Positive electrode active material, positive electrode sheet, secondary battery, and electric device

Abstract

The invention relates to the technical field of secondary batteries, and particularly provides a positive active material, a positive pole piece, a secondary battery and an electric device. The positive electrode active material includes a lithium-containing phosphate and a lithium-containing metal oxide. Wherein the lithium-containing metal oxide accounts for 1%-20% of the positive electrode active material in percentage by mass. An X-ray diffraction pattern of the lithium-containing metal oxide comprises a diffraction peak of a crystal face (003) and a diffraction peak of a crystal face (104), the diffraction peak of the crystal face (003) and the diffraction peak of the crystal face (104) meet the condition that the value of I (003) / I (104) is smaller than or equal to 1.2, I (003) represents the intensity of the diffraction peak of the crystal face (003), and I (104) represents the intensity of the diffraction peak of the crystal face (104). The positive electrode plate comprises a current collector and a positive electrode film layer arranged on the current collector. The positive electrode film layer comprises the positive electrode active material. And the positive electrode active material accounts for 90-97% of the mass of the positive electrode film layer. The positive electrode active material provided by the invention can provide cycle performance of the secondary battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a positive electrode active material, a positive electrode sheet, a secondary battery and an electrical device. Background Art

[0002] Secondary batteries are widely used in various consumer electronic products and electric vehicles due to their outstanding features of light weight, no pollution and no memory effect. With the continuous development of the new energy industry, users have put forward higher requirements for the reliability of secondary batteries. However, the secondary battery will cause the loss of active lithium during the charging and discharging process, which will reduce the cycle performance of the secondary battery. Summary of the invention

[0003] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, a positive electrode plate, a secondary battery and an electrical device, aiming to solve the cycle performance of the secondary battery.

[0004] In order to solve the above technical problems, the first technical solution adopted by the present application is: to provide a positive electrode active material, which includes a lithium-containing phosphate and a lithium-containing metal oxide. Wherein, the mass percentage of the lithium-containing metal oxide in the positive electrode active material is 1%-20%. The X-ray diffraction spectrum of the lithium-containing metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the diffraction peak of the (003) crystal plane and the diffraction peak of the (104) crystal plane satisfy: I(003) / I(104)≤1.2, wherein I(003) represents the intensity of the diffraction peak of the (003) crystal plane, and I(104) represents the intensity of the diffraction peak of the (104) crystal plane. Li + When released from lithium-containing metal oxides, lithium-containing metal oxides easily transform from a layered structure to a spinel / rock salt phase structure, which can increase the Li + The embedding impedance affects its lithium embedding capacity, that is, the released Li+ can no longer be transferred back to the lithium-containing metal oxide through discharge. Therefore, the lithium-containing metal oxide with a high degree of cation mixing has a low capacity retention rate, which can remove lithium during each charge and discharge process, making Li + It is irreversibly released and transferred to the negative electrode to supplement the active lithium. Therefore, during the cycle, the active lithium of the battery can be continuously supplemented without increasing the charging voltage, thereby improving the cycle performance of the secondary battery.

[0005] In any embodiment of the present application, the lithium-containing phosphate includes a molecular formula of Li x A y Me a M b P 1-c X c Y zCompounds and their modified compounds, where 0 < x ≤ 1.3, 0 ≤ y < 1.3, and 0.9 ≤ x + y ≤ 1.3, 0 < a ≤ 1.5, 0 ≤ b ≤ 0.7, 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 at least one of lithium iron phosphate and lithium vanadium phosphate; Optionally, the lithium-containing phosphate includes one or more of LiFePO4, LiNiPO4, LiCoPO4, LiV 0.67 PO4, LiMnPO4, LiMn 0.2 Fe 0.8 PO4, and LiMn 0.5 Fe 0.5 PO4.

[0006] In the technical solution of the embodiment of the present application, restricting the lithium-containing phosphate within the above range can continuously supplement the active lithium of the battery without increasing the charging voltage, thereby improving the cycle performance of the secondary battery.

