Battery cell, secondary battery and electric device

Abstract

The present application provides a battery cell. The battery cell comprises a positive electrode sheet and an electrolyte; in a positive electrode active material layer of the positive electrode sheet, the mass ratio of Co element in a first positive electrode active material to Fe element in a second positive electrode active material is A; a first cationic salt in the electrolyte comprises first cations with the ion radius greater than that of lithium ions; the mass percentage of the first cationic salt in an electrolyte salt is B; and 0.47≤A / B≤202.

Description

Battery cells, secondary batteries, and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application number CN2023116403270, filed on November 30, 2023, entitled “Battery Cell, Secondary Battery and Electrical Device,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a battery cell, a secondary battery, and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] As the application of secondary batteries expands, lithium-ion batteries, a leading example, are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants. They are also widely used in smartphones, tablets, smart wearables, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. This expansion and development of applications has placed higher demands on the battery's electrical performance, but at the same time, this can introduce risks such as thermal runaway, leading to poor thermal stability.

[0006] Based on this, it is necessary to develop new secondary battery technologies with good electrical performance and thermal stability.

[0007] Summary of the Invention

[0008] According to various embodiments and examples of the present application, the present application provides a battery cell, a secondary battery, and an electrical device. The battery cell has excellent electrical performance, good thermal stability, and low thermal runaway risk.

[0009] In a first aspect of the present application, a battery cell is provided, which includes a positive electrode plate and an electrolyte; in the positive electrode active material layer of the positive electrode plate, 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 cationic salt in the electrolyte includes a first cation having an ionic radius greater than that of a lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is B; 0.47≤A / B≤202.

[0010] In some embodiments, a battery cell is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, and the electrolyte salt comprises a first cation salt and an electrolyte lithium salt;

[0011] The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements;

[0012] 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;

[0013] The first cationic salt includes a first cation, the ionic radius of the first cation is larger than the ionic radius of the lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is recorded as B;

[0014] Then A and B satisfy 0.47≤A / B≤202.

[0015] It can be understood that when the positive electrode plate includes the first positive electrode active material and the second positive electrode active material, the active ions in the battery cell include lithium ions.

[0016] The positive electrode sheet in this battery cell is a composite positive electrode sheet, which is provided with different positive electrode active materials. The composite positive electrode sheet includes a first positive electrode active material containing cobalt (Co) and M1, the M1 element including one or both of manganese (Mn) and aluminum (Al), and a second positive electrode active material containing iron (Fe) and Mn. Although the composite positive electrode sheet design can theoretically complement the advantages of different positive electrode active materials, it is hoped that it can improve the overall electrical performance in aspects such as material structure stability, battery safety, rate performance, and cycle performance, while taking into account the voltage platform and manufacturing cost. However, lithium oxide containing Co and M1 elements and lithium oxide containing Fe and Mn elements are different positive electrode active materials, and have different activities and ionic conductivities, resulting in different degrees of utilization during the charge and discharge cycle. Among them, lithium oxide containing Co and M1 elements is easily over-utilized, causing damage to the surface structure of the first positive electrode active material and releasing oxygen, and may even cause the material structure to collapse, posing a risk of thermal runaway of the battery; in addition, the released oxygen may also trigger side reactions in the electrolyte. The active ion diffusion in the composite positive electrode plate design is presumably one-dimensional channel diffusion. By introducing a first cationic salt, a first cation with an ion radius larger than that of lithium (Li) ions is introduced. The first cation can replace part of the active ions and be embedded in the first positive electrode active material, blocking the active ion diffusion channel in the first positive electrode active material, reducing the utilization 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, hindering the removal of active ions during discharge, further increasing the stability of oxygen on the surface of the positive electrode active material, and reducing oxygen release. The first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, and reduce the risk of thermal runaway. Furthermore, by adjusting the mass ratio A (also denoted as I) of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material, the first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, and reduce the risk of thermal runaway. Co / II Fe The ratio of the first positive electrode active material to the second positive electrode active material can be adjusted. Furthermore, the A / B value can be used to collaboratively adjust the mass percentage (B) of the first cationic salt relative to the electrolyte salt in the electrolyte. This allows the concentration of the first cation in the electrolyte to better match the first positive electrode active material's need to appropriately reduce its utilization, thereby achieving better overall electrical performance. This can significantly improve the thermal stability of the composite positive electrode sheet and the battery cell, reduce the risk of thermal runaway, and also facilitate the composite positive electrode sheet to have good active ion transport performance as a whole. As can be seen, the battery cell has excellent overall performance, good thermal stability, and low risk of thermal runaway.

[0017] 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 recorded as Xσ, then Xσ≥10 4 ;

[0018] Optionally, Xσ≥10 6 , further optionally Xσ≥10 10 ;

[0019] Optionally, the ionic conductivity of the first positive electrode active material at 25° C. is σ1, satisfying σ1≥3.2×10 -6 S / cm, further optionally σ1≥1.7×10 -3 S / cm;

[0020] Optionally, the ionic conductivity of the second positive electrode active material at 25° C. is σ2, satisfying σ2≤10 -9 S / cm, further optionally σ2≤10 -12 S / cm.

[0021] When the ionic conductivity of the first positive electrode active material is significantly different from that of the second positive electrode active material, 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 demand for the first positive electrode active material to appropriately reduce its utilization and the comprehensive demand for good transmission 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.

[0022] The ionic conductivity of the first positive electrode active material (lithium oxide containing Co and M1 elements) can be adjusted by adjusting the nickel (Ni) content 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.

[0023] The ionic conductivity of the second positive electrode active material (lithium oxide containing Fe and Mn) can be adjusted by adjusting the manganese (Mn) content. Generally, the higher the Mn content, the lower the ionic conductivity of the second positive electrode active material.

[0024] Based on any suitable embodiment herein, in some embodiments, 1.3≤A / B≤25.4.

[0025] By adjusting the A / B value within a more appropriate range, it is more conducive to achieving better thermal stability while effectively improving the overall performance of the battery.

[0026] Based on any suitable embodiment in this application, in some embodiments, 0.19≤A≤10.1; optionally, 0.28≤A≤2.53.

[0027] By adjusting the A value, the content ratio of the first positive electrode active material to the second positive electrode active material can be adjusted. By regulating the A value within the above range, the combined advantages of the first and second positive electrode active materials can be better utilized, achieving better electrical performance.

[0028] Based on any suitable embodiment in the present application, in some embodiments, 5%≤B≤40%; alternatively, 10%≤B≤20%.

[0029] By adjusting the B value, the mass percentage of the first cationic salt relative to the electrolyte salt can be adjusted. By regulating the B value within the above range, the concentration of the first cation in the electrolyte can be better matched to the first positive electrode active material's requirement for appropriately reducing its utilization, thereby achieving better overall battery performance.

[0030] 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:

[0031] The atomic molar ratio of Co to Li is denoted as R c , then R c Satisfy 0.05≤R c ≤0.5, optionally, 0.05≤R c ≤0.3, optionally, 0.05≤R c ≤0.2;

[0032] The atomic molar ratio of the M1 element to the Li element is recorded as R d , then R d Satisfy 0.05≤R d ≤0.5, optionally, 0.05≤R d ≤0.3;

[0033] The M1 element includes Mn element, and the atomic molar ratio of Mn element to Li element is recorded as R d-Mn , then R d-Mn Satisfy 0.05≤R d-Mn ≤0.4, further optionally, 0.05≤R d-Mn ≤0.3;

[0034] 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 recorded as R c+d , then R c+d Satisfying 0.1≤R c+d≤0.5, further optionally, 0.1≤R c+d ≤0.3, further optionally, 0.1≤R c+d ≤0.2.

[0035] The presence of the Co element is beneficial to improving the structural stability of the material. By adjusting the Co element content in the first positive electrode active material within a more appropriate range, it is more conducive to improving the charge and discharge rate performance and cycle performance of the battery.

[0036] 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 for improving the thermal stability of the first positive electrode active material; when the M1 element includes the Al element, the Al element is beneficial for increasing the capacity and thermal stability of the material, reducing the internal resistance and improving the rate performance and cycle performance.

[0037] The content ratio of the Co element and the M1 element can be adjusted as needed to balance the comprehensive effects of the Co element and the M1 element on battery performance.

[0038] Based on any suitable embodiment of the present application, in some embodiments, the first positive electrode active material further comprises 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 Satisfy 0.5≤R b <1;

[0039] Optionally, 0.5≤R b ≤0.9;

[0040] Further optionally, 0.6≤R b ≤0.9;

[0041] Further optionally, 0.65≤R b ≤0.9;

[0042] Further optionally, 0.8≤R b ≤0.9.

[0043] When the first positive electrode active material contains the element Ni, it is beneficial to give the first positive electrode active material a 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 the more beneficial it is to improve the ionic conductivity; however, when the first positive electrode active material is highly utilized, the risk of damage to the surface structure of the first positive electrode active material or even structural collapse is greater. At this time, by introducing the first cation and adjusting the A / B value, the thermal stability of the composite positive electrode sheet is more significantly improved.

[0044] 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 demand of the first positive electrode active material for appropriately reducing the utilization rate, thereby achieving a better match of the overall comprehensive performance of the battery and a higher energy density. It can significantly improve the thermal stability of the composite positive electrode sheet and the battery cell, reduce the risk of thermal runaway, and is beneficial for the composite positive electrode sheet as a whole to have good active ion transport performance.

[0045] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a The first positive electrode active material satisfies one or more of the following characteristics:

[0046] Atomic molar equivalent of Co element Q c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2;

[0047] The atomic molar equivalent Q of the M1 element d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3;

[0048] The M1 element includes a Mn element, and the atomic molar equivalent of the Mn element is ≤0.4. Optionally, the atomic molar equivalent of the Mn element is ≤0.3;

[0049] The sum of the atomic molar equivalents of Co element and the M1 element Q c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d ≤0.3, Q c+d ≤0.2.

[0050] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and further optionally 1, the first positive active material comprises Ni element, the atomic molar equivalent of Ni element Q b Satisfy 0.5≤Q b <1, optionally, 0.6≤Q b <1, further optionally, 0.65≤Q b <1.

[0051] When the Li element in the first positive electrode active material has a certain atomic molar equivalent, the adjustment of the content of the corresponding elements can be achieved by adjusting the atomic molar equivalents of the Co element, the M1 element and the Ni element.

[0052] Based on any suitable implementation manner in the present application, in some implementation manners, the first positive electrode active material includes a first body, and may further include or 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;

[0053] Optionally, 0.8 ≤ a ≤ 1.2, further optionally, 0.9 ≤ a ≤ 1.1, further optionally, 0.95 ≤ a ≤ 1.05;

[0054] Optionally, 0.5 ≤ b < 1, further optionally, 0.5 ≤ b ≤ 0.9, still further optionally, 0.6 ≤ b ≤ 0.9; <​​​​​​​​​​​​​​​

[0060] 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:

[0061] The atomic molar ratio of the Mn element to the Fe element is 0.42 to 9, and optionally, the atomic molar ratio of the Mn element to the Fe element is 0.66 to 4;

[0062] Based on the atomic molar equivalent of the Li element being 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, the atomic molar equivalent of the Mn element is 0.5 to 0.999, and optionally 0.5 to 0.6;

[0063] The atomic molar equivalent of the Li element is 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, and the atomic molar equivalent of the Fe element is 0.001 to 0.5, optionally 0.4 to 0.5.

[0064] Increasing the Mn content in the second positive electrode active material is beneficial for improving the energy density, voltage platform, and material cost of the second positive electrode active material. By controlling the Mn content within the above range, it is beneficial to maximize the effect of the Mn element while also facilitating the formation of a uniform solid solution. It can also minimize or avoid defects and pores, thereby reducing or avoiding defects and pores that extend the insertion and migration paths of active ions. Therefore, by controlling the Mn content within the above range, it is beneficial for the second active material to have a good ion migration rate, shortening the difference in active ion conductivity between the second positive electrode active material and the first positive electrode active material, thereby reducing the probability of overutilization and delithiation of the first positive electrode active material, and further improving the thermal stability of the composite positive electrode sheet.

