore, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then ranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 can all be assumed. In this application, unless otherwise specified, the numerical range “a to b” represents an abbreviated expression of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply a shortened expression for combinations of these numbers. Also, expressing a parameter as an integer ≥ 2 is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0042] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if a method mentioned may further include step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0043] Rechargeable batteries generally include ion batteries and metallic batteries. Metallic batteries, such as lithium metal batteries and sodium metal batteries, have relatively high negative electrode activity, a relatively high risk of dendrite formation, and thus relatively low battery reliability. Ion batteries, on the other hand, have relatively high reliability and are therefore widely used.

[0044] A lithium-ion battery generally comprises an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is provided between the positive and negative electrode plates to isolate them. The positive electrode plate includes a positive electrode film layer containing a positive electrode active material, which is a donor that provides lithium ions to the lithium-ion battery. The negative electrode plate includes a negative electrode film layer containing a negative electrode active material, which can act as a lithium ion acceptor. The electrolyte provides a pathway for the movement of lithium ions between the positive and negative electrode plates.

[0045] To improve the energy density of lithium-ion batteries, a positive electrode active material with a relatively high capacity is generally used, for example, by increasing the nickel content in the positive electrode active material. However, as the nickel content increases, the positive electrode active material is more prone to developing microcracks in its structure during the cycle process, leading to structural destruction and ultimately collapse of the positive electrode active material. In particular, in the later stages of the cycle, the cumulative degree of destruction of the positive electrode active material increases, resulting in poor cycle performance.

[0046] In view of the above problems, an embodiment of the present application provides a lithium-ion battery. The cathode active material of this lithium-ion battery has a molecular formula of Li d Ni a Co b Mn c M (1-a-b-c) Y z where d is 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 contains 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. The Y element contains at least one element among O, F. The nickel element content of this cathode active material is relatively high. In order to improve the stability of the cathode active material structure, the cathode active material of the embodiment of the present application further contains the M element. The introduction of the M element can improve the stability of the cathode active material crystal structure and the cycle performance of the lithium-ion battery. However, with the progress of the cycle, both the metal elements and non-metal elements in the cathode active material have a risk of elution. The eluted metal elements and non-metal elements can move to the surface of the negative electrode plate through the electrolyte and deteriorate the cycle life. The embodiment of the present application further combines a high content of lithium hexafluorophosphate. The mass content of lithium hexafluorophosphate LiPF6 in the total mass of the electrolyte is 15% to 20%. The high content of lithium hexafluorophosphate can form a protective layer with lithium fluoride LiF as the main film component on the surface of the cathode active material, thereby alleviating the elution of metal elements and non-metal elements to a certain extent and further improving the cycle performance of the lithium-ion battery. Next, the technical solution of the present application will be described in detail.

[0047] Lithium-ion battery According to a first aspect, an embodiment of the present application provides a lithium-ion battery, which includes an electrolyte and a positive electrode plate. The electrolyte contains a lithium salt, and the lithium salt contains lithium hexafluorophosphate. The mass content of lithium hexafluorophosphate in the total mass of the electrolyte is 15% to 20%. The positive electrode plate contains a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector and containing a positive electrode active material. The positive electrode active material contains a compound with the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) Q z 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 contains 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. The Q element contains at least one element among O, F.

[0048] The nickel element content of the positive electrode active material is relatively high, for example, 0.6 < a < 1, and selectively, 0.85 ≤ a ≤ 0.95. In order to improve the stability of the positive electrode active material structure or improve other characteristics advantageous to the electrical performance of the positive electrode active material, the positive electrode active material of the embodiment of the present application further contains an M element. The introduction of the M element can improve the stability of the positive electrode active material crystal structure and improve the cycle performance of the lithium-ion battery. However, as the cycle progresses, both the metal elements and non-metal elements in the positive electrode active material have the risk of elution. The eluted metal elements and non-metal elements can move to the surface of the negative electrode plate through the electrolyte, may destroy the solid electrolyte interface (SEI) film on the surface of the negative electrode plate, and may precipitate as a metal single body on the surface of the negative electrode plate, thereby deteriorating the cycle performance. The embodiment of the present application further combines a high content of lithium hexafluorophosphate. The mass content of lithium hexafluorophosphate LiPF6 in the total mass of the electrolyte is 15% to 20%. The high content of lithium hexafluorophosphate can form a protective layer with lithium fluoride LiF as the main film component on the surface of the positive electrode active material, thereby alleviating the elution of metal elements and non-metal elements to a certain extent and further improving the cycle performance of the lithium-ion battery.

[0049] When the mass content of lithium hexafluorophosphate is less than 15%, the protection performance for the surface of the positive electrode active material weakens. Therefore, it is necessary to adjust the mass content of lithium hexafluorophosphate to 15% or more. When the mass content of lithium hexafluorophosphate is greater than 20%, it significantly increases the viscosity of the electrolyte, which is disadvantageous for the movement of lithium ions from the bulk inside of the negative electrode active material to the surface, slows down the movement speed of lithium ions from the negative electrode surface to the positive electrode surface, is disadvantageous for the movement of lithium ions from the surface of the negative electrode active material to the bulk of the negative electrode active material, and is disadvantageous for the improvement of the cycle performance. Therefore, it is necessary to adjust the mass content of lithium hexafluorophosphate to 20% or less. Exemplarily, the mass content of lithium hexafluorophosphate with respect to the total mass of the electrolyte may be 15%, 15.5%, 16%, 16.5%, 十七%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20% or a range consisting of any two of the above numerical values.

[0050] [Positive electrode plate] 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 either one or both of the two opposing surfaces of the positive electrode current collector.

[0051] The positive electrode active material contains a compound with the molecular formula Li d Ni a Co b Mn c M (1-a-b-c) Q z 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 contains 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. The Q element contains at least one element among O, F.

[0052] In addition to containing lithium, the positive electrode active material further contains nickel, cobalt, manganese, and M. Nickel can improve the gram capacity of the positive electrode active material, cobalt can stabilize the crystal structure of the positive electrode active material, manganese can improve the overall structural stability of the positive electrode active material, and M can improve the stability of the crystal structure of the positive electrode active material.

[0053] 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, 0.7 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 numbers.

[0054] In some embodiments, 0.85 ≤ a ≤ 0.95.

[0055] a may be within the range of 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 any two of the above values. By combining the positive electrode active material and electrolyte with the above structure, the cycle performance of the lithium-ion battery can be effectively improved.

[0056] 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.

[0057] 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.

[0058] In some embodiments, a+b+c may be a range consisting of 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 any two of the above values.

[0059] In some embodiments, z may be a range consisting of 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 any two of the above values.

[0060] Lithium-ion batteries release and consume active ions, such as Li, during the charge-discharge process, and the molar content of Li differs when the lithium-ion battery is discharged to different states. In the enumeration of positive electrode active materials in the embodiments of this application, the molar content of Li is the initial state of the material, i.e., the state before insertion, and the molar content of Li may change as the positive electrode active material is applied to a battery system and undergoes charge-discharge cycles.

[0061] In the enumeration of positive electrode active materials in the embodiments of this application, the molar content of oxygen O is only a theoretical value, and lattice oxygen release causes a change in the molar content of oxygen O, resulting in actual fluctuations in the molar content of oxygen O.

[0062] In some embodiments, element M includes at least one element from titanium (Ti) and zirconium (Zr).

[0063] Selectively, M contains the element Ti. Ti can stabilize the structure of the positive electrode active material, thereby improving cycle performance.

[0064] Selectively, M contains the element Zr. Zr can stabilize the structure of the positive electrode active material, thereby improving cycle performance.

[0065] In some embodiments, the total mass content of Ti and Zr elements is between 1600 ppm and 6000 ppm, based on the total mass of the positive electrode active material. When the amounts of Ti and Zr elements added are within this range, the crystalline structure of the positive electrode active material can be further improved, and the cycle performance can be enhanced.

[0066] 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.

[0067] For example, the total mass content of Ti and Zr elements may be in the range of 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, 4000 ppm, 5000 ppm, 6000 ppm, or any two of the above values.

[0068] In some embodiments, the mass content of Ti element is 100 ppm to 600 ppm with respect to the total mass of the positive electrode active material, and may be in the range of, for example, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 450 ppm, 500 ppm, 600 ppm, or any two of the above values.

[0069] In some embodiments, the mass content of element Zr, based on the total mass of the positive electrode active material, is between 500 ppm and 5000 ppm, selectively between 1500 ppm and 5000 ppm, and may be in the range of, for example, 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, 3000 ppm, 3500 ppm, 4000 ppm, 5000 ppm, or any two of the above values.

[0070] In some embodiments, the electrolyte includes a first additive, the first additive including at least one of lithium difluoro(oxalato)borate LiDFOB and lithium tetrafluoroborate LiBF4. In the later stages of the lithium-ion battery cycle, metal ions such as Ti and Zr ions in the positive electrode active material are at risk of dissolving into the electrolyte and migrating to the surface of the negative electrode plate. The first additive includes fluoride ions and boron ions, which have a relatively strong binding ability with the above metal ions, thereby reducing the risk of metal ions migrating to the surface of the negative electrode plate and improving the cycle performance of the lithium-ion battery. While Ti and Zr ions can improve the stability of the material structure, they can adversely affect the conduction of lithium ions within the crystal lattice, potentially causing power degradation. The first additive can further compensate for the power degradation caused by Ti and Zr ions.

[0071] In some embodiments, the positive electrode active material includes one or more single-crystal particles and polycrystalline particles. By combining the positive electrode active material with the electrolyte having the above structure, the cycle performance of the lithium-ion battery can be effectively improved.

[0072] In some embodiments, the positive electrode active material includes single-crystal particles and polycrystalline particles. By combining the positive electrode active material with the electrolyte having the above structure, the cycle performance of the lithium-ion battery can be effectively improved.

[0073] In some embodiments, the positive electrode active material comprises single crystal particles, each comprising an inner region and an outer region, the outer region being a region extending 500 nm directly into the interior of the single crystal particle from any point on the outer surface of the single crystal particle, and the M element comprising aluminum (Al), with the aluminum (Al) element distributed at least in the outer region.

