Positive electrode active material, battery cell, battery, and electric device

Abstract

The invention relates to a positive active material, a battery cell, a battery and an electric device. The positive active material comprises lithium-containing phosphate and lithium-containing transition metal oxide, and the mass content of the lithium-containing phosphate relative to the total mass of the positive active material is A%; the mass content of the lithium-containing transition metal oxide relative to the total mass of the positive electrode active material is B%, the lithium-containing transition metal oxide comprises secondary particles, and the positive electrode active material meets the condition that A / B > 1.

Description

Technical Field

[0001] The present application relates to a positive electrode active material, a battery cell, a battery and an electrical device. Background Art

[0002] Battery cells are widely used because of their reliable working performance, no pollution, and no memory effect. For example, as environmental protection issues are increasingly valued and new energy vehicles become more popular, the demand for power battery cells will show explosive growth.

[0003] As battery applications become more and more extensive, the requirements for battery performance are becoming increasingly stringent. However, the cycle life of battery cells is still relatively low and needs to be further improved. Summary of the invention

[0004] The present application provides a positive electrode active material, a battery cell, a battery and an electrical device. The cycle life of the battery cell described in the present application can be improved.

[0005] In the first aspect, an embodiment of the present application proposes a positive electrode active material, which includes a lithium-containing phosphate and a lithium-containing transition metal oxide, the mass content of the lithium-containing phosphate relative to the total mass of the positive electrode active material is A%; the mass content of the lithium-containing transition metal oxide relative to the total mass of the positive electrode active material is B%, and the lithium-containing transition metal oxide includes secondary particles, wherein the positive electrode active material satisfies: A / B>1.

[0006] Therefore, the positive electrode active material proposed in the embodiment of the present application has a lithium-containing phosphate with a mass content greater than that of the lithium-containing transition metal oxide. The lithium-containing phosphate, as the main active material in the positive electrode active material, has a relatively high capacity and can provide a relatively high energy density for the battery cell. The lithium-containing transition metal oxide is added to the positive electrode active material, and the lithium-containing transition metal oxide includes secondary particles, which are formed by the agglomeration of multiple primary particles. The volume average particle size of the secondary particles is relatively large, and different primary particles may have different crystal plane orientations and slip planes, so that the contraction and expansion of the grains show anisotropy, and the lithium-containing transition metal oxide is prone to lithium delithiation, that is, the voltage required for the secondary particles to delithiate is relatively low; as the lithium ions are released, microcracks are easily generated inside the grains; as the cycle deepens, the grains are subjected to greater stress, which can further aggravate the penetration of the electrolyte in the battery cell, causing the secondary particles to further collapse, causing the lithium ions to be released irreversibly, and transferred to the negative electrode plate for lithium replenishment, thereby replenishing the active lithium lost in the negative electrode plate due to the formation of the SEI film and the normal charging and discharging process, and improving the capacity and cycle life of the battery cell. Moreover, during the charging and discharging process of the battery cell, it is not necessary to use the activation voltage of the lithium-containing transition metal oxide, that is, it is not necessary to use the high-voltage charging method. The lithium-containing transition metal oxide can be delithiated under the working voltage of the lithium-containing phosphate, and the active lithium can be basically released under the working voltage of the lithium-containing phosphate, and can be continuously released during the cycle of the battery cell, thereby continuously replenishing lithium to the negative electrode plate and improving the cycle life of the battery cell.

[0007] In some embodiments, the ratio of the volume average particle size Dv50 of the secondary particles to the volume average particle size Dv50 of the lithium-containing phosphate is greater than 1; can be 2 to 40; can be further 3 to 37.5; and can further be 3 to 30.

[0008] Therefore, in the embodiment of the present application, the particle sizes of the lithium-containing phosphate and the lithium-containing transition metal oxide are coordinated with each other, the large-particle lithium-containing transition metal oxides are stacked on each other, and there is a pore structure between adjacent lithium-containing transition metal oxides. The pore structure is filled with small-particle lithium-containing phosphate. In this structure, when the lithium-containing transition metal oxide collapses and releases lithium ions, the small-particle lithium-containing phosphate can maintain the overall structural stability of the positive electrode film layer and improve the cycle life of the battery cell; and this structure can reduce the spacing between the positive electrode active material particles, increase the conductivity of the positive electrode plate, and improve the compaction density of the positive electrode active material, thereby improving the energy density of the battery cell.

[0009] In some embodiments, the volume average particle size Dv50 of the secondary particles is 10 μm to 20 μm, or optionally 12 μm to 20 μm. The volume average particle size of the lithium-containing transition metal oxide within the above range can further improve the delithiation effect of the lithium-containing transition metal oxide.

