Positive electrode sheet, battery cell, secondary battery and electric device

Abstract

The present application relates to a positive electrode sheet, a battery cell, a secondary battery and an electric device. The positive electrode sheet comprises a positive electrode active material and a lithium supplement additive, wherein the lithium supplement additive meets the following relational expression: R≤Cmin / (100*m*Q). In the expression, m represents a loading capacity on the positive electrode sheet per unit of area, and the loading capacity comprises the total mass of the positive electrode active material and the lithium supplement additive; Cmin represents the minimum magnification value applied to the positive electrode sheet during an actual application process; Q represents the theoretical gram capacity of the lithium supplement additive; and R represents the mass percentage content of the lithium supplement additive in the loading capacity on the positive electrode sheet per unit of area.

Description

Positive electrode sheet, battery cell, secondary battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202310759849.6 filed on June 26, 2023, entitled “Positive electrode sheet, battery cell, secondary battery and electrical device”, which is incorporated into this application in its entirety by reference. Technical Field

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

[0004] Secondary batteries, represented by lithium-ion batteries, have high capacity and long lifespan, and are therefore widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools. As the scope of battery applications becomes increasingly broad, the requirements for secondary battery performance are becoming increasingly stringent. In order to improve the performance of secondary batteries, materials within the secondary batteries, such as the positive electrode materials, are typically optimized and improved. However, when the improved positive electrode materials are currently applied to secondary batteries, the secondary batteries still suffer from poor charging capacity during use.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a positive electrode sheet, a battery cell, a secondary battery and an electrical device, which can improve the charging capacity of the secondary battery.

[0007] In order to achieve the above-mentioned object, the first aspect of the present application provides a positive electrode plate, comprising a positive electrode active material and a lithium supplement additive, wherein the lithium supplement additive satisfies the following relationship: R≤Cmin / (100*m*Q), where m represents the load per unit area of ​​the positive electrode plate, and the load includes the total mass of the positive electrode active material and the lithium supplement additive;

[0008] Cmin represents the minimum rate value applied to the positive electrode during actual application;

[0009] Q represents the theoretical gram capacity of the lithium supplement additive;

[0010] R represents the mass percentage of the lithium supplement additive in the load per unit area of ​​the positive electrode sheet.

[0011] The positive electrode plate provided in the present application includes a lithium supplement additive, which can increase the gram capacity of the positive electrode active material, thereby increasing the charging capacity of the battery cell. At the same time, the mass percentage of the lithium supplement additive in the positive electrode plate satisfies the above relationship. Therefore, the mass percentage of the lithium supplement additive in the positive electrode plate can be controlled by regulating Cmin, m and Q. By controlling the mass percentage of the lithium supplement additive, it is helpful to slowly delithiate the lithium supplement additive during the cycle, so that its capacity can be slowly and continuously released, thereby continuously improving the charging capacity of the battery cell and the secondary battery.

[0012] In some embodiments of the present application, the positive electrode plate satisfies the following condition: 0.1%≤R≤20%, optionally 1%≤R≤10%.

[0013] By controlling the mass percentage of the lithium replenishing additive within this range and coordinating it with a specific voltage range during the actual cycle, it is beneficial for the lithium replenishing additive to slowly delithiate, allowing its capacity to be slowly released, thereby achieving continuous lithium replenishment during the cycle and a continuous improvement in charging capacity.

[0014] In some embodiments of the present application, the positive electrode sheet satisfies at least one of the following conditions:

[0015] (1) 0.01C≤Cmin≤1C, which can be 0.05C≤Cmin≤0.95C;

[0016] (2)0.1g / mm 2 ≤m≤0.5g / mm 2 , optional 0.2g / mm 2 ≤m≤0.4g / mm 2 ;

[0017] (3) 150mAh / g≤Q≤300mAh / g, optionally 190mAh / g≤Q≤280mAh / g.