[0065] In the second positive electrode active material, the introduction of Fe element is conducive to achieving better ion transport and higher ion conductivity, and is also conducive to promoting the embedding and extraction of active ions, thereby improving the battery charge and discharge efficiency and energy density.

[0066] When the Li element in the second 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 the Fe element and the Mn element.

[0067] 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 located on at least a portion 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 M3y P 1-z Q z O4, wherein -0.1≤x≤0.1, 0.1≤w≤0.5, 0.001≤y≤0.5, and 0.001≤z≤0.1, the M3 element in the second active material includes one or more elements selected from the group consisting of 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 the group consisting of B, Si, N, S, F, Cl, and Br;

[0068] Optionally, 0.1≤y≤0.5, further optionally, 0.2≤y<0.5, further optionally, 0.3≤y<0.5;

[0069] Optionally, 0.2≤w≤0.5, further optionally, 0.3≤w<0.5, further optionally, 0.4≤w<0.5;

[0070] Optionally, 0.001≤z≤0.1, further optionally, 0.001≤z<0.05, further optionally, 0.001≤z<0.002;

[0071] Optionally, the M3 element in the second active material includes one or more elements selected from the group consisting of Ti, V, Ni, Co, and Mg;

[0072] Optionally, the Q element in the second active material includes one of B, Si, N and S;

[0073] Optionally, the second coating layer comprises one or more of pyrophosphate, phosphate and carbon;

[0074] Optionally, the second coating layer is a single-layer structure or a multi-layer structure.

[0075] Based on any suitable embodiment of the present application, in some embodiments, the total mass proportion of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer is R I+II ≥85%;

[0076] Optionally, R I+II ≥90%; further optionally, R I+II ≥95%.

[0077] 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.

[0078] Based on any suitable embodiment in the present application, in some embodiments, the first cation includes cations of one or more elements selected from alkali metal elements and alkaline earth metal elements;

[0079] Optionally, the first cation includes one or more of sodium ions, potassium ions, calcium ions and magnesium ions;

[0080] Optionally, the anion in the first cationic salt includes 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;

[0081] Further optionally, the first cationic salt comprises 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;

[0082] Further optionally, the first cationic salt includes one or two of sodium hexafluorophosphate, sodium tetrafluoroborate and sodium perchlorate.

[0083] When the first cation has a larger ionic radius than a lithium ion, the type of first cation and the corresponding anion can be flexibly selected. As a non-limiting example, sodium hexafluorophosphate is low-cost and can be used on a large scale. The smaller radius difference between sodium ions and lithium ions makes it more suitable for embedding into the active material.

[0084] Based on any suitable embodiment of the present application, in some embodiments, the negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; the mass percentage of the silicon-based material in the negative electrode active material is recorded as X1,

[0085] Optionally, X1 ≥ 3%, further optionally 3% ≤ X1 ≤ 50%;

[0086] 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.

[0087] When the negative electrode active material layer of the negative electrode plate includes a silicon-based material, it is beneficial to further improve the energy density of the battery cell.

[0088] 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.

[0089] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0090] In a 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.

[0091] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] In order to better describe and illustrate the embodiments, examples, or examples of the applications disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed applications, the embodiments, examples, or examples currently described, and the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same parts. In the drawings:

[0093] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0094] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0095] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0096] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0097] FIG5 is an exploded view of the battery pack shown in FIG4 according to an embodiment of the present application.

[0098] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0099] Description of reference numerals:

[0100] 1 is the battery pack; 2 is the upper box; 3 is the lower box; 4 is the battery module; 5 is the battery cell; 51 is the shell; 52 is the electrode assembly; 53 is the cover plate; 6 is the electrical device. DETAILED DESCRIPTION

[0101] Below, some embodiments and examples of the battery cells, secondary batteries, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same 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 described in the claims.

[0102] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0103] In this application, "a plurality of", "multiple", "multiple", "several", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or greater than or equal to (≥, greater than or equal to) two.

[0104] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0105] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0106] Those skilled in the art will appreciate that, in the method for each embodiment or embodiment, the writing order of each step does not mean a strict execution order and constitutes any limitation to the implementation process, and the detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the application can be performed in sequence, or can be performed randomly, or can preferably be performed in sequence. For example, method M includes steps (a) and (b), indicating that method M may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, method M may also include step (c), indicating 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 include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0107] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include additional members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3," and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0108] In this application, unless otherwise specified, 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.

[0109] In this application, "optionally," "optional," and "optional" mean optional, that is, they refer to either option selected from the two parallel options of "yes" or "no." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" is independent. Unless otherwise specified, the descriptions "optionally include," "optionally include," etc. in this application, using "optionally include" as an example, mean "may include or not include."

[0110] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more relevant listed items, and also include any and all combinations of the relevant listed items, wherein the arbitrary and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. For example, "A and / or B" means a group consisting of A, B, and "a combination of A and B." Among them, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be appropriately understood according to the sentence in which it is located.

[0111] As used herein, "combination thereof", "any combination thereof", "any combination thereof" and the like include all suitable combinations of any two or more of the listed items.

[0112] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the technical solution that can implement the present application.

[0113] Herein, the terms "preferred," "better," "more preferable," "suitable," "comparatively better," and "preferable" are used solely to describe preferred implementations or examples and should not be construed as limiting the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, each "preferred" term is considered independent unless otherwise specified and there are no contradictions or mutual constraints.

[0114] In this application, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0115] In this application, the terms "first," "second," and "third," etc., in "the first aspect," "the second aspect," "the third aspect," etc., are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, "first," "second," and "third," etc., are only used for non-exhaustive enumeration and description purposes and should be understood not to constitute closed-ended limitations on quantity.

[0116] In this application, the term "room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this application, room temperature refers to 20°C to 30°C.

[0117] In this application, when referring to a data range, if the unit is followed only by the right endpoint, it means that the units of the left and right endpoints are the same. For example, "3~5h" or "3-5h" both mean that the units of the left endpoint "3" and the right endpoint "5" are both hours, and both have the same meaning as "3h~5h". Similarly, descriptions of other parameters such as temperature and size are to be understood in the same manner.

[0118] In this application, unless otherwise specified, "approximate number" covers the number itself and its approximate value within a reasonable fluctuation range based on the number. The reasonable fluctuation range may vary depending on the type and value of the number.

[0119] The weight of the relevant components mentioned in the embodiment of the present application or the examples can not only refer to the content of each component, but also represent the proportional relationship of the weight between the components. Therefore, as long as the content of the relevant components in accordance with the embodiment of the present application or the examples is proportionally enlarged or reduced, it is within the scope described in the present application. Further, the mass involved in the embodiment of the present application or the examples can be mass units known to the chemical industry such as micrograms (μg), milligrams (mg), grams (g), kilograms (kg). Unless otherwise specified, the mass ratio is equal to the corresponding weight ratio, such as the mass of substance A is m1 and the weight is W1, the mass of substance B is m2 and the weight is W2, then the mass ratio m1 / m2 of the two is numerically equal to the corresponding weight ratio W1 / W2.

[0120] In this application, unless otherwise specified, wt% represents weight percentage by weight, which is numerically equal to the corresponding mass percentage by mass.

[0121] In this application, "greater than or equal to", "greater 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 providing two solutions of "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be regarded as providing two solutions of "less than" and "equal to".

[0122] In this application, if there is no other indication, the unit of parameter is ℃, which means "degrees Celsius", the unit of time is min, which means "minute", the unit of length is μm, which means "micrometer", the unit of viscosity is mPa·s, which means "milliPascal·second", and the unit of surface density is mg / cm 2 Indicates "milligrams per square centimeter", volume density unit g / cm 3Both mean "grams per cubic centimeter", the amount of substance unit mol means "mole", the molar concentration unit mol / L means "mole per liter", and the conductivity unit S / cm means "Siemens per centimeter".

[0123] In this application, exemplary descriptions such as "in some embodiments (or examples)" and "in one embodiment (or example)" may include but are not limited to the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0124] In this application, reference to "based on any suitable embodiment in this application, in some embodiments," or similar exemplary descriptions may include but not be limited to the following meanings: these solutions can be combined with each other in a suitable manner to form new technical solutions.

[0125] In order to improve the overall electrical performance of the battery, it is possible to consider setting different positive electrode active materials in the positive electrode active material layer of the positive electrode sheet. For example, in theory, at least two positive electrode active materials can be set in the hope of achieving complementary advantages of different positive electrode active materials. Non-limitingly, for example, when a positive electrode active material with high energy density is used in combination with a positive electrode active material with a better voltage platform and lower manufacturing cost, it is expected that the corresponding positive electrode sheet can have both high energy density, better voltage platform and lower manufacturing cost. However, positive electrode active materials with different properties often have different activities and ionic conductivities, which leads to different utilization levels of different positive electrode active materials under charge and discharge cycles. If the ionic conductivities of different positive electrode active materials differ too much, one of the positive electrode active materials will be overutilized, which can easily cause the surface structure of the positive electrode active material to be damaged and release oxygen, and may even cause the material structure to collapse, posing a risk of thermal runaway of the battery. In addition, the released oxygen may also trigger electrolyte side reactions.

[0126] The present application provides at least one battery cell, a secondary battery, and an electrical device.

[0127] In some embodiments, the battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode active material layer in the positive electrode sheet includes a first positive electrode active material and a second positive electrode active material. The electrolyte salt in the electrolyte includes a first cationic salt. The first positive electrode active material is a lithium oxide containing Co and M1, where M1 includes one or both of Mn and Al. The second positive electrode active material is a lithium oxide containing Fe and Mn. The mass ratio of Co in the first positive electrode active material to Fe in the second positive electrode active material is A. The first cationic salt includes a first cation having an ionic radius larger than that of a 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 excellent electrical performance and thermal stability, with a low risk of thermal runaway.

[0128] In this application, unless otherwise specified, "battery cell" refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy. Generally, a battery cell 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 released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0129] In this application, unless otherwise specified, the electrode plate can be a positive electrode plate or a negative electrode plate, and the "active material" in the electrode plate refers to a substance that can reversibly embed and release active ions. Unless otherwise specified, "negative electrode active material" refers to a substance used for the negative electrode plate that can reversibly embed and release active ions; "positive electrode active material" refers to a substance used for the positive electrode plate that can reversibly release and embed active ions. When the secondary battery is charged, the active ions are released from the positive electrode and embedded in the negative electrode through the electrolyte; when the secondary battery is discharged, the active ions are released from the negative electrode and embedded in the positive electrode. The active ions are not particularly limited and are non-restrictive. The active ions can be lithium ions, which corresponds to a lithium-ion secondary battery.

[0130] In this application, "electrode active material", "electrode active substance", "active material" and "active substance" have the same meaning and can be used interchangeably; "positive electrode active substance" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative electrode active substance" and "negative electrode active material" have the same meaning and can be used interchangeably. "Positive electrode active substance" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative electrode active substance" and "negative electrode active material" have the same meaning and can be used interchangeably.

[0131] In this application, unless otherwise specified, an "electrode active material layer" includes at least one of the positive electrode active material layer of a positive electrode sheet and the negative electrode active material layer of a negative electrode sheet. Depending on the specific circumstances, the electrode active material layer may refer to either the positive electrode active material layer or the negative electrode active material layer. It is understood that the positive electrode active material layer contains a positive electrode active substance, and the negative electrode active material layer contains a negative electrode active substance. In this application, an "electrode active material layer" may also be simply referred to as an "active material layer."

[0132] In a first aspect of the present application, a battery cell is provided, which includes a positive electrode plate and an electrolyte; in the positive electrode active material layer of the positive electrode plate, 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 cationic salt in the electrolyte includes a first cation having an ionic radius greater than that of a lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is B; 0.47≤A / B≤202.

[0133] In some embodiments, a battery cell is provided, comprising a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, and the electrolyte salt comprises a first cationic salt;

[0134] The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements;

[0135] 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;

[0136] The first cationic salt includes a first cation, the ionic radius of the first cation is larger than the ionic radius of the lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is denoted as B;

[0137] Optionally, 0.47≤A / B≤202.