[0010] In some embodiments, the volume average particle size Dv50 of the lithium-containing phosphate is 0.5 μm to 5.0 μm, or optionally 1 μm to 3 μm. The volume average particle size of the lithium-containing phosphate within the above range can further improve the cycle performance of the battery cell.

[0011] In some embodiments, 3.85≤A / B≤97; optionally, 18.4≤A / B≤96. When the ratio of the mass content of the lithium-containing phosphate to the mass content of the lithium-containing transition metal oxide is within the above range, the lithium supplementation effect can be further improved to increase the capacity and cycle life of the battery system.

[0012] In some embodiments, 78≤A≤99.18; optionally, 89≤A≤99. The lithium-containing phosphate is used as the main active material in the positive electrode active material, and its mass content is within the above range, which can provide a relatively high energy density for the battery cell.

[0013] In some embodiments, 0.82≤B≤22; optionally, 1≤B≤10. The lithium-containing transition metal oxide is used as a lithium supplement material for the battery system, and its mass content is within the above range, which can provide a better lithium supplement effect for the negative electrode plate and improve the cycle performance.

[0014] In some embodiments, the lithium-containing phosphate includes a molecular formula of Li x A y Me a M b P 1-c X c Y z Compounds and modified compounds thereof, wherein 0<x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0<a≤1.5, 0≤b≤0.7, and 0.6≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of Al, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. The lithium-containing phosphate and lithium-containing transition metal oxide of the above materials can be combined to further improve the cycle performance of the battery monomer.

[0015] In some embodiments, the lithium-containing phosphate includes LiFePO4, LiNiPO4, LiCoPO4, LiV 0.67 PO4, LiMnPO4, LiMn 0.2 Fe 0.8 PO4 and LiFe 0.5 Mn 0.5 The combination of the lithium-containing phosphate and the lithium-containing transition metal oxide of the above materials can further improve the cycle performance of the battery cell.

[0016] In some embodiments, the lithium-containing transition metal oxide comprises a molecular formula of Li d Ni g Co h R k S j O r C t Compounds and modified compounds thereof, wherein 0.8≤d≤1.2, 0<g<1, 0<h<1, 0<k<1, 0≤j≤0.1, 1≤r≤2, 0≤t≤1, t+r≤2, R includes at least one of Mn and Al, S includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and C includes one or more of N, F, S, and Cl. The combination of the lithium-containing transition metal oxide and the lithium-containing phosphate of the above materials can further improve the cycle performance of the battery monomer.

[0017] In some embodiments, the lithium-containing transition metal oxide comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 The combination of the lithium-containing transition metal oxide and the lithium-containing phosphate of the above materials can further improve the cycle performance of the battery cell.

[0018] In some embodiments, the lithium-containing transition metal oxide comprises LiNi 0.85 Co 0.15 Al 0.05 O2、LiNi 0.8 Co 0.1 Al 0.1 O2、LiNi 0.5Co 0.2 Al 0.3 O2 and LiNi 1 / 3 Co 1 / 3 Al 1 / 3 The combination of the lithium-containing transition metal oxide and the lithium-containing phosphate of the above materials can further improve the cycle performance of the battery cell.

[0019] In the second aspect, the embodiment of the present application further proposes a battery cell, the battery cell includes a positive electrode plate, the positive electrode plate includes a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, the positive electrode film layer includes the positive electrode active material as described in any embodiment of the first aspect of the present application.

[0020] In a third aspect, the embodiments of the present application further provide a battery, wherein the battery comprises a battery cell as described in any embodiment of the second aspect of the present application.

[0021] In a fourth aspect, an embodiment of the present application further proposes an electrical device, comprising a battery as described in any embodiment of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0023] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0024] Figure 2 yes Figure 1 An exploded schematic diagram of an embodiment of a battery cell.

[0025] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0026] Figure 4 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0027] Figure 5 yes Figure 4 An exploded schematic diagram of an embodiment of a battery pack is shown.

[0028] Figure 6 It is a schematic diagram of an embodiment of an electric device including the battery cell of the present application as a power source.

[0029] The drawings are not necessarily drawn to scale.

[0030] The following are the descriptions of the reference numerals:

[0031] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 51. Shell; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. DETAILED DESCRIPTION

[0032] Hereinafter, the embodiments of the positive electrode active material, battery cell, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the 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 descriptions 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.

[0033] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, 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 a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] 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.