[0018] During actual application, the minimum rate value Cmin applied to the positive electrode plate, the load m per unit area of ​​the positive electrode plate, and the theoretical gram capacity Q of the lithium replenishing additive are within the above ranges, which helps to achieve the lithium replenishment effect on the positive electrode and fully improve the gram capacity of the positive electrode active material; at the same time, it helps to regulate the mass percentage of the lithium replenishing additive and control the added amount within an appropriate range, thereby helping to achieve a slow and continuous lithium replenishment effect and achieve a continuous improvement in the charging capacity of the battery cell and the secondary battery.

[0019] In some embodiments of the present application, the lithium supplement additive includes one or more of lithium manganese oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material and lithium nickel oxide, and can be a nickel-cobalt-manganese ternary material.

[0020] In some embodiments of the present application, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobaltate and lithium manganese iron phosphate, and lithium iron phosphate can be selected.

[0021] The above-mentioned types of positive electrode active materials belong to lithium iron phosphate-based positive electrode materials, which usually have relatively low theoretical gram capacity. By adding the above-mentioned types of lithium supplement additives with relatively high gram capacity to them, it is beneficial to increase the gram capacity of the positive electrode active materials, thereby increasing the charging capacity of the battery cells and secondary batteries.

[0022] The second aspect of the present application also provides a battery cell, comprising the positive electrode sheet of the first aspect of the present application.

[0023] In some embodiments of the present application, the cycle voltage range of the battery cell is 2.5 volts (V) to 3.65V.

[0024] During the actual charge and discharge cycle process, within the above-mentioned cycle voltage range, the capacity of the positive electrode active material can be fully released. At the same time, the lithium supplement additive can slowly delithiate during multiple cycles, thereby achieving a continuous and slow release of capacity, which is conducive to the continuous improvement of the battery cell charging capacity.

[0025] In some embodiments of the present application, the cycle rate range of the battery cell is 0.33 rate (C) to 2C.

[0026] In actual charge and discharge cycles, the above cycle rate range applies to the normal cycling of the positive electrode active material. However, within this cycle rate range, the lithium replenishing additive can be cycled at a high rate. This high-rate cycling can easily destroy the crystal structure of the lithium replenishing additive, causing the released lithium ions to be unable to be re-intercalated into the positive electrode and remain on the negative electrode side, thereby achieving the effect of replenishing lithium to the negative electrode, thereby improving the cycle life of the battery cell.

[0027] A third aspect of the present application provides a secondary battery, comprising the battery cell according to the second aspect of the present application.

[0028] A fourth aspect of the present application provides an electrical device comprising the secondary battery according to the third aspect of the present application.

[0029] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive work. In the drawings:

[0031] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0032] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0033] FIG3 is a schematic diagram of a secondary battery according to another embodiment of the present application.

[0034] FIG. 4 is a schematic diagram of a secondary battery according to another embodiment of the present application.

[0035] FIG. 5 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 4 .

[0036] FIG6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0037] Reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0038] Below, the embodiments of the positive electrode sheet, battery cell, secondary battery and electrical device 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 are 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.

[0039] " range " disclosed in the present application is 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 can be arbitrarily combined, that is, any lower limit can form a range 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 the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the 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 simply an abbreviation for these numerical combinations. 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.

[0040] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0041] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

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

[0043] At present, the positive electrode active materials used in secondary batteries, especially lithium iron phosphate-based positive electrode active materials, have a low gram capacity, so when used in secondary batteries, there is usually a problem of poor charging capacity. In order to improve the charging capacity, the current commonly used method is to replenish lithium in the positive electrode of the secondary battery, that is, mainly by adding lithium-rich compounds to the positive electrode active materials, taking advantage of the irreversible decomposition of the compounds during formation, and the release of lithium ions to participate in the formation of the negative electrode solid electrolyte interface film (SEI) film, thereby making up for the active lithium ions lost for the first time during the formation of traditional lithium-ion batteries, thereby improving the charging capacity. However, this method can only replenish lithium during the formation stage of the battery, and the lithium-rich compounds can only release the capacity once during the formation stage. It is impossible to slowly and gradually release the capacity of the lithium-rich compounds and continuously replenish lithium during the subsequent cycles, and it is impossible to achieve a continuous improvement in capacity.

