Battery cell, secondary battery, and electric device

Abstract

The invention provides a battery cell, a secondary battery and an electric device. The battery monomer comprises a positive pole piece, a negative pole piece, an isolating membrane and an electrolyte, a positive active material layer in the positive pole piece comprises a first positive active material and a second positive active material, and an electrolyte salt in the electrolyte comprises a first cationic salt; the first positive electrode active material is a lithium oxide containing Co element and M1 element, and the M1 element comprises one or two of Mn element and Al element; the second positive electrode active material is a lithium oxide containing an Fe element and an Mn element; the mass ratio of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material is A; the first cation salt comprises first cations with the ion radius larger than that of lithium ions; the mass percentage of the first cation salt in the electrolyte salt is B; 0.47 < = A / B < = 202. The battery monomer has better electrical property, good thermal stability and low thermal runaway risk.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a battery cell, a secondary battery, and an electrical device. Background Art

[0002] The statements herein only provide background information related to the present application and do not necessarily constitute prior art.

[0003] With the increasingly wide application scope of secondary batteries, secondary batteries represented by lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, and are also widely used in many fields such as smart phones, tablet computers, smart wearables, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the broadening and development of applications, higher requirements are put forward for the electrical performance of the batteries. However, at the same time, risks such as thermal runaway may be brought, resulting in poor thermal stability of the batteries.

[0004] Based on this, it is necessary to develop new technologies for secondary batteries with good electrical performance and good thermal stability. Summary of the Invention

[0005] In view of the above problems, the present application provides a battery cell, a secondary battery, and an electrical device. The battery cell has better electrical performance, good thermal stability, and low risk of thermal runaway.

[0006] In a first aspect of the present application, a battery cell is provided, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first positive electrode active substance and a second positive electrode active substance. The electrolyte includes an electrolyte salt, and the electrolyte salt includes a first cationic salt and an electrolyte lithium salt;

[0007] Wherein, the first positive electrode active substance is a lithium oxide containing Co element and M1 element, and the second positive electrode active substance is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first positive electrode active substance includes one or two of Mn element and Al element;

[0008] The mass ratio of the Co element in the first positive electrode active substance to the Fe element in the second positive electrode active substance is denoted as A;

[0009] The first cationic salt includes a first cation, and the ionic radius of the first cation is greater than the ionic radius of the lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is denoted as B;

[0010] Then A and B satisfy 0.47 ≤ A / B ≤ 202.

[0011] It can be understood that in the case where the positive electrode plate includes a first positive electrode active material and a second positive electrode active material, the active ions in the battery cell include lithium ions.

[0012] The positive electrode plate in the battery cell is a composite positive electrode plate, in which different positive electrode active materials are provided. The composite positive electrode plate includes a first positive electrode active material containing cobalt (Co) element and M1 element, and M1 element includes one or both of manganese (Mn) element and aluminum (Al) element. It also includes a second positive electrode active material containing iron (Fe) element and Mn element. Although theoretically, the design of using this composite positive electrode plate can make different positive electrode active materials complement each other, it is hoped that the comprehensive electrical performance can be improved in aspects such as material structure stability, battery safety, rate performance, and cycle performance, and the voltage platform and manufacturing cost can be taken into account. However, lithium oxides containing Co element and M1 element and lithium oxides containing Fe element and Mn element are different positive electrode active materials, which will have different activities and ionic conductivities, resulting in different degrees of utilization during the charge-discharge cycle. Among them, lithium oxides containing Co element and M1 element are easily over-utilized, causing damage to the surface structure of the first positive electrode active material and releasing oxygen, and may even lead to the collapse of the material structure, posing a risk of battery thermal runaway; in addition, the released oxygen may also trigger side reactions of the electrolyte. The diffusion of active ions in the design of this composite positive electrode plate is presumably one-dimensional channel diffusion. By introducing a first cation salt, a first cation with an ionic radius larger than that of lithium (Li) ion is introduced. This first cation can replace part of the active ions and embed into the first positive electrode active material, blocking the active ion diffusion channel in the first positive electrode active material, reducing the utilization degree of the first positive electrode active material, reducing oxygen release. The first cation can also play a role in supporting the surface structure of the first positive electrode active material, hindering the removal of active ions during discharge, further increasing the stability of oxygen on the surface of the positive electrode active material, reducing oxygen release, and the first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, reducing the risk of thermal runaway. Further, by adjusting the mass ratio A of Co element in the first positive electrode active material to Fe element in the second positive electrode active material (which can also be denoted as I Co / II FeBy adjusting the content ratio between the first positive electrode active material and the second positive electrode active material, and further using the A / B value to synergistically adjust the mass percentage B of the first cation salt relative to the electrolyte salt in the electrolyte, the concentration of the first cation in the electrolyte can be better matched with the demand of the first positive electrode active material for appropriately reducing the utilization rate. Thus, better comprehensive electrical performance can be achieved overall, the thermal stability of the composite positive electrode sheet and the battery cell can be significantly improved, the risk of thermal runaway can be reduced, and it is also beneficial for the composite positive electrode sheet to have good active ion transport performance as a whole. It can be seen that the battery cell has better comprehensive performance, good thermal stability, and low risk of thermal runaway.

[0013] Based on any suitable embodiment of the present application, in some embodiments, at 25 °C, the ratio of the ionic conductivity of the first positive electrode active material to the ionic conductivity of the second positive electrode active material is denoted as Xσ, then Xσ ≥ 10 4 ;

[0014] Optionally, Xσ ≥ 10 6 , and further optionally Xσ ≥ 10 10 ;

[0015] Optionally, the ionic conductivity of the first positive electrode active material at 25 °C is σ 1 , satisfying σ 1 ≥ 3.2×10 - 6 S / cm, and further optionally σ 1 ≥ 1.7×10 -3 S / cm;

[0016] Optionally, the ionic conductivity of the second positive electrode active material at 25 °C is σ 2 , satisfying σ 2 ≤ 10 -9 S / cm, and further optionally σ 2 ≤ 10 -12 S / cm.

[0017] When the difference in ionic conductivity between the first positive electrode active material and the second positive electrode active material is large, the probability of the first positive electrode active material being over-utilized increases significantly. At this time, by adjusting the A / B value to balance the comprehensive requirements such as the demand of the first positive electrode active material for appropriately reducing the utilization rate and the good transport of active ions in the composite positive electrode sheet, the improvement effect on the thermal stability of the positive electrode sheet and the overall comprehensive performance of the battery cell is more significant.

[0018] The ionic conductivity of the first positive electrode active material (lithium oxide containing Co element and M1 element) can be adjusted by adjusting the content of nickel (Ni) element in the first positive electrode active material. Generally, the higher the Ni content, the higher the ionic conductivity of the first positive electrode active material.

[0019] The ionic conductivity of the second positive electrode active material (lithium oxide containing Fe element and Mn element) can be adjusted by adjusting the content of manganese (Mn) element. Generally, the higher the Mn element content, the lower the ionic conductivity of the second positive electrode active material.

[0020] Based on any suitable embodiment of the present application, in some embodiments, 1.3 ≤ A / B ≤ 25.4.

[0021] By adjusting the A / B value within a more suitable range, it is more conducive to achieving better thermal stability while effectively improving the comprehensive performance of the battery.

[0022] Based on any suitable embodiment of the present application, in some embodiments, 0.19 ≤ A ≤ 10.1; optionally, 0.28 ≤ A ≤ 2.53.

[0023] By adjusting the value of A, the content ratio between the first positive electrode active material and the second positive electrode active material can be adjusted. By controlling the value of A within the above range, it is more conducive to exerting the comprehensive advantages of the first positive electrode active material and the second positive electrode active material and achieving better electrical performance.

[0024] Based on any suitable embodiment of the present application, in some embodiments, 5% ≤ B ≤ 40%; optionally, 10% ≤ B ≤ 20%.

[0025] By adjusting the value of B, the mass percentage of the first cation salt relative to the electrolyte salt can be adjusted. By controlling the value of B within the above range, the concentration of the first cation in the electrolyte can better match the demand of the first positive electrode active material for appropriately reducing the utilization rate, thereby achieving better comprehensive performance of the battery as a whole.

[0026] Based on any suitable embodiment of the present application, in some embodiments, the first positive electrode active material satisfies one or more of the following characteristics:

[0027] The atomic molar ratio of Co element to Li element is denoted as R c , then R c satisfies 0.05 ≤ R c ≤ 0.5, optionally, 0.05 ≤ R c ≤ 0.3, optionally, 0.05 ≤ R c ≤ 0.2;

[0028] The atomic molar ratio of the M1 element to the Li element is denoted as R d , then R d satisfies 0.05 ≤ R d ≤ 0.5. Optionally, 0.05 ≤ R d ≤ 0.3;

[0029] The M1 element includes the Mn element. The atomic molar ratio of the Mn element to the Li element is denoted as R d-Mn , then R d-Mn satisfies 0.05 ≤ R d-Mn ≤ 0.4. Further optionally, 0.05 ≤ R d-Mn ≤ 0.3;

[0030] The ratio of the sum of the atomic molar equivalents of the Co element and the M1 element to the atomic molar equivalent of the Li element is denoted as R c+d , then R c+d satisfies 0.1 ≤ R c+d ≤ 0.5. Further optionally, 0.1 ≤ R c+d ≤ 0.3. Even further optionally, 0.1 ≤ R c+d ≤ 0.2.

[0031] The presence of the Co element is beneficial to improving the structural stability of the material. By adjusting the content of the Co element in the first positive electrode active material within a more appropriate range, it is more beneficial to improve the charge-discharge rate performance and cycle performance of the battery.

[0032] By adjusting the content of the M1 element in the first positive electrode active material, the thermal stability of the first positive electrode active material can be adjusted. For example, when the M1 element includes the Mn element, the Mn element is beneficial to improving the thermal stability of the first positive electrode active material; when the M1 element includes the Al element, the Al element is beneficial to improving the capacity and the thermal stability of the material, and is beneficial to reducing the internal resistance and improving the rate performance and cycle performance.

[0033] The content ratio of the Co element and the M1 element can be adjusted as needed to balance the comprehensive influence of the Co element and the M1 element on the battery performance.

[0034] Based on any suitable implementation manner in the present application, in some implementation manners, the first positive electrode active material further contains the Ni element; in the first positive electrode active material, the atomic molar ratio of the Ni element to the Li element is denoted as R b , then R b satisfies 0.5 ≤ R b < 1;

[0035] Optionally, 0.5 ≤ R b ≤ 0.9;

[0036] Further optionally, 0.6 ≤ R b ≤ 0.9;

[0037] Even further optionally, 0.65 ≤ R b ≤ 0.9;

[0038] Even further optionally, 0.8 ≤ R b ≤ 0.9.

[0039] When the first positive electrode active material contains Ni element, it is beneficial to endow the first positive electrode active material with higher energy density and higher ionic conductivity. The higher the nickel (Ni) content, the higher the energy density of the composite positive electrode sheet, and it is also more beneficial to improve the ionic conductivity. However, in the case where the first positive electrode active material is highly utilized, the risk of damage or even structural collapse of the surface layer structure of the first positive electrode active material is greater. At this time, by introducing the first cation and regulating the A / B value, the improvement effect on the thermal stability of the composite positive electrode sheet is more significant.

[0040] In the case where the first positive electrode active material contains Ni element, by introducing the first cation and regulating the A / B value, the concentration of the first cation in the electrolyte can be better matched with the demand of the first positive electrode active material for appropriately reducing the utilization degree, and a better match of the overall battery performance can be achieved, a higher energy density can be realized, the thermal stability of the composite positive electrode sheet and the battery cell can be significantly improved, the risk of thermal runaway can be reduced, and it is also beneficial for the composite positive electrode sheet to have good active ion transport performance as a whole.

[0041] Based on any suitable embodiment of the present application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and even further optionally 1, the first positive electrode active material satisfies one or more of the following characteristics:

[0042] The atomic molar equivalent Q of Co element c ≤ 0.4, optionally, Q c ≤ 0.3, further optionally, Q c ≤ 0.2;

[0043] The atomic molar equivalent Q of the M1 element d ≤ 0.5, optionally, Q d ≤ 0.4, further optionally, Q d ≤ 0.3;

[0044] The M1 element includes Mn element, and the atomic molar equivalent of Mn element ≤ 0.4, optionally, the atomic molar equivalent of Mn element ≤ 0.3;

[0045] The sum Q of the atomic molar equivalents of Co element and the M1 element c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d ≤0.3, Q c+d ≤0.2.

[0046] Based on any suitable embodiment in the present application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the first positive electrode active material contains Ni element, and the atomic molar equivalent Q of Ni element b satisfies 0.5 ≤ Q b <1, optionally, 0.6 ≤ Q b <1, further optionally, 0.65 ≤ Q b <1.

[0047] When the Li element in the first positive electrode active material has a certain atomic molar equivalent, the content of the corresponding elements can be adjusted by adjusting the atomic molar equivalents of Co element, M1 element and Ni element.

[0048] Based on any suitable embodiment in the present application, in some embodiments, the first positive electrode active material includes a first body, and further includes or does not include a first coating layer located on at least a part of the surface of the first body; wherein, the chemical composition of the first body is Li a Ni b Co c M1 d M2 e O f R g , where 0.75 ≤ a ≤ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≤ e ≤ 0.2, b + c + d + e = 1, 1 ≤ f ≤ 2.5, 0 ≤ g ≤ 1, f + g ≤ 3, the M2 element in the first positive electrode active material includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb, and the R element in the first positive electrode active material includes one or more of N, F, S and Cl;

[0049] Optionally, 0.8 ≤ a ≤ 1.2, further optionally, 0.9 ≤ a ≤ 1.1, further optionally, 0.95 ≤ a ≤ 1.05;

[0050] Optionally, 0.5 ≤ b < 1, further optionally, 0.5 ≤ b ≤ 0.9, still further optionally, 0.6 ≤ b ≤ 0.9;

[0051] Optionally, 0.05 ≤ c < 1, further optionally, 0.05 ≤ c ≤ 0.5, still further optionally, 0.05 ≤ c ≤ 0.3;

[0052] Optionally, 0.05 ≤ d < 1, further optionally, 0.05 ≤ d ≤ 0.5, still further optionally, 0.05 ≤ d ≤ 0.3;

[0053] Optionally, 0 ≤ e < 0.1, further optionally, 0 ≤ e ≤ 0.05, still further optionally, 0 ≤ e ≤ 0.03;

[0054] Optionally, 1 ≤ f ≤ 2.1, further optionally, 1.8 ≤ f ≤ 2.05, still further optionally, 1.95 ≤ f ≤ 2.05;

[0055] Optionally, 0 ≤ g < 0.5, further optionally, 0 ≤ g ≤ 0.1, still further optionally, 0 ≤ g ≤ 0.05.