[0036] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0038] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0039] A battery cell includes a positive electrode sheet, a negative electrode sheet, and an electrolyte. The positive electrode sheet includes a positive active substance. The positive active substance is a donor of metal ions such as lithium ions and sodium ions provided by the battery cell. The negative electrode sheet is an acceptor of metal ions. The electrolyte provides a migration path for metal ions between the positive electrode sheet and the negative electrode sheet. In the production process of battery cells, it is necessary to go through processes such as battery formation, that is, to activate the active substances on the positive and negative electrodes by chemical and electrochemical reactions, so that they are converted into positive and negative electrodes with electrochemical properties. In the formation process, the solvent in the electrolyte decomposes, and the decomposed solvent molecules react chemically with electrons and metal ions to form a passivation film, namely the solid electrolyte interface (SEI) film, on the surface of the active material. The SEI film is an interface film that is electrically insulating and has excellent ion conductivity, and can reduce excessive decomposition of the electrolyte.

[0040] However, the formation of SEI film is a process of consuming active metal ions. Due to the loss of metal ions in the positive electrode active material, the capacity of the battery cell decreases and its cycle performance deteriorates. In order to improve the capacity and cycle life of the battery cell, it is considered to supplement the battery system with lithium. In the related art, it is considered to add active materials different from lithium phosphate to the positive electrode active material system mainly containing lithium phosphate. However, since the charging voltage of lithium phosphate and active materials different from lithium phosphate may be different, when the battery system is supplemented with lithium, side reactions may occur in the pole piece, deteriorating the performance of the battery cell.

[0041] In view of the above problems, in the implementation mode of the present application, a lithium-containing transition metal oxide is added to the positive electrode active material system mainly composed of lithium phosphate. The lithium-containing transition metal oxide includes secondary particles. The particle size of the secondary particles is relatively large. When the positive electrode active material is applied to a battery cell, during the cyclic charge and discharge process of the battery cell, the lithium-containing transition metal oxide can continuously release lithium ions, and the lithium ions migrate to the negative electrode plate to replenish the negative electrode lithium, thereby improving the cycle life of the battery cell.

[0042] Positive active material

[0043] In the first aspect, an embodiment of the present application proposes a positive electrode active material, which includes a lithium-containing phosphate and a lithium-containing transition metal oxide, wherein the mass content of the lithium-containing phosphate relative to the total mass of the positive electrode active material is A%; the mass content of the lithium-containing transition metal oxide relative to the total mass of the positive electrode active material is B%, and the lithium-containing transition metal oxide includes secondary particles, wherein the positive electrode active material satisfies: A / B>1.

[0044] The working voltage of lithium-containing phosphates is relatively lower than that of lithium-containing transition metal oxides. In order to allow lithium-containing transition metal oxides to smoothly release lithium ions, the working voltage of the battery cell is usually increased in the relevant technology so that the working voltage reaches the activation voltage of the lithium-containing transition metal oxide, and the lithium-containing transition metal oxide is activated and delithium is removed. However, such operation will cause side reactions in the electrode, resulting in increased electrode interface impedance, increased polarization, and deterioration of the performance of the battery cell. Moreover, this method may only be able to remove lithium within the activation voltage range of the lithium-containing transition metal oxide, and cannot continuously remove lithium, that is, it is impossible to continuously replenish lithium to the negative electrode, resulting in relatively poor lithium replenishment effect and insignificant improvement in the cycle performance of the battery cell.

[0045] Compared with lithium-containing phosphates, lithium-containing transition metal oxides decay faster during the battery cell cycle. In a system with lithium-containing phosphates as the main active substance, the lithium-containing transition metal oxides that decay faster can provide active lithium for the negative electrode.

[0046] According to the positive electrode active material proposed in the embodiment of the present application, the mass content of the lithium-containing phosphate is greater than that of the lithium-containing transition metal oxide. As the main active material in the positive electrode active material, the lithium-containing phosphate has a relatively high capacity and can provide a relatively high energy density for the battery cell. The lithium-containing transition metal oxide is added to the positive electrode active material. Since the normal operating voltage of the lithium-containing transition metal oxide is higher than that of the lithium-containing phosphate, the decay of the lithium-containing transition metal oxide is relatively slow under the operating voltage of the lithium-containing phosphate. In order to accelerate the decay of the lithium-containing transition metal oxide, the embodiment of the present application increases the volume average particle size of the lithium-containing transition metal oxide to achieve accelerated cycle decay under a relatively low operating voltage. Specifically, the lithium-containing transition metal oxide includes secondary particles, which are formed by the agglomeration of multiple primary particles. The volume average particle size of the secondary particles is relatively large, and different primary particles may have different crystallinity. The surface orientation and slip plane make the contraction and expansion of the grains show anisotropy, and the lithium-containing transition metal oxide is prone to delithiation, that is, the voltage required for the secondary particles to delithiate is relatively low; as the lithium ions are released, microcracks are easily generated inside the grains; as the cycle deepens, the grains are subjected to greater stress, which can further aggravate the penetration of the electrolyte in the battery cell, causing the secondary particles to further collapse, resulting in the irreversible release of lithium ions, and transferring to the negative electrode plate for lithium replenishment, thereby replenishing the active lithium lost in the negative electrode plate due to the formation of the SEI film and the normal charging and discharging process, and improving the capacity and cycle life of the battery cell. Moreover, during the charging and discharging process of the battery cell, it is not necessary to use the activation voltage of the lithium-containing transition metal oxide, that is, it is not necessary to use the high-voltage charging method, and the lithium-containing transition metal oxide can be delithiated at the working voltage of the lithium-containing phosphate, and the active lithium can basically be released at the working voltage of the lithium-containing phosphate, and can be continuously released during the cycle of the battery cell, thereby continuously replenishing the negative electrode plate with lithium and improving the cycle life of the battery cell.