[0074] The inner region of a single crystal grain may be understood as the nucleus of the single crystal grain, the outer region covers the outside of the inner region, and there may be no clear boundary between the outer and inner regions. The outer and inner regions may also be considered as two artificially defined regions. The outer region is a region where any point on the outer surface of the single crystal grain extends 500 nm inward towards the interior of the single crystal grain, and the extension path is a straight path. The outer region may also be understood as an annular structure, and the radial spacing of the annular structure is 500 nm or less.

[0075] The element aluminum (Al) is distributed at least in the outer region and helps to form aluminum oxide (Al2O3) in the positive electrode active material, passivating side reactions between the positive electrode active material and the electrolyte, further improving the stability of the positive electrode active material structure, and thus improving the cycle performance of the lithium-ion battery. Of course, in addition to being distributed in the outer region, the element Al may also be further distributed in the inner region.

[0076] In some embodiments, the mass content of Al element is 500 ppm to 3000 ppm, and selectively 1000 ppm to 2000 ppm, based on the total mass of the positive electrode active material.

[0077] For example, the mass content of Al may be in the range of 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 any two of the above values.

[0078] In some embodiments, the electrolyte includes a second additive, the second additive being lithium difluorophosphate (LiPO2F2). Lithium difluorophosphate (LiPO2F2), when combined with the element Al in the positive electrode active material, can improve the DCR of the surface of the positive electrode active material and enhance the interfacial power.

[0079] In some embodiments, element M further comprises at least one of elements phosphorus (P), sulfur (S), and boron (B), where at least one of elements B, P, and S is distributed in the outer region.

[0080] Selectively, element M includes elements phosphorus (P), sulfur (S), and boron (B). These elements adsorb into the oxygen layer and stabilize lithium, thereby improving the stability of the positive electrode active material structure and enhancing the cycle performance of lithium-ion batteries.

[0081] In some embodiments, the total mass content of elements P, S, and B is 0 to 800 ppm, selectively 10 ppm to 500 ppm, relative to the total mass of the positive electrode active material, and is in the range of, 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, or any two of the above values. A total mass content of elements P, S, and B of 0 means that these elements are not added.

[0082] In some embodiments, the total mass content of element P, based on the total mass of the positive electrode active material, is between 10 ppm and 500 ppm, and may be in the range of, 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 any two of the above values.

[0083] In some embodiments, the total mass content of element S is between 10 ppm and 500 ppm, based on the total mass of the positive electrode active material, and may be in the range of, 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 any two of the above values.

[0084] In some embodiments, the total mass content of element B is 10 ppm to 500 ppm, based on the total mass of the positive electrode active material, and may be in the range of, 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 any two of the above values.

[0085] In some embodiments, the electrolyte includes a third additive, the third additive comprising lithium fluorosulfonate, which can form a low-resistance film component on the surface of the positive electrode active material. The third additive, in combination with the elements phosphorus (P), sulfur (S), and boron (B) in the positive electrode active material, can reduce the DCR on the surface of the positive electrode active material and improve the interfacial power.

[0086] In the embodiments of this application, the elemental content in the positive electrode active material is in the sense known in the art and can be detected using instruments and methods known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectroscopy and measured using plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). First, 0.4 g of positive electrode active material is weighed and 10 ml of aqua regia (50% concentration) is added to it. Then it is placed on a plate at 180°C for 30 minutes. After decomposition on the plate, the volume is set to 100 mL and a quantitative test is performed using the standard curve method.

[0087] In some embodiments, the cathode film layer further selectively includes a cathode conductive agent. The embodiments of this application are not particularly limited to the type of cathode conductive agent, and as an example, the cathode conductive agent includes 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 cathode conductive agent is ≤5% based on the total mass of the cathode film layer.

[0088] In some embodiments, the positive electrode film layer further selectively includes a positive electrode adhesive. The embodiments of this application are not particularly limited to the type of positive electrode adhesive, and for example, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resins. In some embodiments, the mass content of the positive electrode adhesive is ≤5% based on the total mass of the positive electrode film layer.

[0089] In some embodiments, the ratio of the compaction density of the positive electrode film layer to the compaction density of the negative electrode film layer is (2 to 2.5):1. For example, it may be in the range of 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, or any two of the above values.

[0090] In some embodiments, the compaction density PD of the positive electrode film layer is 3.0 g / cm³. 3 From 3.5 g / cm³ 3 Therefore, selectively 3.2 g / cm³. 3 From 3.5 g / cm³ 3 For example, 3 g / cm³ 3 3.1 g / cm³ 3 3.2 g / cm³ 3 3.3 g / cm³ 3 3.35 g / cm³ 3 3.4 g / cm³ 3 3.5 g / cm³3 Alternatively, it may be a range consisting of any two of the above values.

[0091] In the embodiments of this application, the compaction density of the positive electrode active material layer is as 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 it is a positive electrode plate coated on both sides, the positive electrode film on one side may be wiped off first) is taken, punched out into a small disc with an area of ​​S1, weighed, and recorded as M1. Next, the positive electrode film on the positive electrode plate after weighing is wiped off, the weight of the positive electrode current collector is weighed, and recorded as M0. The surface density of the positive electrode active material layer is (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 is (surface density of positive electrode active material layer / thickness of positive electrode active material layer).

[0092] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Aluminum foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. For example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0093] In some embodiments, the thickness of the positive electrode current collector is 13 μm or less, selectively 8 μm to 13 μm, and selectively 10 μm to 13 μm.

[0094] The relatively thin thickness of the positive electrode current collector can weaken the heat dissipation path of the lithium-ion battery, and especially when using a relatively thin metal current collector, the heat dissipation path of the lithium-ion battery can be further weakened, allowing some of the heat to be retained within the lithium-ion battery in a low SOC discharge state, which is advantageous for improving the DCR at low SOC, and thereby improving the discharge power at low SOC.

[0095] For example, the thickness of the positive electrode current collector may be within the range of 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 any two of the above values.

[0096] In the embodiments of this application, the thickness of the positive electrode current collector is a known concept in the art and can be detected using instruments and methods known in the art. For example, a positive electrode plate is used as a sample, the positive electrode film layer on the surface of the positive electrode plate is then cleaned with an organic solvent such as alcohol, and the thickness of the positive electrode current collector is measured with a micrometer.

[0097] The positive electrode film layer is generally obtained by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0098] [Electrolyte] Organic solvents In some embodiments, the electrolyte further comprises an organic solvent.

[0099] In some embodiments, the organic solvent may contain 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 selectively (1.00 to 1.65):1.

[0100] The expected beneficial effects are as follows: When the ratio of the mass content of cyclic carbonate to the mass content of lithium hexafluorophosphate is within the above range, it is advantageous to sufficiently dissociate more lithium ions from lithium hexafluorophosphate, thereby allowing the electrolyte system to contain more lithium ions even at the end of low SOC discharge, and enabling continuous dissociation of lithium ions as the battery reaction progresses, thereby improving the battery's power performance.

[0101] For example, the ratio of the mass content of cyclic carbonate to the mass content of lithium hexafluorophosphate, based on the total mass of the electrolyte, may be within the range of 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 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 any two of the above values.

[0102] In some embodiments, the mass content of cyclic carbonate is 10% to 45%, and more selectively 20% to 30%, relative to the total mass of the electrolyte. 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.

[0103] For example, the mass content of cyclic carbonate, based on the total mass of the electrolyte, may be in the range of 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 any two of the above values.

[0104] In some embodiments, the cyclic carbonate may include at least one of ethylene carbonate EC, propylene carbonate PC, and butylene carbonate BC.

[0105] In some embodiments, the organic solvent may contain linear carbonates, and the ratio of the mass content of linear carbonates to the mass content of cyclic carbonates, based on the total mass of the electrolyte, is (0.9 to 6):1, and selectively (1.5 to 2.65):1. When the ratio of the mass content of linear carbonates to cyclic carbonates satisfies the above range, improvements in both the viscosity and ionic conductivity of the electrolyte can be achieved, and the kinetic performance of lithium ions can be improved.

[0106] For example, the ratios of the mass content of cyclic carbonates to the mass content of linear carbonates 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, and 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 numbers.

[0107] In some embodiments, the mass content of linear carbonate is 35% to 75% of the total mass of the electrolyte, and more selectively 50% to 75%. The viscosity of linear carbonate is relatively low, which is advantageous for the rapid movement of lithium ions, and it can have higher electrochemical stability and improve the low-temperature performance of the electrolyte.

[0108] For example, based on the total mass of the electrolyte, the mass content of linear carbonate may be in the range of 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%, 68%, 70%, 71%, 72%, 73%, 74%, 75%, or any two of the above values.

[0109] In some embodiments, the linear carbonate comprises at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC).

[0110] additives In some embodiments, the electrolyte may further contain additives.

[0111] In some embodiments, the additive includes a first additive comprising at least one of lithium difluoro(oxalato)borate LiDFOB and lithium tetrafluoroborate LiBF4. In the later stages of the lithium-ion battery cycle, metal ions such as Ti and Zr ions in the positive electrode active material are at risk of dissolving into the electrolyte and migrating to the surface of the negative electrode plate. The first additive comprises fluoride ions and boron ions, which have a relatively strong binding ability with the above-mentioned metal ions, thereby reducing the risk of metal ions migrating to the surface of the negative electrode plate, improving the cycle performance of the lithium-ion battery, and also compensating for the power degradation caused by Ti and Zr ions.

[0112] In some embodiments, the mass content of the first additive is 30 ppm to 1200 ppm, selectively 100 ppm to 400 ppm, relative to the total mass of the electrolyte, the combined mass content of Ti is 100 ppm to 600 ppm, and the mass content of Zr is 500 ppm to 2550 ppm, and the first additive can improve the binding ability to Ti and Zr ions, further improving the cycle performance of the lithium-ion battery.