[0138] In the present application, the first positive electrode active material and the second positive electrode active material are two different positive electrode active materials in the positive electrode active material layer.

[0139] It can be understood that when the positive electrode plate includes the first positive electrode active material and the second positive electrode active material, the active ions in the battery cell include lithium ions.

[0140] In some embodiments, the electrolyte salt includes a first cation salt and an electrolyte lithium salt. The electrolyte lithium salt facilitates the conduction of active lithium ions.

[0141] In some embodiments, a battery cell is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, the electrolyte salt comprises a first cation salt and an electrolyte lithium salt;

[0142] The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements;

[0143] 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;

[0144] The first cationic salt includes a first cation, the ionic radius of the first cation is larger than the ionic radius of the lithium ion; the mass percentage of the first cationic salt in the electrolyte salt is denoted as B;

[0145] Then A and B satisfy 0.47≤A / B≤202.

[0146] The positive electrode sheet in this battery cell is a composite positive electrode sheet, which is provided with different positive electrode active materials. The composite positive electrode sheet includes a first positive electrode active material containing cobalt (Co) and M1, the M1 element including one or both of manganese (Mn) and aluminum (Al), and a second positive electrode active material containing iron (Fe) and Mn. Although the composite positive electrode sheet design can theoretically complement the advantages of different positive electrode active materials, it is hoped that it can improve the overall electrical performance in aspects such as material structure stability, battery safety, rate performance, and cycle performance, while taking into account the voltage platform and manufacturing cost. However, lithium oxide containing Co and M1 elements and lithium oxide containing Fe and Mn elements are different positive electrode active materials, and have different activities and ionic conductivities, resulting in different degrees of utilization during the charge and discharge cycle. Among them, lithium oxide containing Co and M1 elements is easily over-utilized, causing damage to the surface structure of the first positive electrode active material and releasing oxygen, and may even cause the material structure to collapse, posing a risk of thermal runaway of the battery; in addition, the released oxygen may also trigger side reactions in the electrolyte. The active ion diffusion in the composite positive electrode plate design is presumably one-dimensional channel diffusion. By introducing a first cationic salt, a first cation with an ion radius larger than that of lithium (Li) ions is introduced. The first cation can replace part of the active ions and be embedded in the first positive electrode active material, blocking the active ion diffusion channel in the first positive electrode active material, reducing the utilization 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, hindering the removal of active ions during discharge, further increasing the stability of oxygen on the surface of the positive electrode active material, and reducing oxygen release. The first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, and reduce the risk of thermal runaway. Furthermore, by adjusting the mass ratio A (also denoted as I) of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material, the first cation can improve the thermal stability of the composite positive electrode plate and the battery cell, and reduce the risk of thermal runaway. Co / II Fe The ratio of the first positive electrode active material to the second positive electrode active material can be adjusted. Furthermore, the A / B value can be used to collaboratively adjust the mass percentage (B) of the first cationic salt relative to the electrolyte salt in the electrolyte. This allows the concentration of the first cation in the electrolyte to better match the first positive electrode active material's need to appropriately reduce its utilization, thereby achieving better overall electrical performance. This can significantly improve the thermal stability of the composite positive electrode sheet and the battery cell, reduce the risk of thermal runaway, and also facilitate the composite positive electrode sheet to have good active ion transport performance as a whole. As can be seen, the battery cell has excellent overall performance, good thermal stability, and low risk of thermal runaway.

[0147] In this application, unless otherwise specified, the elemental composition and chemical composition of the positive electrode sheets, negative electrode sheets and electrolyte in battery cells and secondary batteries can be tested using existing technologies in the art, including but not limited to inductively coupled plasma (ICP) methods.

[0148] Without limitation, for the positive electrode active material in the positive electrode sheet, or the negative electrode active material in the negative electrode sheet, an energy dispersive spectrometer (EDS), an inductively coupled plasma (ICP) method and the like can be used for testing and analysis. EDS can be used to identify different types of active materials, and ICP can be used to perform quantitative testing and analysis of the component content. The active material sample can be extracted from the electrode sheet, and the 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 inductively coupled plasma optical emission spectrometry (ICP-OES). EDS testing can be used to obtain a two-dimensional image with different color markings for different components, and different particles corresponding to different active materials can be distinguished according to the type of component and the aggregation mode. For example, the positive electrode active material layer can be digested with a reagent (such as nitric acid, perchloric acid, etc.), and the chemical composition of the positive electrode active material can be tested by inductively coupled plasma optical emission spectrometry. For another example, a reagent (such as aqua regia, reverse aqua regia, a combination of aqua regia and hydrogen fluoride, etc.) can be used to digest the negative electrode active material layer, and the chemical composition of the negative electrode active material can be tested by inductively coupled plasma optical emission spectrometry.

[0149] According to the chemical composition and elemental analysis results of the positive electrode active material in the positive electrode sheet, the content of each element in the first positive electrode active material and the second positive electrode active material can be identified, the total mass proportion of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer can be calculated, and the mass ratio (A) of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material can also be calculated. The element content relationship described in the context can also be tested, such as the R in the first positive electrode active material. 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 Wait, like 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 value of each element subscript, such as the ratio of the atomic molar equivalent of the Mn element and the Fe element in the second positive electrode active material (which can be recorded as R2 Mn / Fe ), Li 1+x Mn 1-y-w Fe w M3 y P 1-z Q z The composition of M3 elements in O4 and the numerical values ​​of each element's subscripts, etc.

[0150] 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 whether it contains silicon-based materials can be determined. If contained, the type and composition of the silicon-based materials and their mass percentage in the negative electrode active material (which can be recorded as X1) can also be determined.

[0151] The electrolyte salt in the electrolyte can be quantitatively tested based on GB / T36240-2018 and an ion chromatograph. According to the identified cation types in the electrolyte and the atomic number of the element, it can be determined whether there is a first cation with an ionic radius larger than that of a lithium ion in the electrolyte. If so, it can also be determined what types of first cations are present. According to the quantitative test analysis results of the electrolyte salt, the composition of the electrolyte salt in the electrolyte and the content of different electrolyte salts can be determined. Since the cations and anions in the electrolyte are in a free state and can migrate, they are not limited to the cation and anion coordination mode when the electrolyte salt is added, but the electrolyte system as a whole maintains charge balance. Therefore, in this application, unless otherwise specified, the mass percentage of the first cation salt in the electrolyte salt (denoted as B) is calculated as "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 B value can be numerically equal to "the mass of the first cation in the electrolyte relative to the mass of the metal cation in the electrolyte". For another example, when the cations contained in the electrolyte salt in the electrolyte consist of lithium ions and first cations, the B value may be numerically equal to "the percentage of the mass of the first cations in the electrolyte relative to the total mass of the first cations and lithium ions."

[0152] Unless otherwise specified, generally, the cations in the electrolyte salt are metal cations.

[0153] In some embodiments, a battery cell is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, the electrolyte salt comprises a first cationic salt and an electrolyte lithium salt; the electrolyte salt comprises a cation and an anion, and the cation in the electrolyte salt is a metal cation;

[0154] The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements;

[0155] 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;

[0156] The first cationic salt includes a first cation, the ionic radius of the first cation is larger than the ionic radius 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 recorded as B;

[0157] At this time, A and B satisfy 0.47≤A / B≤202.

[0158] In some embodiments, the battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode active material layer in the positive electrode sheet includes a first positive electrode active material and a second positive electrode active material. The electrolyte salt in the electrolyte includes a metal cation, wherein the metal cation includes a first cation. The first positive electrode active material is a lithium oxide containing Co and M1, wherein M1 includes one or both of Mn and Al. The second positive electrode active material is a lithium oxide containing Fe and Mn. The mass ratio of Co in the first positive electrode active material to Fe in the second positive electrode active material is A. The ionic radius of the first cation is greater than the ionic radius of the lithium ion. The mass percentage of the first cation relative to the metal cation in the electrolyte salt is denoted as B'. 0.47≤A / B'≤202. This battery cell has excellent electrical performance and thermal stability, with a low risk of thermal runaway.

[0159] In some embodiments, a battery cell is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, the electrolyte salt comprises a metal cation and an anion, the metal cation comprises a first cation and a lithium ion;

[0160] The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements;

[0161] 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;

[0162] The ionic radius of the first cation is greater than the ionic radius of the lithium ion;

[0163] The mass percentage of the first cation relative to the metal cation in the electrolyte salt is recorded as B';

[0164] Then A and B satisfy 0.47≤A / B'≤202.

[0165] In this application, the values ​​of B' and their value ranges and the values ​​of A / B' and their value ranges can refer to the values ​​of B and their value ranges and the values ​​of A / B and their value ranges, respectively. 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 values ​​and value ranges of B in the context of this application can be applied to B', and the definitions of the values ​​and value ranges of A / B in the context of this application can be applied to A / B'.

[0166] 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 recorded 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 an interval consisting of 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 wait.

[0167] In this application, the value aEb described in scientific notation is equivalent to a×10 b For example, 1×10 4 It can be recorded as 1E4.

[0168] In some embodiments, the ionic conductivity of the first positive electrode active material at 25° C. is σ1, satisfying σ1≥3.2×10 -6 S / cm, further optionally σ1≥1.7×10 -3 S / cm. Without limitation, the ionic conductivity σ1 of the first positive electrode active material at 25°C may 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 an interval consisting of any two of the following values ​​(which may 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 -5S / 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, σ1 can also be selected from any of the following ranges: 1×10 -3 S / cm~3×10 -3 S / cm, 3×10 -3 S / cm~5×10 -3 S / cm, 5×10 -3 S / cm~7×10 -3 S / cm, 7×10 -3 S / cm~9×10 -3 S / cm, 3.2×10 -6 S / cm~1×10 -3 S / cm, 1×10 -3 S / cm<σ1<3×10 -3 S / cm, 3×10 -3 S / cm<σ1<5×10 -3 S / cm, 5×10 -3 S / cm<σ1<7×10 -3 S / cm, 7×10 -3 S / cm<σ1<9×10 -3 S / cm, 3.2×10 -6 S / cm<σ1<1×10 -3 S / cm, etc.

[0169] In some embodiments, the ionic conductivity of the second positive electrode active material at 25° C. is σ2, satisfying σ2≤10 -9S / cm, further optionally σ2≤10 -12 S / cm. Without limitation, the ionic conductivity σ2 of the second positive electrode active material at 25°C may 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 an interval consisting of any two of the following values ​​(which may 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, etc.

[0170] In this application, unless otherwise specified, "ionic conductivity" refers to the ionic conductivity when the active ions are lithium ions. Without limitation, σ2 can also be selected from any of the following ranges: 3×10 -13 S / cm~9×10 -13 S / cm, 1×10 -13 S / cm~3×10 -13 S / cm, 3×10 -13 S / cm<σ2<9×10 -13 S / cm, 1×10 -13 S / cm<σ2<3×10-13 S / cm, etc.

[0171] 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 positive electrode active materials in the positive electrode active material layer:

[0172] The positive electrode active material to be tested is made into a positive electrode plate for testing, and the lithium plate is used as the negative electrode plate, and then assembled into a button battery for testing; the battery is discharged to 3.0V at 1C and then subjected to AC impedance spectroscopy test. The test parameters are selected as follows: the test temperature is room temperature (such as 25℃), the scanning frequency is 0.1Hz~10 5 Hz, the voltage amplitude is 5mV, and the test results are fitted using Zview software to obtain the ionic conductivity.

[0173] Unless otherwise specified, the positive electrode sheet used in the test was made of aluminum foil as the positive current collector, the mass percentage of the positive active material in the positive active material layer was controlled at 95% ± 1%, polyvinylidene fluoride (PVDF) was used as the binder, conductive carbon was used as the conductive agent, and the compaction density was 3.0 g / cm 3 ~3.6g / cm 3 .

[0174] For the positive active material in the electrode plate, battery cell or secondary battery, a positive active material with the same chemical composition can be prepared according to the component analysis results and used as the positive active material to be tested, and its ion conductivity can be tested using the above method.