[0047] The particle size of the lithium-containing transition metal oxide has a certain influence on the delithiation effect. In order to further improve the delithiation effect of the lithium-containing transition metal oxide, in some embodiments, the volume average particle size Dv50 of the secondary particles of the lithium-containing transition metal oxide is regulated to be 10μm to 20μm; in order to further improve the delithiation effect of the lithium-containing transition metal oxide, the volume average particle size Dv50 of the secondary particles can be selected to be 12μm to 20μm. Exemplarily, the volume average particle size Dv50 of the secondary particles can be 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm or a range consisting of any two of the above values.

[0048] The particle sizes of lithium-containing phosphate and lithium-containing transition metal oxide are coordinated with each other, large-particle lithium-containing transition metal oxides are stacked with each other, and there is a pore structure between adjacent lithium-containing transition metal oxides, and the pore structure is filled with small-particle lithium-containing phosphate. In this structure, when the lithium-containing transition metal oxide collapses and releases lithium ions, the small-particle lithium-containing phosphate can maintain the overall structural stability of the positive electrode film layer and improve the cycle life of the battery cell; and this structure can reduce the spacing between the positive electrode active material particles, increase the conductivity of the positive electrode plate, and improve the compaction density of the positive electrode active material, thereby improving the energy density of the battery cell. In some embodiments, the ratio of the volume average particle size Dv50 of the secondary particles to the volume average particle size Dv50 of the lithium-containing phosphate is greater than 1; in order to further improve the cycle life of the battery cell, the ratio of the volume average particle size Dv50 of the secondary particles to the volume average particle size Dv50 of the lithium-containing phosphate can be selected from 2 to 40, further selected from 3 to 37.5; and further selected from 3 to 30. Illustratively, the ratio of the volume average particle size Dv50 of the secondary particles to the volume average particle size Dv50 of the lithium phosphate can be 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 7.5, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37.5, 40, 50 or a range consisting of any two of the above values.

[0049] In order to further improve the cycle performance of the battery cell, in some embodiments, the volume average particle size Dv50 of the lithium-containing phosphate is 0.5 μm to 5.0 μm; optionally 1 μm to 3 μm. Exemplarily, the volume average particle size Dv50 of the lithium-containing phosphate can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range consisting of any two of the above values.

[0050] In the embodiment of the present application, the volume average particle size Dv50 of the material is a well-known meaning in the art, specifically referring to the particle size corresponding to 50% in the volume distribution, which can be measured by testing methods and instruments known in the art. For example, according to GB / T19077-2016, a certain amount of the negative electrode active material sample prepared above is taken, and the volume average particle size Dv50 is tested by a Mastersizer 2000E laser particle size analyzer.

[0051] In the positive electrode active material with lithium-containing phosphate as the main material, the mass content of lithium-containing phosphate is greater than the mass content of lithium-containing transition metal oxide. The added amount of lithium-containing transition metal oxide has a certain influence on the lithium replenishment effect in the battery system. In order to further improve the lithium replenishment effect and enhance the capacity and cycle life of the battery system, in some embodiments, 3.41≤A / B≤120.25; optionally, 3.85≤A / B≤99; further optionally, 3.85≤A / B≤97; further optionally, 18.4≤A / B≤96. Illustratively, A / B may be 3.41, 3.50, 3.854, 4.5, 5, 5.5, 6, 6.5, 7, 8, 9, 10, 12, 15, 16, 17, 18, 18.4, 19, 20, 23, 25, 28, 30, 32, 34, 35, 40, 45, 48, 50, 52, 55, 58, 60, 62, 65, 70, 75, 80, 85, 90, 92, 94, 95, 96, 97, 98, 99, or a range consisting of any two of the above values.