[0007] In any implementation manner of the present application, the lithium-containing metal oxide includes compounds and their modified compounds with the molecular formula Li d Ni g Co h R k Q j O r T t where 0.8 ≤ d ≤ 1.2, 0 < g < 1, 0 < h < 1, 0 < k < 1, 0 ≤ j ≤ 0.1, 1 ≤ r ≤ 2, 0 ≤ t ≤ 1, and t + r ≤ 2; R includes at least one of Mn and Al; Q includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb; T includes one or more of N, F, S, and Cl; Optionally, the lithium-containing metal oxide includes at least one of lithium nickel cobalt manganate and lithium nickel cobalt aluminate; Optionally, the lithium-containing metal oxide includes 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 0.2O2 and LiNi 0.8 Co 0.1 Mn 0.1 At least one of O2; optionally, the lithium-containing metal oxide includes 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 / 3Al 1 / 3 At least one of O2.

[0008] In the technical solution of the embodiment of the present application, the lithium-containing metal oxide is limited to the above range, which can continuously replenish the active lithium of the battery without increasing the charging voltage, thereby improving the cycle performance of the secondary battery.

[0009] In any embodiment of the present application, in the lithium-containing metal oxide, the molar ratio of nickel element to all metal elements except lithium element is greater than or equal to 50%.

[0010] In the technical solution of the embodiment of the present application, by increasing the content of nickel to be greater than or equal to 50%, enough Ni 2+ Occupy Li + The position in the crystal lattice makes it impossible for the released Li+ to return to the lithium-containing metal oxide through discharge transfer, thus playing the role of lithium replenishment.

[0011] In any embodiment of the present application, the lithium-containing metal oxide accounts for 1%-5% by mass of the positive electrode active material.

[0012] In the technical solution of the embodiment of the present application, the mass percentage of the lithium-containing metal oxide is controlled within the above range, which can not only not affect the role of the lithium-containing phosphate in the positive electrode active material, but also play the role of lithium supplementation.

[0013] In any embodiment of the present application, the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is ≤1.

[0014] In the technical solution of the embodiment of the present application, the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is further limited to the above range, which can further improve the effect of the lithium-containing metal oxide as a lithium supplement, that is, can further improve the cycle performance of the secondary battery.

[0015] The second technical solution adopted in the present application is: to provide a positive electrode plate, which includes a current collector and a positive electrode film layer arranged on the current collector. The positive electrode film layer includes the positive electrode active material as described above. Optionally, the positive electrode active material accounts for 90%-97% of the mass of the positive electrode film layer.

[0016] In the technical solution of the embodiment of the present application, controlling the mass percentage of the positive electrode active material within the above range can improve the energy density of the secondary battery, thereby improving the cycle performance of the secondary battery.

[0017] The third technical solution adopted by the present application is to provide a secondary battery, which includes the positive electrode sheet, the negative electrode sheet and the separator as described above. The separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0018] In the technical solution of the embodiment of the present application, the secondary battery includes the above-mentioned positive electrode active material, and thus has the same advantage of good cycle performance.

[0019] In any embodiment of the present application, the input voltage of the secondary battery is 2.0V-3.8V.

[0020] In the technical solution of the embodiment of the present application, the secondary battery can continuously replenish lithium during each charge and discharge process when the input voltage is between 2.0V and 3.8V, without the need to increase the charging voltage to replenish lithium.

[0021] In any embodiment of the present application, the charging temperature of the secondary battery is 30-45°C.

[0022] In the technical solution of the embodiment of the present application, the charging temperature of the secondary battery is within the above temperature range, the charging efficiency of the lithium battery is the highest, the charging time is the shortest, and at the same time, the lithium replenishment effect is good, and the reliability and life of the battery can also be improved.

[0023] The fourth technical solution adopted in the present application is to provide an electrical device, which includes the secondary battery as described above.

[0024] In the technical solution of the embodiment of the present application, the electrical device includes the above-mentioned secondary battery, and thus has the same advantage of good cycle performance.

[0025] In any embodiment of the present application, the electrical device further comprises a temperature regulator, and the temperature regulator is used to adjust the ambient temperature of the secondary battery to 30-45°C.

[0026] In the technical solution of the embodiment of the present application, by providing a temperature regulator in the power-consuming device, the ambient temperature of the secondary battery can be adjusted, so that the secondary battery can be charged within a corresponding temperature range, thereby improving the charging efficiency.

[0027] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0029] Figure 1 It is a schematic diagram of one embodiment of a secondary battery.

[0030] Figure 2 yes Figure 1 Exploded diagram of .

[0031] Figure 3 is a schematic diagram of an embodiment of a battery module.

[0032] Figure 4 is a schematic diagram of one embodiment of a battery pack.