[0044] Based on this, the present application proposes a positive electrode plate, which adds a lithium-supplementing additive and controls the content of the lithium-supplementing additive in the positive electrode plate, while controlling the voltage and rate range of the positive electrode plate (and the battery cell) during actual use, so that the capacity of the lithium-supplementing additive can be slowly and gradually released during the actual cycle process, thereby achieving a continuous improvement in the charging capacity of the battery cell and the secondary battery.

[0045] Positive electrode

[0046] In a first aspect of the present application, a positive electrode plate is proposed, comprising a positive electrode active material and a lithium supplement additive, wherein the lithium supplement additive satisfies the following relationship: R≤Cmin / (100*m*Q), where m represents the load per unit area of ​​the positive electrode plate, and the load includes the total mass of the positive electrode active material and the lithium supplement additive; Cmin represents the minimum rate value applied to the positive electrode plate during actual application; Q represents the theoretical gram capacity of the lithium supplement additive; and R represents the mass percentage of the lithium supplement additive in the load per unit area of ​​the positive electrode plate.

[0047] It should be noted that the minimum rate value applied to the positive electrode plate during actual application refers to the fact that after the positive electrode plate is assembled into battery cells of different specifications, in the actual application process, based on the different specifications of the battery cells and actual usage conditions, there will be corresponding different usage rate range reference values ​​(including upper and lower limits). The lower limit value of each different usage rate range is the minimum rate value applied to the positive electrode plate during actual application.

[0048] It should be noted that the actual application process refers to the actual cycle process of the battery cells after the positive electrode plates are assembled into battery cells of different specifications.

[0049] The positive electrode plate provided in the present application includes a lithium supplement additive, which can increase the gram capacity of the positive electrode active material, thereby increasing the charging capacity of the battery cell. At the same time, the mass percentage of the lithium supplement additive in the positive electrode plate satisfies the above relationship. Therefore, the mass percentage of the lithium supplement additive in the positive electrode plate can be controlled by regulating Cmin, m and Q. By controlling the mass percentage of the lithium supplement additive, it is helpful to slowly delithiate the lithium supplement additive during the cycle, so that its capacity can be slowly and continuously released, thereby continuously improving the charging capacity of the battery cell and the secondary battery.

[0050] In addition, in the positive electrode sheet, by limiting the mass percentage of the lithium-supplementing additive to the range satisfied by the above-mentioned relationship, it is helpful for the lithium-supplementing additive to circulate at a high rate. Specifically, when the mass percentage of the lithium-supplementing additive is controlled within the range satisfied by the above-mentioned relationship, in the actual cycle process, the charge and discharge rate applicable to the positive electrode active material will be a high rate for the lithium-supplementing additive in the above-mentioned content range, that is, under the charge and discharge rate of the normal cycle applicable to the positive electrode active material, the lithium-supplementing additive can be circulated at a high rate. This high-rate cycle can easily destroy the crystal structure of the lithium-supplementing additive, causing the lithium ions released to remain on the negative electrode side because they cannot be reinserted back into the positive electrode body, thereby achieving the effect of replenishing lithium to the negative electrode, thereby improving the cycle life of the battery cell and the secondary battery. At the same time, by limiting the mass percentage of the lithium-supplementing additive to the range satisfied by the above-mentioned relationship, while improving the gram capacity, it will not affect the cycle stability of the positive electrode active material.

[0051] In the above relationship, the physical phase of the lithium-replenishing additive added to the electrode can be determined by testing the X-ray diffraction spectrum (XRD) of the positive electrode before the cycle, and the chemical structure can be determined; then, by testing the inductively coupled plasma mass spectrometry (ICP) of the positive electrode, the metal elements other than iron in the electrode can be determined, and the mass percentage of the lithium-replenishing additive in the positive electrode, i.e., R, can be determined by the test results of XRD and ICP.