[0052] In some embodiments, 78≤A≤99.18; further optionally, 89≤A≤99. For example, the mass content of the lithium-containing phosphate may be 78%, 78.35%, 79%, 79.38%, 79.5%, 80%, 81%, 82%, 85%, 86%, 88%, 89%, 89.5%, 89.69%, 90%, 92%, 93%, 94%, 94.5%, 94.85%, 95%, 96%, 96.2%, 97%, 98%, 98.97%, 99%, 99.18% or a range consisting of any two of the above values.

[0053] In some embodiments, 0.82≤B≤22; further optionally, 1≤B≤10. For example, the mass content of the lithium-containing transition metal oxide can be 0.82%, 1%, 1.03%, 1.1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.15%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, 10%, 10.31%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 20.2%, 20.5%, 20.62%, 21%, 21.2%, 21.5%, 21.65%, or a range consisting of any two of the above values.

[0054] In order to further improve the cycle life of the battery cell, the types of lithium-containing phosphates and lithium-containing transition metal oxides are further selected. In some embodiments, the lithium-containing phosphate includes a molecular formula of Li x A y Mea M b P 1-c X c Y z Compounds and modified compounds thereof, wherein 0<x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0<a≤1.5, 0≤b≤0.7, and 0.6≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5;

[0055] A includes one or more of Na, K, and Mg;

[0056] Me includes one or more of Mn, Fe, Co, and Ni;

[0057] M includes one or more of Al, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce;

[0058] X includes one or more of S, Si, Cl, B, C, and N;

[0059] Y includes O, F or one or more.

[0060] In some embodiments, M includes at least one of V, Ti, Zn, Sn, Nb, Zr, Mg and Al. By further selecting the element, it can better cooperate with the lithium-containing transition metal oxide to improve the cycle performance of the battery cell.

[0061] Illustratively, x may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or a range consisting of any two of the above values.

[0062] Illustratively, y may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or a range consisting of any two of the above values.

[0063] Illustratively, x+y may be 0.9, 1.0, 1.1, 1.2, 1.3, or a range consisting of any two of the above values.

[0064] Illustratively, a can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two of the above values.

[0065] Illustratively, b may be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or a range consisting of any two of the above values.

[0066] Illustratively, a+b may be 0.6, 0.67, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two of the above values.

[0067] Illustratively, c may be 0, 0.1, 0.2, 0.3, 0.4, 0.5, or a range consisting of any two of the above values.

[0068] Illustratively, z may be 3, 3.1, 3.2, 3.3, 3.5, 3.6, 3.8, 4, 4.1, 4.2, 4.5, 4.8, 4.9, 5, or a range consisting of any two of the above values.

[0069] In some embodiments, when Me includes Mn and Fe, the molar amount of Mn is less than or equal to the molar amount of Fe.

[0070] Exemplarily, the lithium-containing phosphate includes LiFePO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, LiMnPO4, LiMn 0.2 Fe 0.8 PO4 and LiFe 0.5 Mn 0.5 It is understood that Li3V2(PO4)3 can be converted to LiV 0.67 PO4.

[0071] The modified compound may refer to a doping modification in the compound, or a coating modification by setting a coating layer on the surface of the particle. The coating layer may be set as a conductive layer such as a carbon layer, an organic polymer layer, etc.

[0072] In some embodiments, the lithium-containing transition metal oxide comprises a molecular formula of Li d Ni g Co h R k S j O r C t Compounds and modified compounds thereof, wherein 0.8≤d≤1.2, 0<g<1, 0<h<1, 0<k<1, 0≤j≤0.1, 1≤r≤2, 0≤t≤1, t+r≤2,

[0073] R includes at least one of Mn and Al,

[0074] S includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb,

[0075] C includes one or more of N, F, S, and Cl.

[0076] Illustratively, d may be 0.8, 0.9, 1.0, 1.1, 1.2, or a range consisting of any two of the above values.

[0077] Illustratively, g may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, or a range consisting of any two of the above values.

[0078] Illustratively, h may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, or a range consisting of any two of the above values.

[0079] Illustratively, k may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, or a range consisting of any two of the above values.

[0080] Illustratively, j may be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a range consisting of any two of the above values.

[0081] Illustratively, r may be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range consisting of any two of the above values.

[0082] Illustratively, t may be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, 1, or a range consisting of any two of the foregoing values.

[0083] Illustratively, t+r may be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range consisting of any two of the above values.

[0084] In some embodiments, R includes Mn, and the lithium-containing transition metal oxide includes a molecular formula of Li d Ni g Co h Mn k S j O r C tCompounds and modified compounds thereof.

[0085] Exemplarily, the lithium-containing transition metal oxide includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622) and LiNi 0.8 Co 0.1 Mn 0.1 At least one of O2 (NCM811).

[0086] In some embodiments, R comprises Al, and the lithium-containing transition metal oxide comprises a molecular formula of Li d Ni g Co h Al k S j O r C t Compounds and modified compounds thereof.