[0113] In some embodiments, the mass content of the first additive is 30 ppm to 1200 ppm, selectively 100 ppm to 400 ppm, relative to the total mass of the electrolyte, and the mass content of the combined Zr element is 500 ppm to 5000 ppm, and the first additive can improve the binding ability to Zr ions and further improve the cycle performance of the lithium-ion battery.

[0114] For example, the mass content of the first additive is 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 210 ppm, 220 ppm, 230 ppm, 240 ppm, 250 ppm, 260 ppm, 270 ppm, 280 ppm, 290 ppm, and 300 ppm. The values ​​may be 310ppm, 320ppm, 330ppm, 340ppm, 350ppm, 360ppm, 370ppm, 380ppm, 390ppm, 400ppm, 410ppm, 420ppm, 430ppm, 440ppm, 450ppm, 460ppm, 470ppm, 480ppm, 490ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, or any two of the above values.

[0115] In some embodiments, the additive includes a second additive containing lithium difluorophosphate (LiPO2F2). Lithium difluorophosphate (LiPO2F2) can form an inorganic component-rich film layer on the surface of the positive electrode active material, which is advantageous for improving the ion and electron conduction performance of the film layer, and the interfacial ion resistance of the formed film layer is relatively low, which is advantageous for lithium ion transport and can improve the DCR at low SOC. In particular, lithium difluorophosphate, when combined with the element Al in the positive electrode active material, can improve the DCR on the surface of the positive electrode active material and improve interfacial power.

[0116] In some embodiments, the mass content of the second additive is 100 ppm to 3000 ppm, and selectively 1000 ppm to 2000 ppm, relative to the total mass of the electrolyte. The second additive in the above mass content can be combined with 500 ppm to 3000 ppm of Al element to better improve the DCR of the surface of the positive electrode active material and enhance the interfacial power.

[0117] For example, the mass content of the second additive may be in the range of 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 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, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, or any two of the above values.

[0118] In some embodiments, the additive includes a third additive, the third additive being lithium fluorosulfonate, which can form an inorganic component-rich film layer on the surface of the positive electrode active material, which is advantageous for improving the ion and electron conduction performance of the film layer, and the interfacial ion resistance of the formed film layer is relatively low, which is advantageous for lithium ion transport, and can improve the DCR at low SOC. In particular, lithium difluorophosphate, when combined with phosphorus (P), sulfur (S), and boron (B) elements in the positive electrode active material, can improve the DCR on the surface of the positive electrode active material and improve interfacial power.

[0119] For example, lithium fluorosulfonate may include at least one of lithium trifluoromethanesulfonate and lithium perfluorohexanesulfonate.

[0120] In some embodiments, the mass content of the third additive is 50 ppm to 200 ppm relative to the total mass of the electrolyte. The third additive with the above mass content can be combined with elements of phosphorus (P), sulfur (S), and boron (B) in concentrations of 10 ppm to 800 ppm, which can better improve the DCR of the surface of the positive electrode active material and enhance the interfacial power.

[0121] For example, the mass content of the third additive may be in the range of 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 200 ppm, or any two of the above values.

[0122] In some embodiments, the additive includes a fourth additive, the fourth additive may further include at least one of 1,3-propanesultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F.

[0123] In some embodiments, the ratio of the mass content of 1,3-propanesultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F, based on the total mass of the electrolyte, is (0.050 to 0.300):(0.100 to 0.500):(0.001 to 0.300). The mass content of one component in the additive is 0, indicating that this component is not added to the electrolyte. When the ratio of the mass content of 1,3-propanesultone PS, vinylene carbonate VC, and lithium fluorosulfonate LiSO3F is within the above range, the above components can essentially contribute to 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-based material.

[0124] In some embodiments, the mass content of 1,3-propanesultone PS is 0.1% to 1% based on the total mass of the electrolyte, and may be in the range of, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any two of the above values.

[0125] In some embodiments, the mass content of vinylene carbonate (VC) is 0.1% to 1% based on the total mass of the electrolyte, and may be in the range of, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any two of the above values.

[0126] In some embodiments, the mass content of lithium fluorosulfonate LiSO3F is 0.1% to 1% based on the total mass of the electrolyte, and may be in the range of, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any two of the above values.

[0127] In some embodiments, the additive may include a fluorinated cyclic carbonate. The fluorinated cyclic carbonate can be involved in the formation of an SEI film on the surface of the negative electrode active material, effectively protecting the negative electrode active material. Furthermore, the fluorinated cyclic carbonate has a certain desolvation capacity, which is advantageous for lithium ion movement, improving DCR at low SOC and increasing discharge power.

[0128] In some embodiments, the fluorinated cyclic carbonate comprises at least one of monofluoroethylene carbonate FEC, bisfluoroethylene carbonate DFEC, and trifluoropropylene carbonate TFPC, and selectively comprises monofluoroethylene carbonate FEC. FEC contains a relatively small number of fluorine atoms, is more polar, and is more readily detached from fluorine and participates in the SEI film formation reaction.

[0129] In some embodiments, the ratio of the mass content of fluorinated cyclic carbonate to the mass content of silicon relative to the total mass of the electrolyte is (0.01 to 9.5):1, selectively (0.01 to 0.15):1. For example, the ratio of the mass content of silicon element to the total mass of the electrolyte of fluorinated cyclic carbonate is 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, 0.2:1, 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, and 1.5:1. , 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.

[0130] Fluorinated cyclic carbonates can contribute to the formation of SEI films on the surface of the negative electrode active material, improving film composition and properties and effectively protecting the negative electrode active material. In particular, when the negative electrode contains silicon, the film composition for SEI film formation needs to be optimized due to the expansion properties of silicon. This optimization of film composition is adjusted by adjusting the relative ratio of film-forming additives in the electrolyte. Fluorinated cyclic carbonates contribute to the film formation, improving the flexibility of the SEI film and mitigating structural collapse caused by the rapid release of large amounts of lithium ions at the end of discharge. Furthermore, fluorinated cyclic carbonates possess a certain desolvation capacity, which is advantageous for lithium ion movement, improving DCR at low SOC and increasing discharge power. Through research, it was discovered that when the ratio of silicon content in the negative electrode active material to FEC content in the electrolyte satisfies (0.01 to 9.5):1, the battery's rate performance at the end of discharge is significantly improved.

[0131] When the negative electrode active material contains a silicon-carbon composite, the carbon element can effectively mitigate the volume change of silicon, and therefore the volume change of silicon can be controlled using a relatively small amount of FEC. For example, the ratio of the mass content of fluorinated cyclic carbonate to the total mass of the electrolyte to the mass content of silicon is (0.01 to 0.15):1, in which case the FEC can effectively control the volume change of silicon. Furthermore, the FEC of the above mass content reduces the risk that its own acidity will damage the surface of the alkaline positive electrode active material, improving the cycle stability of the positive electrode active material and thereby further improving the cycle performance of the lithium-ion battery.

[0132] In some embodiments, the mass content of the fluorinated cyclic carbonate relative to the total mass of the electrolyte is 0.05 to 5.8%, and selectively 0.1 to 1.0%.

[0133] 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%, 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.

[0134] Lithium salt After dissolving in an organic solvent, lithium salts can release a large amount of active lithium ions and participate in charging and discharging.

[0135] In some embodiments, the ratio of the mass content of fluorinated cyclic carbonate to the mass content of lithium salt, based on the total mass of the electrolyte, is (0.005 to 0.30):1, and selectively (0.005 to 0.03):1.

[0136] Fluorinated cyclic carbonates can form organic matter on the surface of silicon-based materials, improving the flexibility of the SEI film. Lithium salts can participate in the formation of the SEI film, incorporating inorganic components into the SEI film, which is advantageous for improving the ion and electron conduction performance of the SEI film. This can improve the ion and electron conduction performance of the entire negative electrode plate. When the ratio of the mass content of fluorinated cyclic carbonate to the mass content of lithium salt is within the above range, it is possible to improve the flexibility, ion conduction, and electron conduction performance of the SEI film while simultaneously reducing the DCR and improving the discharge power of the lithium-ion battery.

[0137] For example, the ratios of the mass content of fluorinated cyclic carbonate to the mass content of lithium salt are 0.005:1, 0.008:1, 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, 0.10:1, 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.

[0138] The qualitative and quantitative determination of each substance or element in this application can be performed using appropriate apparatus and methods known to those skilled in the art. Relevant detection methods can refer to detection standards in China and abroad, enterprise standards in China and abroad, etc., and those skilled in the art may adaptively modify several detection steps / instrument parameters, etc., from the viewpoint of detection accuracy to obtain more accurate detection results. Qualitative or quantitative determination may be performed using a single detection method, or multiple detection methods may be combined to perform qualitative or quantitative measurements.

[0139] In the embodiments of this application, the types and content of inorganic components / lithium salts in the electrolyte are as known in the art and can be detected using instruments and methods known in the art. For example, the concentration of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis, referring to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis." In the embodiments of this application, a newly manufactured electrolyte can be used as a sample, or a battery that has already been discharged (discharged to the lower cutoff voltage, resulting in a charge state of approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample and detected using ion chromatography analysis.

[0140] In the embodiments of this application, the types and content of organic components in the electrolyte are as known in the art and can be detected using instruments and methods known in the art. For example, qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography, referring to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, a newly manufactured electrolyte can be used as a sample, or a battery that has already been discharged (discharged to the lower cutoff voltage, resulting in a charge state of approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample and detected using ion chromatography analysis.

[0141] Furthermore, for example, to test the components of a certain additive in the electrolyte using liquid-phase nuclear magnetic resonance (NMR) and detect lithium difluorophosphate and lithium hexafluorophosphate, one 7 ml glass bottle was prepared in a nitrogen gas glove box, 5 ml of nuclear magnetic reagent premix was added to the glass bottle, and the mixture was left to stand for 24 hours at room temperature (20-25°C) in a nitrogen atmosphere glove box, allowing the electrolytes in the electrode plates and separators to diffuse into the nuclear magnetic premix, thereby obtaining a nuclear magnetic test sample. The nuclear magnetic premix contained 100 ml of deuterated acetonitrile with 3 ml of trifluoromethylbenzene CF3ph added. The above nuclear magnetic reagent premix was pre-dried using a molecular sieve 4A (15 g of newly opened 4A molecular sieve was added to 100 ml of nuclear magnetic reagent premix and dried in a nitrogen gas glove box at room temperature (20-25°C) for more than 30 days). Measurement was performed using 19F NMR (nuclear magnetic (NMR): Bruker Avance 400HD).