[0175] When the ionic conductivity of the first positive electrode active material is significantly different from that of the second positive electrode active material, 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 demand for the first positive electrode active material to appropriately reduce its utilization and the comprehensive demand for good transmission 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.

[0176] The ionic conductivity of the first positive electrode active material (lithium oxide containing Co and M1 elements) can be adjusted by adjusting the nickel (Ni) content 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.

[0177] The ionic conductivity of the second positive electrode active material (lithium oxide containing Fe and Mn) can be adjusted by adjusting the manganese (Mn) content. Generally, the higher the Mn content, the lower the ionic conductivity of the second positive electrode active material.

[0178] In some embodiments, 0.47≤A / B≤202. Without limitation, A / B can also be any of the following values, or an interval consisting of 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, 1 5, 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.

[0179] Based on any suitable embodiment herein, in some embodiments, 1.3≤A / B≤25.4.

[0180] By adjusting the A / B value within a more appropriate range, it is more conducive to achieving better thermal stability while effectively improving the overall performance of the battery.

[0181] Based on any suitable embodiment in the present application, in some embodiments, 0.19≤A≤10.1; alternatively, 0.28≤A≤2.53. Without limitation, A can also be any of the following values, or an interval consisting of 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, 0.01, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2 .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.

[0182] By adjusting the A value, the content ratio of the first positive electrode active material to the second positive electrode active material can be adjusted. By regulating the A value within the above range, the combined advantages of the first and second positive electrode active materials can be better utilized, achieving better electrical performance.

[0183] Based on any suitable embodiment in the present application, in some embodiments, 5% ≤ B ≤ 40%; alternatively, 10% ≤ B ≤ 20%. Without limitation, B can also be any of the following percentages, or an interval consisting of 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.

[0184] By adjusting the B value, the mass percentage of the first cationic salt relative to the electrolyte salt can be adjusted. By regulating the B value within the above range, the concentration of the first cation in the electrolyte can be better matched to the first positive electrode active material's requirement for appropriately reducing its utilization, thereby achieving better overall battery performance.

[0185] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of the Co element to the Li element can be recorded as R c , R c Satisfy 0.05≤R c ≤0.5, optionally, 0.05≤R c ≤0.3, optionally, 0.05≤R c ≤0.2. Without limitation, R c It can also be any of the following values, or an interval consisting of 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.

[0186] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of the Co element to the oxygen (O) element can be recorded as R Co / O , R Co / O Satisfy 0.025≤R Co / O ≤0.25, optionally, 0.025≤R Co / O ≤0.15, optionally, 0.025≤R Co / O ≤0.1. Without limitation, R Co / OIt can also be any of the following values, or an interval consisting of any two of the following values: 0.025, 0.03, 0.035, 0.04, 0.045, 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, etc.

[0187] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the ratio of the sum of the atomic molar ratios of the Co element to the non-lithium metal element can be recorded as R Co / all , R Co / all Satisfy 0.05≤R Co / all ≤0.5, optionally, 0.05≤R Co / all ≤0.3, optionally, 0.05≤R Co / all ≤0.2. Without limitation, R Co / all It can also be any of the following values, or an interval consisting of 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.

[0188] In this application, unless otherwise specified, “non-lithium metal elements” refer to metal elements other than lithium.

[0189] The types of elements in the positive electrode active material to be tested can be obtained according to the elemental analysis method, and then the atomic molar ratio between different elements can be calculated in combination with the relative atomic masses of different elements.

[0190] The presence of the Co element is beneficial to improving the structural stability of the material. By adjusting the Co element content in the first positive electrode active material within a more appropriate range, it is more conducive to improving the charge and discharge rate performance and cycle performance of the battery.

[0191] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of the M1 element to the Li element can be recorded as R d , R d Satisfy 0.05≤R d ≤0.5, optionally, 0.05≤R d ≤0.3. Without limitation, R dIt can also be any of the following values, or an interval consisting of 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. d It can also be any of the following ranges: R d ≤0.2、0.05≤R d ≤0.2, etc.

[0192] In this application, unless otherwise specified, the atomic molar ratio of the M1 element to the O element in the first positive electrode active material can be expressed as R M1 / O , R M1 / O Satisfy 0.025≤R M1 / O ≤0.25, optionally, 0.025≤R M1 / O ≤0.15. Without limitation, R M1 / O It can also be any of the following values, or an interval consisting of any two of the following values: 0.025, 0.03, 0.035, 0.04, 0.045, 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, etc. M1 / O It can also be any of the following ranges: R M1 / O ≤0.1、0.025≤R M1 / O ≤0.1, etc.

[0193] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of the M1 element to the non-lithium metal element can be recorded as R M1 / all , R M1 / all Satisfy 0.05≤R M1 / all ≤0.5, optionally, 0.05≤R M1 / all ≤0.3. Without limitation, R M1 / allIt can also be any of the following values, or an interval consisting of 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. M1 / all It can also be any of the following ranges: R M1 / all ≤0.2、0.05≤R M1 / all ≤0.2, etc.

[0194] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, 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 , optionally, R d-Mn Satisfy 0.05≤R d-Mn ≤0.4, further optionally, 0.05≤R d-Mn ≤0.3. Without limitation, R d-Mn It can also be any of the following values, or an interval consisting of 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, etc.

[0195] In this application, unless otherwise specified, the atomic molar ratio of the Mn element to the O element in the first positive electrode active material is denoted as R Mn / O , optionally, R Mn / O Satisfy 0.025≤R Mn / O ≤0.2, further optionally, 0.025≤R Mn / O ≤0.15. Without limitation, R Mn / O It can also be any of the following values, or an interval consisting of any two of the following values: 0.025, 0.03, 0.035, 0.04, 0.045, 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, 0.19, 0.2, etc.

[0196] Based on any suitable embodiment of the present application, in some embodiments, the atomic molar ratio of the Mn element to the non-lithium metal element is recorded as R Mn / all , optionally, R Mn / all Satisfy 0.05≤R Mn / all ≤0.4, further optionally, 0.05≤R Mn / all ≤0.3. Without limitation, R Mn / all It can also be any of the following values, or an interval consisting of 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, etc.

[0197] 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 for improving the thermal stability of the first positive electrode active material; when the M1 element includes the Al element, the Al element is beneficial for increasing the capacity and thermal stability of the material, reducing the internal resistance and improving the rate performance and cycle performance.

[0198] Based on any suitable embodiment of 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 recorded as R c+d , R c+d Satisfying 0.1≤R c+d ≤0.5, further optionally, 0.1≤R c+d ≤0.3, further optionally, 0.1≤R c+d ≤0.2. Without limitation, R c+d It can also be any of the following values, or an interval consisting of any two of the following 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.

[0199] Based on any suitable embodiment of 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 O element is recorded as R(Co+M1) / O , R (Co+M1) / O Satisfy 0.05≤R (Co+M1) / O ≤0.25, further optionally, 0.05≤R (Co+M1) / O ≤0.15, further optionally, 0.05≤R (Co+M1) / O ≤0.1. Without limitation, R (Co+M1) / O It can also be any of the following values, or an interval consisting of any two of the following values: 0.05, 0.06, 0.07, 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, etc.

[0200] Based on any suitable embodiment of 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 non-lithium metal element is recorded as R (Co+M1) / all , R (Co+M1) / all Satisfying 0.1≤R (Co+M1) / all ≤0.5, further optionally, 0.1≤R (Co+M1) / all ≤0.3, further optionally, 0.1≤R (Co+M1) / all ≤0.2. Without limitation, R (Co+M1) / all It can also be any of the following values, or an interval consisting of any two of the following 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.

[0201] The content ratio of the Co element and the M1 element can be adjusted as needed to balance the comprehensive effects of the Co element and the M1 element on battery performance.

[0202] 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:

[0203] The atomic molar ratio of Co to Li is denoted as R c , then R c Satisfy 0.05≤R c ≤0.5, optionally, 0.05≤R c ≤0.3, optionally, 0.05≤R c ≤0.2(R cIt can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0204] The atomic molar ratio of M1 element to Li element is denoted as R d , then R d Satisfy 0.05≤R d ≤0.5, optionally, 0.05≤R d ≤0.3(R d It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0205] M1 elements include Mn elements, and the atomic molar ratio of Mn elements to Li elements is recorded as R d-Mn , then R d-Mn Satisfy 0.05≤R d-Mn ≤0.4, further optionally, 0.05≤R d-Mn ≤0.3(R d-Mn It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0206] The ratio of the sum of the atomic molar equivalents of Co and M1 to the atomic molar equivalent of Li is denoted as R. c+d , then R c+d Satisfying 0.1≤R c+d ≤0.5, further optionally, 0.1≤R c+d ≤0.3, further optionally, 0.1≤R c+d ≤0.2(R c+d It can also be selected from the numerical values ​​or ranges in any suitable embodiment of the present application).

[0207] 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:

[0208] The atomic molar ratio of Co to Li is denoted as R c , then R c Satisfy 0.05≤R c ≤0.5, optionally, 0.05≤R c ≤0.3, optionally, 0.05≤R c ≤0.2(R c It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0209] The atomic molar ratio of Co to O is denoted as R Co / O , then R Co / O Satisfy 0.025≤R Co / O ≤0.25, optionally, 0.025≤R Co / O≤0.15, optionally, 0.025≤R Co / O ≤0.1(R Co / O It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0210] The ratio of the sum of the atomic molar ratios of Co element to non-lithium metal elements can be recorded as R Co / all , satisfying 0.05≤R Co / all ≤0.5, optionally, 0.05≤R Co / all ≤0.3, optionally, 0.05≤R Co / all ≤0.2(R Co / all It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0211] The atomic molar ratio of M1 element to Li element is denoted as R d , then R d Satisfy 0.05≤R d ≤0.5, optionally, 0.05≤R d ≤0.3(R d It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0212] The atomic molar ratio of M1 element to O element is denoted as R M1 / O , then R M1 / O Satisfy 0.025≤R M1 / O ≤0.25, optionally, 0.025≤R M1 / O ≤0.15(R M1 / O It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0213] The atomic molar ratio of the M1 element to the non-lithium metal element can be expressed as R M1 / all , R M1 / all Satisfy 0.05≤R M1 / all ≤0.5, optionally, 0.05≤R M1 / all ≤0.3(R M1 / all It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0214] M1 elements include Mn elements, and the atomic molar ratio of Mn elements to Li elements is recorded as R d-Mn , then R d-Mn Satisfy 0.05≤R d-Mn ≤0.4, further optionally, 0.05≤R d-Mn ≤0.3(R d-Mn It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0215] M1 elements include Mn elements, and the atomic molar ratio of Mn elements to O elements is recorded as R Mn / O , then R Mn / O Satisfy 0.025≤R Mn / O ≤0.2, further optionally, 0.025≤R Mn / O ≤0.15(R Mn / O It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0216] M1 elements include Mn elements, and the atomic molar ratio of Mn elements to non-lithium metal elements is recorded as R Mn / all , optionally, R Mn / all Satisfy 0.05≤R Mn / all ≤0.4, further optionally, 0.05≤R Mn / all ≤0.3(R Mn / all It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0217] The ratio of the sum of the atomic molar equivalents of Co and M1 to the atomic molar equivalent of Li is denoted as R. c+d , then R c+d Satisfying 0.1≤R c+d ≤0.5, further optionally, 0.1≤R c+d ≤0.3, further optionally, 0.1≤R c+d ≤0.2(R c+d It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0218] The ratio of the sum of the atomic molar equivalents of Co and M1 to the atomic molar equivalent of Li is denoted as R. (Co+M1) / O , then R (Co+M1) / O Satisfy 0.05≤R (Co+M1) / O ≤0.25, further optionally, 0.05≤R (Co+M1) / O ≤0.15, further optionally, 0.05≤R (Co+M1) / O ≤0.1(R (Co+M1) / O It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0219] The ratio of the sum of the atomic molar equivalents of Co and M1 to the atomic molar equivalent of the non-lithium metal element is recorded as R (Co+M1) / all , R (Co+M1) / all Satisfying 0.1≤R (Co+M1) / all ≤0.5, further optionally, 0.1≤R (Co+M1) / all ≤0.3, further optionally, 0.1≤R (Co+M1) / all ≤0.2(R (Co+M1) / allIt can also be selected from the numerical values ​​or ranges in any suitable embodiment of the present application).