[0056] Based on any suitable embodiment of the present application, in some embodiments, the second positive electrode active material satisfies one or more of the following characteristics:

[0057] The atomic molar ratio of Mn element and Fe element is 0.42 - 9, optionally, the atomic molar ratio of Mn element and Fe element is 0.66 - 4;

[0058] Calculated based on the atomic molar equivalent of Li element being 0.9 - 1.1, optionally 0.9 - 1.05, further optionally 1, the atomic molar equivalent of Mn element is 0.5 - 0.999, optionally, the atomic molar equivalent of Mn element is 0.5 - 0.6;

[0059] Calculated based on the atomic molar equivalent of Li element being 0.9 - 1.1, optionally 0.9 - 1.05, further optionally 1, the atomic molar equivalent of Fe element is 0.001 - 0.5, optionally, the atomic molar equivalent of Fe element is 0.4 - 0.5.

[0060] Increasing the content of Mn element in the second cathode active material is beneficial to improving the energy density, voltage plateau and material cost of the second cathode active material. By controlling the Mn element within the above range, it is beneficial to form a uniform solid solution while exerting the role of the Mn element, and can also minimize or avoid defects and pores, thereby reducing or avoiding the extension of the insertion and extraction paths of active ions due to defects and pores. Therefore, by controlling the Mn element within the above range, it is beneficial to endow the second active material with good ion migration rate, shorten the gap in the ionic conductivity between the second cathode active material and the first cathode active material, thereby reducing the probability of over-utilization and de-lithiation of the first cathode active material, and is beneficial to further improving the thermal stability of the composite cathode sheet.

[0061] In the second cathode active material, the introduction of Fe element is beneficial to achieving better ion transportability and higher ionic conductivity, and is also beneficial to promoting the insertion and extraction of active ions, and improving the charge-discharge efficiency and energy density of the battery.

[0062] When the Li element in the second cathode active material has a certain atomic molar equivalent, the adjustment of the atomic molar equivalents of Fe element and Mn element can be used to adjust the content of the corresponding elements.

[0063] Based on any suitable embodiment of the present application, in some embodiments, the second active material includes a second body, and may or may not include a second coating layer covering at least a part of the surface of the second body; wherein, the chemical formula of the second body is Li 1+x Mn 1-y-w Fe w M3 y P 1-z Q z O 4 , where -0.1 ≤ x ≤ 0.1, 0.1 ≤ w ≤ 0.5, 0.001 ≤ y ≤ 0.5, 0.001 ≤ z ≤ 0.1, the M3 element in the second active material includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb and Ge, and the Q element in the second active material includes one or more elements selected from B, Si, N, S, F, Cl and Br;

[0064] Optionally, 0.1 ≤ y ≤ 0.5, further optionally, 0.2 ≤ y < 0.5, and more preferably, 0.3 ≤ y < 0.5;

[0065] Optionally, 0.2 ≤ w ≤ 0.5, further optionally, 0.3 ≤ w < 0.5, and more preferably, 0.4 ≤ w < 0.5;

[0066] Optionally, 0.001 ≤ z ≤ 0.1, further optionally, 0.001 ≤ z < 0.05, and still further optionally, 0.001 ≤ z < 0.002;

[0067] Optionally, the M3 element in the second active material includes one or more elements of Ti, V, Ni, Co, and Mg;

[0068] Optionally, the Q element in the second active material includes one element of B, Si, N, and S;

[0069] Optionally, the second coating layer includes one or more of pyrophosphate, phosphate, and carbon;

[0070] Optionally, the second coating layer is a single-layer structure or a multi-layer structure.

[0071] Based on any suitable embodiment in the present application, in some embodiments, the total mass ratio R of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer I+II ≥ 85%;

[0072] Optionally, R I+II ≥ 90%; further optionally, R I+II ≥ 95%.

[0073] By adjusting the total mass ratio R of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer I+II within the above range, it is more conducive to promoting the comprehensive advantages of the two positive electrode active materials.

[0074] Based on any suitable embodiment in the present application, in some embodiments, the first cation includes cations of one or more elements of alkali metal elements and alkaline earth metal elements;

[0075] Optionally, the first cation includes one or more of sodium ions, potassium ions, calcium ions, and magnesium ions;

[0076] Optionally, the anions in the first cation salt include one or more of hexafluorophosphate ions, perchlorate ions, tetrafluoroborate ions, bis(trifluoromethylsulfonyl)imide ions, trifluoromethanesulfonate ions, bis(fluorosulfonyl)imide ions, and tris(trifluoromethylsulfonyl)methyl ions;

[0077] Further optionally, the first cationic salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium tris(trifluoromethylsulfonyl)methide, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bis(trifluoromethylsulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(fluorosulfonyl)imide, and potassium tris(trifluoromethylsulfonyl)methide;

[0078] Even further optionally, the first cationic salt includes one or two of sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium perchlorate.

[0079] When the ionic radius of the first cation is greater than that of lithium ion, the type of the first cation and the corresponding anion can have a flexible selection range. As a non-limiting example, for instance, sodium hexafluorophosphate has low cost and can be used on a large scale; the radius difference between sodium ion and lithium ion is relatively small, which is more conducive to embedding into the active material.

[0080] Based on any suitable implementation manner in the present application, in some implementation manners, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes a silicon-based material; the mass percentage of the silicon-based material in the negative electrode active substance is denoted as X1.

[0081] Optionally, X1 ≥ 3%, and further optionally 3% ≤ X1 ≤ 50%;

[0082] Optionally, the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy, silicon-graphene composite, silicon-carbon nanotube, and silicon-containing conductive polymer.

[0083] When the negative electrode active material layer of the negative electrode sheet includes a silicon-based material, it is beneficial to further improve the energy density of the battery cell.

[0084] In the second aspect of the present application, a secondary battery is provided, which includes the battery cell described in the first aspect of the present application.

[0085] In some implementation manners, the secondary battery is a lithium-ion secondary battery.

[0086] In the third aspect of the present application, an electrical device is provided, which includes at least one of the battery cell described in the first aspect of the present application and the secondary battery described in the second aspect of the present application.

[0087] Details of one or more implementation manners of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] To better describe and illustrate the embodiments, examples, or instances of the applications disclosed herein, one or more drawings may be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments, examples, or instances, or the best mode of these applications currently understood. Also, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0089] Figure 1 Schematic diagram of a battery cell according to an embodiment of the present application.

[0090] Figure 2 is Figure 1 Exploded view of the battery cell according to an embodiment of the present application shown.

[0091] Figure 3 Schematic diagram of a battery module according to an embodiment of the present application.

[0092] Figure 4 Schematic diagram of a battery pack according to an embodiment of the present application.

[0093] Figure 5 is Figure 4 Exploded view of the battery pack according to an embodiment of the present application shown.

[0094] Figure 6 Schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0095] Explanation of reference numerals:

[0096] 1 is the battery pack; 2 is the upper box body; 3 is the lower box body; 4 is the battery module; 5 is the battery cell; 51 is the housing; 52 is the electrode assembly; 53 is the cover plate; 6 is the electrical device. Detailed implementation manners

[0097] Hereinafter, some embodiments and some examples of the battery cell, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where non-essential details are omitted. For example, there are cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0098] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or exclude the end values. Any end value can be independently included or excluded, and any combination can be made, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are understood to be contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are also listed, the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when stating that a certain parameter is an integer selected from "2 - 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0099] In this application, when referring to "a plurality of", "a variety of", "multiple items", "several", etc., unless otherwise specifically defined, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to (≥, greater than or equal to) two.

[0100] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0101] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in combination with the embodiments can be included in at least one embodiment or implementation manner of this application. The occurrence of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to "implementation manners" mentioned herein.

[0102] Those skilled in the art can understand that in the methods of each embodiment or example, the written order of each step does not mean a strict execution order that constitutes any limitation to the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, if method M includes steps (a) and (b), it means that method M may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, if method M further includes step (c), it means that step (c) can be added to method M in any order. For example, method M may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0103] In this application, in an open technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, if A includes a1, a2, and a3, without other instructions, it may also include other members or may not include additional members, and it can be regarded as providing both a feature or solution of "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3", and also providing a feature or solution of "A not only includes a1, a2, and a3, but also includes other members".

[0104] In this application, without other instructions, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0105] In this application, "optionally", "optional", "option" mean "may or may not", that is, it refers to any one of two alternative options of "having" or "not having". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual restrictions, each "optional" is independent. Without other instructions, descriptions such as "optionally include" and "optionally contain" in this application, taking "optionally include" as an example, mean "may include or may not include".

[0106] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more related listed items, and also include any and all combinations of the related listed items. The said any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" represents the group composed of A, B, and the combination of A and B. Among them, "including A and / or B" can mean "including A, including B, and including the combination of A and B", and can also mean "including A, including B, or including the combination of A and B", which can be appropriately understood according to the sentence where it is located.

[0107] As used herein, "its combination", "any combination thereof", "any combination mode thereof", etc. include all suitable combination modes of any two or more of the listed items.

[0108] In this document, the "suitable" in "suitable combination mode", "suitable mode", "any suitable mode", etc. is subject to being able to implement the technical solution of this application.

[0109] In this document, "preferred", "better", "more preferable", "should preferably be", "relatively better", "more preferable" are only used to describe implementation manners or embodiments with better effects. It should be understood that they do not constitute a limitation on the protection scope of this application. If "preferred" appears in a technical solution in multiple places, unless otherwise specified and there is no contradiction or mutual restriction relationship, each "preferred" is independent of each other.

[0110] In this application, "further", "even further", "especially", "for example", "such as", "example", "exemplification", etc. are used for descriptive purposes and represent differences in content, but should not be understood as a limitation on the protection scope of this application.

[0111] In this application, in "the first aspect", "the second aspect", "the third aspect", etc., the terms "first", "second", "third", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", etc. only serve the purpose of non-exhaustive listing description, and it should be understood that they do not constitute a closed limitation on quantity.

[0112] In this application, the term "room temperature" generally refers to 4°C to 35°C, and can refer to 20°C ± 5°C. In some embodiments of this application, room temperature refers to 20°C to 30°C.

[0113] In this application, for units related to data ranges, if a unit is only attached to the right endpoint, it means that the units of the left and right endpoints are the same. For example, both 3~5h and 3-5h indicate that the units of the left endpoint "3" and the right endpoint "5" are both h (hours), and they have the same meaning as 3h~5h. In addition, similar descriptions of other parameters such as temperature and size are understood in the same way.

[0114] In the embodiments or examples of this application, the weight of the relevant components mentioned not only refers to the content of each component, but also represents the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the embodiments or examples of this application is enlarged or reduced in proportion, it is within the scope described in this application. Further, the weight involved in the embodiments or examples of this application can be mass units well-known in the chemical industry such as micrograms (μg), milligrams (mg), grams (g), kilograms (kg), etc. Unless otherwise specified, the mass ratio is equal to the corresponding weight ratio. For example, if the mass of substance A is m1 and the weight is W1, and the mass of substance B is m2 and the weight is W2, then the mass ratio m1 / m2 is numerically equal to the corresponding weight ratio W1 / W2.

[0115] In this application, unless otherwise specified, wt% represents the weight percentage by weight, which is numerically equal to the corresponding mass percentage by mass.

[0116] In this application, "greater than or equal to", "more than or equal to" and "≥" have the same meaning and can be used interchangeably; "less than or equal to", "less than or equal to" and "≤" have the same meaning and can be used interchangeably; "greater than" can be equivalently expressed as ">", and "less than" can be equivalently expressed as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be regarded as also providing two options of "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be regarded as also providing two options of "less than" and "equal to".

[0117] In this application, for exemplary descriptions such as "in some embodiments (or examples)" and "in one embodiment (or example)", it can cover but is not limited to the following meanings: These solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0118] In this application, for exemplary descriptions such as "based on any suitable embodiment in this application, in some embodiments," or similar ones, it can cover but is not limited to the following meanings: These solutions can be combined with each other in a suitable manner to form new technical solutions.

[0119] To improve the comprehensive electrical performance of a battery, it is possible to consider setting different cathode active materials in the cathode active material layer of the cathode electrode sheet. For example, in theory, at least two cathode active materials can be set to achieve the complementary advantages of different cathode active materials. Non-limitingly, for example, when a cathode active material with a high energy density is combined with a cathode active material with a better voltage platform and a lower manufacturing cost, it is expected that the corresponding cathode electrode sheet can have both a high energy density, a better voltage platform, and a lower manufacturing cost. However, cathode active materials with different properties often have different activities and ionic conductivities, which leads to different utilization degrees of different cathode active materials during charge and discharge cycles. If the ionic conductivities of different cathode active materials differ too much, one of the cathode active materials will be over-utilized, easily causing damage to the surface structure of the cathode active material and releasing oxygen, and even possibly leading to the collapse of the material structure, posing a risk of battery thermal runaway. In addition, the released oxygen may also trigger side reactions of the electrolyte.

[0120] This application provides at least a battery cell, a secondary battery, and an electrical device.

[0121] In some embodiments, the battery cell includes a cathode electrode sheet, an anode electrode sheet, a separator, and an electrolyte. The cathode active material layer in the cathode electrode sheet includes a first cathode active material and a second cathode active material. The electrolyte salt in the electrolyte includes a first cationic salt. The first cathode active material is a lithium oxide containing Co element and M1 element, and the M1 element therein includes one or both of Mn element and Al element. The second cathode active material is a lithium oxide containing Fe element and Mn element. The mass ratio of the Co element in the first cathode active material to the Fe element in the second cathode active material is A. The first cationic salt includes a first cation with an ionic radius larger than that of lithium ion. The mass percentage of the first cationic salt in the electrolyte salt is B. 0.47 ≤ A / B ≤ 202. This battery cell has better electrical performance, good thermal stability, and low thermal runaway risk.

[0122] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Generally, a battery cell includes a cathode electrode sheet, an anode electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the cathode electrode sheet and the anode electrode sheet. The electrolyte plays a role in conducting ions between the cathode electrode sheet and the anode electrode sheet. The separator is disposed between the cathode electrode sheet and the anode electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0123] In this application, unless otherwise specified, the electrode plate can be a positive electrode plate or a negative electrode plate. The "active material" in the electrode plate refers to a material that can reversibly insert and extract active ions. Unless otherwise specified, the "negative active material" refers to a material used for the negative electrode plate that can reversibly insert and extract active ions; the "positive active material" refers to a material used for the positive electrode plate that can reversibly extract and insert active ions. When the secondary battery is charged, the active ions are extracted from the positive electrode and inserted into the negative electrode through the electrolyte; when the secondary battery is discharged, the active ions are extracted from the negative electrode and inserted into the positive electrode. The active ions are not particularly limited and can be, for example, lithium ions, corresponding to a lithium-ion secondary battery.