[0033] Figure 5 yes Figure 4 Exploded diagram of .

[0034] Figure 6 It is a schematic diagram of one embodiment of a device in which a secondary battery is used as a power source. DETAILED DESCRIPTION

[0035] The present application is further described below in conjunction with specific implementations. It should be understood that these specific implementations are only used to illustrate the present application and are not used to limit the scope of the present application.

[0036] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0037] In the description herein, unless otherwise specified, the term "or" is inclusive. That is, the phrase "A or (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).

[0038] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and "several" in "one or several" means two or more.

[0039] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0040] [Positive electrode active material]

[0041] The positive electrode active material provided in the embodiment of the present application is applied to a secondary battery. The positive electrode active material of the secondary battery includes lithium-containing phosphates and lithium-containing metal oxides, so it can also be called a lithium-ion battery or a lithium battery. The positive electrode active material is the decisive factor in the electrochemical performance of the lithium battery, directly determining the energy density and reliability of the battery, and thus affecting the overall performance of the battery. In addition to lithium-containing phosphates and lithium-containing metal oxides, the positive electrode active material of the lithium battery may also include a conductive agent, a solvent, an adhesive, an additive, an auxiliary material, and the like.

[0042] The mass percentage of the lithium-containing metal oxide in the positive electrode active material is 1%-20%. For example, the mass percentage of the lithium-containing metal oxide in the positive electrode active material can be 1%, 3%, 5%, 8%, 10%, 11.5%, 12%, 14%, 15%, 16%, 18%, 20%, etc., or a range formed by any two of the above values, for example, it can be 1%-8%, 3%-12%, 8%-12%, 3%-16%, 16%-20%, etc.

[0043] The X-ray diffraction spectrum of the lithium-containing metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the diffraction peak of the (003) crystal plane and the diffraction peak of the (104) crystal plane satisfy: I(003) / I(104)≤1.2, wherein I(003) represents the intensity of the diffraction peak of the (003) crystal plane, and I(104) represents the intensity of the diffraction peak of the (104) crystal plane. For example, the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide can be 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, etc., or a range consisting of any two of the above values, for example, 0.3-0.5, 0.5-0.7, 0.7-0.9, 0.9-1.1, 1.0-1.2, etc.

[0044] In the embodiments of the present application, the intensity I(003) of the diffraction peak of the (003) crystal plane and the intensity I(104) of the diffraction peak of the (104) crystal plane are expressed as the integrated areas of the corresponding diffraction peaks, and can be tested using instruments and methods known in the art and with reference to the standard JIS K0131-1996 General Rules for X-ray Diffraction Analysis.

[0045] The value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide (abbreviated as R value) is a semi-quantitative and semi-empirical measure of the degree of cationic disorder. The (003) crystal plane diffraction peak reflects the hexagonal structure, while the (104) crystal plane diffraction peak reflects the sum of the hexagonal structure and the cubic structure. The larger the R value, the higher the degree of order of the hexagonal unit cell of the lithium-containing metal oxide, the closer it is to the ideal hexagonal structure, and the more complete the crystal structure. An R value greater than 1.2 indicates that the lithium-containing metal oxide has a good layered structure, and when the R value is less than or equal to 1.2, it indicates that the degree of cation disorder in the layered positive electrode material is high. During the cyclic charging process at the operating voltage, Li + When the lithium-containing metal oxide is extracted, the lithium-containing metal oxide changes from a layered structure to a spinel / rock salt phase structure. Compared with the layered structure, the spinel / rock salt phase structure can increase the Li + The embedding impedance affects its lithium embedding ability, that is, the Li + Therefore, lithium-containing metal oxides with high cation mixing have low capacity retention, which can remove lithium during each charge and discharge process, making Li +脱出は不可逆的で、負極に移動してSEI(固体電解質界面)膜の形成と充放電過程で消耗した活性リチウムを補充する。このように、サイクル過程では、充電電圧を上げることなく、二次電池の活性リチウムを持続的に補充し、二次電池のサイクル性能を向上させることができる。