[0220] In some embodiments, the first positive electrode active material may be a lithium oxide containing Co, M1, and Ni. In this case, the first positive electrode active material may have a layered structure, achieving high ionic conductivity within the first positive electrode active material. As a non-limiting example, lithium nickel cobalt manganese oxide and its modified forms, wherein the modified form may include one or more of doping modification and coating modification.

[0221] Based on any suitable embodiment of the present application, in some embodiments, the first positive electrode active material further comprises Ni element. In the first positive electrode active material, the atomic molar ratio of Ni element to Li element can be expressed as R b In some embodiments, R b Satisfy 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. Without limitation, 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 an interval consisting of 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.

[0222] In the present application, the atomic molar ratio of Ni element to O element in the first positive electrode active material can be expressed as R Ni / O In some embodiments, R Ni / O Satisfy 0.25≤R Ni / O <0.5, optionally, 0.25≤R Ni / O ≤0.45; further optionally, 0.3≤R Ni / O ≤0.45; further optionally, 0.325≤R b ≤0.45; further optionally, 0.4≤R Ni / O ≤0.45. Without limitation, R bIt can also be any of the following values, or greater than or equal to any of the following values ​​and less than 0.5, or an interval consisting of any two of the following values: 0.25, 0.3, 0.325, 0.35, 0.4, 0.45, 0.46, 0.47, 0.475, 0.48, 0.49, 0.495, etc.

[0223] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the atomic molar ratio of the Ni element to the non-lithium metal element can be recorded as R Ni / all In some embodiments, R Ni / all Satisfy 0.5≤R Ni / all <1, optionally, 0.5≤R Ni / all ≤0.9; further optionally, 0.6≤R Ni / all ≤0.9; further optionally, 0.65≤R Ni / all ≤0.9; further optionally, 0.8≤R Ni / all ≤0.9. Without limitation, R Ni / all 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 an interval consisting of 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.

[0224] When the first positive electrode active material contains the element Ni, it is beneficial to give the first positive electrode active material a 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 the more beneficial it is to improve the ionic conductivity; however, when the first positive electrode active material is highly utilized, the risk of damage to the surface structure of the first positive electrode active material or even structural collapse is greater. At this time, by introducing the first cation and adjusting the A / B value, the thermal stability of the composite positive electrode sheet is more significantly improved.

[0225] 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 demand of the first positive electrode active material for appropriately reducing the utilization rate, thereby achieving a better match of the overall comprehensive performance of the battery and a higher energy density. It can significantly improve the thermal stability of the composite positive electrode sheet and the battery cell, reduce the risk of thermal runaway, and is beneficial for the composite positive electrode sheet as a whole to have good active ion transport performance.

[0226] It is understandable that the battery is accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the Li content in the positive electrode plate is different when the battery is discharged to different states.

[0227] In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the Li content can be the initial state of the material or the non-initial state after charge and discharge cycles. The positive electrode active material is applied to the positive electrode plate in the battery system. After charge and discharge cycles, the Li content in the positive electrode active material contained in the positive electrode plate will usually change. Among them, the Li content can be measured using atomic molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It can be understood that new materials or new substances obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive electrode active material, and a non-limiting example is coating modification.

[0228] Understandably, test R c 、R d 、R d-Mn 、R c+d 、R b When the parameters are equal to those of Li element measurement, before extracting the sample of the positive electrode active material in the positive electrode sheet from the battery, the battery can be fully discharged first, and then the battery can be disassembled and the positive electrode sheet can be taken to obtain the sample of the positive electrode active material.

[0229] In the exemplary descriptions of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the atomic molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by atomic molar content, but is not limited to this.

[0230] For battery cells and secondary batteries containing lithium ions as active ions, the context of Q a The limitation of atomic ratios such as , a, and x may include the atomic molar content of Li under different charge and discharge states of the battery (usually the battery voltage is between 2V and 5V).

[0231] Based on any suitable embodiment of the present application, in some embodiments, in the first positive electrode active material, the "atomic molar equivalent Q of the Li element" is a ”, Q a It can be 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1. In a non-limiting manner, Q in the first positive electrode active material aIt can also be any of the following values, or an interval consisting 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. In a non-limiting manner, Q in the first positive electrode active material a It can also be any of the following values, or an interval consisting of any two of the following values: 0.75, 0.8, 0.85, 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. Q a Non-limiting examples include 0.9-1, 0.85-1, 0.8-1, 0.75-1, etc.

[0232] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a The atomic molar equivalent Q of the Co element is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and further optionally 1. c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2. Without limitation, Q c It can also be any of the following values, or less than or equal to any of the following values, or an interval consisting of any two of the following 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.

[0233] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a The atomic molar equivalent Q of the M1 element is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and further optionally 1. d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3. Without limitation, Q d It can also be any of the following values, or less than or equal to any of the following values, or an interval consisting 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, etc.

[0234] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, further optionally 1, M1 element includes Mn element, further, the atomic molar equivalent of Mn element (which can be recorded as Q1 Mn ) can satisfy ≤0.4, optionally, the atomic molar equivalent of the Mn element is ≤0.3. Without limitation, the atomic molar equivalent of the Mn element can also be any of the following values, or less than or equal to any of the following values, or selected from the interval consisting of any two of the following 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.

[0235] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a The sum of the atomic molar equivalents of the Co element and the M1 element, Q, is calculated as 0.75 to 1.2, optionally as 0.8 to 1.1, further optionally as 0.9 to 1.05, and further optionally as 1. c+d ≤0.5, optionally, Q c+d ≤0.4, Q c+d ≤0.3, Q c+d ≤0.2. Without limitation, 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 consisting 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.

[0236] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a The first positive electrode active material satisfies one or more of the following characteristics:

[0237] Atomic molar equivalent of Co element Q c ≤0.4, optionally, Q c ≤0.3, further optionally, Q c ≤0.2(Qc It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0238] Atomic molar equivalent Q of element M1 d ≤0.5, optionally, Q d ≤0.4, further optionally, Q d ≤0.3(Q d It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0239] The M1 element includes the Mn element, and the atomic molar equivalent of the Mn element is ≤0.4. Optionally, the atomic molar equivalent of the Mn element is ≤0.3 (the atomic molar equivalent of the Mn element can be recorded as Q1 Mn , can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0240] The sum of the atomic molar equivalents of Co and M1 elements 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 selected from the numerical values ​​or ranges in any suitable embodiment of the present application).

[0241] Based on any suitable embodiment in the present application, in some embodiments, the atomic molar equivalent Q of the Li element is a is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and further optionally 1. The first positive electrode active material includes Ni element, and the atomic molar equivalent of Ni element Q b Satisfy 0.5≤Q b <1, optionally, 0.6≤Q b <1, further optionally, 0.65≤Q b <1. Without limitation, Q 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 an interval consisting of 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.

[0242] 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 the Co element, the M1 element, and the Ni element.

[0243] Based on any suitable embodiment of 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.

[0244] 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.

[0245] 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.

[0246] In some embodiments, 0.8 ≤ a ≤ 1.2. Further optionally, 0.9 ≤ a ≤ 1.1. Further optionally, 0.95 ≤ a ≤ 1.05. a may also be any one of the following values, or selected from the intervals 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.

[0247] In some embodiments, 0.5≤b<1, further optionally, 0.5≤b≤0.9, and even further optionally, 0.6≤b≤0.9. 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 an interval consisting of 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.

[0248] In some embodiments, 0.05≤c<1, further optionally, 0.05≤c≤0.5, and even further optionally, 0.05≤c≤0.3. c can also be any of the following values, or an interval consisting of 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.

[0249] In some embodiments, 0.05≤d<1, further optionally, 0.05≤d≤0.5, and even further optionally, 0.05≤d≤0.3. d can also be any of the following values, or an interval consisting of 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.

[0250] In some embodiments, 0≤e<0.1, further optionally, 0≤e≤0.05, and even further optionally, 0≤e≤0.03. e can also be any of the following values, or an interval consisting of any two of the following values: 0.03, 0.035, 0.04, 0.045, 0.05, etc.

[0251] In some embodiments, 1≤f≤2.1, further optionally, 1.8≤f≤2.05, and even further optionally, 1.95≤f≤2.05. f can also be any of the following values, or an interval consisting of 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.

[0252] In some embodiments, 0≤g<0.5, further optionally, 0≤g≤0.1, and even further optionally, 0≤g≤0.05. g can also be any of the following values, or an interval consisting of 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.

[0253] 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 manganese oxide), lithium nickel cobalt aluminum oxide, and modified compounds thereof. Non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.80 Co 0.15 Al 0.05 O2.

[0254] Based on any appropriate embodiment in the present application, in some embodiments, in the second positive electrode active material, with respect to the "atomic molar equivalent of the Li element", the atomic molar equivalent of the Li element may be 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1. Without limitation, in the second positive electrode active material, the atomic molar equivalent of the Li element may also be any of the following values, or an interval consisting 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. Without limitation, in the second positive electrode active material, the atomic molar equivalent of the Li element may be any of the following values, or a range consisting of any two of the following values: 0.75, 0.8, 0.85, 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. Non-limiting examples of the atomic molar equivalent of the Li element in the second positive electrode active material include 0.9-1, 0.85-1, 0.8-1, 0.75-1, etc.

[0255] Based on any suitable embodiment of the present application, in some embodiments, in the second positive electrode active material, the atomic molar ratio of the Mn element to the Fe element (which can be recorded as R2 Mn / Fe ) is 0.42 to 9, and optionally, the atomic molar ratio of the Mn element to the Fe element is 0.66 to 4. In a non-limiting manner, R2 Mn / Fe It can also be any of the following values, or an interval consisting 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.

[0256] Based on any suitable embodiment of the present application, in some embodiments, in the second positive electrode active material, the atomic molar equivalent of the Li element is 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, and the atomic molar equivalent of the Mn element (which can be recorded as Q2 Mn ) is 0.5 to 0.999, optionally, Q2 Mn 0.5~0.6. Q2 MnIt can also be any of the following values, or an interval consisting of any two of the following 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.

[0257] Based on any suitable embodiment of the present application, in some embodiments, in the second positive electrode active material, the atomic molar equivalent of the Li element is 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, and the atomic molar equivalent of the Fe element (which can be recorded as Q2 Fe ) is 0.001 to 0.5, optionally, Q2 Fe is 0.4 to 0.5. Without limitation, Q2 Fe It can also be any of the following values, or an interval consisting of 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, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0258] 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:

[0259] The atomic molar ratio of Mn and Fe (which can be expressed as R2 Mn / Fe ) is 0.42 to 9, optionally, R2 Mn / Fe 0.66~4(R2 Mn / Fe It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0260] The atomic molar equivalent of the Li element is 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, and the atomic molar equivalent of the Mn element (which can be recorded as Q2 Mn ) is 0.5 to 0.999, optionally, Q2 Mn 0.5~0.6(Q2 Mn It can also be selected from the numerical value or range in any suitable embodiment of the present application);

[0261] The atomic molar equivalent of the Li element is 0.9 to 1.1, optionally 0.9 to 1.05, and further optionally 1, and the atomic molar equivalent of the Fe element (which can be recorded as Q2 Fe ) is 0.001 to 0.5, optionally, Q2 Fe 0.4~0.5(Q2 FeIt can also be selected from the numerical values ​​or ranges in any suitable embodiment of the present application).

[0262] Increasing the Mn content in the second positive electrode active material is beneficial for improving the energy density, voltage platform, and material cost of the second positive electrode active material. By controlling the Mn content within the above range, it is beneficial to maximize the effect of the Mn element while also facilitating the formation of a uniform solid solution. It can also minimize or avoid defects and pores, thereby reducing or avoiding defects and pores that extend the insertion and migration paths of active ions. Therefore, by controlling the Mn content within the above range, it is beneficial for the second active material to have a good ion migration rate, shortening the difference in active ion conductivity between the second positive electrode active material and the first positive electrode active material, thereby reducing the probability of overutilization and delithiation of the first positive electrode active material, and further improving the thermal stability of the composite positive electrode sheet.