[0087] Exemplarily, the lithium-containing transition metal oxide includes LiNi 0.85 Co 0.15 Al 0.05 O2、LiNi 0.8 Co 0.1 Al 0.1 O2(NCA811), LiNi 0.5 Co 0.2 Al 0.3 O2(NCA523), LiNi 1 / 3 Co 1 / 3 Al 1 / 3 At least one of O2.

[0088] The modified compound may refer to a doping modification in the compound, or a coating modification by setting a coating layer on the surface of the particle. The coating layer may be set as a conductive layer such as a carbon layer, an organic polymer layer, etc.

[0089] The types and mass contents of various materials in the positive electrode active material in the embodiments of the present application are well known in the art and can be tested and / or calculated using equipment and methods well known in the art. For example, X-ray diffraction patterns can be used to distinguish various materials, specifically by comparing the positions and intensities of the peaks with those of the standard cards of the various materials.

[0090] Battery Cell

[0091] In a second aspect, the present application proposes a battery cell, the battery cell comprising a positive electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material according to any embodiment of the first aspect of the present application, and the positive electrode active material is used to extend the cycle life of the battery cell.

[0092] [Positive electrode]

[0093] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0094] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0095] 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.).

[0096] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. In some embodiments, based on the total weight of the positive electrode film layer, the mass percentage of the binder is ≤5wt%.

[0097] In some embodiments, the positive electrode film layer may further include a conductive agent. As an 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. In some embodiments, based on the total weight of the positive electrode film layer, the mass percentage of the conductive agent is ≤5wt%.

[0098] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the optional conductive agent, the optional 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 collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0099] [Negative electrode]

[0100] The secondary battery also includes a negative electrode sheet.

[0101] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0102] The negative electrode active material may be a negative electrode active material for a secondary battery known in the art. As an example, the negative electrode active material may include but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0103] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The embodiment of the present application has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the negative electrode conductive agent is ≤5wt%.

[0104] In some embodiments, the negative electrode film layer may also optionally include a negative electrode binder. The embodiment of the present application has no particular restrictions on the type of the negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the negative electrode binder is ≤5wt%.

[0105] In some embodiments, the negative electrode film layer may further include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass percentage of the other additives is ≤2wt%.

[0106] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0107] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0108] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the embodiments 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 collector and the negative electrode film layer and disposed on the surface of the negative electrode collector. In some other embodiments, the negative electrode plate described in the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0109] [Electrolyte]

[0110] In some embodiments, the battery cell further includes an electrolyte.

[0111] During the charge and discharge process of the battery cell, active ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays a role in conducting active ions between the positive electrode and the negative electrode. The present application has no particular restrictions on the type of electrolyte, which can be selected according to actual needs.

[0112] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0113] As an example, the electrolyte salt may include, but is not limited to, at least one 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).

[0114] As an example, the solvent may include, but is not limited to, at least one of 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), fluoroethylene carbonate (FEC), 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).

[0115] In some embodiments, the electrolyte may further include additives, for example, the additives may include positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.

[0116] [Isolation film]

[0117] In some embodiments, the battery cell further includes a separator.

[0118] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0119] In some embodiments, the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0120] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly by a winding process and / or a lamination process.

[0121] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0122] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0123] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0124] In some embodiments, Figure 2 As shown, the outer package 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 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process and / 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, which can be adjusted according to demand.

[0125] The preparation method of the battery cell of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the battery cell is obtained through vacuum packaging, standing, forming, shaping and other processes.

[0126] In some embodiments of the present application, the battery cells according to the present application may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module.

[0127] Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0128] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0129] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0130] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0131] The battery according to the embodiment of the present application may include one battery cell or a plurality of battery cells. When the battery includes a plurality of battery cells, the battery may include a battery module or a battery pack.

[0132] Electrical devices

[0133] The third aspect of the embodiment of the present application provides an electric device, which includes at least one of the battery cells, battery modules or battery packs of the present application. The battery cells, battery modules or battery packs can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0134] The electrical device may select a battery cell, a battery module or a battery pack according to its usage requirements.

[0135] Figure 6 Schematic diagram of an exemplary electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device 6 for high power and high energy density, a battery pack or a battery module may be used.

[0136] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0137] Example

[0138] The following embodiments describe the contents disclosed in the present application in more detail, and these embodiments are only used for illustrative explanations, because it is obvious to those skilled in the art that various modifications and changes are made within the scope of the present application disclosure. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods, and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0139] Example 1 Preparation of lithium ion battery

[0140] 1. Preparation of positive electrode

[0141] Aluminum foil with a thickness of 15 μm was used as the positive electrode current collector.