[0142] To identify and quantify the various types, the following settings were used for the inversion angle and scanning time.

[0143] Fluorine spectrum test pulse sequence: 2gfhigqn.2, Delay time: 1 second, Number of scans: 16 times, The relative content of trifluoromethylbenzene and LiPF6 was calculated based on the signal peak integrated intensities of the two substances in F-NMR. Calculation method: PF6 - Relative content = (I PF6 - ×M PF6 - / 6) / (I CF3ph ×M CF3ph / 3), where I is the corresponding nuclear magnetic peak area and M is the corresponding relative molecular mass, and then the content of lithium hexafluorophosphate in the electrolyte is calculated based on the molar ratio relationship between hexafluorophosphate and lithium ions.

[0144] The content of lithium hexafluorophosphate (LiPF6) in the deuterated reagent of the electrolyte is calculated based on its content.

[0145] Trifluoromethylbenzene and PO2F2 in F-NMR - The relative content of the two substances is calculated based on the signal peak integrated intensity of the two substances, and the calculation method is as follows: PO2F2 - Relative content = (I PO2F2- ×M PO2F2- / 2) / (I CF3ph ×M CF3ph / 3), where I is the corresponding nuclear magnetic peak area and M is the corresponding relative molecular mass, and then the content of lithium difluorophosphate in the electrolyte is calculated based on the molar ratio relationship between difluorophosphate and lithium ions.

[0146] In some embodiments, the electrolyte retention coefficient of the lithium-ion battery is between 1.0 g / Ah and 2.5 g / Ah, and selectively between 1.8 g / Ah and 2.2 g / Ah.

[0147] The electrolyte retention coefficient of a lithium-ion battery can reflect the electrolyte's ability to retain fluid. When the electrolyte retention coefficient of a lithium-ion battery is within the above range, the electrolyte can effectively penetrate the positive and negative electrodes, maintain a certain gap between the negative electrode and the separator, and provide space for the volume expansion of the silicon-based material, thereby reducing the risk of the entire battery expanding.

[0148] In some embodiments, the electrolyte retention coefficient of the lithium-ion battery is between 1.0 g / Ah and 2.5 g / Ah, and selectively between 1.0 g / Ah and 1.5 g / Ah.

[0149] In some embodiments, the various solutes or solvents in the electrolyte referred to in this application include not only substances that are actively added when the electrolyte is manufactured, but also substances that are derived from substances already present in some / some electrolytes during the process of manufacturing the electrolyte, or manufacturing a battery from the electrolyte, or storing or using a battery containing the electrolyte.

[0150] The fluid retention coefficient of a lithium-ion battery can reflect the fluid retention capacity of the electrolyte. When the fluid retention coefficient of a lithium-ion battery is within the above range, the electrolyte can perform a good penetration action on the positive and negative electrode plates, and a certain gap can be maintained between the negative electrode plate and the separator, providing expansion space for the volume expansion of the silicon-based material, thereby reducing the risk of the entire lithium-ion battery expanding.

[0151] For example, the electrolyte retention coefficient of a lithium-ion battery may be within the range of 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 any two of the above values.

[0152] In the embodiments of this application, the fluid retention coefficient of the lithium-ion battery is a known value in the art and can be detected using instruments and methods known in the art, for example, according to GB / T 31486-2015 "Electrical performance requirements and test methods for power storage batteries for electric vehicles", the lithium-ion battery is charged to 4.35V at 1C at 25°C, then discharged to 2.8V at 1C, the released capacity C is obtained and used as the denominator, the lithium-ion battery is weighed and designated as M0, the positive electrode plate, negative electrode plate, separator and electrolyte are then disassembled, where the free electrolyte is present in the housing / bag, and all of the above solid assemblies are baked in a 60°C oven for 4 hours or more (including but not limited to the positive electrode plate, negative electrode plate and separator, and further including other mechanical parts of the disassembled lithium-ion battery that contribute to M0), the entire assembly of the lithium-ion battery is then weighed and designated as M1, where the weight difference between M0 and M1 is used as the numerator. The fluid retention coefficient is equal to the value obtained by dividing the volume C by the weight difference between M0 and M1.

[0153] [Negative electrode plate] In some embodiments, the lithium-ion battery further includes a negative electrode plate.

[0154] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0155] In some embodiments, the negative electrode film layer contains a negative electrode active material comprising carbon and silicon elements, with the mass content of silicon being 0.30% to 10.00% based on the total mass of the negative electrode active material. Therefore, the mass content of carbon is 90% to 99.7%.

[0156] The negative electrode active material of a lithium-ion battery includes a carbon-based material that provides carbon elements and a silicon-based material that provides silicon elements. The carbon-based material that provides carbon elements mainly contains carbon elements, may also contain silicon elements, or may contain only carbon elements. The silicon-based material that supplies silicon elements may contain silicon elements, may also contain carbon elements, or may contain only silicon elements. The negative electrode active material simultaneously includes a carbon-based material and a silicon-based material. Because the lithium discharge voltage plateau of the silicon-based material is relatively higher than that of the carbon-based material, the silicon-based material can still participate in discharge even at low SOC (e.g., SOC ≤ 10%), compensating for the shortcomings of the carbon-based material, which is that it is difficult to discharge or cannot continue to discharge at low SOC, improving the DC internal resistance DCR during the battery discharge process, and further improving the power performance during the battery discharge process.

[0157] The reason for adjusting the silicon element mass content to a lower level is as follows: Although silicon-based materials have a higher lithium release potential than carbon-based materials, they experience relatively large volume expansion or contraction during the charge-discharge process, which can lead to defects such as structural collapse and pulverization of the negative electrode active material, and can also cause undesirable side reactions inside the battery. Furthermore, silicon-based materials themselves have relatively poor conductivity, and excessively high silicon content is detrimental to improving DCR. Therefore, when other conditions are met, the power performance of a battery with a negative electrode active material containing too much silicon will be inferior to that of a battery with a lower silicon content.

[0158] The electrolyte of the embodiment of this application is further used in combination with 15% to 20% lithium hexafluorophosphate, and the synergistic action of the electrolyte and the negative electrode improves the power performance of the battery at the end of its discharge phase.

[0159] Lithium hexafluorophosphate can be involved in the formation of the solid electrolyte interface (SEI) film component on the surface of the negative electrode active material. Lithium hexafluorophosphate with a high fluorine atom ratio can optimize the SEI film component, and the improvement effect of high mass content lithium hexafluorophosphate on the SEI film component is more pronounced, improving the ratio of lithium fluoride (e.g., lithium fluoride) in the SEI film. Such an SEI film with a relatively high lithium fluoride ratio can, on the one hand, mitigate the problem of pulverization of silicon-based materials and improve the overall structural stability of the negative electrode active material, and on the other hand, it can delay side reactions between the electrolyte and the surface of the negative electrode active material, thereby improving the discharge stability in the later stages of discharge of silicon-based materials and further improving the power performance of the battery.

[0160] Furthermore, at the end of discharge when lithium-ion batteries have a low state of charge (SOC), the concentration of lithium ions in the negative electrode active material is relatively low, making it relatively difficult for lithium ions to detach from the negative electrode active material. This reduces the concentration difference of lithium salts in the electrolyte system, improving the internal resistance of the lithium-ion battery and further decreasing the discharge power. The electrolyte in the embodiment of this application contains a high content of lithium hexafluorophosphate, which can contribute more lithium ions to the battery system, improve the concentration of lithium ions in the electrolyte, effectively reduce the concentration polarization of lithium salts, promote the movement of lithium ions from the negative electrode plate to the positive electrode plate, and further improve the power performance of the lithium-ion battery.

[0161] The mass content of the silicon element relative to the total mass of the negative electrode active material is from 0.3% to 10.0%, for example, 0.3%, 0.32%, 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%, 8%, 9%, 10% or a range consisting of any two of the above numerical values.

[0162] As described above, the silicon element may be derived from a silicon-based material, and the silicon-based material may be a raw material constituting the negative electrode film layer. In some embodiments, the silicon element contained in the negative electrode active material is elemental silicon, a silicon-carbon composite, silicon oxide SiO x (0 < x ≤ 2) exists in the negative electrode film layer in at least one form. Here, the elemental silicon, the silicon-carbon composite, and the silicon oxide SiO x (0 < x ≤ 2) may refer to a silicon-based material or the form of the silicon element in the negative electrode plate in the battery after formation. Regarding the 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.

[0163] Here, the silicon-carbon composite may refer to the existence form of silicon elements in the negative electrode plate of the battery after formation. The silicon-carbon composite may be a silicon-carbon composite formed by silicon elements and carbon elements through a specific chemical reaction in the battery cell. The silicon-carbon composite may also be formed by physically mixing elemental silicon and elemental carbon. For example, the elemental carbon includes a porous skeleton, and the elemental silicon may be located within the pores of the porous skeleton or on the surface of the porous skeleton. The silicon-carbon composite may be coated with a carbon layer or the like on the surface of the elemental silicon.

[0164] When the silicon element exists in the form of silicon oxide SiO x (0 < x ≤ 2) in the negative electrode film layer, the mass content of the silicon element relative to the total mass of the negative electrode active material is from 0.3% to 3.0%.

[0165] When the silicon element exists in the form of a silicon-carbon composite in the negative electrode film layer, the mass content of the silicon element relative to the total mass of the negative electrode active material is from 0.3 to 10.0%, and selectively from 4% or more and 7.0% or less. The silicon-carbon composite contains carbon elements, and carbon can play a role in alleviating the volume expansion of silicon. Therefore, the upper limit of the mass content of the silicon element in the silicon-carbon composite may be slightly higher.