[0263] In the second positive electrode active material, the introduction of Fe element is conducive to achieving better ion transport and higher ion conductivity, and is also conducive to promoting the embedding and extraction of active ions, thereby improving the battery charge and discharge efficiency and energy density.

[0264] When the Li element in the second 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 the Fe element and the Mn element.

[0265] 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 located on at least a portion 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 O4, wherein -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).

[0266] In some embodiments, the M3 element in the second active material can be selected from, but not limited to, one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Ni, Co, Ga, Sn, Sb, Nb, and Ge.

[0267] In some embodiments, the Q element in the second active material may be selected from, but not limited to, one or more elements including B, Si, N, S, F, Cl, and Br.

[0268] In some embodiments, 0.1≤y≤0.5, further optionally, 0.2≤y<0.5, and even further optionally, 0.3≤y<0.5. y may also be any of the following values, or an interval consisting of 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.

[0269] In some embodiments, 0.2≤w≤0.5, further optionally, 0.3≤w<0.5, and even further optionally, 0.4≤w<0.5. w can also be any of the following values, or an interval consisting of any two of the following values: 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0270] In some embodiments, 0.001≤z≤0.1, further optionally, 0.001≤z<0.05, and even further optionally, 0.001≤z<0.002. Without limitation, z can also be any of the following values, or an interval consisting of 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.

[0271] In some embodiments, the M3 element in the second active material includes one or more elements selected from titanium (Ti), vanadium (V), nickel (Ni), cobalt (Co), and magnesium (Mg). Furthermore, the M3 element in the second active material can be selected from, but not limited to, one or more elements selected from Ti, V, Ni, Co, and Mg.

[0272] In some embodiments, the Q element in the second active material includes one of boron (B), silicon (Si), nitrogen (N), and sulfur (S). Furthermore, the Q element in the second active material can be selected from, but not limited to, one of B, Si, N, and S.

[0273] In some embodiments, the second coating layer includes one or more of pyrophosphate, phosphate, and carbon.

[0274] In some embodiments, the second coating layer may be a single-layer structure or a multi-layer structure.

[0275] Based on any suitable embodiment of the present application, in some embodiments, the total mass ratio of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer is R I+II ≥85%; optionally, R I+II ≥90%; further optionally, R I+II ≥95%. R I+II It can also be any of the following percentages, or greater than or equal to any of the following percentages, or an interval consisting of any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc.

[0276] 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.

[0277] Based on any suitable embodiment in the present application, in some embodiments, the first cation includes a cation of one or more elements of an alkali metal element and an alkaline earth metal element. Without limitation, the first cation may include one or more of a sodium ion, a potassium ion, a calcium ion, and a magnesium ion.

[0278] Without limitation, the anion in the first cationic salt may include one or more of hexafluorophosphate ion, perchlorate ion, tetrafluoroborate ion, bistrifluoromethylsulfonyl imide ion, trifluoromethanesulfonate ion, bisfluorosulfonylimide ion, and tris(trifluoromethylsulfonyl)methyl ion.

[0279] Without limitation, the anions in the electrolyte salt may include one or more of hexafluorophosphate ion, perchlorate ion, tetrafluoroborate ion, bistrifluoromethylsulfonyl imide ion, trifluoromethanesulfonate ion, bisfluorosulfonylimide ion, and tris(trifluoromethylsulfonyl)methyl ion.

[0280] Without limitation, the first cationic salt may include one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bistrifluoromethylsulfonyl imide, sodium trifluoromethanesulfonate, sodium bisfluorosulfonyl imide, sodium tris(trifluoromethylsulfonyl)methyl, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bistrifluoromethylsulfonyl imide, potassium trifluoromethanesulfonate, potassium bisfluorosulfonyl imide, and potassium tris(trifluoromethylsulfonyl)methyl.

[0281] In some embodiments, the first cationic salt includes one or both of sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium perchlorate.

[0282] In some embodiments, the first cationic salt comprises sodium hexafluorophosphate.

[0283] When the first cation has a larger ionic radius than a lithium ion, the type of first cation and the corresponding anion can be flexibly selected. As a non-limiting example, sodium hexafluorophosphate is low-cost and can be used on a large scale. The smaller radius difference between sodium ions and lithium ions makes it more suitable for embedding into the active material.

[0284] Based on any suitable embodiment in the present application, in some embodiments, the negative electrode plate 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 recorded as X1.

[0285] In some embodiments, X1 ≥ 3%, and further optionally 3% ≤ X1 ≤ 50%. X1 can also be any of the following percentages, or an interval consisting 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.

[0286] Without limitation, the silicon-based material may include 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.

[0287] When the negative electrode active material layer of the negative electrode plate includes a silicon-based material, it is beneficial to further improve the energy density of the battery cell.

[0288] The following is some description about the positive electrode.

[0289] Without limitation, 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. The positive electrode active material layer includes a positive electrode active material. The definition of positive electrode active material can be found above. The positive electrode active material includes at least the first positive electrode active material and the second positive electrode active material described above.

[0290] In a non-limiting manner, the mass percentage of the positive electrode active material in the positive electrode active material layer may be ≥85%, further ≥90%, and further ≥95%.

[0291] Based on any suitable embodiment in the present application, in some embodiments, the percentage of the sum of the mass of the first positive electrode active material and the second positive electrode active material in the total mass of the positive electrode active material in the positive electrode active material layer may satisfy ≥85%, optionally ≥95%, further optionally ≥96%, etc., and further optionally 100%, etc. Without limitation, the percentage of the first positive electrode active material and the second positive electrode active material in the total mass of the positive electrode active material in the positive electrode active material layer may 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 an interval consisting of any two of the following percentages: 85%, 86%, 88%, 95%, 96%, 98%, 100%, etc.

[0292] In some embodiments, the positive electrode active material in the positive electrode active material layer consists of a first positive electrode active material and a second positive electrode active material.

[0293] As a non-limiting example, the positive electrode current collector has two surfaces facing away from each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0294] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, the polymer material substrate may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0295] In some embodiments, the positive electrode active material layer may further optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. The mass percentage of the binder in the positive electrode active material layer may be 0-10%, further 0-8%, and further 1%-5%.

[0296] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As non-limiting examples, 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 0-8%, and further may be 0-5%.

[0297] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry. Furthermore, the positive electrode slurry is coated on at least one surface of a positive electrode current collector. After drying and cold pressing, the positive electrode sheet can be obtained. Cold pressing can be performed using a cold rolling mill. The type of solvent can include, but is not limited to, any of the aforementioned embodiments, for example, including N-methylpyrrolidone (NMP), and further can be NMP. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 3000 mPa·s to 25000 mPa·s, and optionally 3000 mPa·s to 10000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm 2 ~35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0298] In this application, unless otherwise stated, for the positive and negative electrode sheets, the sheet area does not change much before and after cold pressing, and the corresponding compaction density is calculated as follows:

[0299] Compaction density = coating surface density / (thickness of the electrode after cold pressing - thickness of the current collector).

[0300] Coating surface density = slurry dry weight / electrode area before cold pressing.

[0301] The following is some description about the negative electrode.

[0302] In a non-limiting manner, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material. The definition of the negative electrode active material can be found in the above text.

[0303] In a non-limiting manner, the mass percentage of the negative electrode active material in the negative electrode active material layer may be ≥85%, further ≥90%, and further ≥95%.

[0304] As a non-limiting example, the negative electrode current collector has two surfaces facing away from each other in its thickness direction, and the negative electrode active material layer may be disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0305] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate. In the negative electrode current collector, the metal material may include but is not limited to one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, the polymer material substrate may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0306] Without limitation, the negative electrode active material can adopt the negative electrode active material for batteries known in the art. As a non-limiting example, the negative electrode active material may 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. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials or substances, and other traditional materials or substances that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0307] 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, as well as modified forms of any of the foregoing materials, wherein the modified form includes one or more of a doping modification and a coating modification. Both the doping modification method and the coating modification method can adopt or refer to existing modification methods in the art, including but not limited to the selection of element types and doping amounts. Carbon-based materials may include but are not limited to one or more of graphite materials, soft carbon, hard carbon, etc. Graphite materials may include one or more of artificial graphite and natural graphite.

[0308] In some embodiments, the negative electrode active material includes a carbon-based material and a silicon-based material. Without limitation, the combined mass of the carbon-based material and the silicon-based material may account for ≥85% of the total mass of the negative electrode active material, optionally ≥90%, further optionally ≥95%, further optionally ≥96%, and further optionally 100%. Without limitation, the combined mass of the graphite material and the silicon-based material may account for any of the following percentages, or a percentage greater than or equal to any of the following percentages and less than or equal to 100%, or a range consisting of any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, and the like. The definitions of carbon-based materials and silicon-based materials are as described above. For example, the carbon-based material may be a graphite material. The content of the carbon-based material and the silicon-based material may also be described in any appropriate embodiment herein.

[0309] 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%, further optionally ≥96%, etc., further optionally 100%, etc. Without limitation, 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 interval consisting of any two of the following percentages: 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definition of carbon-based materials can be found above. For example, the carbon-based material can be a graphite material.

[0310] In some embodiments, the negative electrode active material layer may further optionally include a binder. The binder may 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 may be 0-10%, further 0-5%, further 1%-5%, and further optionally 1%-3%.

[0311] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. As non-limiting examples, 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 weight percentage of the conductive agent in the negative electrode active material layer may be 0-15%, further preferably 0-10%, and even more preferably 0-5%.

[0312] In some embodiments, the negative electrode active material layer may further include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)). The mass percentage of the other additives in the negative electrode active material layer may be 0-15%, further 0-10%, further 0-5%, further 0-3%, and further 0-2%.

[0313] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed 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 side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet 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 sheet can be 1.2g / cm 3 ~2.0g / cm 3 , optional 1.2g / cm 3 ~1.8g / cm 3 .

[0314] The electrolyte will be described below.

[0315] The electrolyte conducts ions between the positive and negative electrodes. In this application, the electrolyte includes a liquid electrolyte. A liquid electrolyte can also be referred to as an electrolyte solution. The electrolyte includes an electrolyte salt.

[0316] In some embodiments, the electrolyte is an electrolyte solution.

[0317] In some embodiments, the electrolyte is a non-aqueous electrolyte. Furthermore, the non-aqueous electrolyte includes an electrolyte salt and a solvent. The definition of the electrolyte salt can be found above and includes at least a first electrolyte salt. In some embodiments, the electrolyte salt also includes a lithium electrolyte salt. The concentration of the electrolyte salt can typically be 0.5 mol / L to 5 mol / L.

[0318] In some embodiments, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0319] 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), butylene 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) One or more.

[0320] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0321] 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), trifluoromethylethylene carbonate (TFPC), and the like.

[0322] The separator will be described below.

[0323] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0324] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

[0325] In some embodiments, the thickness of the isolation film is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0326] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0327] 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.

[0328] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy into electrical energy, and further, generally includes at least a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the battery's charge and discharge process, active ions are intercalated and released back and forth between the positive and negative electrode sheets. The electrolyte conducts active ions between the positive and negative electrode sheets. The definition of a battery cell can be found in the context, for example, in the first aspect of this application.

[0329] As you can understand, a secondary battery typically consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0330] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0331] In some embodiments, the secondary battery is a lithium ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt.

[0332] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0333] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0334] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0335] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 5 with a square structure as an example.

[0336] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0337] The secondary battery may be a battery module 4 or a battery pack 1 .

[0338] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0339] FIG3 shows an example battery module 4. Referring to FIG3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0340] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0341] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0342] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0343] In a 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.

[0344] In some embodiments, the present application further provides an electrical device, which includes a secondary battery of any embodiment provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, electric tools, etc., but are not limited thereto. The electrical device can also be used in military equipment, aerospace and other fields, and can also be used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations.