[0142] The positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:1:1 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode film layer on the aluminum foil is obtained through drying, cold pressing, slitting, cutting and other processes. The positive electrode sheet includes the positive electrode film layer and the positive electrode current collector. The compacted density of the positive electrode active material is 2.6g / cm 3 The positive electrode active material includes 92% of lithium-containing phosphate LiFePO4 and 5% of lithium-containing transition metal oxide NCM811, and the mass contents of the lithium-containing phosphate and the lithium-containing transition metal oxide are calculated based on the total mass of the positive electrode film layer.

[0143] 2. Preparation of negative electrode sheet

[0144] A copper foil with a thickness of 10 μm was used as the negative electrode current collector.

[0145] The natural graphite, sodium carboxymethyl cellulose, conductive carbon, and adhesive styrene butadiene rubber (SBR) as negative electrode active materials are mixed evenly in deionized water to prepare negative electrode slurry. The solid content of the negative electrode slurry is 53%, and the mass ratio of natural graphite, sodium carboxymethyl cellulose, conductive carbon, and adhesive styrene butadiene rubber in the solid components is 96:1:1:2. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C and cold pressed to obtain a negative electrode sheet containing a negative electrode film layer.

[0146] 3. Preparation of electrolyte

[0147] In an environment with a water content of less than 10 ppm, organic solvents ethylene carbonate EC and diethyl carbonate DEC are mixed in a volume ratio of 3:7 to obtain an electrolyte solvent, and then lithium salt lithium hexafluorophosphate and the mixed solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0148] 4. Preparation of lithium-ion batteries

[0149] The positive electrode sheet, polyethylene PE separator (7 μm thickness), and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0150] Example 2-1 to Example 2-6

[0151] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the lithium-containing transition metal oxide was adjusted in Examples 2-1 to 2-6.

[0152] Example 3-1 to Example 3-4

[0153] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the lithium-containing phosphate was adjusted in Examples 3-1 and 3-4.

[0154] Example 4-1 to Example 4-5

[0155] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size of the lithium-containing phosphate was adjusted in Examples 4-1 to 4-5.

[0156] Example 5-1 to Example 5-5

[0157] A lithium-ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 was that the types of positive electrode active materials were adjusted in Examples 5-1 to 5-5.

[0158] Comparative Example 1

[0159] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that no lithium-containing transition metal oxide was added in Comparative Example 1.

[0160] Comparative Example 2

[0161] A lithium ion battery was prepared by a method similar to that of Example 1. The difference from Example 1 is that the lithium-containing transition metal oxide in Comparative Example 1 is a primary particle.

[0162] The relevant parameters of the embodiments and comparative examples are shown in Table 1.

[0163] Test Section

[0164] 1. Cycle performance test of lithium-ion batteries

[0165] At 25°C, the lithium-ion battery was charged to 3.8V at a charge rate of 0.33C and discharged to 2.0V at a rate of 0.33C. The capacity of the lithium-ion battery decayed to 80% of the initial capacity, and the number of cycles was recorded.

[0166] Test Results

[0167] The test results are shown in Table 1

[0168] Table 1

[0169]

[0170]

[0171] In Table 1, the mass content M% of lithium-containing phosphate is calculated based on the total mass of the positive electrode film layer; the mass content N% of lithium-containing transition metal oxide is calculated based on the total mass of the positive electrode film layer.

[0172] The mass content of lithium-containing phosphate relative to the total mass of the positive electrode active material is A%; the mass content of lithium-containing transition metal oxide relative to the total mass of the positive electrode active material is B%. It should be noted that the value of A / B is the same as that of M / N, so A / B can be calculated by M / N. However, since the positive electrode film layer also includes optional binders and conductive agents, etc., M% is not the same as A%, and N% is not the same as B%.

[0173] In Examples 1 to 5-5, the lithium-containing transition metal oxide is a secondary particle, and its volume average particle size D2 in Table 1 refers to the volume average particle size of the secondary particles; in Comparative Example 2, the lithium-containing transition metal oxide is a primary particle, and its volume average particle size D2 in Table 1 refers to the volume average particle size of the primary particles.

[0174] As shown in Table 1, no lithium-containing transition metal oxide is added in Comparative Example 1. Compared with Comparative Example 1, primary particles of lithium-containing transition metal oxide are added in Comparative Example 2. Under the working voltage of lithium-containing phosphate, the lithium-containing transition metal oxide composed of primary particles is not easy to release lithium ions by cyclic decay, which may lead to a decrease in the available capacity and make it difficult to replenish lithium for the negative electrode plate, which has the risk of deteriorating the cycle performance of the lithium-ion battery. And because the content of lithium-containing phosphate in Comparative Example 1 is relatively high (97%), the capacity it contributes is relatively high, and the cycle performance of the lithium-ion battery of Comparative Example 1 is relatively good.