[0052] In the above relationship, the amount of positive electrode active material and lithium supplement additive added to the positive electrode sheet before the cycle can be determined by XRD and ICP tests, respectively, as m1 and m2. This can then yield the total mass of the positive electrode active material layer per unit area of ​​the positive electrode sheet, i.e., m=m1+m2. A button battery is then made using the positive electrode sheet to test the capacity of the button battery. For example, it can be charged at room temperature at a constant current rate of 0.5C to a voltage above 4.35V, and then further charged at a constant voltage of 4.35V to a current below 0.05C, placing it in a fully charged state at 4.35V. The button battery is then discharged at a constant current rate of 1C to a voltage of 3V (cut-off voltage), and the released capacity value is recorded as q, which is the capacity value of the button battery. Based on this, according to the capacity value q, the added amount m1 of the positive electrode active material and its theoretical gram capacity (denoted as q1), and the added amount m2 of the lithium supplement additive, the theoretical gram capacity Q of the added lithium supplement additive can be obtained through the formula q = (m1 / m)*q1+(m2 / m)*Q.

[0053] In some embodiments, 0.01C≤Cmin≤1C. For example, Cmin can be 0.01C, 0.05C, 0.08C, 0.1C, 0.3C, 0.5C, 0.8C, 1C, or any range thereof. Alternatively, 0.05C≤Cmin≤0.95C.

[0054] During actual application, the minimum rate value Cmin applied to the positive electrode plate is within the above range, which is helpful to maximize the capacity of the positive electrode active material and regulate the mass percentage of the lithium replenishing additive. At the same time, it can also enable the lithium replenishing additive to circulate at a high rate, thereby replenishing lithium to the negative electrode side, thereby comprehensively improving the capacity and cycle performance of the battery cell and secondary battery.

[0055] In some embodiments, 0.1 g / mm 2 ≤m≤0.5g / mm 2 For example, m can be 0.1 g / mm² (g / mm 2 ), 0.2g / mm 2 , 0.3g / mm 2 , 0.4g / mm 2 , 0.5g / mm 2 Or within the range of any of the above values. Optionally, 0.2g / mm 2 ≤m≤0.4g / mm 2 .

[0056] The loading amount m per unit area of ​​the positive electrode plate, that is, the total mass of the positive electrode active material and the lithium replenishing additive loaded per unit area of ​​the positive electrode plate, is within the above range, which helps the lithium replenishing additive to fully exert its lithium replenishing effect on the positive electrode, and helps to slowly and continuously release the capacity of the lithium replenishing additive, thereby continuously improving the charging capacity of the battery cell and the secondary battery.

[0057] In some embodiments, 150 milliampere hours per gram (mAh / g) ≤ Q ≤ 300 mAh / g. For example, Q can be 150 mAh / g, 170 mAh / g, 190 mAh / g, 210 mAh / g, 230 mAh / g, 250 mAh / g, 270 mAh / g, 290 mAh / g, 300 mAh / g, or any range thereof. Alternatively, 190 mAh / g ≤ Q ≤ 280 mAh / g.

[0058] The theoretical gram capacity Q of the lithium replenishing additive is within the above range, which helps to achieve the lithium replenishing effect on the positive electrode and fully improve the gram capacity of the positive electrode active material; at the same time, it helps to regulate the mass percentage of the lithium replenishing additive and control the added amount within an appropriate range, thereby helping to achieve a slow and continuous lithium replenishing effect and achieve a continuous improvement in the charging capacity of the battery cell and secondary battery.

[0059] In some embodiments, 0.01% ≤ R ≤ 20%. For example, R can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, or any range thereof. Alternatively, 1% ≤ R ≤ 10%.

[0060] In the aforementioned relationship, controlling the value range of each parameter helps to regulate the mass percentage of the lithium supplement additive and keep it within the above range. By controlling the mass percentage of the lithium supplement additive within this range and coordinating it with a specific voltage interval during the actual cycle, it is beneficial for the lithium supplement additive to slowly delithiate, allowing its capacity to be slowly released, achieving continuous lithium supplementation during the cycle and achieving a continuous improvement in charging capacity. At the same time, it also helps the lithium supplement additive to circulate at a high rate, achieving the effect of replenishing lithium to the negative electrode, thereby improving the cycle life of the battery cell and secondary battery.