[0124] In this application, "electrode active material", "electrode active substance", "active material" and "active substance" have the same meaning and can be used interchangeably; "positive active material" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative active material" and "negative electrode active material" have the same meaning and can be used interchangeably. "Positive active material" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative active material" and "negative electrode active material" have the same meaning and can be used interchangeably.

[0125] In this application, unless otherwise specified, the "electrode active material layer" includes at least one of the positive electrode active material layer of the positive electrode plate and the negative electrode active material layer of the negative electrode plate. Depending on the specific situation, the electrode active material layer can refer to the positive electrode active material layer or the negative electrode active material layer. It can be understood that the positive electrode active material layer contains the positive active material, and the negative electrode active material layer contains the negative active material. In this application, the "electrode active material layer" can also be abbreviated as the "active material layer".

[0126] In the first aspect of this application, a battery cell is provided. The battery cell includes a positive electrode plate and an electrolyte. The positive electrode plate includes a positive electrode active material layer. The positive electrode active material layer includes a first positive active material and a second positive active material. The electrolyte includes an electrolyte salt, and the electrolyte salt includes a first cationic salt;

[0127] Wherein, the first positive active material is a lithium oxide containing Co element and M1 element, and the second positive active material is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first positive active material includes one or two of Mn element and Al element;

[0128] The mass ratio of the Co element in the first positive active material to the Fe element in the second positive active material is denoted as A;

[0129] The first cationic salt includes a first cation, and the ionic radius of the first cation is greater than that of a lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is denoted as B;

[0130] Optionally, 0.47 ≤ A / B ≤ 202.

[0131] In the present application, the first cathode active material and the second cathode active material are two different cathode active materials in the cathode active material layer.

[0132] It can be understood that in the case where the positive electrode tab includes the first cathode active material and the second cathode active material, the active ions in the battery cell include lithium ions.

[0133] In some embodiments, the electrolyte salt includes a first cationic salt and an electrolyte lithium salt. The electrolyte lithium salt is beneficial to the conduction of active lithium ions.

[0134] In some embodiments, a battery cell is provided, which includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte solution. The separator is disposed between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a cathode active material layer, and the cathode active material layer includes a first cathode active material and a second cathode active material. The electrolyte solution includes an electrolyte salt, and the electrolyte salt includes a first cationic salt and an electrolyte lithium salt;

[0135] Wherein, the first cathode active material is a lithium oxide containing Co element and M1 element, and the second cathode active material is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first cathode active material includes one or both of Mn element and Al element;

[0136] The mass ratio of the Co element in the first cathode active material to the Fe element in the second cathode active material is denoted as A;

[0137] The first cationic salt includes a first cation, and the ionic radius of the first cation is greater than that of a lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is denoted as B;

[0138] Then A and B satisfy 0.47 ≤ A / B ≤ 202.

[0139] The positive electrode plate in the battery cell is a composite positive electrode plate, in which different positive electrode active materials are provided. The composite positive electrode plate includes a first positive electrode active material containing cobalt (Co) element and M1 element, and the M1 element includes one or both of manganese (Mn) element and aluminum (Al) element. It also includes a second positive electrode active material containing iron (Fe) element and Mn element. Although theoretically, the design of using this composite positive electrode plate can make different positive electrode active materials complement each other's advantages, it is hoped that the comprehensive electrical performance can be improved in aspects such as material structure stability, battery safety, rate performance, and cycle performance, and the voltage platform and manufacturing cost can be taken into account. However, lithium oxides containing Co element and M1 element and lithium oxides containing Fe element and Mn element are different positive electrode active materials, which will have different activities and ionic conductivities, resulting in different degrees of utilization during charge and discharge cycles. Among them, lithium oxides containing Co element and M1 element are easily over-utilized, causing damage to the surface structure of the first positive electrode active material and releasing oxygen, and may even lead to the collapse of the material structure, posing a risk of battery thermal runaway; in addition, the released oxygen may also trigger side reactions of the electrolyte. The active ion diffusion in the design of this composite positive electrode plate is presumably one-dimensional channel diffusion. By introducing a first cation salt, a first cation with an ionic radius larger than that of lithium (Li) ion is introduced. This first cation can replace part of the active ions and embed into the first positive electrode active material, blocking the active ion diffusion channel in the first positive electrode active material, reducing the utilization degree of the first positive electrode active material, and reducing oxygen release. The first cation can also play a role in supporting the surface structure of the first positive electrode active material, hinder the removal of active ions during discharge, further increase the stability of oxygen on the surface of the positive electrode active material, reduce oxygen release, and the first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, reducing the risk of thermal runaway. Further, by adjusting the mass ratio A (which can also be denoted as I Co / II Fe ratio) of Co element in the first positive electrode active material to Fe element in the second positive electrode active material, the content ratio between the first positive electrode active material and the second positive electrode active material can be adjusted. Further, by synergistically adjusting the mass percentage B of the first cation salt relative to the electrolyte salt in the electrolyte using the A / B value, the concentration of the first cation in the electrolyte can better match the demand of the first positive electrode active material for appropriately reducing the utilization degree, so as to achieve better comprehensive electrical performance as a whole, significantly improve the thermal stability of the composite positive electrode plate and the battery cell, reduce the risk of thermal runaway, and is also conducive to the composite positive electrode plate having good active ion transport performance as a whole. It can be seen that this battery cell has better comprehensive performance, good thermal stability, and low risk of thermal runaway.

[0140] In this application, unless otherwise specified, the prior art in this field can be used to test the elemental composition and chemical composition of the positive electrode sheet, negative electrode sheet and electrolyte in the battery cell and secondary battery, including but not limited to the inductively coupled plasma (ICP) method.

[0141] Non-limitingly, for the positive active material in the positive electrode sheet or the negative active material in the negative electrode sheet, methods such as an energy dispersive spectrometer (EDS) and an inductively coupled plasma (ICP) method can be used for test analysis. The EDS can be used to identify different types of active materials, and the ICP can be used for quantitative test analysis of the component content. The active material sample can be extracted from the electrode sheet, and solid particles can be collected by methods including but not limited to solvent washing and ultrasonic dispersion, and then the elemental composition of the solid particles can be analyzed by an inductively coupled plasma optical emission spectrometer (ICP-OES). A two-dimensional image with different color markings for different components can be obtained by EDS testing. Different particles corresponding to different active materials can be distinguished according to the component type and aggregation mode. For example, the positive active material layer can be digested with reagents (such as nitric acid, perchloric acid, etc.), and the chemical composition of the positive active material can be tested by an inductively coupled plasma emission spectrometer. For another example, the negative active material layer can be digested with reagents (such as aqua regia, reverse aqua regia, a combination of aqua regia and hydrogen fluoride, etc.), and the chemical composition of the negative active material can be tested by an inductively coupled plasma emission spectrometer.

[0142] According to the chemical composition and elemental analysis results of the positive active material in the positive electrode sheet, the content of each element in the first positive active material and the second active material can be identified, the total mass ratio of the first positive active material and the second positive active material in the positive active material layer can be calculated, and the mass ratio (A) of the Co element in the first positive active material to the Fe element in the second positive active material can also be calculated. The elemental content relationships described in the context can also be tested, such as R c 、R d 、R d-Mn 、R c+d 、R b 、Q c / Q a 、Q d / Q a 、Q c+d / Q a 、Q b etc., and also such as Li a Ni b Co c M1d M2 e O f R g The composition of the M1 element and the M2 element and the numerical values of the subscripts of each element are still like the ratio of the atomic molar equivalents of the Mn element and the Fe element in the second positive electrode active material (which can be denoted as R2 Mn / Fe ),Li 1+x Mn 1-y-w Fe w M3 y P 1-z Q z O 4 The composition of the M3 element and the numerical values of the subscripts of each element, etc.

[0143] According to the chemical composition and elemental analysis results of the negative electrode active material in the negative electrode sheet, the composition of the negative electrode active material in the negative electrode active material layer can be determined, and it can be determined whether a silicon-based material is included. If it is included, the type, composition and mass percentage (denoted as X1) of the silicon-based material in the negative electrode active material can also be determined.

[0144] The electrolyte salt in the electrolyte can be quantitatively tested based on GB / T36240-2018 and an ion chromatograph. According to the types of cations identified in the electrolyte and in combination with the atomic numbers of the elements, it can be determined whether there is a first cation with an ionic radius larger than that of lithium ions in the electrolyte. If so, the types of first cations present can also be determined. According to the quantitative test analysis results of the electrolyte salt, the composition of the electrolyte salt in the electrolyte and the contents of different electrolyte salts can be determined. Since the cations and anions in the electrolyte are in a free state and can migrate, and are not limited to the cation and anion coordination modes during the feeding of the electrolyte salt, but the electrolyte system as a whole maintains charge balance. Therefore, in this application, unless otherwise specified, the mass percentage (denoted as B) of the first cation salt in the electrolyte salt is calculated according to "the percentage of the mass of the first cation in the electrolyte relative to the total mass of all cations in the electrolyte". For example, when the cations contained in the electrolyte salt in the electrolyte are metal cations, the value of B can numerically be equal to "the percentage of the mass of the first cation in the electrolyte relative to the mass of the metal cations in the electrolyte". For another example, when the cations contained in the electrolyte salt in the electrolyte consist of lithium ions and the first cation, the value of B can numerically be equal to "the percentage of the mass of the first cation in the electrolyte relative to the total mass of the first cation and lithium ions".

[0145] Unless otherwise specified, generally, the cations in the electrolyte salt are metal cations.

[0146] In some embodiments, a battery cell is provided, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. The electrolyte includes an electrolyte salt, and the electrolyte salt includes a first cationic salt and an electrolyte lithium salt; the electrolyte salt is composed of cations and anions, and the cations in the electrolyte salt are metal cations;

[0147] Wherein, the first positive electrode active material is a lithium oxide containing Co element and M1 element, and the second positive electrode active material is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first positive electrode active material includes one or both of Mn element and Al element;

[0148] The mass ratio of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material is denoted as A;

[0149] The first cationic salt includes a first cation, and the ionic radius of the first cation is greater than that of the lithium ion; the percentage of the mass of the first cation relative to the total mass of each cation in the electrolyte salt can also be denoted as B;

[0150] At this time, A and B satisfy 0.47 ≤ A / B ≤ 202.

[0151] In some embodiments, the battery cell includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode active material layer in the positive electrode plate includes a first positive electrode active material and a second positive electrode active material. The electrolyte salt in the electrolyte includes metal cations, and the metal cations include a first cation; the first positive electrode active material is a lithium oxide containing Co element and M1 element, and the M1 element therein includes one or both of Mn element and Al element; the second positive electrode active material is a lithium oxide containing Fe element and Mn element; the mass ratio of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material is A; the ionic radius of the first cation is greater than that of the lithium ion; the mass percentage of the first cation relative to the metal cations in the electrolyte salt is denoted as B'; 0.47 ≤ A / B' ≤ 202. The battery cell has better electrical performance, good thermal stability, and low thermal runaway risk.

[0152] In some embodiments, a battery cell is provided, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. The electrolyte includes an electrolyte salt, and the electrolyte salt includes metal cations and anions; the metal cations include a first cation and a lithium ion;

[0153] Among them, the first positive electrode active material is a lithium oxide containing Co element and M1 element, and the second positive electrode active material is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first positive electrode active material includes one or both of Mn element and Al element;

[0154] The mass ratio of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material is denoted as A;

[0155] The ionic radius of the first cation is greater than that of the lithium ion;

[0156] The mass percentage of the first cation relative to the metal cation in the electrolyte salt is denoted as B';

[0157] Then A and B satisfy 0.47 ≤ A / B' ≤ 202.

[0158] In this application, the value and value range of B' and the value and value range of A / B' can respectively refer to the value and value range of B and the value and value range of A / B. When the cations in the electrolyte salt are all metal cations, B and B' are numerically the same. In some embodiments, the definitions of the value and value range of B in the context of this application can all be applied to B', and the definitions of the value and value range of A / B in the context of this application can all be applied to A / B'.

[0159] Based on any suitable embodiment in this application, in some embodiments, at 25 °C, the ratio of the ionic conductivity of the first positive electrode active material to the ionic conductivity of the second positive electrode active material is denoted as Xσ, then Xσ ≥ 10 4 ; Optionally, Xσ ≥ 10 6 , Further optionally Xσ ≥ 10 10 . Without limitation, Xσ can also be any of the following values, or greater than or equal to (≥) any of the following values, or greater than (>) any of the following values, or selected from the intervals formed by any two of the following values (which can be expressed in scientific notation): 1×10 4 (equivalent to 1E4), 2×10 4 , 4×10 4 , 5×10 4 , 6×10 4 , 8×10 4 , 1×10 5 , 2×10 5 , 4×10 5 , 5×10 5 , 6×10 5 , 8×10 5 , 1×10 6 , 2×10 6, 4×10 6 , 5×10 6 , 6×10 6 , 8×10 6 , 1×10 7 , 2×10 7 , 4×10 7 , 5×10 7 , 6×10 7 , 8×10 7 , 1×10 8 , 2×10 8 , 4×10 8 , 5×10 8 , 6×10 8 , 8×10 8 , 1×10 9 , 2×10 9 , 4×10 9 , 5×10 9 , 6×10 9 , 8×10 9 , 1×10 10 , 2×10 10 etc.

[0160] In this application, the value aEb described in scientific notation is equivalent to a×10 b . For example, 1×10 4 can be denoted as 1E4.

[0161] In some embodiments, the ionic conductivity of the first positive electrode active material at 25 °C is σ 1 , satisfying σ 1 ≥ 3.2×10 -6 S / cm, and further optionally σ 1 ≥ 1.7×10 -3 S / cm. The ionic conductivity σ 1 of the first positive electrode active material at 25 °C can also be any of the following values, or greater than or equal to (≥) any of the following values, or greater than (>) any of the following values, or selected from the intervals formed by any two of the following values (which can be expressed in scientific notation): 3.2×10 -6 S / cm, 3.5×10 -6 S / cm, 4×10 -6 S / cm, 5×10 -6 S / cm, 6×10 -6 S / cm, 8×10 -6 S / cm, 1×10 -5 S / cm, 2×10 - 5 S / cm, 4×10-5 S / cm, 5×10 -5 S / cm, 6×10 -5 S / cm, 8×10 -5 S / cm, 1×10 -4 S / cm, 2×10 -4 S / cm, 4×10 -4 S / cm, 5×10 -4 S / cm, 6×10 -4 S / cm, 8×10 -4 S / cm, 1×10 -3 S / cm, 1.5×10 -3 S / cm, 1.7×10 -3 S / cm, 2×10 -3 S / cm, 3×10 -3 S / cm, 3.5×10 -3 S / cm, 4×10 -3 S / cm, 5×10 -3 S / cm, 6×10 -3 S / cm, 7×10 -3 S / cm, 8×10 -3 S / cm, 9×10 -3 S / cm, etc. Without limitation, σ 1 may also be selected from any of the following ranges: 1×10 -3 S / cm to 3×10 -3 S / cm, 3×10 -3 S / cm to 5×10 -3 S / cm, 5×10 -3 S / cm to 7×10 -3 S / cm, 7×10 -3 S / cm to 9×10 -3 S / cm, 3.2×10 -6 S / cm to 1×10 -3 S / cm, 1×10 -3 S / cm < σ 1 < 3×10 -3 S / cm, 3×10 -3 S / cm < σ 1 < 5×10 -3 S / cm, 5×10 -3 S / cm < σ 1 < 7×10 -3 S / cm, 7×10 -3 S / cm < σ 1 < 9×10 -3 S / cm, 3.2×10 -6 S / cm < σ1 <1×10 -3 S / cm or the like.