[0345] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0346] Figure 6 shows an example of an electric device 6. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0347] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0348] Below, some embodiments of the present application are described. The embodiment described below is exemplary, is only used to explain the present application, and cannot be construed as limiting the present application. In the embodiment, if no technology or conditions are indicated, it is carried out according to the description above, or according to the technology or conditions described in the document in this area, or according to the product specification. Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, or can be synthesized in a conventional manner by commercially available products.

[0349] In the following examples, room temperature refers to 20°C to 30°C.

[0350] The following embodiments take a soft-pack laminated battery as an example. It is understood that the outer packaging of the secondary battery is not limited thereto. Similarly, the material selection and assembly method of the tabs can also adopt other methods in the art.

[0351] The ionic conductivity of the positive electrode active materials used below is tested using the following method:

[0352] The positive electrode active material to be tested was made into a positive electrode plate for testing, and the lithium plate was used as the negative electrode plate, and then assembled into a button battery for testing; the battery was discharged at 1C to 3.0V and then subjected to AC impedance spectroscopy testing. The test parameters were selected as follows: test temperature was 25℃, scanning frequency was 0.1Hz~10 5 Hz, the voltage amplitude is 5mV, and the test results are fitted using Zview software to obtain the ionic conductivity.

[0353] Unless otherwise specified, the positive electrode sheet used in the test was made of aluminum foil as the positive current collector, the mass percentage of the positive active material in the positive active material layer was controlled at 95% ± 1%, polyvinylidene fluoride (PVDF) was used as the binder, conductive carbon was used as the conductive agent, and the compaction density was 3.0 g / cm 3 ~3.6g / cm 3 .

[0354] For the first positive electrode active material and the second positive electrode active material, raw materials with the same chemical formula have the same source or are prepared using the same method. Therefore, the raw materials with the same chemical formula have substantially the same ionic conductivity.

[0355] Example 1.

[0356] (1) Preparation of positive electrode sheet:

[0357] The first positive electrode active material and the second positive electrode active material, the binder polyvinylidene fluoride (PVDF) and the conductive carbon are added to the solvent N-methylpyrrolidone (NMP). The mass ratio of the positive electrode active material: the binder: the conductive agent is 95:2.5:2.5. The mixture is stirred in a drying room to form a uniform positive electrode slurry. The viscosity of the positive electrode slurry is controlled to be 3000mPa·S~10000mPa·S. The positive electrode slurry is coated on both sides of the aluminum foil, and the positive electrode sheet is made after drying and cold pressing. The compaction density is 3.4g / cm 3 .

[0358] The first positive electrode active material is lithium nickel cobalt manganese oxide (an NCM material), and the second positive electrode active material is lithium manganese iron phosphate oxide.

[0359] The types and content ratios of the first positive electrode active material and the second positive electrode active material (the ratio of the two is determined by the A value) can be found in Table 1 and Table 2.

[0360] The value A 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.

[0361] (2) Preparation of negative electrode sheet:

[0362] Graphite material (artificial graphite), sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR) and conductive carbon were added to deionized water as a solvent. The mass ratio of graphite material: sodium carboxymethyl cellulose: styrene-butadiene rubber: conductive agent was 95:1:2.5:1.5. The mixture was stirred to form a uniform negative electrode slurry. The viscosity of the negative electrode slurry was controlled to be 3000mPa·S~10000mPa·S. The negative electrode slurry was coated on one side of the copper foil, and the negative electrode sheet was prepared after drying and cold pressing. The compaction density was 1.55g / cm 3 .

[0363] (3) Preparation of electrolyte

[0364] The electrolyte consists of an electrolyte salt, a solvent and an additive: the electrolyte salt is sodium hexafluorophosphate (NaPF6, a first cation salt) and lithium hexafluorophosphate (LiPF6), wherein the relative percentage of the mass of the sodium element in the electrolyte to the sum of the masses of the sodium element and the lithium element is 5wt% (corresponding to a target value of 5% for B), and the concentration of lithium hexafluorophosphate (electrolyte lithium salt) in the electrolyte is 1 mol / L; the solvent is ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1; the additive is fluoroethylene carbonate (FEC), and its mass percentage in the electrolyte is 5wt%.

[0365] In this example, the first cationic salt is sodium hexafluorophosphate, the first cation is a sodium ion, the electrolyte lithium salt is lithium hexafluorophosphate, and the electrolyte salt in the electrolyte solution is composed of a metal cation and an anion, the metal cation being a combination of sodium and lithium ions, and the anion being a hexafluorophosphate ion. The type and amount ratio of the first cationic salt in the electrolyte solution can also be found in Table 1.

[0366] The B value is the mass percentage of the first cationic salt in the electrolyte salt of the electrolyte solution, and is numerically calculated as "the ratio of the mass of the first cation to the total mass of the metal cations in the electrolyte salt".

[0367] (4) Isolation film

[0368] Polyethylene (PE) porous polymer film is used as the isolation membrane.

[0369] (5) Preparation of electrode assembly and secondary battery:

[0370] The prepared positive electrode sheet, negative electrode sheet and separator are made into corresponding electrode assemblies (ie, bare cells) in a Z-shaped stacking structure. The bare cells are vacuum dried at 90°C for 12 hours, and then the positive and negative electrode tabs are ultrasonically welded. The positive electrode uses aluminum tabs and the negative electrode uses nickel tabs. The positive and negative electrode tabs are located on the same side of the cell. The cell after the tabs are welded is placed in an aluminum-plastic film for top-side sealing, electrolyte is injected, allowed to stand, formed, aged, exhausted, and packaged for the second time to obtain a secondary battery with a preset capacity (0.1Ah). This secondary battery is an exemplary soft-pack laminated battery. In other embodiments, a hard shell method can be used.

[0371] Examples 2 to 21 use a method basically the same as Example 1 to prepare secondary batteries, with the following differences: the type of the first positive electrode active material, the type of the second positive electrode active material, the usage ratio A value of the first positive electrode active material and the second positive electrode active material, the type of the first cationic salt in the electrolyte, the usage (B value) of the first cationic salt, the A / B value, and the type and usage of the negative electrode active material. Please refer to Tables 1, 2 and 3.

[0372] Comparative Example 1: A secondary battery was prepared using a method substantially the same as that of Example 1, with the difference being that the A value and the A / B value were different.

[0373] In Comparative Example 2, a secondary battery was prepared using a method substantially the same as that of Example 1, except that the B value and the A / B value were different.

[0374] Comparative Example 3 uses a method substantially the same as that of Example 1 to prepare a secondary battery, except that the second positive electrode active material is omitted from the positive electrode active material, and only the first positive electrode active material is used, and the A value and A / B value are different.

[0375] Comparative Example 4 uses a method substantially the same as that of Example 1 to prepare a secondary battery, except that the first positive electrode active material is omitted from the positive electrode active material, and only the second positive electrode active material is used, and the A value and A / B value are different.

[0376] In Comparative Example 5, a secondary battery was prepared using a method substantially the same as that of Example 1, except that the first cationic salt was not added, and the B value and the A / B value were different.

[0377] Comparative Example 6 uses a method substantially the same as that of Example 8 to prepare a secondary battery, with the differences being that the A value, the B value, and the A / B value are different.

[0378] Comparative Example 7 uses a method substantially the same as that of Example 12 to prepare a secondary battery, with the difference being that the A value, B value, and A / B value are different.

[0379] Comparative Example 8 uses a method substantially the same as that of Example 16 to prepare a secondary battery, except that the B value and the A / B value are different.

[0380] Comparative Example 9 uses a method substantially the same as that of Comparative Example 2 to prepare a secondary battery, except that the ratio of the atomic molar equivalents of the Mn element and the Fe element in the second positive electrode active material (R2 Mn / Fe )different.

[0381] The preparation parameters of Comparative Examples 1 to 9 can be found in Tables 1 to 3.

[0382] The A and B values ​​in Table 1 are the design values ​​calculated based on the raw material composition and usage ratio (corresponding to their respective target values). In Table 2, the Ni content, Mn content and R2 Mn / Fe is the atomic ratio derived from the chemical composition of the raw materials, measured as an atomic number ratio or atomic molar ratio. In each embodiment, the cations in the electrolyte salt of the electrolyte solution are a combination of lithium ions and a first cation. The type and amount ratio of the first cation salt in the electrolyte solution can be found in Table 1. The amount of the first cation salt is determined based on the target value of B. When the electrolyte salt contains different anions, the amount of the first cation salt and the target value of B are determined based on the "ratio of the mass of the first cation to the total mass of the metal cations in the electrolyte salt."

[0383] Table 1.

[0384] In Table 1, the A value is the target value of the mass ratio (A) of the Co element in the first positive electrode active material to the Fe element in the second positive electrode active material; the first cation is a sodium ion, and the B value is the target value of the mass percentage (B) of the first cationic salt in the electrolyte salt of the electrolyte, which is numerically equal to the percentage of the mass of the first cation in the electrolyte relative to the mass of the metal cation in the electrolyte.

[0385] Table 2.

[0386] In Table 2:

[0387] The "nickel (Ni) content" in the first positive electrode active material is the ratio of the atomic molar equivalents of the Ni element to the lithium (Li) element, which is numerically equal to the atomic ratio of the Ni element to the Li element;

[0388] The "manganese (Mn) content" in the first positive electrode active material is the ratio of the atomic molar equivalents of the Mn element to the lithium (Li) element, which is numerically equal to the atomic ratio of the Mn element to the Li element;

[0389] R2 Mn / Fe Refers to the ratio of the atomic molar equivalents of the Mn element and the Fe element in the second positive electrode active material.

[0390] Table 3.

[0391] In Table 3, “mass percentage of silicon-based material” represents the mass percentage of silicon-based material in the negative electrode active material.

[0392] Testing and analysis methods

[0393] 1. Test and analysis of the mass percentage of the first cationic salt in the electrolyte (B value):

[0394] Based on GB / T36240-2018 and ion chromatography, the electrolyte lithium salt and the first cationic salt in the electrolyte are quantitatively tested. In a certain mass of electrolyte sample, the mass of lithium ions in the electrolyte lithium salt is recorded as m1, and the mass of the first cation in the first cationic salt is recorded as m2. Then, the B value can be calculated according to the following formula: B=m2 / (m1+m2)×100%.

[0395] 2. Test the content of Ni, Co and Mn elements in the first positive electrode active material, test the content of Mn and Fe elements in the second positive electrode active material, and test and analyze the element ratio such as A value.

[0396] Take about 0.4g (accurate to 0.0001g) of the positive electrode active material layer sample in a 25mL beaker, add 2mL~5mL nitric acid, leave it overnight, then place it on a hot plate, heat it at about 100℃, adjust the input voltage and temperature with a voltage regulator transformer, heat it until the positive electrode active material layer is digested, add 0.5mL perchloric acid, and heat it at about 140℃ to digest it until the white smoke disappears. The residue should be white, otherwise nitric acid and perchloric acid should be added to repeat the digestion. Finally, dissolve and extract it with 7wt% hydrochloric acid. After the volume is adjusted to an appropriate volume according to the content of the element to be measured, put it on an ICP-OES test instrument (5 11OTCP-OESVDV) to start the test, select Ni, Co, Mn and Fe as the test elements, and the instrument test results are the mass percentages of each element. 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 based on the molar mass and mass percentage of Ni and Co elements; 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, and the chemical formula of the second active material can be obtained based on the molar mass and mass percentage of Mn and Fe elements in the second positive electrode active material. Finally, the mass ratio (A value) of the Co element in the first positive electrode active material and the Fe element in the second positive electrode active material and other ratios to the atomic molar ratios of different elements can be calculated, for example, the mass ratio (R2 Mn / Fe ).

[0397] Based on the A value and B value obtained in the test, the test analysis result of the A / B value can be calculated.

[0398] 3. Battery energy density test

[0399] Test battery capacity: Allow the battery to rest for 3 minutes; discharge at 0.33C to the lower cutoff voltage (e.g., 2.5V); allow to rest for 3 minutes; charge at 0.33C constant current and constant voltage to the upper cutoff voltage (e.g., 4.4V), with the current cutoff at 0.05C; allow to rest for 3 minutes; discharge at 0.33C to the cutoff voltage (this step yields the battery capacity); allow to rest for 3 minutes; calculate the energy released during the first discharge. Divide the calculated energy released during the first discharge by the mass of the battery to obtain the battery's mass energy density, expressed in watt-hours per kilogram (W·h / kg).