[0061] As a non-limiting example, the positive electrode contains 1 gram (g) of lithium iron phosphate, which has a capacity of 160 milliampere hours (mAh); if 0.1g of a lithium supplement additive with a theoretical gram capacity of 180mAh / g is added, during the actual cycle process, by coordinating with the specific cycle voltage range of the battery cell, the lithium supplement additive can achieve slow lithium delithiation, thereby slowly and continuously increasing the capacity of the battery cell, and the capacity can be increased to: 160*(1 / 1.1)+180*(0.1 / 1.1)=162mAh.

[0062] In some embodiments, the lithium supplement additive includes but is not limited to one or more of lithium manganese oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material and lithium nickel oxide, and can be a nickel-cobalt-manganese ternary material.

[0063] In some embodiments, the positive electrode active material includes, but is not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobaltate, and lithium manganese iron phosphate, and lithium iron phosphate may be selected.

[0064] The above-mentioned types of positive electrode active materials belong to lithium iron phosphate-based positive electrode materials, which usually have relatively low theoretical gram capacity. By adding the above-mentioned types of lithium supplement additives with relatively high gram capacity to them, it is beneficial to increase the gram capacity of the positive electrode active materials, thereby increasing the charging capacity of the battery cells and secondary batteries.

[0065] The positive electrode sheet includes a positive electrode active material layer and a positive electrode current collector, wherein the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector.

[0066] It can be understood that the positive electrode active material layer includes the positive electrode active material and lithium replenishing additive mentioned above in this application, that is, the positive electrode active material and lithium replenishing additive included in the positive electrode plate are arranged in the positive electrode plate of this application in the form of a positive electrode active material layer.

[0067] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0068] 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 and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0069] In some embodiments, the positive electrode active material may also include other positive electrode active materials for batteries that are well known in the art. As an example, other positive electrode active materials may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. One or more of these positive electrode active materials may be used in combination with one or more of the positive electrode active materials described above in this application. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), 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 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0070] It should be noted that the battery's charge and discharge processes are accompanied by the intercalation and deintercalation of Li, and the molar content of Li varies when the battery is discharged to different states. The molar content of Li in the list of positive electrode active materials in this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active material is used in a battery system, the molar content of Li will change after charge and discharge cycles.

[0071] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0072] In some embodiments, the positive electrode active material may also include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue-based compound. However, this application is not limited to these materials; other conventional materials that can be used as positive electrode active materials for batteries may also be used. One or more of these positive electrode active materials may be used in combination with one or more of the positive electrode active materials described above.

[0073] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M includes one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0074] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si; n represents (YO4) n- valence.

[0075] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si, and n represents (YO4) n- valence state; halogen includes at least one of F, Cl and Br.

[0076] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y includes at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZO y )m+ valence state; halogen includes at least one of F, Cl and Br.

[0077] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0078] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ) compounds. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0079] In some embodiments, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0080] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, lithium supplement additive, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0082] In some embodiments, the lithium supplement additive accounts for 0.1% to 20% by weight in the positive electrode slurry. For example, the lithium supplement additive accounts for 0.1%, 0.5%, 0.8%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20% by weight in the positive electrode slurry, or any range thereof.

[0083] In some embodiments, the mass percentage of the positive electrode active material in the positive electrode slurry is 90% to 99%. For example, the mass percentage of the positive electrode active material in the positive electrode slurry can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any range thereof.

[0084] The positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode active material layer.

[0085] Negative electrode

[0086] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0087] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0088] 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 base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0089] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials 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.

[0090] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one 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).