[0162] In some embodiments, the ionic conductivity of the second positive electrode active material at 25 °C is σ 2 , satisfying σ 2 ≤10 - 9 S / cm, and further optionally σ 2 ≤10 -12 S / cm. The ionic conductivity σ of the second positive electrode active material at 25 °C 2 can also be any of the following values, or less than or equal to (≤) any of the following values, or less than any of the following values, or selected from the intervals formed by any two of the following values (which can be expressed in scientific notation): 1×10 -9 S / cm, 8×10 -10 S / cm, 6×10 -10 S / cm, 5×10 -10 S / cm, 4×10 -10 S / cm, 2×10 -10 S / cm, 1×10 -10 S / cm, 8×10 -11 S / cm, 6×10 - 11 S / cm, 5×10 -11 S / cm, 4×10 -11 S / cm, 2×10 -11 S / cm, 1×10 -11 S / cm, 8×10 -12 S / cm, 6×10 -12 S / cm, 5×10 -12 S / cm, 4×10 -12 S / cm, 2×10 -12 S / cm, 1×10 -12 S / cm, 9×10 -13 S / cm, 8×10 -13 S / cm, 7×10 -13 S / cm, 6×10 -13 S / cm, 5×10 -13 S / cm, 4×10 -13 S / cm, 3×10 -13 S / cm, 2×10 -13 S / cm, 1×10 -13 S / cm or the like.

[0163] In the present application, unless otherwise specified, "ionic conductivity" refers to the ionic conductivity when the active ion is a lithium ion. Without limitation, σ2 It can also be selected from any of the following ranges: 3×10 -13 S / cm to 9×10 -13 S / cm, 1×10 -13 S / cm to 3×10 -13 S / cm, 3×10 -13 S / cm < σ 2 <9×10 -13 S / cm, 1×10 -13 S / cm < σ 2 <3×10 -13 S / cm, etc.

[0164] In this application, unless otherwise specified, "ionic conductivity" refers to the ionic conductivity at 25°C. In this application, unless otherwise specified, the following method can be used to test the ionic conductivity of different cathode active materials in the cathode active material layer:

[0165] The cathode active material to be tested is made into a test cathode electrode sheet, and a lithium sheet is used as the anode electrode sheet, and an assembled button battery is tested; after the battery is discharged at 1C to 3.0V, an AC impedance spectrum test is carried out. The test parameters are selected as follows: the test temperature is room temperature (such as 25°C), the scanning frequency is 0.1Hz to 10 5 Hz, the voltage amplitude is 5mV, and the Zview software is used to fit the test results to obtain the ionic conductivity.

[0166] Unless otherwise specified, in the test cathode electrode sheet, the cathode current collector is selected as aluminum foil, the mass percentage of the cathode active material in the cathode active material layer is controlled at 95% ± 1%, the binder is selected as polyvinylidene fluoride (PVDF), the conductive agent is selected as conductive carbon, and the compaction density is 3.0g / cm 3 to 3.6g / cm 3 .

[0167] For the cathode active material in the electrode sheet, battery monomer or secondary battery, the cathode active material with the same chemical composition can be prepared according to the component analysis results as the cathode active material to be tested, and its ionic conductivity is tested by the above method.

[0168] When the ionic conductivity difference between the first cathode active material and the second cathode active material is large, the probability of the over-utilization degree of the first cathode active material becomes significantly larger. At this time, when adjusting the A / B value to balance the comprehensive requirements of the first cathode active material for appropriately reducing the utilization degree and the good transmission of active ions in the composite cathode electrode sheet, the improvement effect on the thermal stability of the cathode electrode sheet and the overall comprehensive performance of the battery monomer is more significant.

[0169] The ionic conductivity of the first positive electrode active material (lithium oxide containing Co element and M1 element) can be adjusted by adjusting the content of nickel (Ni) element in the first positive electrode active material. Generally, the higher the Ni content, the higher the ionic conductivity of the first positive electrode active material.

[0170] The ionic conductivity of the second positive electrode active material (lithium oxide containing Fe element and Mn element) can be adjusted by adjusting the content of manganese (Mn) element. Generally, the higher the Mn element content, the lower the ionic conductivity of the second positive electrode active material.

[0171] In some embodiments, 0.47 ≤ A / B ≤ 202. A / B can also be any one of the following values, or a range formed by any two of the following values: 0.47, 0.5, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.9, 1, 1.2, 1.25, 1.5, 1.6, 1.75, 1.8, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9, 9.9, 10, 12, 12.5, 15, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 75, 80, 90, 95, 96, 98, 99, 100, 110, 120, 125, 130, 140, 150, 160, 175, 180, 190, 192, 194, 195, 196, 198, 199, 200, 201, 202, etc.

[0172] Based on any suitable embodiment in the present application, in some embodiments, 1.3 ≤ A / B ≤ 25.4.

[0173] By adjusting the A / B value within a more suitable range, it is more beneficial to achieve better thermal stability while effectively improving the comprehensive performance of the battery.

[0174] Based on any suitable embodiment of the present application, in some embodiments, 0.19 ≤ A ≤ 10.1; optionally, 0.28 ≤ A ≤ 2.53. A can also be any one of the following values, or an interval formed by any two of the following values: 0.19, 0.2, 0.22, 0.24, 0.25, 0.26, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.1, 1.2, 1.25, 1.3, 1.4, 1.5, 1.6, 1.7, 1.75, 1.8, 2, 2.1, 2.2, 2.25, 2.3, 2.4, 2.5, 2.6, 2.8, 3, 3.5, 3.6, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 9.6, 9.8, 9.9, 10, 10.1, etc.

[0175] By adjusting the value of A, the content ratio between the first positive electrode active material and the second positive electrode active material can be adjusted. By controlling the value of A within the above range, it is more conducive to exerting the comprehensive advantages of the first positive electrode active material and the second positive electrode active material, and achieving better electrical performance.

[0176] Based on any suitable embodiment of the present application, in some embodiments, 5% ≤ B ≤ 40%; optionally, 10% ≤ B ≤ 20%. B can also be any one of the following percentages, or an interval formed by any two of the following percentages: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 12.5%, 13%, 14%, 15%, 16%, 18%, 20%, 22%, 22.5%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 38%, 40%, etc.

[0177] By adjusting the value of B, the mass percentage of the first cationic salt relative to the electrolyte salt can be adjusted. By controlling the value of B within the above range, the concentration of the first cation in the electrolyte can better match the demand of the first positive electrode active material for appropriately reducing the utilization rate, thereby achieving better overall battery performance.

[0178] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of Co element to Li element can be denoted as R c , R c satisfies 0.05 ≤ R c ≤ 0.5, optionally, 0.05 ≤ R c ≤ 0.3, optionally, 0.05 ≤ R c ≤ 0.2. Rc It can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, etc.

[0179] The presence of Co element is beneficial to improving the structural stability of the material. By adjusting the content of Co element in the first positive electrode active material within a more appropriate range, it is more beneficial to improve the charge-discharge rate performance and cycling performance of the battery.

[0180] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of M1 element to Li element can be denoted as R d , R d satisfies 0.05 ≤ R d ≤ 0.5. Optionally, 0.05 ≤ R d ≤ 0.3. R d It can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, etc. R d It can also be any of the following ranges: R d ≤ 0.2, 0.05 ≤ R d ≤ 0.2, etc.

[0181] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the M1 element includes Mn element. The atomic molar ratio of Mn element to Li element is denoted as R d-Mn , optionally, R d-Mn satisfies 0.05 ≤ R d-Mn ≤ 0.4. Further optionally, 0.05 ≤ R d-Mn ≤ 0.3. R d-MnIt can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, etc.

[0182] By adjusting the content of the M1 element in the first positive electrode active material, the thermal stability of the first positive electrode active material can be adjusted. For example, when the M1 element includes the Mn element, the Mn element is beneficial to improving the thermal stability of the first positive electrode active material; when the M1 element includes the Al element, the Al element is beneficial to enhancing the capacity and the thermal stability of the material, and is beneficial to reducing the internal resistance and improving the rate performance and the cycle performance.

[0183] Based on any suitable embodiment in the present application, in some embodiments, in the first positive electrode active material, the ratio of the sum of the atomic molar equivalents of the Co element and the M1 element to the atomic molar equivalent of the Li element is denoted as R c+d , R c+d satisfies 0.1 ≤ R c+d ≤ 0.5. Further optionally, 0.1 ≤ R c+d ≤ 0.3. Still further optionally, 0.1 ≤ R c+d ≤ 0.2. R c+d It can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, etc.

[0184] The content ratio of the Co element and the M1 element can be adjusted as needed to balance the comprehensive influence of the Co element and the M1 element on the battery performance.

[0185] Based on any suitable embodiment in the present application, in some embodiments, the first positive electrode active material satisfies one or more of the following characteristics:

[0186] The atomic molar ratio of the Co element to the Li element is denoted as R c , then R c satisfies 0.05 ≤ R c ≤ 0.5. Optionally, 0.05 ≤ R c≤0.3, optionally, 0.05 ≤ R c ≤0.2(R c (which may also be selected from the values or ranges in any suitable embodiment of the present application));

[0187] The atomic molar ratio of element M1 to element Li is denoted as R d , then R d satisfies 0.05 ≤ R d ≤0.5, optionally, 0.05 ≤ R d ≤0.3(R d (which may also be selected from the values or ranges in any suitable embodiment of the present application));

[0188] Element M1 includes element Mn, and the atomic molar ratio of element Mn to element Li is denoted as R d-Mn , then R d-Mn satisfies 0.05 ≤ R d-Mn ≤0.4, further optionally, 0.05 ≤ R d-Mn ≤0.3(R d-Mn (which may also be selected from the values or ranges in any suitable embodiment of the present application));

[0189] The ratio of the sum of the atomic molar equivalents of element Co and element M1 to the atomic molar equivalent of element Li is denoted as R c+d , then R c+d satisfies 0.1 ≤ R c+d ≤0.5, further optionally, 0.1 ≤ R c+d ≤0.3, even more optionally, 0.1 ≤ R c+d ≤0.2(R c+d (which may also be selected from the values or ranges in any suitable embodiment of the present application).

[0190] In some embodiments, the first positive electrode active material may be a lithium oxide containing element Co, element M1, and element Ni. At this time, the first positive electrode active material may have a layered structure, achieving a high ionic conductivity within the first positive electrode active material. As a non-limiting example, such as lithium nickel cobalt manganese oxide and its modified forms, wherein the modified forms may include one or more of doping modification and coating modification.

[0191] Based on any suitable embodiment of the present application, in some embodiments, the first positive electrode active material further contains element Ni. In the first positive electrode active material, the atomic molar ratio of element Ni to element Li may be denoted as R b . In some of these embodiments, R b satisfies 0.5 ≤ R b <1, optionally, 0.5 ≤ R b≤0.9; Further optionally, 0.6 ≤ R b ≤0.9; Still further optionally, 0.65 ≤ R b ≤0.9; Still further optionally, 0.8 ≤ R b ≤0.9. R b It can also be any of the following values, or greater than or equal to any of the following values and less than 1, or selected from the intervals formed by any two of the following values: 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.83, 0.833, 0.85, 0.86, 0.88, 0.9, 0.91, 0.92, 0.94, 0.95, etc.

[0192] When the first positive electrode active material contains Ni element, it is beneficial to endow the first positive electrode active material with higher energy density and higher ionic conductivity. The higher the nickel (Ni) content, the higher the energy density of the composite positive electrode sheet, and it is also more beneficial to improve the ionic conductivity; however, when the first positive electrode active material is highly utilized, the risk of damage or even structural collapse of the surface layer structure of the first positive electrode active material is greater. At this time, by introducing the first cation and regulating the A / B value, the improvement effect on the thermal stability of the composite positive electrode sheet is more significant.

[0193] When the first positive electrode active material contains Ni element, by introducing the first cation and regulating the A / B value, the concentration of the first cation in the electrolyte can be better matched with the requirement of the first positive electrode active material for appropriately reducing the utilization degree, the better matching of the overall battery performance can be achieved, a higher energy density can be realized, the thermal stability of the composite positive electrode sheet and the battery cell can be significantly improved, the risk of thermal runaway can be reduced, and it is also beneficial for the composite positive electrode sheet to have good active ion transport performance as a whole.

[0194] It can be understood that during the charge and discharge process of the battery, the insertion and extraction and consumption of lithium (Li) will occur, and the content of Li in the positive electrode sheet is different when the battery is discharged to different states.

[0195] In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the content of Li can be the initial state of the material or the non-initial state after charge and discharge cycles. When the positive electrode active material is applied to the positive electrode plate in the battery system, after charge and discharge cycles, the content of Li in the positive electrode active material contained in the positive electrode plate usually changes. Among them, the content of Li can be measured by atomic molar content, but is not limited thereto. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials or substances obtained by appropriate modification based on the listed positive electrode active materials are also within the scope of the positive electrode active material. The aforementioned appropriate modification refers to the acceptable modification methods for the positive electrode active material, and non-limiting examples include coating modification.

[0196] In the exemplary description of the positive electrode active material in this application, the content of oxygen (O) is only the theoretical state value. Lattice oxygen release will cause changes in the atomic molar content of oxygen, and the actual content of O will fluctuate. Among them, the content of O can be measured by atomic molar content, but is not limited thereto.

[0197] For battery monomers and secondary batteries in which the active ions include lithium ions, the limitations on the atomic ratios such as Q a , a, x, etc. in the context can include the atomic molar content of Li in different charge and discharge states of the battery (usually the battery voltage is between 2V and 5V).

[0198] Based on any suitable embodiment in this application, in some embodiments, in the first positive electrode active material, regarding "the atomic molar equivalent Q of Li element a ", Q a can be 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1. Q in the first positive electrode active material a can also be any of the following values, or a range formed by any two of the following values: 0.9, 0.92, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.08, 1.1, etc.