[0166] In some embodiments, the mass content of the silicon-carbon composite relative to the total mass of the negative electrode active material is from 0.4% to 14.5% or more, and selectively from 5.75% to 10%. The silicon-carbon composite can further improve the energy density of the battery cell within the above range, 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 is not too large, and the content of the silicon element in the silicon-carbon composite may be slightly higher than the content of the silicon element in the silicon oxide. This can be combined with the above electrolyte system to significantly reduce the internal resistance at the end of the battery discharge and improve the discharge power performance.

[0167] The element carbon is primarily a constituent element of carbon-based materials, and in some embodiments, the carbon-based material may include at least one of artificial graphite and natural graphite.

[0168] Selectively, the carbon-based material may include artificial graphite, and the artificial graphite, when combined with the above-mentioned electrolyte system and in combination with a silicon-carbon composite, can reduce the DCR and improve power.

[0169] Selectively, carbon-based materials may also contain natural graphite, which generally has a smaller particle size and faster lithium ion release. The surface of natural graphite generally contains amorphous carbon, and the presence of amorphous carbon can reduce DCR and improve power.

[0170] The qualitative and quantitative determination of each substance or element in this application can be performed using appropriate apparatus and methods known to those skilled in the art. Relevant detection methods can refer to detection standards in China and abroad, enterprise standards in China and abroad, etc., and those skilled in the art may adaptively modify several detection steps / instrument parameters, etc., from the viewpoint of detection accuracy to obtain more accurate detection results. Qualitative or quantitative determination may be performed using a single detection method, or multiple detection methods may be combined to perform qualitative or quantitative measurements.

[0171] For example, to detect silicon elements in the negative electrode active material, qualitative and quantitative analysis may be performed by referring to JY / T015-1996 "General Rules for Inductively Coupled Plasma Atomic Emission Spectroscopy Analysis," and further analysis may be performed on the surface elements of the negative electrode plate or the cross-sectional elements after ion polishing by referring to the GB-T17359-2012 standard.

[0172] For example, the graphite material in this application can be subjected to X-ray powder diffraction testing and qualitative analysis of the negative electrode plate or negative electrode active material in combination with JIS / K0131-1996 General Rules for X-ray Diffraction Analysis. The silicon element, silicon-carbon composite, and silicon oxide SiO2 in this application are also applicable. x(0 < x ≤ 2) can also use the above X-ray powder diffraction test and qualitative analysis.

[0173] In some embodiments, based on the total mass of the negative electrode active material, the mass content ratio of silicon oxide SiO x (x = 1) to the mass content of artificial graphite is (0.5:99.5 to (5:95). When the negative electrode active material satisfies the above content range, the discharge power at low SOC can be further improved.

[0174] Exemplarily, the mass content ratio of silicon oxide SiO x to the mass content of artificial graphite may be 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 or a range consisting of any two of the above numerical values.

[0175] In some embodiments, the mass content of silicon oxide SiO x may be from 0.5% to 5%, optionally from 2% to 3.5%, for example, 0.5%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.​If the mass content of the synthetic graphite meets the above content range, the discharge power at low SOC can be further improved. The mass content of synthetic graphite may be 95% to 99.5%, and selectively 96.5% to 98%, for example, 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%. The mass content of artificial graphite may be %, 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%, or a range consisting of any two of the above values. If the mass content of artificial graphite meets the above content range, the cycle performance of the battery can be improved.

[0176] In some embodiments, the ratio of the mass content of silicon-carbon composite to the mass content of artificial graphite, based on the total mass of the negative electrode active material, ranges from (0.4:99.6) to (14.5:85.5).

[0177] By ensuring that the negative electrode active material meets the above-mentioned content ratio of silicon-carbon composite and artificial graphite, the discharge power of the battery at low SOC can be further improved.

[0178] For example, the ratio of the mass content of silicon-carbon composite to the mass content of artificial graphite may be within the range of 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 any two of the above values.

[0179] In some embodiments, the mass content of the silicon-carbon composite is 0.4% to 14.5%, selectively 5.75% to 10%, and is a range consisting of, for example, 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 any two of the above values. When the mass content of the silicon-carbon composite satisfies the above content range, the cycle performance of the battery can be improved.

[0180] In some embodiments, the mass content of artificial graphite may be 85.5% to 99.6%, selectively 90% to 94.25%, for example, 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%. The mass content of artificial graphite may be %, 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. If the mass content of artificial graphite meets the above content range, the cycle performance of the battery can be improved.

[0181] In some embodiments, the mass content of the negative electrode active material is 85% or more and less than 100% of the total mass of the negative electrode film layer. For example, the mass content of the negative electrode active material may be in the range of 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any two of the above values.

[0182] In some embodiments, the thickness of the single-sided negative electrode film layer is between 65 μm and 90 μm. The thickness of the negative electrode film layer is the thickness of the single-sided negative electrode film layer. For example, if negative electrode film layers are 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, if a negative electrode film layer is provided on one of the two sides of the negative electrode current collector, the thickness of the negative electrode film layer on this side is the thickness of the single-sided negative electrode film layer. When the thickness of the negative electrode film layer is within the above range, the transport rate of lithium ions at the negative electrode plate and the transport rate at the separator can be made to be nearly identical, reducing the risk of degrading concentration polarization and being advantageous for improving discharge performance.

[0183] For example, the thickness of the negative electrode film layer may be in the range of 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 any two of the above values.

[0184] In the embodiments of this 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 refer to detection standards in China and abroad, company standards in China and abroad, etc., and those skilled in the art may adaptively change some detection steps / instrument parameters from the viewpoint of detection accuracy to obtain more accurate detection results. One detection method may be used for qualitative or quantitative measurement, or multiple detection methods may be combined to measure qualitatively or quantitatively. For example, based on GB / T 17359-2012 "Quantitative Analysis by Microbeam Spectroscopy", the thickness of the negative electrode film layer can be obtained by performing ion polishing cross-sectional elemental analysis on a negative electrode plate that does not contain electrolyte as a sample. Furthermore, for example, multiple measurements are taken with a thousandth of a millimeter and the average value is taken. A negative electrode plate that does not contain electrolyte (a negative electrode plate with a negative electrode film layer coated on both sides) is taken, and first the thickness of any five parts of the negative electrode plate is measured using a thousandth of a millimeter to obtain the average value H1. After wiping off the negative electrode film layer, the thickness of any five remaining parts of the current collector is measured to obtain the average value H2, and the thickness of the single-layer negative electrode film layer is (H2-H1) / 2.

[0185] In some embodiments, the compaction density PD of the negative electrode film layer is 1.3 g / cm³. 3 From 1.7 g / cm³ 3 The compaction density of the negative electrode film layer is within this range, and the negative electrode plate has good dynamic and cyclic performance.

[0186] For example, the compaction density PD of the negative electrode film layer is 1.3 g / cm³. 3 1.35 g / cm³ 3 1.4 g / cm³ 3 1.45 g / cm³ 3 1.5 g / cm³ 3 , 1.55 g / cm³ 3 1.6 g / cm³ 3 1.65 g / cm³ 3 1.7 g / cm³ 3 Alternatively, it may be a range consisting of any two of the above values.

[0187] Surface density = weight of one-sided negative electrode film layer / area of ​​one-sided negative electrode film layer. Here, since both sides of the negative electrode current collector have a negative electrode film layer, the weight of one-sided negative electrode film layer = (average weight of electrode plate - average weight of current collector) / 2. Consolidation density = surface density / average thickness of negative electrode film layer. Here, since both sides of the negative electrode current collector have a negative electrode film layer, the average thickness of the negative electrode film layer = (average thickness of electrode plate - average thickness of current collector) / 2.

[0188] The term "average" here may refer to the average value after five parallel tests have been conducted.

[0189] In some embodiments, the negative electrode film layer further selectively contains a negative electrode conductive agent. The embodiments of this application are not particularly limited to the type of negative electrode conductive agent, and 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.

[0190] In some embodiments, the negative electrode film layer further selectively includes a negative electrode adhesive. The embodiments of this application are not particularly limited to the type of negative electrode adhesive, and as an example, the negative electrode adhesive may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), and aqueous acrylic resins (e.g., polyacrylate (PAA), polymethacrylate (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.

[0191] In some embodiments, the negative electrode film layer may further selectively contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of the other additives is ≤2% based on the total mass of the negative electrode film layer.

[0192] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. Copper foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys. For example, the polymer material base layer may include at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene and polyethylene.

[0193] In some embodiments, the thickness of the negative electrode current collector is 6 μm or less, and selectively a thin current collector between 4.5 μm and 6 μm, such as a thin metal current collector.

[0194] The current collector of the lithium-ion battery described in this application is selectively a thin current collector ranging from 4.5 μm to 6 μm, which weakens the heat dissipation path of the lithium-ion battery and allows some heat to be retained within the battery during low SOC discharge. By combining a low-silicon negative electrode plate with a high-content lithium hexafluorophosphate electrolyte system, the beneficial effect of reducing DCR growth at the end of discharge (under low SOC) is further enhanced, thereby improving discharge power at low SOC.

[0195] For example, the thickness of the negative electrode current collector may be within the range of 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 any two of the above values.

[0196] In the embodiments of this application, the thickness of the negative electrode current collector is a known concept in the art and can be detected using instruments and methods known in the art. For example, a negative electrode plate was used as a sample, the negative electrode film layer on the surface of the negative electrode plate was then cleaned with an organic solvent such as alcohol, and the thickness of the negative electrode current collector was measured with a micrometer.

[0197] The negative electrode film layer is generally obtained by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selective conductive agent, a selective adhesive, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0198] The negative electrode plate does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of this 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 installed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate of the embodiments of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0199] [Separator] In some embodiments, the lithium-ion battery further includes a separator, the porosity of which is 30% to 45%.

[0200] Because the amount of lithium hexafluorophosphate added is relatively high, the overall viscosity of the electrolyte is relatively high, and the porosity of the separator is relatively high. This is advantageous for the relatively high viscosity electrolyte to permeate the separator, allowing lithium ions to move smoothly.

[0201] For example, the porosity of the separator may be in the range of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any two of the above values.