[0046] いくつかの実施形態では、リチウム含有リン酸塩は、分子式Li x A y Me a M b P 1-c X c Y z の化合物およびその改質化合物を含み、ここで、0 < x ≤ 1.3、0 ≤ y < 1.3、かつ0.9 ≤ x + y ≤ 1.3、0 < a ≤ 1.5、0 ≤ b ≤ 0.7、0.6 ≤ a + b ≤ 1.5、0 ≤ c ≤ 0.5、3 ≤ z ≤ 5;AはNa、K、Mgの1種以上を含む;MeはMn、Fe、Co、Niの1種以上を含む;MはAl、Ca、Sc、Ti、V、Cr、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ceの1種以上を含む;XはS、Si、Cl、B、C、Nの1種以上を含む;YはO、Fの1種以上を含む;任意に、前記リチウム含有リン酸塩は、リン酸鉄リチウムおよびリン酸バナジウムリチウムの少なくとも1種を含む;任意に、リチウム含有リン酸塩はLiFePO4、LiNiPO4、LiCoPO4、LiV 0.67 PO4、LiMnPO4、LiMn 0.2 Fe 0.8 PO4およびLiMn 0.5 Fe 0.5 PO4の1種以上を含む。

[0047] LiFePO4は、リン酸鉄リチウム(Lithium Iron Phosphate、略称LFP)に属する。リン酸鉄リチウムの結晶型は通常オリビン構造である。リン酸鉄リチウムの充放電過程は、LiFePO4とFePO4の2相間で行われる。充電時には、Li + がLiFePO4から脱離し、Fe 2+ がFe 3+ になり、FePO4相が形成される;放電時には、Li + がFePO4に挿入され、Fe 3+ がFe 2+ になり、LiFePO4相が形成される。充放電過程では、Li + の可逆的な挿入・脱離は、Fe 3+ / Fe2+ The voltage platform is about 3.45V, and the voltage platform is relatively long. When charging, the voltage of lithium-ion batteries changes as follows: rise, stabilize, and rise. When discharging, the voltage also has a stable process, and this voltage stability value is the voltage platform for charging and discharging. Since the PO bond energy is very large, the PO4 tetrahedron is very stable and plays a structural support role in the charging and discharging process. Therefore, LiFePO4 has good resistance to high temperature and overcharge. At the same time, because the structure of LiFePO4 and FePO4 in a completely delithiated state is very similar, the cycle performance of LiFePO4 is also very good. Li + When completely released, the volume decreases and the density increases; after multiple charge and discharge cycles, the olivine structure remains stable and the iron atoms remain in the octahedral position. In addition, when the lithium-containing phosphate is lithium iron phosphate, the cycle decay of lithium iron phosphate is slower than that of lithium-containing metal oxides. Specifically, because the olivine structure of lithium iron phosphate is more stable than the layered structure of lithium-containing metal oxides, the Li in lithium iron phosphate + and Li in lithium-containing metal oxides + After each charge and discharge process, the Li in lithium iron phosphate is released. + On the contrary, lithium-containing metal oxides can easily transform from a layered structure to a spinel / rock salt phase because their crystal phase can increase the Li + The embedding resistance is Li in lithium-containing metal oxides. + It can no longer be transferred back to the lithium-containing metal oxide through discharge, so that the lithium-containing metal oxide can play a role in replenishing lithium in the positive electrode active material.

[0048] V 0.67 PO4 belongs to lithium vanadium phosphate. Lithium vanadium phosphate is an inorganic compound with monoclinic crystals. PO4 tetrahedrons and VO6 octahedrons are connected to each other through the oxygen at the shared vertex. It has a lantern-shaped structural unit. Each metal V atom is surrounded by six PO4 tetrahedrons, and at the same time, PO4 tetrahedrons are surrounded by four VO6 octahedrons. This structure forms a three-dimensional network structure. Li is in the holes of this framework structure. Three quadruple crystal positions are occupied by Li, resulting in 12 Li positions in one structural unit. In the open three-dimensional space structure, like PO4 3- Such a large anion replaces the position of the oxygen atom, making the structure more stable, and Li +Ions can move faster therein. As a lithium-containing phosphate, lithium vanadium phosphate can reversibly deintercalate and intercalate two lithium ions, and it has good electrochemical and thermodynamic stabilities and a relatively high specific capacity. In addition, when the lithium-containing phosphate is lithium vanadium phosphate, the cycle decay of lithium vanadium phosphate is slower than that of the lithium-containing metal oxide. Specifically, due to the more stable monoclinic crystal structure of lithium vanadium phosphate compared to the layered structure of the lithium-containing metal oxide, the Li + in lithium vanadium phosphate and the Li + in the lithium-containing metal oxide are more likely to return to the positive electrode after being removed during each charge-discharge process. On the contrary, due to the easy transformation of the crystal phase of the lithium-containing metal oxide from the layered structure to the spinel / rock salt phase, and the spinel / rock salt phase structure can increase the Li + insertion impedance, the Li + in the lithium-containing metal oxide cannot return to the lithium-containing metal oxide through discharge transfer anymore, which enables the lithium-containing metal oxide to play a role in supplementing lithium in the positive electrode active material.