[0400] 4. Thermal runaway temperature test:

[0401] The secondary battery to be tested is placed in a constant temperature environment at 25°C. At 2.5V to 4.4V, charge at 1C to 4.4V. Then, charge at 4.4V at a constant voltage to a current ≤0.05C and allow to rest for 5 minutes. Temperature sensors are then placed at the center of the positive and negative tabs, the center of the large surface, and the center of the side surfaces to monitor the temperature of the battery cell. The battery, with the temperature sensors placed, is then transferred to a hot box and heated at 5°C / min to 60°C, then held at that temperature for 5 hours. Thereafter, the temperature is increased at 5°C / min, holding for 30 minutes for each 5°C increase. After reaching 120°C, the temperature is increased at 2°C / min, holding for 30 minutes for each 2°C increase, until the battery cell fails or for 24 hours. The corresponding end temperature is recorded as the "thermal runaway temperature" test result. If no battery cell failure occurs at the end of the test, the "no failure within the test period" is recorded.

[0402] Basis for judging battery cell failure: explosion or fire.

[0403] The higher the thermal runaway temperature, the better the thermal stability of the secondary battery and the higher the thermal safety.

[0404] Test analysis results

[0405] Regarding the ionic conductivity (σ1) 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, and 9 is within 1×10 -3 S / cm~3×10 -3 S / cm, the ionic conductivity of the first positive electrode active material used in Example 13 is within 3×10 -3 S / cm~5×10 -3 S / cm, the ionic conductivity of the first positive electrode active material used in Example 14 is within 5×10 -3 S / cm~7×10 -3S / cm, the ionic conductivity of the first positive electrode active material used in Example 15 is within 7×10 -3 S / cm~9×10 -3 S / cm, the ionic conductivity of the first positive electrode active material used in Example 16 and Comparative Example 8 was within 3.2×10 -6 S / cm~1×10 -3 S / cm range (3.2×10 -6 S / cm<σ1<1×10 -3 S / cm). Among them, σ of Example 16, σ1 of Examples 1 to 12 and 17 to 21, σ1 of Example 13, σ1 of Example 14, and σ1 of Example 15 increase in sequence.

[0406] Regarding the ionic conductivity (σ2) of the second positive electrode active 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 within 3×10 -13 S / cm~9×10 -13 S / cm, the ionic conductivity of the second positive electrode active material used in Examples 18-19 is within 1×10 -13 S / cm~3×10 -13 The σ2 of Examples 1-17 and 20-21 are all greater than the σ2 of Examples 18-19.

[0407] In Examples 1 to 21, the ionic conductivity (σ1) of the first positive electrode active material at 25°C satisfies σ1≥3.2×10 -6 S / cm, most of them satisfy σ1≥1.7×10 -3 S / cm. The ionic conductivity (σ2) of the second positive electrode active material at 25°C satisfies σ2≤10 -9 S / cm, and also satisfy σ2≤10 -12 S / cm, and most of them satisfy σ2≤8×10 -13 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 satisfies Xσ≥10 4 , and also satisfy Xσ≥10 6 , some of which satisfy Xσ≥10 10 .

[0408] 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 is basically consistent with the target values ​​of A and B in Table 1.

[0409] According to the battery energy density test results, the battery mass energy densities of Examples 1-4, 9-12, 17, 20-21 and Comparative Examples 1, 2, 5, 7, and 9 are all within the range of 235W·h / kg to 255W·h / kg, the battery mass energy densities of Examples 13-15 are all within the range of 240W·h / kg to 270W·h / kg, the battery energy densities of Examples 5 to 8 are between the battery energy densities of Examples 1-4 and the battery energy densities of Examples 13 to 16, the battery mass energy densities of Example 16 and Comparative Examples 3, 6, and 8 are all within the range of 235W·h / kg to 265W·h / kg, the battery mass energy densities of Examples 18-19 are all within the range of 220W·h / kg to 245W·h / kg, and the battery mass energy density of Comparative Example 4 is within the range of 220W·h / kg to 230W·h / kg.

[0410] The secondary batteries prepared in Examples 1 to 21 all have good thermal stability, high thermal runaway temperatures, high energy density, and good overall electrical performance. In contrast, the overall performance of Comparative Documents 1 to 9 is significantly worse: the thermal runaway temperatures of some comparative examples are significantly reduced, and the battery energy density does not change much or even decreases, such as Comparative Examples 1, 2, 5, 7, and 9 relative to Example 1, and Comparative Example 6 relative to Example 8, and Comparative Example 8 relative to Example 16; some comparative examples (such as Comparative Example 3) have improved battery energy density relative to some examples, but the thermal runaway temperature is significantly reduced, resulting in poor overall performance; some comparative examples (such as Comparative Example 4) achieve some improvement in thermal stability at the expense of significantly sacrificing battery energy density, resulting in poor overall performance.

[0411] Except for the A / B values ​​of Comparative Examples 1, 2, 7 and 9 being between 0.47 and 202, the thermal runaway temperatures of Comparative Examples 1, 2, 7 and 9 are significantly reduced relative to the embodiments (such as Examples 1-4) having A / B values ​​within the range of 0.47 to 202.

[0412] Comparative Example 3 uses only a single type of first positive electrode active material. Compared with Examples 1-4, although the battery energy density of Comparative Example 3 is improved, its thermal runaway temperature is significantly reduced, and the overall performance is inferior to that of Examples 1-4.

[0413] Comparative Example 4 uses only a single type of second positive electrode active material. Although the thermal runaway temperature is high, the battery energy density is very low (220W·h / kg~230W·h / kg), which is significantly lower than the battery energy density of Examples 1-4 (235W·h / kg~255W·h / kg), and the overall performance is inferior to that of Examples 1-4.

[0414] Comparative Example 5 does not add the first cation. Compared with the examples (such as Example 1) in which the first cation is added, the thermal runaway temperature is significantly worse.

[0415] Comparative Examples 6 and 8 have A / B values ​​between 0.47 and 202, and exhibit relatively low thermal runaway temperatures. Specifically, Comparative Example 6 exhibits a significantly lower thermal runaway temperature than Example 8, which uses the same negative electrode active material; and Comparative Example 8 exhibits a significantly lower thermal runaway temperature than Example 16, which uses the same negative electrode active material.

[0416] The above description of various embodiments and examples tends to emphasize the differences between the various embodiments and examples. The same or similar aspects can be referenced to each other and will not be repeated here for the sake of brevity.

[0417] The technical features of the above-mentioned embodiments and examples can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0418] It should be noted that the present application is not limited to the above-mentioned embodiments and examples. The above-mentioned embodiments and examples are only examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same effect are all included in the technical scope of the present application. The above-described embodiments and examples only express several embodiments of the present application, and the description thereof is relatively detailed, but it cannot be understood as a limitation on the scope of the patent. In addition, without departing from the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and examples, and other methods of constructing by combining some of the constituent elements in the embodiments and examples are also included in the scope of the present application.

Claims

1. A battery cell, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a first positive electrode active material and a second positive electrode active material, the electrolyte comprises an electrolyte salt, and the electrolyte salt comprises a first cation salt and an electrolyte lithium salt; in, The first positive electrode active material is a lithium oxide containing Co and M1 elements, and the second positive electrode active material is a lithium oxide containing Fe and Mn elements, wherein the M1 element in the first positive electrode active material includes one or both of Mn and Al elements; 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; The first cationic salt includes a first cation, 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; Then A and B satisfy 0.47≤A / B≤202.

2. The battery cell according to claim 1, wherein: 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 ; Optionally, the ionic conductivity of the first positive electrode active material at 25° C. is σ1, satisfying σ1≥3.2×10 -6 S / cm, further optionally σ1≥1.7×10 -3 S / cm; Optionally, the ionic conductivity of the second positive electrode active material at 25° C. is σ2, satisfying σ2≤10 -9 S / cm, further optionally σ2≤10 -12 S / cm.

3. The battery cell according to claim 1 or 2, wherein: 1.3≤A / B≤25.

4.

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

53.

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

6. The battery cell according to any one of claims 1 to 5, wherein: The first positive electrode active material satisfies one or more of the following characteristics: The atomic molar ratio of Co to Li is denoted as R c , then R c Satisfy 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 Satisfy 0.05≤R d ≤0.5, optionally, 0.05≤R d ≤0.3; The M1 element includes Mn element, and the atomic molar ratio of Mn element to Li element is denoted as R d-Mn , then R d-Mn Satisfy 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 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 Satisfy 0.1≤R c+d ≤0.5, further optionally, 0.1≤R c+d ≤0.3, further optionally, 0.1≤R c+d ≤0.

2.

7. The battery cell according to any one of claims 1 to 6, wherein: The first positive electrode active material further comprises a 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 Satisfy 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, wherein: The atomic molar equivalent of Li element Q a The ratio of the first positive electrode active material to the first positive electrode active material is 0.75 to 1.2, optionally 0.8 to 1.1, further optionally 0.9 to 1.05, and further optionally 1. The first positive electrode active material satisfies one or more of the following characteristics: Atomic molar equivalent of Co element Q 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 a Mn element, and the atomic molar equivalent of the Mn element is ≤0.4, and optionally, the atomic molar equivalent of the Mn element is ≤0.3; The sum of the atomic molar equivalents of the Co element and the M1 element Q 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, wherein: The first positive electrode active material comprises Ni element, and the atomic molar equivalent of Ni element is Q b Satisfy 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, wherein: 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, further optionally, 0.6≤b≤0.9; Optionally, 0.05≤c<1, further optionally, 0.05≤c≤0.5, further optionally, 0.05≤c≤0.3; Optionally, 0.05≤d<1, further optionally, 0.05≤d≤0.5, further optionally, 0.05≤d≤0.3; Optionally, 0≤e<0.1, further optionally, 0≤e≤0.05, further optionally, 0≤e≤0.03; Optionally, 1≤f≤2.1, further optionally, 1.8≤f≤2.05, further optionally, 1.95≤f≤2.05; Optionally, 0≤g<0.5, further optionally, 0≤g≤0.1, further optionally, 0≤g≤0.

05.

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

5.

12. The battery cell according to any one of claims 1 to 10, wherein: The second active material includes a second body and may include or exclude a second coating layer located at at least a portion 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 O4, wherein -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 of 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 of B, Si, N, S, F, Cl and Br; Optionally, 0.1≤y≤0.5, further optionally, 0.2≤y<0.5, further optionally, 0.3≤y<0.5; Optionally, 0.2≤w≤0.5, further optionally, 0.3≤w<0.5, further optionally, 0.4≤w<0.5; Optionally, 0.001≤z≤0.1, further optionally, 0.001≤z<0.05, further optionally, 0.001≤z<0.002; Optionally, the M3 element in the second active material includes one or more elements selected from Ti, V, Ni, Co and Mg; Optionally, the Q element in the second active material includes one of B, Si, N and S; Optionally, the second coating layer comprises 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, wherein: The total mass proportion of the first positive electrode active material and the second positive electrode active material in the positive electrode active material layer is R 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, wherein: The first cation includes cations of one or more elements selected from the group consisting of alkali metal elements and alkaline earth metal elements; Optionally, the first cation includes one or more of sodium ions, potassium ions, calcium ions and magnesium ions; Optionally, the anion in the first cationic salt includes 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 bistrifluoromethylsulfonyl imide, sodium trifluoromethanesulfonate, sodium bisfluorosulfonyl imide, sodium tris(trifluoromethylsulfonyl)methyl, potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium bistrifluoromethylsulfonyl imide, potassium trifluoromethanesulfonate, potassium bisfluorosulfonyl imide and potassium tris(trifluoromethylsulfonyl)methyl; 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 plate comprises a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active substance, and the negative electrode active substance comprises 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%, 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 comprising 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 comprising 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.

Images