[0091] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0093] In some embodiments, the negative electrode sheet can be prepared by the following method: 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 (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0094] The negative electrode sheet of the present application does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[0095] electrolytes

[0096] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0097] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0098] In some embodiments, the electrolyte salt may be a lithium salt. As an example, the lithium salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0099] In some embodiments, the electrolyte salt may also be a sodium salt. For example, the sodium salt includes, but is not limited to, at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3. One of these sodium salts may be used alone, or two or more may be used simultaneously.

[0100] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0101] In some embodiments, the electrolyte may further 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.

[0102] Isolation film

[0103] 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.

[0104] In some embodiments, the material of the separator can be selected from at least one 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.

[0105] The second aspect of the present application provides a battery cell, comprising the positive electrode sheet of the first aspect of the present application.

[0106] 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.

[0107] In some embodiments, the battery cell includes an electrode assembly and a casing, which can be used to encapsulate the electrode assembly and the electrolyte.

[0108] In some embodiments, the housing can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell; or a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0109] In some embodiments, during the actual charge and discharge cycle, the cycle voltage range of the battery cell is 2.5 V to 3.65 V. For example, the cycle voltage of the battery cell can be 2.5 V, 2.65 V, 2.8 V, 2.95 V, 3.1 V, 3.25 V, 3.4 V, 3.65 V, or any range thereof.

[0110] During the actual charge and discharge cycle process, within the above-mentioned cycle voltage range, the capacity of the positive electrode active material can be fully released. At the same time, since the voltage range of the lithium supplement additive itself is higher than the cycle voltage range, when cycling within this voltage range, combined with the specific addition amount of the aforementioned lithium supplement additive in the positive electrode plate (that is, the mass percentage of the lithium supplement additive in the positive electrode plate must satisfy the aforementioned relationship), the lithium supplement additive can be slowly delithiated during multiple cycles, thereby achieving continuous and slow release of capacity, which is conducive to achieving a continuous improvement in the charging capacity of the battery cell.

[0111] In some embodiments, during the actual charge and discharge cycle, the cycle rate of the battery cell is in the range of 0.33C to 1C. For example, the cycle rate of the battery cell can be 0.33C, 0.5C, 1C, or any range thereof.

[0112] During actual charge and discharge cycles, the aforementioned cycle rate range applies to normal cycling of the positive electrode active material. However, within this cycle rate range, combined with the specific amount of the aforementioned lithium-supplementing additive added to the positive electrode plate (i.e., the mass percentage of the lithium-supplementing additive in the positive electrode plate must satisfy the aforementioned relationship), the lithium-supplementing additive can be cycled at a high rate. This high-rate cycling can easily destroy the crystal structure of the lithium-supplementing additive, resulting in the lithium ions released being unable to be re-intercalated into the positive electrode body and remaining on the negative electrode side, thereby achieving the effect of replenishing lithium at the negative electrode and thus helping to extend the cycle life of the battery cell.

[0113] As a non-limiting example, the positive electrode contains 0.9g of lithium iron phosphate and 0.1g of a lithium supplement additive with a theoretical gram capacity of 180mAh / g, and its capacity is 162mAh. If the minimum rate of the battery cell during actual charge and discharge is 0.3C, the rate actually applied to the particle level of the lithium supplement additive is: 0.3*162 / (180*0.1)=2.7C. When the lithium supplement additive is cycled at this high rate, the material is easily damaged, resulting in the destruction of the crystal structure. As a result, the lithium ions cannot be re-inserted and remain on the negative electrode side, thereby replenishing the negative electrode with lithium.

[0114] The third aspect of the present application provides a secondary battery, which may include the battery cell of the second aspect of the present application, or the secondary battery may be directly assembled from components such as an electrode assembly and an outer packaging.

[0115] 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.

[0116] In some embodiments, an outer package may be used to encapsulate the electrode assembly and the electrolyte.

[0117] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0118] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, referring to FIG1 , the secondary battery may be a battery cell 5 having a square structure.

[0119] In some embodiments, referring to Figure 2, the outer packaging of the secondary battery may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate 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 infiltrated 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 specific actual needs.

[0120] In some embodiments, the secondary battery may also be a battery module assembled from multiple battery cells. The battery module may contain multiple battery cells, and those skilled in the art may adjust the specific number according to the application and capacity of the battery module.