[0199] Based on any suitable embodiment in this application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the atomic molar equivalent Q of Co element c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2. Q cIt can also be any of the following numerical values, or less than or equal to any of the following numerical values, or an interval composed of any two of the following numerical values: 0.4, 0.38, 0.36, 0.35, 0.34, 0.32, 0.3, 0.28, 0.26, 0.25, 0.24, 0.22, 0.20, etc.

[0200] Based on any suitable embodiment in the present application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the atomic molar equivalent Q of M1 element d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3. Q d It can also be any of the following numerical values, or less than or equal to any of the following numerical values, or an interval composed of any two of the following numerical values: 0.5, 0.48, 0.46, 0.45, 0.44, 0.42, 0.4, 0.38, 0.36, 0.35, 0.34, 0.32, 0.3, etc.

[0201] Based on any suitable embodiment in the present application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, M1 element includes Mn element, and further, the atomic molar equivalent of Mn element (which can be denoted as Q1 Mn ) can satisfy ≤0.4, optionally, the atomic molar equivalent of Mn element ≤0.3. The atomic molar equivalent of Mn element can also be any of the following numerical values, or less than or equal to any of the following numerical values, or an interval composed of any two of the following numerical values: 0.4, 0.38, 0.36, 0.35, 0.34, 0.32, 0.3, etc. Q1 Mn It can also be any of the following ranges: Q1 Mn ≤0.2, 0.05 ≤ Q1 Mn ≤0.2, etc.

[0202] Based on any suitable embodiment in the present application, in some embodiments, taking the atomic molar equivalent Q of Li element a as 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the sum of the atomic molar equivalents of Co element and M1 element Q c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d≤0.3, Q c+d ≤0.2. Q c+d It can also be any of the following values, or less than or equal to any of the following values, or an interval composed of any two of the following values: 0.5, 0.48, 0.46, 0.45, 0.44, 0.42, 0.4, 0.38, 0.36, 0.35, 0.34, 0.32, 0.3, 0.28, 0.26, 0.25, 0.24, 0.22, 0.2, etc.

[0203] Based on any suitable embodiment in the present application, in some embodiments, with the atomic molar equivalent Q of Li element a being 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the first positive electrode active material satisfies one or more of the following characteristics:

[0204] The atomic molar equivalent Q of Co element c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2 (Q c can also be selected from the values or ranges in any suitable embodiment of the present application);

[0205] The atomic molar equivalent Q of M1 element d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3 (Q d can also be selected from the values or ranges in any suitable embodiment of the present application);

[0206] M1 element includes Mn element, and the atomic molar equivalent of Mn element ≤0.4, optionally, the atomic molar equivalent of Mn element ≤0.3 (the atomic molar equivalent of Mn element can be denoted as Q1 Mn , and can also be selected from the values or ranges in any suitable embodiment of the present application);

[0207] The sum Q of the atomic molar equivalents of Co element and M1 element c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d ≤0.3, Q c+d ≤0.2 (Q c+d can also be selected from the values or ranges in any suitable embodiment of the present application).

[0208] Based on any suitable embodiment in the present application, in some embodiments, with the atomic molar equivalent Q of Li element aIs from 0.75 to 1.2, optionally from 0.8 to 1.1, further optionally from 0.9 to 1.05, and still further optionally 1. The first positive electrode active material contains Ni element, and the atomic molar equivalent Q of Ni element b Satisfies 0.5 ≤ Q b < 1. Optionally, 0.6 ≤ Q b < 1. Further optionally, 0.65 ≤ Q b < 1. Q b Can also be any of the following values, or greater than or equal to any of the following values and less than 1, or selected from the intervals formed by any two of the following values: 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.83, 0.833, 0.85, 0.86, 0.88, 0.9, 0.91, 0.92, 0.94, 0.95, etc.

[0209] When the Li element in the first positive electrode active material has a certain atomic molar equivalent, the content of the corresponding elements can be adjusted by adjusting the atomic molar equivalents of Co element, M1 element and Ni element.

[0210] Based on any suitable embodiment in the present application, in some embodiments, the first positive electrode active material includes a first body, and may or may not include a first coating layer located on at least a part of the surface of the first body; wherein, the chemical composition of the first body is Li a Ni b Co c M1 d M2 e O f R g , where 0.75 ≤ a ≤ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≤ e ≤ 0.2, b + c + d + e = 1, 1 ≤ f ≤ 2.5, 0 ≤ g ≤ 1, f + g ≤ 3. The M2 element in the first positive electrode active material may include one or more of zirconium (Zr), zinc (Zn), copper (Cu), chromium (Cr), magnesium (Mg), iron (Fe), vanadium (V), titanium (Ti), strontium (Sr), antimony (Sb), yttrium (Y), tungsten (W) and niobium (Nb). The R element in the first positive electrode active material may include one or more of N, F, S and Cl.

[0211] In some embodiments, the M2 element in the first positive electrode active material may be selected from, but not limited to, one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W and Nb.

[0212] In some embodiments, the R element in the first positive electrode active material may be selected from, but not limited to, one or more of N, F, S and Cl.

[0213] In some embodiments, 0.8 ≤ a ≤ 1.2. Further optionally, 0.9 ≤ a ≤ 1.1. Further optionally, 0.95 ≤ a ≤ 1.05. a can also be any of the following values, or an interval formed by any two of the following values: 0.8, 0.85, 0.83, 0.833, 0.85, 0.86, 0.88, 0.9, 0.91, 0.92, 0.94, 0.95, 0.96, 0.98, 0.99, 1, 1.01, 1.02, 1.04, 1.05, 1.06, 1.08, 1.09, 1.1, 1.12, 1.24, 1.15, 1.16, 1.18, 1.2, etc.

[0214] In some embodiments, 0.5 ≤ b < 1. Further optionally, 0.5 ≤ b ≤ 0.9. More further optionally, 0.6 ≤ b ≤ 0.9. b can also be any of the following values, or a value greater than or equal to any of the following values and less than 1, or an interval formed by any two of the following values: 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.83, 0.833, 0.85, 0.86, 0.88, 0.9, 0.91, 0.92, 0.94, 0.95, etc.

[0215] In some embodiments, 0.05 ≤ c < 1. Further optionally, 0.05 ≤ c ≤ 0.5. More further optionally, 0.05 ≤ c ≤ 0.3. c can also be any of the following values, or an interval formed by any two of the following values: 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, etc.

[0216] In some embodiments, 0.05 ≤ d < 1. Further optionally, 0.05 ≤ d ≤ 0.5. Still further optionally, 0.05 ≤ d ≤ 0.3. d can also be any one of the following values, or an interval formed by any two of the following values: 0.05, 0.06, 0.08, 0.09, 0.1, 0.11, 0.12, 0.125, 0.14, 0.15, 0.16, 0.175, 0.18, 0.2, 0.22, 0.225, 0.24, 0.25, 0.26, 0.275, 0.28, 0.3, 0.32, 0.34, 0.35, 0.36, 0.38, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, etc.

[0217] In some embodiments, 0 ≤ e < 0.1. Further optionally, 0 ≤ e ≤ 0.05. Still further optionally, 0 ≤ e ≤ 0.03. e can also be any one of the following values, or an interval formed by any two of the following values: 0.03, 0.035, 0.04, 0.045, 0.05, etc.

[0218] In some embodiments, 1 ≤ f ≤ 2.1. Further optionally, 1.8 ≤ f ≤ 2.05. Still further optionally, 1.95 ≤ f ≤ 2.05. f can also be any one of the following values, or an interval formed by any two of the following values: 1, 1.1, 1.2, 1.25, 1.3, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, etc.

[0219] In some embodiments, 0 ≤ g < 0.5. Further optionally, 0 ≤ g ≤ 0.1. Still further optionally, 0 ≤ g ≤ 0.05. g can also be any one of the following values, or an interval formed by any two of the following values: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.46, 0.48, etc.

[0220] In some embodiments, the first positive electrode active material includes one or more of lithium nickel cobalt manganese oxide (also referred to as lithium nickel cobalt manganate), lithium nickel cobalt aluminum oxide, and modified compounds thereof, etc. Non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25O 2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide can include LiNi 0.80 Co 0.15 Al 0.05 O 2 .

[0221] Based on any suitable embodiment in the present application, in some embodiments, in the second positive electrode active material, regarding the "atomic molar equivalent of Li element", the atomic molar equivalent of Li element can be 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1. In the second positive electrode active material, the atomic molar equivalent of Li element can also be any one of the following values, or a range composed of any two of the following values: 0.9, 0.92, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.08, 1.1, etc.

[0222] Based on any suitable embodiment in the present application, in some embodiments, in the second positive electrode active material, the atomic molar ratio of Mn element and Fe element (which can be denoted as R2 Mn / Fe ) is 0.42 to 9. Optionally, the atomic molar ratio of Mn element and Fe element is 0.66 to 4. R2 Mn / Fe can also be any one of the following values, or a range composed of any two of the following values: 0.42, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 6.5, 7, 7.5, 8, 8.5, 9, etc.

[0223] Based on any suitable embodiment in the present application, in some embodiments, in the second positive electrode active material, based on the atomic molar equivalent of Li element being 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, the atomic molar equivalent of Mn element (which can be denoted as Q2 Mn ) is 0.5 to 0.999. Optionally, Q2 Mn is 0.5 to 0.6. Q2 MnIt can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.9, 0.92, 0.94, 0.95, 0.96, 0.98, 0.99, 0.995, 0.999, etc.

[0224] Based on any suitable embodiment in the present application, in some embodiments, in the second positive electrode active material, taking the atomic molar equivalent of Li element as 0.9 - 1.1, optionally 0.9 - 1.05, and further optionally 1, the atomic molar equivalent of Fe element (which can be denoted as Q2 Fe ) is 0.001 - 0.5, optionally, Q2 Fe is 0.4 - 0.5. Q2 Fe It can also be any of the following numerical values, or an interval composed of any two of the following numerical values: 0.001, 0.002, 0.004, 0.005, 0.006, 0.008, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0225] Based on any suitable embodiment in the present application, in some embodiments, the second positive electrode active material satisfies one or more of the following characteristics:

[0226] The atomic molar ratio of Mn element and Fe element (which can be denoted as R2 Mn / Fe ) is 0.42 - 9, optionally, R2 Mn / Fe is 0.66 - 4 (R2 Mn / Fe can also be selected from the numerical values or ranges in any suitable embodiment of the present application);

[0227] Taking the atomic molar equivalent of Li element as 0.9 - 1.1, optionally 0.9 - 1.05, and further optionally 1, the atomic molar equivalent of Mn element (which can be denoted as Q2 Mn ) is 0.5 - 0.999, optionally, Q2 Mn is 0.5 - 0.6 (Q2 Mn can also be selected from the numerical values or ranges in any suitable embodiment of the present application);

[0228] Taking the atomic molar equivalent of Li element as 0.9 - 1.1, optionally 0.9 - 1.05, and further optionally 1, the atomic molar equivalent of Fe element (which can be denoted as Q2 Fe ) is 0.001 - 0.5, optionally, Q2 Fe is 0.4 - 0.5 (Q2 FeIt can also be selected from the values or ranges in any suitable embodiment of the present application).

[0229] Increasing the content of Mn element in the second positive electrode active material is beneficial to improving the energy density, voltage platform and material cost of the second positive electrode active material. By controlling the Mn element within the above range, it is beneficial to form a uniform solid solution while exerting the role of the Mn element, and can also minimize or avoid defects and pores, thereby reducing or avoiding defects and pores and prolonging the insertion and extraction paths of active ions. Therefore, by controlling the Mn element within the above range, it is beneficial to enable the second active material to have a good ion migration rate, shorten the gap in the ionic conductivity between the second positive electrode active material and the first positive electrode active material, thereby reducing the probability of over-utilization and de-lithiation of the first positive electrode active material, and being beneficial to further improving the thermal stability of the composite positive electrode sheet.

[0230] In the second positive electrode active material, the introduction of Fe element is beneficial to achieving better ion transportability and higher ionic conductivity, and is also beneficial to promoting the insertion and extraction of active ions, and improving the charge and discharge efficiency and energy density of the battery.

[0231] When the Li element in the second positive electrode active material has a certain atomic molar equivalent, the adjustment of the atomic molar equivalents of Fe element and Mn element can be used to adjust the content of the corresponding elements.

[0232] Based on any suitable embodiment in the present application, in some embodiments, the second active material includes a second body, and may or may not include a second coating layer covering at least a part of the surface of the second body; wherein, the chemical formula of the second body is Li 1+x Mn 1-y-w Fe w M3 y P 1-z Q z O 4 , where, -0.1 ≤ x ≤ 0.1, 0.1 ≤ w ≤ 0.5, 0.001 ≤ y ≤ 0.5, 0.001 ≤ z ≤ 0.1, the M3 element in the second active material may include one or more elements of zinc (Zn), aluminum (Al), sodium (Na), potassium (K), magnesium (Mg), molybdenum (Mo), tungsten (W), titanium (Ti), vanadium (V), zirconium (Zr), nickel (Ni), cobalt (Co), gallium (Ga), tin (Sn), antimony (Sb), niobium (Nb) and germanium (Ge), and the Q element in the second active material may include one or more elements of boron (B), silicon (Si), nitrogen (N), sulfur (S), fluorine (F), chlorine (Cl) and bromine (Br).

[0233] In some embodiments, the M3 element in the second active material may be selected from one or more elements including but not limited to Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge.

[0234] In some embodiments, the Q element in the second active material may be selected from one or more elements including but not limited to B, Si, N, S, F, Cl, and Br.

[0235] In some embodiments, 0.1 ≤ y ≤ 0.5. Further optionally, 0.2 ≤ y < 0.5. Still further optionally, 0.3 ≤ y < 0.5. y may also be any one of the following values, or selected from any interval formed by any two of the following values: 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0236] In some embodiments, 0.2 ≤ w ≤ 0.5. Further optionally, 0.3 ≤ w < 0.5. Still further optionally, 0.4 ≤ w < 0.5. w may also be any one of the following values, or selected from any interval formed by any two of the following values: 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0237] In some embodiments, 0.001 ≤ z ≤ 0.1. Further optionally, 0.001 ≤ z < 0.05. Still further optionally, 0.001 ≤ z < 0.002. z may also be any one of the following values, or selected from any interval formed by any two of the following values: 0.001, 0.002, 0.004, 0.005, 0.006, 0.008, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, etc.

[0238] In some embodiments, the M3 element in the second active material includes one or more elements of titanium (Ti), vanadium (V), nickel (Ni), cobalt (Co), and magnesium (Mg). Further, the M3 element in the second active material may be selected from one or more elements including but not limited to Ti, V, Ni, Co, and Mg.