[0202] In the embodiments of this application, porosity refers to the percentage of the total volume of the separator that is occupied by the volume of pores within the separator. Porosity can be tested according to the standard GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries".

[0203] In some embodiments, the separator includes an organic substrate and a coating provided 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 the surface of the organic substrate and the organic layer being provided on the surface of the heat-resistant layer away from the organic substrate. The separator, when combined with the electrolyte and the negative electrode plate, can significantly improve the power performance of the battery cell.

[0204] The heat-resistant layer selectively contains inorganic particles. The separator, when combined with the electrolyte and negative electrode plate, can significantly improve the power performance of the battery cell.

[0205] The organic layer selectively comprises one of a non-fluorinated polymer and a fluorine-containing polymer, and selectively comprises a non-fluorinated polymer, for example, the non-fluorinated polymer is polyacrylate, in which case the organic layer is a polyacrylate layer. The above separator, when combined with the above electrolyte and negative electrode plate, can significantly improve the power performance of the battery cell.

[0206] In some embodiments, the separator includes an organic substrate and a coating provided on at least one side of the organic substrate, the coating including a ceramic layer and / or a polyacrylate layer. The coating may include only a ceramic layer, only a polyacrylate layer, or both a ceramic layer and a polyacrylate layer.

[0207] Selectively, if the coating includes a ceramic layer and a polyacrylate layer, the polyacrylate layer may be provided on at least one surface of the organic substrate and the ceramic layer may be provided on the surface of the polyacrylate layer away from the organic substrate, or the ceramic layer may be provided on at least one surface of the organic substrate and the polyacrylate layer may be provided on the surface of the ceramic layer away from the organic substrate.

[0208] The separator has a polyacrylate layer on its outer surface, which provides a certain degree of flexibility to the outer surface of the separator, effectively mitigating the volume expansion or contraction of the silicon-based material and improving the overall structural stability of the electrode assembly.

[0209] The material of the organic substrate is not particularly limited, and any known base film having good chemical and mechanical stability can be selected. For example, the organic substrate includes at least one of porous polyolefin resin films (e.g., polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride), porous glass fibers, and porous nonwoven fabrics. The organic substrate may be selected from single-layer films or multilayer composite films. If the organic substrate is a multilayer composite film, the materials of each layer may be the same or different.

[0210] In some embodiments, the thickness of the organic substrate is 6.6 μm to 7.6 μm.

[0211] When the thickness of the organic substrate is within the above range, the transport rate of lithium ions at the negative electrode plate and the transport rate at the separator can be made to be nearly identical, reducing the risk of degrading concentration polarization and being advantageous for improving discharge performance.

[0212] For example, the thickness of the organic substrate may be in the range of 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 any two of the above values.

[0213] In some embodiments, the polyacrylate in the polyacrylate layer may be formed by polymerizing polymer monomers, the polymer monomers comprising at least one of a first polymer monomer, a second polymer monomer, and a third polymer monomer. Selectively, the polymer monomers comprise the first polymer monomer, the second polymer monomer, and the third polymer monomer. The polyacrylate is formed by polymerizing the above three polymer monomers, allowing the separator to acquire appropriate adhesion to the electrode plate and improving the dynamic performance of the lithium-ion battery.

[0214] The first polymer monomer has at least one ester bond and is selectively 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, and is further selectively one or more of methyl methacrylate, lauryl acrylate, lauryl methacrylate, or trimethylolpropane triacrylate.

[0215] The second polymer monomer has at least one cyanide bond and is selectively one or more of acrylonitrile, methacrylonitrile, and ethacrylonitrile, and is further selectively one or more of acrylonitrile and methacrylonitrile.

[0216] The third polymer monomer has at least one amide bond and is selectively one or more of acrylamide, N-methylolacrylamide, and N-butoxymethacrylamide, and more selectively one or more of acrylamide and N-methylolacrylamide.

[0217] In some embodiments, the weight ratio of the first polymer monomer, the second polymer monomer, and the third polymer monomer in the formed polyacrylate is (45 to 70):(10 to 25):(10 to 35), for example (50 to 70):(10 to 25):(10 to 35), (55 to 70):(10 to 25):(10 to 35), (60 to 70):(10 to 25):(10 to 35), (65 to 70):(10 to 25):(10 to 35), (4 The age ranges are as follows: 5 to 70: (15 to 25): (10 to 35), (45 to 70): (20 to 25): (10 to 35), (45 to 70): (22 to 25): (10 to 35), (45 to 70): (10 to 25): (15 to 35), (45 to 70): (10 to 25): (20 to 35), (45 to 70): (10 to 25): (25 to 35), (45 to 70): (10 to 25): (30 to 35), (45 to 70): (10 to 25): (32 to 35), etc.

[0218] In some embodiments, the ceramic layer includes heat-resistant inorganic particles, the inorganic particles may include at least one of inorganic particles with a dielectric constant of 5 or more, inorganic particles capable of transporting active ions, and inorganic particles on which electrochemical oxidation and reduction can occur.

[0219] In some embodiments, inorganic particles having a dielectric constant of 5 or higher include boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), and silicon oxide (SiO2). x(0 < x ≤ 2), tin dioxide (SnO2), titanium dioxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium dioxide (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 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1) and at least one of Pb(Mg3Nb 2 / 3 )O3 - PbTiO3 (abbreviated as PMN - PT).

[0220] In some embodiments, the inorganic particles having the ability to transport 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 (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 < 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 z , 0 < x < 3, 0 < y < 3, 0 < z < 7), at least one of them.

[0221] In some embodiments, the inorganic particles capable of electrochemical oxidation and reduction include at least one of lithium-containing transition metal oxides, lithium-containing phosphates with an olivine structure, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0222] In some embodiments, the ceramic layer may further contain an adhesive, which optionally comprises one or more of the following: polyacrylate, acrylic acid, carboxymethylcellulose, polyvinylidene fluoride-co-trichloroethylene copolymer, polymethyl methacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose butyrate acetate, cellulose propionate acetate, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, and cyanoethyl pullulan.

[0223] In some embodiments, the coating thickness is 1.5 μm to 2.5 μm.

[0224] The coating thickness is the thickness of the coating on one side, specifically including the total thickness of the ceramic layer and the polyacrylate layer. For example, if coatings are provided on both sides of an organic substrate, the thickness of the coating on one side of the organic substrate is the thickness of the coating on one side, or if coatings are provided on one side of the organic substrate, the thickness of the coating on this side is the thickness of the coating on one side. When the coating thickness is within the above range, the transport rate of lithium ions at the negative electrode plate and the transport rate at the separator can be made to be nearly identical, reducing the risk of degrading concentration polarization and being advantageous for improving discharge performance.

[0225] For example, the coating thickness may be in the range of 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 any two of the above values.

[0226] In some embodiments, the ratio of the thickness of the ceramic layer to the thickness of the polyacrylate layer is (0.5 to 2.0):1, and may be, for example, 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 any two of the above values.

[0227] In the embodiments of this application, the meanings of the organic substrate and coating thickness are known in the art and can be detected using instruments and methods known in the art, for example, by testing in combination with a scanning electron microscope using an ion cross-sectional polishing apparatus. For example, the procedure can be carried out according to the following steps. First, the separator is cut to a test sample of a certain size (e.g., 6 mm x 6 mm), the test sample is sandwiched between two conductive and thermally conductive sheets (e.g., copper foil), the test sample and the copper foil are fixed together with an adhesive (e.g., double-sided adhesive), a flat iron block of a certain mass (e.g., about 400 g) is pressed down for a certain time (e.g., 1 h) to reduce the gap between the test sample and the copper foil, and then the edges are trimmed with scissors so that they are aligned, and the sample is placed on a sample stage with conductive adhesive so that the sample protrudes slightly beyond the edge of the sample stage. The sample stage was then placed in the sample rack and locked in place. The argon ion cross-sectional polishing meter was powered on and vacuumed (for example, to 10 Pa-4 Pa). The argon gas flow rate (for example, to 0.15 MPa), voltage (for example, to 8 KV), and polishing time (for example, 2 hours) were set. The sample stage was adjusted to the oscillating mode and polishing was started. After polishing was completed, a scanning electron microscope (for example, ZEISS Sigma 300) was used to obtain an ion polishing cross-sectional morphology (CP) image of the test sample, and the thickness of the coating and the thickness of the organic substrate were measured.

[0228] In some embodiments, the positive electrode plate, separator and negative electrode plate may be manufactured into an electrode assembly by a winding process and / or a lamination process, and the electrode assembly may be understood to be a wound electrode assembly or a lamination electrode assembly, and selectively, the electrode assembly is a lamination electrode assembly, which can make the space between the positive and negative electrode plates tighter and further improve the DCR.

[0229] In some embodiments, the lithium-ion battery may include an outer casing. This casing may be used to package the electrode assembly and the electrolyte.

[0230] In some embodiments, the casing of the lithium-ion battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the lithium-ion battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be at least one of plastics, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0231] The embodiments of this application are not particularly limited to the shape of the lithium-ion battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular lithium-ion battery 5 as an example.

[0232] In some embodiments, as shown in Figure 2, the casing 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, the bottom plate and side plates enclosing and forming a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The positive electrode plate, negative electrode plate and separator can be formed into an electrode assembly 52 by a winding process and / or a lamination process. The electrode assembly 52 is packaged into the housing cavity. The electrolyte is infused into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the lithium-ion battery 5 may be one or more and can be adjusted according to demand.

[0233] The method for manufacturing a lithium-ion battery according to the embodiments of this application is known. In some embodiments, a lithium-ion battery may be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, separator, and negative electrode plate can be formed into an electrode assembly through a winding process and / or a lamination process, the electrode assembly is placed in an outer casing, dried, and then the electrolyte is injected, followed by processes such as vacuum packaging, settling, chemical conversion, and shaping to obtain a lithium-ion battery.

[0234] In some embodiments of the present invention, the lithium-ion battery according to the present invention can be assembled into a battery module, and the number of lithium-ion batteries included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0235] Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, the multiple lithium-ion batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple lithium-ion batteries 5 may be fixed in place with fasteners.