[0121] 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.

[0122] 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.

[0123] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0124] In some embodiments, the battery cells mentioned above may also be directly assembled into a battery pack, and the number of battery cells contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0125] 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.

[0126] In addition, the present application also provides an electrical device, which includes the secondary battery 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 (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0127] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0128] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0129] 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.

[0130] Example

[0131] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0132] Example 1

[0133] Preparation of positive electrode

[0134] The positive electrode active material is lithium iron phosphate (LiFePO4), NCM (LiNi 0.7 Co 0.15 Mn 0.15 O2) material, conductive agent conductive carbon black (Super-P), and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone in a mass ratio of 94:2:2:2 and mixed evenly to form a positive electrode slurry. The positive electrode slurry is then evenly coated on the front and back sides of the current collector aluminum foil, and then dried at 85°C. After cold pressing and cutting, the positive electrode sheet is obtained.

[0135] Preparation of negative electrode sheet

[0136] The negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder (SBR) are dissolved in solvent deionized water in a weight ratio of 95:1:2:1, and then evenly mixed with deionized water to prepare a negative electrode slurry; the negative electrode slurry is then coated on the front and back sides of the current collector copper foil, dried, and cold pressed and cut to obtain the negative electrode sheet.

[0137] Preparation of electrolyte

[0138] In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate (EC), polycarbonate (PC), and dimethyl carbonate (DMC) were mixed in a weight ratio of EC:PC:DMC = 3:3:3 to obtain a mixed organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the above mixed organic solvent and stirred evenly to obtain an electrolyte in which the concentration of LiPF6 was 1 mol / L.

[0139] Preparation of isolation membrane

[0140] PE porous film is used as the isolation membrane.

[0141] Preparation of lithium-ion batteries

[0142] The positive electrode sheet, the separator and the negative electrode sheet are wound into a soft-pack battery cell, which is then filled with liquid, placed at high temperature and tested for capacity after formation to obtain a lithium-ion battery.

[0143] Examples 2 to 18

[0144] The preparation method of the positive electrode sheet and the lithium-ion battery is similar to that of Example 1, except that the parameters related to the positive electrode sheet and its preparation process are adjusted. The specific parameters are detailed in Table 1 below. Wherein, “ / ” indicates that the corresponding parameter does not exist.

[0145] Comparative Example 1

[0146] The preparation method of the positive electrode sheet and the lithium-ion battery is similar to that of Example 1, except that no lithium supplement additive is added to the positive electrode sheet.

[0147] Comparative Example 2

[0148] The preparation method of the positive electrode sheet and the lithium ion battery is similar to that of Example 1, except that the positive electrode sheet does not satisfy the relationship R≤C min / (100*m*Q).

[0149] Table 1

[0150] In addition, the positive electrode sheets and lithium-ion batteries obtained in Examples 1 to 18 and Comparative Examples 1 to 2 were subjected to relevant performance tests, and the test results are shown in Table 2 below.

[0151] Test section

[0152] (1) Charging capacity test

[0153] At an ambient temperature of 25 degrees Celsius (℃), ① use a constant current charge rate of 0.33C to charge the battery cell to 3.65V, and then use a constant voltage to 0.05C. The capacity measured in this step is the charging capacity value. ② Let it stand for 30 minutes (min). ③ Use a constant current discharge rate of 0.33C to discharge the battery cell to 2.5V.

[0154] Charging capacity per unit area = charging capacity / positive electrode area.

[0155] (2) Cycle life test

[0156] ① When the ambient temperature reaches the required cycle temperature, start the cycle test process, ② use a 1C rate to charge the battery to 3.65V, and then use a constant voltage to 0.05C, ③ let it stand for 5 minutes, ④ use a 1C rate to discharge the battery to 2.5V, ⑤ let it stand for 5 minutes, ⑥ repeat steps ②-⑤ to test the cycle performance of the battery.