[0239] In some embodiments, the Q element in the second active material includes one element of boron (B), silicon (Si), nitrogen (N), and sulfur (S). Further, the Q element in the second active material may be selected from one element including but not limited to B, Si, N, and S.

[0240] In some embodiments, the second coating layer includes one or more of pyrophosphate, phosphate, and carbon.

[0241] In some embodiments, the second coating layer may be a single-layer structure or a multi-layer structure.

[0242] Based on any suitable embodiment in the present application, in some embodiments, the total mass ratio R of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer I+II ≥85%; optionally, R I+II ≥90%; further optionally, R I+II ≥95%. R I+II It may also be any one of the following percentages, or greater than or equal to any one of the following percentages, or an interval composed of any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc.

[0243] By adjusting the total mass ratio R of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer I+II Within the above range, it is more conducive to promoting the comprehensive advantages of the two positive electrode active materials.

[0244] Based on any suitable embodiment in the present application, in some embodiments, the first cation includes one or more cations of alkali metal elements and alkaline earth metal elements. Without limitation, the first cation may include one or more of sodium ions, potassium ions, calcium ions, and magnesium ions.

[0245] Without limitation, the anion in the first cation salt may include one or more of hexafluorophosphate ions, perchlorate ions, tetrafluoroborate ions, bis(trifluoromethylsulfonyl)imide ions, trifluoromethanesulfonate ions, bis(fluorosulfonyl)imide ions, and tris(trifluoromethylsulfonyl)methyl ions.

[0246] Without limitation, the anion in the electrolyte salt may include one or more of hexafluorophosphate ions, perchlorate ions, tetrafluoroborate ions, bis(trifluoromethylsulfonyl)imide ions, trifluoromethanesulfonate ions, bis(fluorosulfonyl)imide ions, and tris(trifluoromethylsulfonyl)methyl ions.

[0247] Without limitation, the first cation salt may include one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium tris(trifluoromethylsulfonyl)methyl, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bis(trifluoromethylsulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(fluorosulfonyl)imide, and potassium tris(trifluoromethylsulfonyl)methyl.

[0248] In some embodiments, the first cation salt includes one or two of sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium perchlorate.

[0249] In some embodiments, the first cationic salt includes sodium hexafluorophosphate.

[0250] When the ionic radius of the first cation is greater than that of lithium ion, the type of the first cation and the corresponding anion can have a flexible selection range. As a non-limiting example, for instance, sodium hexafluorophosphate has low cost and can be used on a large scale; the radius difference between sodium ion and lithium ion is relatively small, which is more conducive to embedding into the active material.

[0251] Based on any suitable embodiment in the present application, in some embodiments, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes a silicon-based material; the mass percentage of the silicon-based material in the negative electrode active substance is denoted as X1.

[0252] In some embodiments, X1≥3%, and further optionally 3%≤X1≤50%. X1 can also be any one of the following percentages, or a range composed of any two of the following percentages: 3%, 4%, 5%, 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 5%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, etc.

[0253] Non-limitingly, the silicon-based material can include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy, silicon-graphene composite material, silicon-carbon nanotube, and silicon-containing conductive polymer.

[0254] When the negative electrode active material layer of the negative electrode sheet includes a silicon-based material, it is beneficial to further improve the energy density of the battery cell.

[0255] The following are some descriptions about the positive electrode sheet.

[0256] Non-limitingly, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active substance. The definition of the positive electrode active substance can refer to the foregoing. The positive electrode active substance at least includes the aforementioned first positive electrode active substance and second positive electrode active substance.

[0257] Non-limitingly, the mass percentage of the positive electrode active substance in the positive electrode active material layer can be ≥85%, further can be ≥90%, and still further can be ≥95%.

[0258] Based on any suitable embodiment of the present application, in some embodiments, the percentage of the sum of the masses of the first cathode active material and the second cathode active material in the total mass of the cathode active materials in the cathode active material layer can satisfy ≥85%, optionally ≥95%, further optionally ≥96%, etc., and still further optionally be 100%, etc. The percentage of the first cathode active material and the second cathode active material in the total mass of the cathode active materials in the cathode active material layer can also be any one of the following percentages, or be greater than or equal to any one of the following percentages and less than or equal to 100%, or be selected from the intervals formed by any two of the following percentages: 85%, 86%, 88%, 95%, 96%, 98%, 100%, etc.

[0259] In some embodiments, the cathode active materials in the cathode active material layer are composed of a first cathode active material and a second cathode active material.

[0260] As a non-limiting example, the positive electrode current collector has two surfaces facing away from each other in its own thickness direction, and the cathode active material layer is provided on any one or both of the two surfaces of the positive electrode current collector facing away from each other.

[0261] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. In the positive electrode current collector, the metal material can include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive electrode current collector, the polymer material substrate can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0262] In some embodiments, the cathode active material layer may further optionally include a binder. As a non-limiting example, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The mass percentage of the binder in the cathode active material layer can be 0 to 10%, further can be 0 to 8%, and still further can be 1% to 5%.

[0263] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The mass percentage of the conductive agent in the positive electrode active material layer may be 0 to 8%, and further may be 0 to 5%.

[0264] In some embodiments, the positive electrode plate can be prepared in the following manner: Disperse the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry. Further, coat the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained. Cold pressing can be carried out using a cold rolling mill. The types of solvents may include, but are not limited to, any one of the foregoing embodiments, for example, it may include N-methylpyrrolidone (NMP), and further may be NMP. The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 3000mPa·s to 25000mPa·s, and can be optionally 3000mPa·s to 10000mPa·s. When coating the positive electrode slurry, the coating unit surface density calculated based on the dry weight (deducting the solvent) can be 15g / cm 3 ~35mg / cm 2 。The compaction density of the positive electrode plate can be 3.0g / cm 3 ~3.6g / cm 3 ,and can be optionally 3.3g / cm 3 ~3.5g / cm 3 。

[0265] In the present application, unless otherwise specified, for the positive electrode plate and the negative electrode plate, the area change of the electrode plate before and after cold pressing is not significant, and the calculation formula for the corresponding compaction density is:

[0266] Compaction density = coating surface density / (thickness of the electrode plate after cold pressing - thickness of the current collector).

[0267] Coating surface density = dry weight of the slurry / area of the electrode plate before cold pressing.

[0268] The following are some descriptions about the negative electrode plate.

[0269] Non-limitingly, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active substance. The definition of the negative electrode active substance can be referred to the foregoing text.

[0270] Non - restrictively, the mass percentage of the negative electrode active material in the negative electrode active material layer can be ≥85%, further can be ≥90%, and still further can be ≥95%.

[0271] As a non - restrictive example, the negative electrode current collector has two surfaces facing away from each other in its own thickness direction, and the negative electrode active material layer can be disposed on either or both of the two surfaces of the negative electrode current collector facing away from each other.

[0272] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material on the polymer material substrate. In the negative electrode current collector, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, the polymer material substrate can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0273] Non - restrictively, the negative electrode active material can be a negative electrode active material known in the art for batteries. As a non - restrictive example, the negative electrode active material can include one or more of the following substances or materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon - based materials, tin - based materials, and lithium titanate, etc. The silicon - based materials can include one or more of elemental silicon, silicon oxides, silicon - carbon composites, silicon - nitrogen composites, and silicon alloys. The tin - based materials can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials or substances, and other conventional materials or substances that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0274] In some embodiments, the negative electrode active material includes one or more of a carbon - based material, a silicon - based material, a tin - based material, and lithium titanate, and a modified form of any one of the foregoing substances, wherein the modified form includes one or more of doping modification and coating modification. The doping modification method and the coating modification method can both adopt or refer to the existing modification methods in the art, including but not limited to the selection of element types and doping amounts. The carbon - based material can include, but is not limited to, one or more of graphite materials, soft carbon, hard carbon, etc. The graphite materials can include one or more of artificial graphite and natural graphite.

[0275] In some embodiments, the negative electrode active material includes a carbon-based material and a silicon-based material. Without limitation, the total mass percentage of the carbon-based material and the silicon-based material in the total mass of the negative electrode active material can be ≥85%, optionally ≥90%, further optionally ≥95%, still further optionally ≥96%, etc., and still further optionally 100%, etc. The total mass percentage of the graphite material and the silicon-based material in the total mass of the negative electrode active material can also be any of the following percentages, or greater than or equal to any of the following percentages and less than or equal to 100%, or selected from the intervals formed by any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definitions of the carbon-based material and the silicon-based material can be referred to the foregoing. For example, the carbon-based material can be a graphite material. The contents of the carbon-based material and the silicon-based material can also be referred to any suitable embodiment in the context.

[0276] In some embodiments, the negative electrode active material includes a carbon-based material. Without limitation, the mass percentage of the carbon-based material in the negative electrode active material can be ≥85%, optionally ≥90%, further optionally ≥95%, still further optionally ≥96%, etc., and still further optionally 100%, etc. The mass percentage of the carbon-based material in the negative electrode active material can also be any of the following percentages, or greater than or equal to any of the following percentages and less than or equal to 100%, or selected from the intervals formed by any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definition of the carbon-based material can be referred to the foregoing. For example, the carbon-based material can be a graphite material.

[0277] In some embodiments, the negative electrode active material layer may further optionally include a binder. The binder can include, but is not limited to, one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Without limitation, the mass percentage of the binder in the negative electrode active material layer can be 0 to 10%, further can be 0 to 5%, still further can be 1% to 5%, and still further optionally 1% to 3%.

[0278] In some embodiments, the negative electrode active material layer may further optionally include a conductive agent. As a non-limiting example, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In the negative electrode active material layer, the mass percentage of the conductive agent can be 0 to 15%, further optionally 0 to 10%, and still further optionally 0 to 5%.

[0279] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The mass percentage of other additives in the negative electrode active material layer may be 0 to 15%, further optionally 0 to 10%, still further optionally 0 to 5%, still further optionally 0 to 3%, and still further optionally 0 to 2%.

[0280] In some embodiments, the negative electrode plate can be prepared by the following method: dispersing the above components for preparing the negative electrode plate, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry. Further, the negative electrode slurry is coated on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 30wt% to 70wt%, optionally 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s to 10000mPa·s, optionally 3000mPa·s to 10000mPa·s. The compaction density of the negative electrode plate can be 1.2g / cm 3 ~2.0g / cm 3 ,optionally 1.2g / cm 3 ~1.8g / cm 3 .

[0281] The electrolyte is described below.

[0282] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. In the present application, the electrolyte includes a liquid electrolyte. The liquid electrolyte can also be referred to as an electrolytic solution, that is, the electrolyte includes an electrolytic solution. The electrolytic solution includes an electrolyte salt.

[0283] In some embodiments, the electrolyte is an electrolytic solution.

[0284] In some embodiments, the electrolytic solution is a non-aqueous electrolyte. Further, the non-aqueous electrolyte includes an electrolyte salt and a solvent. The definition of the electrolyte salt can be referred to the foregoing, and at least includes a first electrolyte salt. In some embodiments, the electrolyte salt further includes an electrolyte lithium salt. The concentration of the electrolyte salt can generally be 0.5mol / L to 5mol / L.

[0285] In some embodiments, the electrolyte lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6) Lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or one or more of them.

[0286] In some embodiments, the solvent in the non-aqueous electrolyte may include fluoroethylene carbonate (FEC), ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate (BC, ), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE), or one or more of them.

[0287] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include anode film-forming additives, cathode film-forming additives, and may also include additives that can improve certain battery performance, such as additives for improving battery overcharge performance, additives for improving battery high-temperature or low-temperature performance, etc.

[0288] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate (TFPC), etc.

[0289] The separator is described below.

[0290] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0291] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0292] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0293] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0294] In a second aspect of the present application, a secondary battery is provided, which includes the battery cell described in the first aspect of the present application.

[0295] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The definition of the battery cell can be referred to in the context, for example, it can be referred to the first aspect of the present application.

[0296] It can be understood that generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0297] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0298] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the electrolyte salt can include an electrolyte lithium salt.

[0299] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0300] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0301] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0302] The present application has no particular limitation on the shape of the battery cell, and it can be cylindrical, square, or any other shape. For example, Figure 1The battery cell 5 is a square structure as an example.

[0303] In some of these embodiments, with reference to Figure 2 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0304] The secondary battery can be a battery module 4 or a battery pack 1.

[0305] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0306] Figure 3 The battery module 4 is an example. With reference to Figure 3 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0307] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0308] In some of these embodiments, the above battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0309] Figure 4 and Figure 5 The battery pack 1 is an example. With reference to Figure 4 and Figure 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 and form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0310] In the third aspect of the present application, an electrical device is provided, which includes at least one of the battery cell described in the first aspect of the present application and the secondary battery described in the second aspect of the present application.

[0311] In some embodiments, the present application further provides an electrical device, which includes a secondary battery according to any one of the embodiments provided by the present application. The secondary battery can be used as a power source of the electrical device or as an energy storage unit of the electrical device. The electrical device may include a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, an electric motorcycle, an electric tool, etc., but is not limited thereto. The electrical device can also be applied to military equipment, aerospace and other fields, and can also be applied to energy storage power systems such as hydraulic, thermal, wind and solar power stations.

[0312] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0313] Figure 6 Shown is an electrical device 6 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0314] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a secondary battery can be used as the power source.

[0315] Hereinafter, some embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the embodiments regarding techniques or conditions, they shall be carried out according to the descriptions above, or according to the techniques or conditions described in the literature in this field, or according to the product specifications. For those reagents or instruments not specified regarding the manufacturer, they are all conventional products that can be obtained through commercial purchase, or can be synthesized from commercially available products in a conventional manner.

[0316] In the following embodiments, room temperature refers to 20°C to 30°C.

[0317] In the following embodiments, a soft-pack laminated battery is taken as an example. It can be understood that the outer packaging method of the secondary battery is not limited thereto. Similarly, other methods in this field can also be adopted for the material selection and assembly method of the tab.

[0318] The ionic conductivity of the positive electrode active material used hereinafter is tested by the following method:

[0319] The positive electrode active material to be tested is made into a positive electrode sheet for testing, and a lithium sheet is used as the negative electrode sheet, and a button battery is assembled for testing; after the battery is discharged to 3.0 V at 1 C, an alternating current impedance spectrum test is carried out. The test parameters are selected as follows: the test temperature is 25 °C, the scanning frequency is 0.1 Hz to 10 5 Hz, the voltage amplitude is 5 mV, and the test results are fitted by Zview software to obtain the ionic conductivity.