[0236] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of lithium-ion batteries 5 are housed.

[0237] 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.

[0238] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed inside the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and used to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0239] power consumption equipment A third embodiment of the present invention provides a power consumption device comprising at least one of the lithium-ion battery, battery module, or battery pack of the embodiments of the present invention. The lithium-ion battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0240] The power consumption device can be configured to use a lithium-ion battery, battery module, or battery pack, depending on its usage needs.

[0241] FIG. 6 is a schematic diagram of a power consumption device 6 as an example. This power consumption device 6 is, for example, a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the demand for high output and high energy density of this power consumption device 6, a battery pack or a battery module may be adopted.

[0242] As another example of a power consumption device, it may be a mobile phone, a tablet computer, a notebook computer, etc. This power consumption device generally requires thinning and can adopt a lithium-ion battery as a power source.

[0243] Examples The following examples describe more specifically the content disclosed in the embodiments of the present application. These examples are only for discussion and explanation purposes, and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the content disclosed in the embodiments of the present application. Unless otherwise declared, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples can be obtained commercially or synthesized according to ordinary methods, and can be used directly without further processing, and all instruments used in the examples can be obtained commercially.

[0244] Example 1 1. Manufacture of the positive electrode plate 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 is a film layer formed by uniformly coating the surface of the aluminum foil of the positive electrode current collector with a positive electrode slurry (the solvent is N-methylpyrrolidone NMP), followed by drying and cold pressing. The positive electrode film layer contains a positive electrode active material, a conductive agent carbon black, and an adhesive polyvinylidene fluoride (PVDF) with a weight ratio of 97.5:1.4:1.1. The consolidation density of the positive electrode film layer was 3.35 g / cm 3 and was.

[0245] The positive electrode active material has a single crystal structure and its molecular formula is Lid Ni a Co b Mn c M (1-a-b-c) O z It contains a compound, where 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 a compound that is O2.

[0246] The M element contains 450 ppm of Ti, 1700 ppm of Zr, 1600 ppm of Al, and 120 ppm of (B, S, and P) elements.

[0247] 2. Manufacturing of the negative electrode plate 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 is formed by uniformly coating the surface of the negative electrode current collector copper foil with a negative electrode slurry (solvent is deionized water), drying, and cold pressing. The negative electrode film layer contains 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 sodium carboxymethylcellulose (CMC-Na), and a conductive agent carbon black (Super P).

[0248] The negative electrode active material contained 97% artificial graphite and 3% silicon oxide (SiO), and the mass content of silicon relative to the total mass of the negative electrode active material was 1.91%. The compaction density of the negative electrode film layer was 1.4 g / cm³. 3 That was the case.

[0249] 3. Separator The separator can be purchased directly from the separator supplier. The separator has a porosity of 30% and comprises an organic substrate (porous polypropylene PP (7 μm)) and a coating. The coating comprises a ceramic layer (1 μm) and a polyacrylate layer (1 μm). The ceramic layer is provided on two surfaces of the organic substrate and includes a film layer formed by dissolving an adhesive and inorganic aluminum oxide in N-methylpyrrolidone NMP and applying it to the organic substrate. The polyacrylate layer is provided on the surface of the ceramic layer that is separated from the organic substrate and is a film layer formed by applying a substance containing polyacrylates to the surface of the ceramic layer.

[0250] 4. Manufacturing of electrolyte The electrolyte comprises an organic solvent, a lithium salt, and an additive. The organic solvent includes cyclic carbonates (EC, PC, and BC, with a mass ratio of 1:1:1) and linear carbonates (EMC, DMC, and DEC, with a mass ratio of 1:1:1).

[0251] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator positioned between the positive and negative electrode plates to act as a separator. The assembly was then wound up to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then injected with electrolyte. After going through processes such as vacuum packaging, standing, chemical formation, and shaping, a lithium-ion battery was obtained, and the electrolyte retention coefficient of the lithium-ion battery was 2.0 g / Ah.

[0252] Comparative Example 1 A lithium-ion battery was manufactured using a method similar to that of Example 1, the only difference being that the positive electrode active material of Comparative Example 1 is different, and the positive electrode active material does not contain element M.

[0253] Comparative Example 2 and Comparative Example 3 A lithium-ion battery was manufactured using a method similar to that of Example 1, except that in Comparative Examples 2 and 3, the electrolyte components, particularly the content of lithium hexafluorophosphate, were adjusted.

[0254] Example 2 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the form of the positive electrode active material in Example 2 is different, and the positive electrode active material in Example 2 uses polycrystalline particles.

[0255] Examples 3-1 and 3-2 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the components of the electrolyte, especially the content of lithium hexafluorophosphate, were adjusted from Example 3-1 to Example 3-2.

[0256] Examples 4-1 to 4-4 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the positive electrode active materials in Examples 4-1 to 4-4 are different, and the content of at least one of Ti and Zr in the M element of the positive electrode active material was adjusted.

[0257] Examples 4-5 to 4-7 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the electrolytes in Examples 4-5 to 4-7 are different, and the content of the first additive in the electrolyte was adjusted.

[0258] Examples 5-1 and 5-2 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the positive electrode active materials in Examples 5-1 and 5-2 are different, and the content of Al in the M element of the positive electrode active material was adjusted.

[0259] Examples 5-3 to 5-4 A lithium-ion battery was manufactured in a method similar to that of Example 1. The difference from Example 1 is that the electrolytes in Examples 5-3 to 5-4 are different, and the content of the second additive in the electrolyte was adjusted.

[0260] Examples 6-1 to 6-3 Lithium-ion batteries were manufactured using a method similar to that of Example 1, but differing from Example 1 in that the positive electrode active material and electrolyte of Examples 6-1 to 6-3 were different, with the total content of P, B, and S in the M element of the positive electrode active material being adjusted, and the content of the third additive in the electrolyte being adjusted.

[0261] Examples 7-1 and 7-2 Lithium-ion batteries were manufactured using a method similar to that of Example 1, except that the electrolytes in Examples 7-1 and 7-2 were different, with fluorinated cyclic carbonate added to the electrolyte.

[0262] Example 8 A lithium-ion battery was manufactured in a manner similar to that of Example 1, except that the electrolyte in Example 8 was different, and a fourth additive was added to the electrolyte.

[0263] The parameters for the examples and comparative examples are as shown in Tables 1 to 3.

[0264] Performance testing 1. Lithium-ion cycle performance test At 25°C, the lithium-ion batteries produced in the examples and comparative examples were charged to 4.35V at a rate of 1C and discharged to 2.8V at a rate of 1C, and the cycle was repeated 500 times. The percentage of the remaining capacity of the lithium-ion battery relative to its initial capacity was recorded.

[0265] Test results The test results are shown in Tables 1 to 3.

[0266] [Table 1]

[0267] In Table 1, the positive electrode active material of Example 1 has a single crystal structure, and its molecular formula is LiNi a Co b Mn c M (1-a-b-c)The compound contains O2, and 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 The compound contains O2. The M element contains 450 ppm of Ti, 1700 ppm of Zr, 1600 ppm of Al, and 120 ppm of (B, S, and P). The molecular formulas of the positive electrode active material in Examples 2, 3-1, and 3-2 are the same as in Example 1. Example 2 uses a polycrystalline structure, while Examples 3-1 and 3-2 use single-crystal particles.

[0268] The positive electrode active material of Comparative Example 1 has the molecular formula LiNi 0.70 Co 0.10 Mn 0.20 The compound contains O2, and single-crystal particles were used.

[0269] As can be seen from Table 1, Although the lithium hexafluorophosphate content in Comparative Example 1 is relatively high, the positive electrode active material in Comparative Example 1 is LiNi 0.70 Co 0.10 Mn 0.20 It is O2, and its structural stability is relatively low, which means that the cycle performance of lithium-ion batteries remains low.

[0270] Comparative Examples 2 and 3 both used appropriate positive electrode active material systems. The positive electrode active material contained M elements, such as Ti, Zr, Al, B, S, and P, which are advantageous in improving the lattice stability of the positive electrode active material system. However, Comparative Example 2 used a relatively low content of lithium hexafluorophosphate (12%). The relatively low content of lithium hexafluorophosphate resulted in relatively few lithium fluorides being formed on the surface of the positive electrode active material, and it could not adequately protect the positive electrode active material. As a result, there was still a risk of transition metal ions in the positive electrode active material leaching into the electrolyte, which worsened the battery cycle performance. Comparative Example 3 used a relatively high content of lithium hexafluorophosphate (23%). The relatively high content of lithium hexafluorophosphate resulted in excessively high viscosity of the electrolyte system, which was unfavorable for lithium ion movement, and the dynamic performance of the battery was relatively poor.

[0271] The positive electrode active material of Example 1 further contains element M, and the introduction of element M can improve the stability of the positive electrode active material crystal structure. Furthermore, lithium hexafluorophosphate is combined with it, and the mass content of lithium hexafluorophosphate (LiPF6) relative to the total mass of the electrolyte is 15% to 20%. The lithium hexafluorophosphate can form a protective layer on the surface of the positive electrode active material, with lithium fluoride (LiF) as the main film component, thereby mitigating the leaching of metallic and nonmetallic elements to some extent and improving the cycle performance of the lithium-ion battery. Compared to the positive electrode active material of Example 2, which uses polycrystalline particles, Example 1 uses single-crystal particles, resulting in a relatively smaller contact interface between the single-crystal particles and the electrolyte, a lower risk of side reactions, and a greater advantage in improving cycle performance.

[0272] [Table 2]

[0273] As can be seen from Table 2, By using the first additive in Examples 4-1 to 4-7 in combination with Ti and Zr in the positive electrode active material, Ti and Zr can improve the stability of the positive electrode active material structure, and the first additive can compensate for the power degradation caused by Ti and Zr ions, thereby improving the cycle performance of the lithium-ion battery.