[0175] Compared with Comparative Example 1, the lithium-containing transition metal oxide with secondary particles added in the embodiment of the present application is more likely to undergo cyclic decay and release lithium ions under the working voltage of the lithium-containing phosphate, and can replenish lithium for the negative electrode plate, which can improve the cycle performance of the lithium-ion battery; the present application is applicable to a variety of lithium-containing phosphate materials and a variety of lithium-containing transition metal oxide materials. In addition, the embodiment of the present application can further improve the cycle performance of the lithium-ion battery by adjusting the volume average particle size of the lithium-containing transition metal oxide; by adjusting the volume average particle size of the lithium-containing phosphate, the cycle performance of the lithium-ion battery can be further improved; by adjusting the mass content of the lithium-containing phosphate, the cycle performance of the lithium-ion battery can be further improved. It should be noted that Examples 4-1 to 4-5 can improve the cycle performance of lithium-ion batteries by adjusting the amount of lithium-containing phosphate and lithium-containing transition metal oxide added; compared with Comparative Example 1, Examples 4-3 and 4-4 have relatively low capacities due to relatively less added lithium-containing phosphate, so the cycle performance of Comparative Example 1 is slightly higher; however, compared with Comparative Example 2, the cycle performance of Examples 4-1 to 4-5 are all improved, and the contribution of large-particle lithium-containing transition metal salts to the cycle performance can still be reflected.

[0176] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode active material, comprising: A lithium-containing phosphate, the mass content of which relative to the total mass of the positive electrode active material is A%; A lithium-containing transition metal oxide, whose mass content relative to the total mass of the positive electrode active material is B%, and the lithium-containing transition metal oxide includes secondary particles, wherein: The positive electrode active material satisfies: A / B>1.

2. The positive electrode active material according to claim 1, wherein The ratio of the volume average particle size Dv50 of the secondary particles to the volume average particle size Dv50 of the lithium-containing phosphate is greater than 1; it can be 2 to 40, further can be 3 to 37.5, and further can be 3 to 30.

3. The positive electrode active material according to claim 1 or 2, wherein The volume average particle size Dv50 of the secondary particles is 10 μm to 20 μm, and can be optionally 12 μm to 20 μm.

4. The positive electrode active material according to any one of claims 1 to 3, wherein The volume average particle size Dv50 of the lithium-containing phosphate is 0.5 μm to 5.0 μm; The range is selectable from 1 μm to 3 μm.

5. The positive electrode active material according to any one of claims 1 to 4, wherein 3.85≤A / B≤97; optionally, 18.4≤A / B≤96.

6. The positive electrode active material according to any one of claims 1 to 5, wherein 78≤A≤99.18; optionally, 89≤A≤99.

7. The positive electrode active material according to any one of claims 1 to 6, wherein 0.82≤B≤22; optionally, 1≤B≤10.

8. The positive electrode active material according to any one of claims 1 to 7, wherein The lithium-containing phosphate includes a molecular formula of Li x A y Me a M b P 1-c X c Y z Compounds and modified compounds thereof, wherein 0<x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0<a≤1.5, 0≤b≤0.7, and 0.6≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of Al, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F; Optionally, the lithium-containing phosphate includes LiFePO4, LiNiPO4, LiCoPO4, LiV 0.67 PO4, LiMnPO4, LiMn 0.2 Fe 0.8 PO4 and LiFe 0.5 Mn 0.5 One or more of PO4.

9. The positive electrode active material according to any one of claims 1 to 8, wherein The lithium-containing transition metal oxide includes a molecular formula of Li d Ni g Co h R k S j O r C t Compounds and modified compounds thereof, wherein 0.8≤d≤1.2, 0<g<1, 0<h<1, 0<k<1, 0≤j≤0.1, 1≤r≤2, 0≤t≤1, t+r≤2, R includes at least one of Mn and Al, S includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, C includes one or more of N, F, S, and Cl; Optionally, the lithium-containing transition metal oxide comprises LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2 and LiNi 0.8 Co 0.1 Mn 0.1 At least one of O2; Optionally, the lithium-containing transition metal oxide comprises LiNi 0.85 Co 0.15 Al 0.05 O2、LiNi 0.8 Co 0.1 Al 0.1 O2、LiNi 0.5 Co 0.2 Al 0.3 O2 and LiNi 1 / 3 Co 1 / 3 Al 1 / 3 At least one of O2.

10. A battery cell, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material according to any one of claims 1 to 9.

11. A battery comprising the battery cell according to claim 10.

12. An electrical device comprising the battery as claimed in claim 11.

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