[0320] Unless otherwise specified, in the positive electrode sheet for testing, the positive electrode current collector is selected as aluminum foil, the mass percentage of the positive electrode active material in the positive electrode active material layer is controlled at 95% ± 1%, the binder is selected as polyvinylidene fluoride (PVDF), the conductive agent is selected as conductive carbon, and the compaction density is 3.0 g / cm 3 ~3.6 g / cm 3 。

[0321] For the first positive electrode active material and the second positive electrode active material, the raw materials with the same chemical formula are from the same source or are prepared by the same method. Therefore, the ionic conductivities of the raw materials with the same chemical formula are basically the same.

[0322] Example 1.

[0323] (1) Preparation of the positive electrode sheet:

[0324] The first positive electrode active material, the second positive electrode active material, the binder polyvinylidene fluoride (PVDF), and conductive carbon are added to the solvent N-methylpyrrolidone (NMP). The mass ratio of the positive electrode active material: binder: conductive agent is 95:2.5:2.5. The positive electrode slurry is stirred evenly in a drying room, and the viscosity of the positive electrode slurry is controlled to be 3000 mPa·S to 10000 mPa·S. The above positive electrode slurry is coated on both sides of the aluminum foil, and after drying and cold pressing, a positive electrode sheet is made. The compaction density is 3.4 g / cm 3 。

[0325] The first positive electrode active material is a nickel cobalt manganese lithium oxide (an NCM material), and the second positive electrode active material is a lithium iron manganese phosphate oxide.

[0326] The types and content ratios of the first positive electrode active material and the second positive electrode active material (the dosage ratio of the two is determined by the A value) can be referred to in Table 1 and Table 2.

[0327] The A value is the mass ratio of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material.

[0328] (2) Preparation of the negative electrode sheet:

[0329] Graphite material (artificial graphite), sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR), and conductive carbon were added to deionized water as the solvent. The mass ratio of graphite material : sodium carboxymethyl cellulose : styrene-butadiene rubber : conductive agent was 95 : 1 : 2.5 : 1.5. They were stirred to form a uniform negative electrode slurry, and the viscosity of the negative electrode slurry was controlled to be 3000 mPa·S to 10000 mPa·S. The above-mentioned negative electrode slurry was coated on one side surface of the copper foil, and after drying and cold pressing treatments, a negative electrode sheet was made. The compaction density was 1.55 g / cm 3 .

[0330] (3) Preparation of electrolyte

[0331] The electrolyte consists of electrolyte salts, solvents, and additives: The electrolyte salts are sodium hexafluorophosphate (NaPF 6 , the first cationic salt) and lithium hexafluorophosphate (LiPF 6 ). Among them, the relative percentage of the mass of sodium element in the electrolyte with respect to the sum of the masses of sodium element and lithium element is 5 wt% (the target value corresponding to B is 5%). The concentration of lithium hexafluorophosphate (electrolyte lithium salt) in the electrolyte is 1 mol / L; the solvents are ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) with a volume ratio of 1 : 1 : 1; the additive is fluoroethylene carbonate (FEC), and its mass percentage in the electrolyte is 5 wt%.

[0332] In this example, the first cationic salt is sodium hexafluorophosphate, the first cation is sodium ion, the electrolyte lithium salt is lithium hexafluorophosphate, and the electrolyte salts in the electrolyte consist of metal cations and anions. The metal cations are a combination of sodium ions and lithium ions, and the anion is hexafluorophosphate ion. For the types and dosage ratios of the first cationic salts in the electrolyte, reference can also be made to Table 1.

[0333] The B value is the mass percentage of the first cationic salt in the electrolyte salts of the electrolyte, and numerically it is calculated according to "the ratio of the mass of the first cation to the total mass of all metal cations in the electrolyte salts".

[0334] (4) Separator

[0335] A polyethylene (PE) porous polymer film was used as the separator.

[0336] (5) Preparation of electrode assembly and secondary battery:

[0337] The prepared positive electrode sheet, negative electrode sheet and separator are made into a corresponding electrode assembly (i.e., a bare battery cell) according to a Z-shaped stacking structure. The bare battery cell is vacuum dried at 90 °C for 12 h, and then the positive electrode tab and the negative electrode tab are ultrasonically welded. The positive electrode uses an aluminum tab, and the negative electrode uses a nickel tab. The positive electrode tab and the negative electrode tab are located on the same side of the battery cell. The battery cell after welding the tabs is placed in an aluminum plastic film for top-side sealing packaging, electrolyte is injected, and then it is left standing, formed, aged, degassed, and subjected to a second packaging to obtain a secondary battery with a preset capacity (0.1 Ah). This secondary battery is an exemplary soft-pack stacked battery. In other embodiments, a hard shell method can be used.

[0338] In Examples 2 to 21, secondary batteries were prepared using substantially the same method as in Example 1, except that: the types of the first positive electrode active material and the second positive electrode active material, the dosage ratio A value of the first positive electrode active material and the second positive electrode active material, the type of the first cation salt in the electrolyte, the dosage (B value) of the first cation salt, the A / B value, and the type and dosage of the negative electrode active material. Refer to Tables 1, 2 and 3.

[0339] In Comparative Example 1, a secondary battery was prepared using substantially the same method as in Example 1, except that the A value and the A / B value were different.

[0340] In Comparative Example 2, a secondary battery was prepared using substantially the same method as in Example 1, except that the B value and the A / B value were different.

[0341] In Comparative Example 3, a secondary battery was prepared using substantially the same method as in Example 1, except that the second positive electrode active material was omitted from the positive electrode active material, and only the first positive electrode active material was used, and the A value and the A / B value were different.

[0342] In Comparative Example 4, a secondary battery was prepared using substantially the same method as in Example 1, except that the first positive electrode active material was omitted from the positive electrode active material, and only the second positive electrode active material was used, and the A value and the A / B value were different.

[0343] In Comparative Example 5, a secondary battery was prepared using substantially the same method as in Example 1, except that the first cation salt was not added, and the B value and the A / B value were different.

[0344] In Comparative Example 6, a secondary battery was prepared using substantially the same method as in Example 8, except that the A value, the B value and the A / B value were different.

[0345] In Comparative Example 7, a secondary battery was prepared using substantially the same method as in Example 12, except that the A value, the B value and the A / B value were different.

[0346] In Comparative Example 8, a secondary battery was prepared using substantially the same method as in Example 16, except that the B value and the A / B value were different.

[0347] Comparative Example 9 prepared a secondary battery using substantially the same method as Comparative Example 2, except that: the ratio (R2 Mn / Fe ) of the atomic molar equivalent of Mn element and Fe element in the second positive electrode active material was different.

[0348] The preparation parameters of Comparative Examples 1 to 9 can be referred to in Tables 1 to 3.

[0349] The A value and B value in Table 1 are design values (corresponding to their respective target values) calculated based on the raw material composition and dosage ratio. In Table 2, the Ni content, Mn content, and R2 Mn / Fe are atomic ratios obtained from the chemical composition of the raw materials, calculated as the atomic number ratio or atomic molar ratio. In each example, the cation in the electrolyte salt of the electrolyte is a combination of lithium ions and a first cation. The type and dosage ratio of the first cation salt in the electrolyte can be referred to in Table 1, and the dosage of the first cation salt is determined according to the target value of B; when the anions of the electrolyte salts are different, the dosage of the first cation salt and the target value of B are determined by "the mass ratio of the first cation to the total mass of each metal cation in the electrolyte salt".

[0350] Table 1.

[0351]

[0352]

[0353] In Table 1, the A value is the target value of the mass ratio (A) of Co element in the first positive electrode active material to Fe element in the second positive electrode active material; the first cation is sodium ion, and the B value is the target value of the mass percentage (B) of the first cation salt in the electrolyte salt of the electrolyte, which numerically equals the percentage of the mass of the first cation in the electrolyte relative to the mass of the metal cations in the electrolyte.

[0354] Table 2.

[0355]

[0356] In Table 2:

[0357] The "nickel (Ni) content" in the first positive electrode active material is the ratio of the atomic molar equivalent of Ni element to lithium (Li) element, which numerically also equals the atomic ratio of Ni element to Li element;

[0358] The "manganese (Mn) content" in the first positive electrode active material is the ratio of the atomic molar equivalent of Mn element to lithium (Li) element, which numerically also equals the atomic ratio of Mn element to Li element;

[0359] R2 Mn / FeIt refers to the ratio of the atomic molar equivalents of Mn element and Fe element in the second positive electrode active material.

[0360] Table 3.

[0361]

[0362] In Table 3, the "mass percentage of silicon-based material" represents the mass percentage of the silicon-based material in the negative electrode active material.

[0363] Testing and analysis methods

[0364] 1. Testing and analysis of the mass percentage (B value) of the first cation salt in the electrolyte:

[0365] Based on GB / T36240-2018 and an ion chromatograph, quantitative tests are carried out on the electrolyte lithium salt and the first cation salt in the electrolyte. In a certain mass of electrolyte sample, the mass of lithium ions in the electrolyte lithium salt is denoted as m1, and the mass of the first cation in the first cation salt is denoted as m2. Then, the B value can be calculated according to the following formula: B = m2 / (m1 + m2) × 100%.

[0366] 2. Testing the contents of Ni element, Co element and Mn element in the first positive electrode active material, testing the contents of Mn element and Fe element in the second positive electrode active material, and testing and analysis of element ratios such as the A value.

[0367] Take about 0.4 g of the positive electrode active material layer sample (accurate to 0.0001 g) in a 25 mL beaker, add 2 mL to 5 mL of nitric acid, let it stand overnight, then place it on a hot plate and heat at about 100 °C. Use a voltage regulator transformer to adjust the input voltage for temperature control. After heating until the positive electrode active material layer is digested, add 0.5 mL of perchloric acid and heat and digest at about 140 °C until white smoke disappears completely. The residue should be white, otherwise, repeat the digestion by adding nitric acid and perchloric acid again. Finally, dissolve and extract with 7 wt% hydrochloric acid. After diluting to an appropriate volume according to the content of the element to be measured, start testing on an ICP-OES test instrument (511OTCP-OESVDV). Select Ni, Co, Mn, and Fe as the test elements. The test result of the instrument is the mass percentage of each element. Then, the chemical formula of the first positive electrode active material and the content of Mn element in the first positive electrode active material can be obtained according to the molar mass and mass percentage of Ni element and Co element; after removing the content of Mn in the first positive electrode active material, the mass percentage of Mn in the second positive electrode active material can be obtained. According to the molar mass and mass percentage of Mn element and Fe element in the second positive electrode active material, the chemical formula of the second active material can be obtained. Finally, the mass ratio (A value) of Co element in the first positive electrode active material and Fe element in the second positive electrode active material and the ratio of the atomic molar ratio of other different elements can be calculated. For example, the mass ratio of Mn element and Fe element in the second positive electrode active material (R2 Mn / Fe ).

[0368] According to the A value and B value obtained from the test, the test analysis result of the A / B value can be calculated.

[0369] 3. Battery energy density test

[0370] Test the battery capacity: Leave the battery to be tested for 3 min; Discharge at 0.33C to the lower cut-off voltage (such as 2.5 V); Leave it for 3 min; Charge at 0.33C constant current and constant voltage to the upper cut-off voltage (such as 4.4 V), and cut off at 0.05C current; Leave it for 3 min; Discharge at 0.33C to the cut-off voltage (the battery capacity is obtained in this step); Leave it for 3 min; Calculate the energy value released by the first discharge of the battery. Divide the energy value released by the first discharge of the battery by the mass of the battery to be tested to obtain the mass energy density of the battery, with the unit of watt-hour per kilogram (W·h / kg).

[0371] 4. Thermal runaway temperature test:

[0372] Place the secondary battery to be tested in a constant temperature environment of 25°C. Under the voltage range of 2.5V to 4.4V, charge it at 1C until 4.4V, then perform constant voltage charging at 4.4V until the current ≤ 0.05C. Let it stand for 5 minutes, and then arrange temperature sensing wires at the center of the positive electrode tab, the center of the negative electrode tab, the center of the large surface, and the center of the side of the secondary battery to monitor the temperature of the battery core; transfer the secondary battery with the temperature sensing wires arranged into a thermal chamber, heat it up to 60°C at a rate of 5°C / min and then keep it warm for 5 hours. After that, heat it up at a rate of 5°C / min and keep it warm for 30 minutes every time it rises by 5°C. When it reaches 120°C, heat it up at a rate of 2°C / min and keep it warm for 30 minutes every time it rises by 2°C until the battery core fails or until 24 hours; extract the corresponding end temperature as the test result of the "thermal runaway temperature". If the battery core does not fail at the end of the test, record "no failure during the test period".

[0373] Basis for judging battery core failure: explosion or fire.

[0374] The higher the thermal runaway temperature, the better the thermal stability and the higher the thermal safety of the secondary battery.

[0375] Test analysis results

[0376] Regarding the ionic conductivity (σ 1 ) of the first positive electrode active material raw material at 25°C, the ionic conductivity of the first positive electrode active material used in Examples 1 to 12, 17 to 21, and Comparative Examples 1 - 3, 5 - 7, 9 is in the range of 1×10 -3 S / cm to 3×10 -3 S / cm. The ionic conductivity of the first positive electrode active material used in Example 13 is in the range of 3×10 -3 S / cm to 5×10 -3 S / cm. The ionic conductivity of the first positive electrode active material used in Example 14 is in the range of 5×10 -3 S / cm to 7×10 -3 S / cm. The ionic conductivity of the first positive electrode active material used in Example 15 is in the range of 7×10 -3 S / cm to 9×10 -3 S / cm. The ionic conductivity of the first positive electrode active material used in Example 16 and Comparative Example 8 is in the range of 3.2×10 -6 S / cm to 1×10 -3 S / cm (3.2×10 -6 S / cm < σ 1 < 1×10 -3 S / cm). Among them, σ of Example 16, σ 1 of Examples 1 to 12 and 17 to 21, σ 1 of Example 13, σ 1, and σ of Example 15 1 Increase successively.

[0377] Regarding the ionic conductivity (σ 2 ) of the second positive electrode active material raw material at 25 °C, the ionic conductivity of the second positive electrode active material used in Examples 1-17, 20-21 and Comparative Examples 1-2, 4-9 is in the range of 3×10 -13 S / cm to 9×10 -13 S / cm, and the ionic conductivity of the second positive electrode active material used in Examples 18-19 is in the range of 1×10 -13 S / cm to 3×10 -13 S / cm. The σ 2 of Examples 1-17, 20-21 are all greater than the σ 2 of Examples 18-19.

[0378] In Examples 1 to 21, the ionic conductivity (σ 1 ) of the first positive electrode active material at 25 °C all satisfies σ 1 ≥3.2×10 -6 S / cm, and most satisfy σ 1 ≥1.7×10 -3 S / cm. The ionic conductivity (σ 2 ) of the second positive electrode active material at 25 °C all satisfies σ 2 ≤10 -9 S / cm, and also all satisfy σ 2 ≤10 -12 S / cm, and most satisfy σ 2 ≤8×10 -13 S / cm. In Examples 1 to 21, the ratio (Xσ) of the ionic conductivity of the first positive electrode active material at 25 °C to the ionic conductivity of the second positive electrode active material at 25 °C all satisfies Xσ≥10 4 , and also all satisfy Xσ≥10 6 , and a part of them satisfy Xσ≥10 10 .