[0274] By using the second additive in Examples 5-1 to 5-4 in combination with Al in the positive electrode active material, and in particular by combining lithium difluorophosphate with the Al element in the positive electrode active material, the DCR on the surface of the positive electrode active material can be improved and the interfacial power can be enhanced.

[0275] [Table 3]

[0276] As can be seen from Table 3, By combining the third additive in Examples 6-1 to 6-3 with at least one element from phosphorus (P), sulfur (S), and boron (B) in the positive electrode active material, the DCR of the surface of the positive electrode active material can be improved, and the interfacial power can be enhanced.

[0277] Examples 7-1 and 7-2 further involve adding a fluorinated cyclic carbonate to the electrolyte. The fluorinated cyclic carbonate can contribute to the formation of an SEI film on the surface of the negative electrode active material, effectively protecting the negative electrode active material and thereby improving the cycle performance of the lithium-ion battery.

[0278] Example 8 further involves adding a fourth additive to the electrolyte, the fourth additive which can participate in the formation of an SEI film on the surface of the negative electrode active material, effectively protecting the negative electrode active material and thereby improving the cycle performance of the lithium-ion battery.

[0279] Example 9-1 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 a 12 μm thick aluminum foil. The positive electrode film layer is formed by uniformly coating the surface of the aluminum foil of the positive electrode current collector with a positive electrode slurry (solvent is N-methylpyrrolidone NMP), drying, and cold pressing. The positive electrode film layer contains a positive electrode active material, a conductive agent carbon black, and an adhesive polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1. The compaction density of the positive electrode film layer is 3.35 g / cm³. 3 That was the case.

[0280] The positive electrode active material is a single-crystal particle or a polycrystalline particle, and its molecular formula is Li d Ni a Co b Mn c M (1-a-b-c) O z It contains a compound, where the nickel-cobalt-manganese oxide substrate in the positive electrode active material has the molecular formula LiNi 0.90 Co 0.05 Mn 0.05 Contains a compound that is O2.

[0281] The M element contains 3000 ppm of Zr, 1800 ppm of Al, and 120 ppm of (B, S, P) elements.

[0282] 2. Manufacturing of the negative electrode plate 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 is formed by uniformly coating the surface of the negative electrode current collector copper foil with a negative electrode slurry (solvent is deionized water), drying, and cold pressing. The negative electrode film layer contains 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 sodium carboxymethylcellulose (CMC-Na), and a conductive agent carbon black (Super P).

[0283] The negative electrode active material consisted of 93% artificial graphite and 7% silicon-carbon composite, with a silicon content of 4.9% relative to the total mass of the negative electrode active material.

[0284] The compaction density of the negative electrode film layer is 1.4 g / cm³. 3 That was the case.

[0285] 3. Separator The separator can be purchased directly from the separator supplier. The separator has a porosity of 30% and comprises an organic substrate (porous polypropylene PP (7 μm)) and a coating. The coating comprises a ceramic layer (1 μm) and a polyacrylate layer (1 μm). The ceramic layer is provided on two surfaces of the organic substrate and includes a film layer formed by dissolving an adhesive and inorganic aluminum oxide in N-methylpyrrolidone NMP and applying it to the organic substrate. The polyacrylate layer is provided on the surface of the ceramic layer that is separated from the organic substrate and is a film layer formed by applying a substance containing polyacrylates to the surface of the ceramic layer.

[0286] 4. Manufacturing of electrolyte The electrolyte contains an organic solvent, a lithium salt, and 0.25% fluorinated cyclic carbonate FEC. The organic solvent contains cyclic carbonates (EC, PC, and BC, with a mass ratio of 1:1:1) and linear carbonates (EMC, DMC, and DEC, with a mass ratio of 1:1:1). The lithium salt contains 18.2% lithium hexafluorophosphate.

[0287] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator positioned between the positive and negative electrode plates to act as a separator, and then wound up to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then injected with electrolyte. After going through processes such as vacuum packaging, standing, chemical formation, and shaping, a lithium-ion battery was obtained, and the electrolyte retention coefficient of the lithium-ion battery was 1.3 g / Ah.

[0288] Examples 9-2 and 9-3 A lithium-ion battery was manufactured using a method similar to that of Example 9-1, the only difference being that the Ni content in the positive electrode active material was adjusted.

[0289] Example 10 A lithium-ion battery was manufactured using a method similar to that of Example 9-1, the only difference being that the mass content of Zr was adjusted.

[0290] Example 11 A lithium-ion battery was manufactured using a method similar to that of Example 9-1, the only difference being that the mass content of fluorinated cyclic carbonate FEC in the electrolyte was adjusted.

[0291] Performance testing Lithium-ion cycle performance testing At 25°C, the lithium-ion batteries produced in the examples and comparative examples were charged to 4.25V at a rate of 1C, discharged to 2.8V at a rate of 1C, and the cycle was repeated 500 times. The percentage of the remaining capacity of the lithium-ion battery relative to its initial capacity was recorded.

[0292] The test results are shown in Table 4. [Table 4]

[0293] As can be seen from Table 4, Examples 9-1 to 11 demonstrate that cycle performance can be significantly improved by adjusting the content of Zr, Ni, and FEC in a high nickel-content cathode active material system, and by combining it with an appropriate electrolyte system (with a mass content of lithium hexafluorophosphate of 15% to 20%).

[0294] While exemplary embodiments have been provided for this explanation, those skilled in the art should understand that the embodiments described above should not be construed as limitations on this application, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principles, and scope of this application. [Explanation of Symbols]

[0295] 1: Battery pack, 2: Upper casing, 3: Lower casing, 4: Battery module, 5: Lithium-ion battery, 51: Case, 52: Electrode assembly, 53: Cover plate, 6: Power consumption device.

Claims

1. It is a lithium-ion battery, An electrolyte comprising a lithium salt, wherein the lithium salt comprises lithium hexafluorophosphate, and the mass content of lithium hexafluorophosphate relative to the total mass of the electrolyte is 15% to 20%. A positive electrode plate comprising a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode active material has the molecular formula Li ｄ Ni ａ Co ｂ Mn ｃ M （１－ａ－ｂ－ｃ） Q ｚ The compound comprises a positive electrode plate in which 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, and element M comprises at least one element from 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 element Q comprises at least one element from O, F. The electrolyte contains a first additive, the first additive being lithium difluoro(oxalato)borate LiDFOB and lithium tetrafluoroborate LiBF ４ It includes at least one of the following: Based on the total mass of the electrolyte, the mass content of the first additive is between 30 ppm and 1200 ppm. A lithium-ion battery wherein the positive electrode active material includes one or more single-crystal particles and polycrystalline particles.

2. The lithium-ion battery according to claim 1, wherein element M comprises at least one element from Ti and Zr.

3. The lithium-ion battery according to claim 2, wherein the element M includes the element Zr.

4. The lithium-ion battery according to claim 2, wherein the mass content of element Zr is 500 ppm to 5000 ppm, based on the total mass of the positive electrode active material.

5. The lithium-ion battery according to claim 1, wherein the positive electrode active material includes single-crystal particles and polycrystalline particles.

6. The single crystal particle includes an inner region and an outer region, the outer region being a region that extends 500 nm directly inward from any point on the outer surface of the single crystal particle towards the interior of the single crystal particle. The lithium-ion battery according to claim 1, wherein the M element includes at least the Al element distributed in the outer region.

7. The lithium-ion battery according to claim 6, wherein the electrolyte comprises a second additive, and the second additive comprises lithium difluorophosphate.

8. Based on the total mass of the positive electrode active material, the mass content of Al is between 500 ppm and 3000 ppm. The lithium-ion battery according to claim 7, wherein the mass content of the second additive is 100 ppm to 3000 ppm, based on the total mass of the electrolyte.

9. Element M further comprises at least one element from among P, S, and B, wherein at least one of the elements P, S, and B is distributed in the outer region. The lithium-ion battery according to claim 6, wherein the electrolyte comprises a third additive, and the third additive comprises lithium fluorosulfonate.

10. Based on the total mass of the positive electrode active material, the total mass content of elements P, S, and B is between 10 ppm and 800 ppm. The lithium-ion battery according to claim 9, wherein the mass content of the third additive is 50 ppm to 200 ppm, based on the total mass of the electrolyte.

11. The lithium-ion battery according to claim 1, wherein the electrolyte contains a cyclic carbonate, and the ratio of the mass content of the cyclic carbonate to the mass content of the lithium hexafluorophosphate is (0.60 to 2.50):1 based on the total mass of the electrolyte.

12. The lithium-ion battery according to claim 11, wherein 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 (1.00 to 1.65):

1.

13. With respect to the total mass of the electrolyte, the mass content of the cyclic carbonate is 20% to 30%, and / or The lithium-ion battery according to claim 11, wherein the cyclic carbonate comprises at least one of ethylene carbonate EC, propylene carbonate PC, and butylene carbonate BC.

14. The lithium-ion battery according to claim 1, further comprising a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector and containing a negative electrode active material, the negative electrode active material comprising carbon and silicon, and the mass content of silicon is 0.30% to 10.00% based on the total mass of the negative electrode active material.

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

1.

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

1.

17. Based on the total mass of the electrolyte, the mass content of the fluorinated cyclic carbonate is 0.05% to 5.80%, and / or The lithium-ion battery according to claim 15, wherein the fluorinated cyclic carbonate comprises at least one of monofluoroethylene carbonate FEC, bisfluoroethylene carbonate DFEC, and trifluoropropylene carbonate TFPC.

18. With respect to the total mass of the electrolyte, the mass content of the fluorinated cyclic carbonate is 0.1% to 1.0%, and / or The lithium-ion battery according to claim 17, wherein the fluorinated cyclic carbonate includes monofluoroethylene carbonate FEC.

19. The lithium-ion battery according to claim 14, wherein the ratio of the compaction density of the positive electrode film layer to the compaction density of the negative electrode film layer is (2 to 2.5):

1.

20. A lithium-ion battery according to any one of claims 1 to 19, wherein 0.85 ≤ a ≤ 0.

95.

21. A battery comprising the lithium-ion battery described in claim 20.

22. A power consumption device comprising the battery described in claim 21.

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