[0157] Capacity retention rate = (charge capacity after 400 / 800 cycles) / first cycle charge capacity

[0158] Capacity retention rate decrease = (capacity retention rate after 400 cycles - capacity retention rate after 800 cycles) / capacity retention rate after 400 cycles

[0159] Table 2

[0160] In Table 2 above, by comparing the embodiment with the comparative example 1, it can be seen that the capacity retention rate of the embodiment after 400 cycles and the capacity retention rate after 800 cycles are both higher than those of the comparative example 1, indicating that compared with not adding the lithium replenishing additive, the addition of the lithium replenishing additive to the positive electrode plate in the present application can improve the charging capacity of the battery.

[0161] Comparing the embodiment with the comparative example 2, it can be seen that the capacity retention rate of the embodiment after 400 cycles and the capacity retention rate after 800 cycles are both higher than those of the comparative example 2, and the decrease in the capacity retention rate is also higher than that of the comparative example 2, indicating that when the positive electrode sheet does not satisfy the relationship R≤C min / (10*m*Q), the lithium supplement additive has little effect on improving the battery charging capacity, and it is difficult to achieve a slow increase in capacity.

[0162] Comparing Example 1 with Examples 16 to 18, it can be seen that the decrease in the capacity retention rate of Examples 16 to 18 is significantly lower than that of Example 1, indicating that when the cycle voltage range or the cycle rate range is not within the scope of this application, it will have a certain impact on the slow release of the capacity of the lithium supplement additive.

[0163] It should also be noted that in Examples 6 to 7, Examples 10 to 13 and Example 15, since the load m per unit area of ​​the positive electrode sheet is lower than that of other examples, the charging capacity per unit area is correspondingly lower than that of other examples.

[0164] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode plate, comprising a positive electrode active material and a lithium supplement additive, wherein the lithium supplement additive satisfies the following relationship: R≤C min / (100*m*Q), In the formula, m represents the loading amount per unit area on the positive electrode sheet, and the loading amount includes the total mass of the positive electrode active material and the lithium supplement additive; C min Indicates the minimum rate value applied to the positive electrode plate during actual application; Q represents the theoretical gram capacity of the lithium supplement additive; R represents the mass percentage of the lithium supplement additive in the load per unit area on the positive electrode plate.

2. The positive electrode sheet according to claim 1, wherein: The following conditions are met: 0.1%≤R≤20%.

3. The positive electrode sheet according to claim 1 or 2, wherein: The following conditions are met: 1%≤R≤10%.

4. The positive electrode sheet according to any one of claims 1 to 3, wherein: One or more of the following conditions are met: (1)0.01C≤C min ≤1C; (2)0.1g / mm 2 ≤m≤0.5g / mm 2 ; (3)150mAh / g≤Q≤300mAh / g.

5. The positive electrode sheet according to any one of claims 1 to 4, wherein: Meet the following conditions: 0.05C≤C min ≤0.95C.

6. The positive electrode sheet according to any one of claims 1 to 5, wherein: Meet the following conditions: 0.2g / mm 2 ≤m≤0.4g / mm 2 .

7. The positive electrode sheet according to any one of claims 1 to 6, wherein: The following conditions are met: 190mAh / g≤Q≤280mAh / g.

8. The positive electrode sheet according to any one of claims 1 to 7, wherein: The lithium supplement additive includes one or more of lithium manganese oxide, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobalt oxide and lithium nickel oxide.

9. The positive electrode sheet according to any one of claims 1 to 8, wherein: The positive electrode active material includes one or more of lithium iron phosphate, lithium manganese phosphate and lithium manganese iron phosphate.

10. A battery cell comprising the positive electrode sheet according to any one of claims 1 to 9.

11. The battery cell according to claim 10, wherein: The cycle voltage range of the battery cell is 2.5V to 3.65V.

12. The battery cell according to claim 10 or 11, wherein: The cycle rate range of the battery cell is 0.33C to 2C.

13. A secondary battery comprising the battery cell according to any one of claims 10 to 12.

14. An electrical device comprising the secondary battery according to claim 13.

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