[0379] The A value calculated based on the test analysis results of the B value and the elemental analysis results of the positive electrode active material in the positive electrode sheet basically coincides with the target values of A and B in Table 1.

[0380] According to the battery energy density test results, the battery mass energy density of Examples 1-4, 9-12, 17, 20-21 and Comparative Examples 1, 2, 5, 7, 9 is within the range of 235 W·h / kg to 255 W·h / kg. The battery mass energy density of Examples 13-15 is within the range of 240 W·h / kg to 270 W·h / kg. The battery energy density of Examples 5-8 is between the battery energy density of Examples 1-4 and the battery energy density of Examples 13-16. The battery mass energy density of Examples 16 and Comparative Examples 3, 6, 8 is within the range of 235 W·h / kg to 265 W·h / kg. The battery mass energy density of Examples 18-19 is within the range of 220 W·h / kg to 245 W·h / kg. The battery mass energy density of Comparative Example 4 is within the range of 220 W·h / kg to 230 W·h / kg.

[0381] The secondary batteries prepared in Examples 1-21 all have good thermal stability, high thermal runaway temperature, and at the same time have high energy density and good comprehensive electrical performance. Relatively speaking, the comprehensive performance of Comparative Documents 1-9 has deteriorated significantly: the thermal runaway temperature of some comparative examples has decreased significantly, and the battery energy density has changed little or even decreased, such as Comparative Examples 1, 2, 5, 7 and 9 compared with Example 1, etc., and also such as Comparative Example 6 compared with Example 8, and Comparative Example 8 compared with Example 16; some comparative examples (such as Comparative Example 3) although the battery energy density has increased compared with some examples, but the thermal runaway temperature has decreased significantly, and the comprehensive performance is not good; some comparative examples (such as Comparative Example 4) achieve some improvement in thermal stability at the cost of significantly sacrificing the battery energy density, and the comprehensive performance is not good.

[0382] The A / B values of Comparative Example 1, Comparative Example 2, Comparative Example 7 and Comparative Example 9 are outside 0.47-202. Compared with the examples within the range of 0.47-202 (such as Examples 1-4, etc.), the thermal runaway temperatures of Comparative Example 1, Comparative Example 2, Comparative Example 7 and Comparative Example 9 have decreased significantly.

[0383] Comparative Example 3 only uses a single type of first positive electrode active material. Compared with Examples 1-4, although the battery energy density of Comparative Example 3 has increased, its thermal runaway temperature has decreased significantly, and the comprehensive performance is inferior to Examples 1-4.

[0384] Comparative Example 4 only uses a single type of second positive electrode active material. Although the thermal runaway temperature is relatively high, the battery energy density is very low (220 W·h / kg to 230 W·h / kg), which is significantly lower than the battery energy density of Examples 1-4 (235 W·h / kg to 255 W·h / kg), and the comprehensive performance is inferior to Examples 1-4.

[0385] In Comparative Example 5, the first cation was not added, and the thermal runaway temperature was significantly inferior compared to each of the Examples (such as Example 1) in which the first cation was added.

[0386] The A / B values of Comparative Example 6 and Comparative Example 8 were outside the range of 0.47 to 202, and the thermal runaway temperature was relatively low. Among them, the thermal runaway temperature of Comparative Example 6 was significantly lower than that of Example 8 using the same negative electrode active material; the thermal runaway temperature of Comparative Example 8 was significantly lower than that of Example 16 using the same negative electrode active material.

[0387] The descriptions of the above various embodiments and examples tend to emphasize the differences between the various embodiments and examples. Their similarities or resemblances can be referred to each other. For the sake of brevity, they will not be elaborated herein again.

[0388] The technical features of the above various embodiments and examples can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0389] It should be noted that this application is not limited to the above embodiments and examples. The above embodiments and examples are only for illustration. Embodiments having the same constitution and achieving the same effects within the technical scope of this application are included in the technical scope of this application. The above-described embodiments and examples only represent several embodiments of this application, and their descriptions are relatively detailed, but should not be construed as a limitation of the patent scope. In addition, within the scope not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments and examples, and other ways constructed by combining some of the constituent elements in the embodiments and examples are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, it includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The separator is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material layer. The positive electrode active material layer includes a first positive electrode active substance and a second positive electrode active substance. The electrolyte includes an electrolyte salt. The electrolyte salt includes a first cation salt and an electrolyte lithium salt; wherein, the first positive electrode active substance is a lithium oxide containing Co element and M1 element, and the second positive electrode active substance is a lithium oxide containing Fe element and Mn element. Among them, the M1 element in the first positive electrode active substance includes one or both of Mn element and Al element; The mass ratio of the Co element in the first positive electrode active substance to the Fe element in the second positive electrode active substance is denoted as A; The first cation salt includes a first cation, and the ionic radius of the first cation is greater than that of the lithium ion; the mass percentage of the first cation salt in the electrolyte salt is denoted as B; then A and B satisfy 0.47 ≤ A / B ≤ 202.

2. The battery cell according to claim 1, characterized in that, At 25 °C, the ratio of the ionic conductivity of the first positive electrode active material to the ionic conductivity of the second positive electrode active material is denoted as Xσ, and Xσ ≥ 10 4 ; Optionally, Xσ ≥ 10 6 , and further optionally Xσ ≥ 10 10 ; Optionally, the ionic conductivity of the first positive electrode active material at 25 °C is σ 1 , satisfying σ 1 ≥3.2×10 -6 S / cm, and further optionally σ 1 ≥1.7×10 -3 S / cm; Optionally, the ionic conductivity of the second positive electrode active material at 25 °C is σ 2 , satisfying σ 2 ≤10 -9 S / cm, and further optionally σ 2 ≤10 -12 S / cm.

3. The battery cell according to claim 1 or 2, characterized in that, 1.3 ≤ A / B ≤ 25.

4.

4. The battery cell according to any one of claims 1 to 3, characterized in that, 0.19 ≤ A ≤ 10.1; optionally, 0.28 ≤ A ≤ 2.

53.

5. The battery cell according to any one of claims 1 to 4, characterized in that, 5% ≤ B ≤ 40%; optionally, 10% ≤ B ≤ 20%.

6. The battery cell according to any one of claims 1 to 5, characterized in that, the first positive electrode active substance satisfies one or more of the following characteristics: The atomic molar ratio of Co element to Li element is denoted as R c , then R c satisfies 0.05 ≤ R c ≤ 0.

5. Optionally, 0.05 ≤ R c ≤ 0.

3. Optionally, 0.05 ≤ R c ≤ 0.2; The atomic molar ratio of the M1 element to the Li element is denoted as R d , then R d satisfies 0.05 ≤ R d ≤ 0.

5. Optionally, 0.05 ≤ R d ≤ 0.3; The M1 element includes an Mn element, and the atomic molar ratio of the Mn element to the Li element is denoted as R d-Mn , then R d-Mn satisfies 0.05 ≤ R d-Mn ≤ 0.

4. Further optionally, 0.05 ≤ R d-Mn ≤ 0.3; The ratio of the sum of the atomic molar equivalents of Co element and the M1 element to the atomic molar equivalent of Li element is denoted as R c+d , then R c+d satisfies 0.1 ≤ R c+d ≤ 0.

5. Further optionally, 0.1 ≤ R c+d ≤ 0.

3. Still further optionally, 0.1 ≤ R c+d ≤ 0.

2.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The first positive electrode active material further contains Ni element; in the first positive electrode active material, the atomic molar ratio of Ni element to Li element is denoted as R b , then R b satisfies 0.5 ≤ R b < 1; Optionally, 0.5 ≤ R b ≤ 0.9; Further optionally, 0.6 ≤ R b ≤ 0.9; Further optionally, 0.65 ≤ R b ≤ 0.9; Further optionally, 0.8 ≤ R b ≤ 0.

9.

8. The battery cell according to any one of claims 1 to 5, characterized in that, Based on the atomic molar equivalent Q of Li element a being 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and still further optionally 1, the first positive electrode active material satisfies one or more of the following characteristics: Atomic molar equivalent Q of Co element c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2; The atomic molar equivalent Q of the M1 element d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3; the M1 element includes Mn element, and the atomic molar equivalent of Mn element ≤ 0.4, optionally, the atomic molar equivalent of Mn element ≤ 0.3; The sum Q of the atomic molar equivalents of Co element and the M1 element c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d ≤0.3, Q c+d ≤0.

2.

9. The battery cell according to claim 8, characterized in that, The first positive electrode active material contains Ni element, and the atomic molar equivalent Q of Ni element b satisfies 0.5 ≤ Q b < 1, optionally, 0.6 ≤ Q b < 1, further optionally, 0.65 ≤ Q b < 1.

10. The battery cell according to any one of claims 1 to 5, characterized in that, The first positive electrode active material includes a first body, and may or may not include a first coating layer located on at least a part of the surface of the first body; wherein, the chemical composition of the first body is Li a Ni b Co c M1 d M2 e O f R g , where 0.75 ≤ a ≤ 1.2, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≤ e ≤ 0.2, b + c + d + e = 1, 1 ≤ f ≤ 2.5, 0 ≤ g ≤ 1, f + g ≤ 3, the M2 element in the first positive electrode active material includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and the R element in the first positive electrode active material includes one or more of N, F, S, and Cl; optionally, 0.8 ≤ a ≤ 1.2, further optionally, 0.9 ≤ a ≤ 1.1, further optionally, 0.95 ≤ a ≤ 1.05; optionally, 0.5 ≤ b < 1, further optionally, 0.5 ≤ b ≤ 0.9, still further optionally, 0.6 ≤ b ≤ 0.9; optionally, 0.05 ≤ c < 1, further optionally, 0.05 ≤ c ≤ 0.5, still further optionally, 0.05 ≤ c ≤ 0.3; optionally, 0.05 ≤ d < 1, further optionally, 0.05 ≤ d ≤ 0.5, still further optionally, 0.05 ≤ d ≤ 0.3; optionally, 0 ≤ e < 0.1, further optionally, 0 ≤ e ≤ 0.05, still further optionally, 0 ≤ e ≤ 0.03; Optionally, 1 ≤ f ≤ 2.1, further optionally, 1.8 ≤ f ≤ 2.05, still further optionally, 1.95 ≤ f ≤ 2.05; Optionally, 0 ≤ g < 0.5, further optionally, 0 ≤ g ≤ 0.1, still further optionally, 0 ≤ g ≤ 0.

05.

11. The battery cell according to any one of claims 1 to 10, characterized in that the second positive electrode active material satisfies one or more of the following characteristics: The atomic molar ratio of Mn element and Fe element is 0.42 - 9, optionally, the atomic molar ratio of Mn element and Fe element is 0.66 - 4; Based on the atomic molar equivalent of Li element being 0.9 - 1.1, optionally 0.9 - 1.05, further optionally 1, the atomic molar equivalent of Mn element is 0.5 - 0.999, optionally, the atomic molar equivalent of Mn element is 0.5 - 0.6; Based on the atomic molar equivalent of Li element being 0.9 - 1.1, optionally 0.9 - 1.05, further optionally 1, the atomic molar equivalent of Fe element is 0.001 - 0.5, optionally, the atomic molar equivalent of Fe element is 0.4 - 0.

5.

12. The battery cell according to any one of claims 1 to 10, characterized in that The second active material includes a second body, and may or may not include a second coating layer covering at least a part of the surface of the second body; wherein, the chemical formula of the second body is Li 1+x Mn 1-y-w Fe w M3 y P 1-z Q z O 4 , where, -0.1 ≤ x ≤ 0.1, 0.1 ≤ w ≤ 0.5, 0.001 ≤ y ≤ 0.5, 0.001 ≤ z ≤ 0.1, the M3 element in the second active material includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and the Q element in the second active material includes one or more elements selected from B, Si, N, S, F, Cl, and Br; Optionally, 0.1 ≤ y ≤ 0.5, further optionally, 0.2 ≤ y < 0.5, still further optionally, 0.3 ≤ y < 0.5; Optionally, 0.2 ≤ w ≤ 0.5, further optionally, 0.3 ≤ w < 0.5, still further optionally, 0.4 ≤ w < 0.5; Optionally, 0.001 ≤ z ≤ 0.1, further optionally, 0.001 ≤ z < 0.05, still further optionally, 0.001 ≤ z < 0.002; Optionally, the M3 element in the second active material includes one or more elements of Ti, V, Ni, Co, and Mg; Optionally, the Q element in the second active material includes one element of B, Si, N, and S; Optionally, the second coating layer includes one or more of pyrophosphate, phosphate, and carbon; Optionally, the second coating layer is a single-layer structure or a multi-layer structure.

13. The battery cell according to any one of claims 1 to 12, characterized in that The total mass ratio R of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer I+II ≥85%; Optionally, R I+II ≥ 90%; Further optionally, R I+II ≥ 95%.

14. The battery cell according to any one of claims 1 to 13, characterized in that The first cation includes cations of one or more elements among alkali metal elements and alkaline earth metal elements; Optionally, the first cation includes one or more of sodium ion, potassium ion, calcium ion, and magnesium ion; Optionally, the anions in the first cation salt include one or more of hexafluorophosphate ion, perchlorate ion, tetrafluoroborate ion, bis(trifluoromethylsulfonyl)imide ion, trifluoromethanesulfonate ion, bis(fluorosulfonyl)imide ion, and tris(trifluoromethylsulfonyl)methyl ion; Further optionally, the first cationic salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium tris(trifluoromethylsulfonyl)methide, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bis(trifluoromethylsulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis(fluorosulfonyl)imide, and potassium tris(trifluoromethylsulfonyl)methide; Even further optionally, the first cationic salt includes one or two of sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium perchlorate.

15. The battery cell according to any one of claims 1 to 14, wherein, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes a silicon-based material; the mass percentage of the silicon-based material in the negative electrode active substance is denoted as X1, optionally, X1 ≥ 3%, and further optionally 3% ≤ X1 ≤ 50%; optionally, the silicon-based material includes one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon alloy, silicon-graphene composite, silicon-carbon nanotube, and silicon-containing conductive polymer.

16. A secondary battery, wherein, it includes the battery cell according to any one of claims 1 to 15.

17. The secondary battery according to claim 16, wherein, the secondary battery is a lithium-ion secondary battery.

18. An electrical device, wherein, it includes at least one of the battery cell according to any one of claims 1 to 15 and the secondary battery according to claim 16 or 17.

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