[0049] In some embodiments, the lithium-containing metal oxide includes a compound with the molecular formula Li d Ni g Co h R k Q j O r T t and its modified compounds, 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, and t + r ≤ 2; R includes at least one of Mn and Al; Q includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb; T includes one or more of N, F, S, Cl; optionally, the lithium-containing metal oxide includes at least one of lithium nickel cobalt manganate and lithium nickel cobalt aluminate; optionally, the lithium-containing metal oxide includes at least one of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), 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 O2 (NCM811); optionally, the lithium-containing 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 0.7 Co 0.2 Al 0.1 O2(NCA721), LiNi 0.5 Co 0.2 Al 0.3 O2(NCA523), LiNi 0.6 Co 0.2 Al 0.2 O2(NCA622) and LiNi 1 / 3 Co 1 / 3 Al 1 / 3 At least one of O2 (NCA333).

[0050] The above lithium-containing metal oxides can also be called ternary materials. 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), 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 O2 (NCM811) belongs to lithium nickel cobalt manganese oxide, LiNi 0.85 Co 0.15 Al 0.05 O2、LiNi 0.8 Co 0.1 Al 0.1 O2(NCA811), LiNi 0.7 Co 0.2 Al 0.1 O2(NCA721), LiNi 0.5 Co 0.2 Al 0.3 O2(NCA523), LiNi 0.6 Co 0.2 Al 0.2 O2(NCA622) and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 (NCA333) belongs to lithium nickel cobalt aluminum oxide. Lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide have the advantages of good cycle performance, high voltage platform, good thermal stability, long cycle performance, ideal crystal structure, small self-discharge, and no memory effect. For example, the lithium-containing metal oxide may include lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, or a mixture of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. Both lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide have a layered structure.

[0051] In some embodiments, the lithium-containing metal oxide includes lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, and the molar ratio of lithium nickel cobalt manganese oxide to lithium nickel cobalt aluminum oxide can be 0.01-100:100:0.01. For example, it can be 0.01:100, 1:100, 1:2, 1:1, 5:1, 7:100, 100:7, 2:1, 50:1, 100:1, 100:0.01, etc., or a range consisting of any two of the above values, for example, it can be 0.01:100-1:2, 1:1-7:100, 100:7-50:1, 100:1-100:0.01, etc.

[0052] During the cyclic charging process of lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide at the working voltage, Ni 2+ With Li + The radius is similar. Due to the high degree of cation mixing, in Li + When Ni is extracted from lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide, 2+ Will occupy Li + This ion dislocation phenomenon reduces the lattice thickness and changes the lattice type, such as lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide from a layered structure to a spinel / rock salt phase structure. Compared with the layered structure, the spinel / rock salt phase structure can increase the Li + The embedding impedance affects its lithium embedding ability, that is, the Li + It can no longer be transferred back to lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide through discharge. Therefore, lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide with a high degree of cation mixing have a low capacity retention rate, which can remove lithium during each charge and discharge process, making Li + It is irreversibly released and transferred to the negative electrode to supplement the formation of SEI film and the active lithium lost during the charge and discharge process. In this way, during the cycle, without increasing the charging voltage, the active lithium of the battery can be continuously replenished, thereby improving the cycle performance of the secondary battery.

[0053] In some embodiments, in the lithium-containing metal oxide, the molar ratio of nickel to all metal elements except lithium is greater than or equal to 50%. For example, the content of nickel can be 50%, 52%, 54%, 56%, 58%, 60%, 65%, 68%, 70%, 80%, etc., or a range composed of any two of the above values, for example, it can be 50%-60%, 52%-56%, 56%-60%, 52%-68%, 68%-80%, etc. Among them, the ratio of nickel, cobalt and manganese in lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide can be adjusted according to actual needs so that the content of nickel is greater than or equal to 50%. During the cyclic charging process of lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide at the working voltage, Ni 2+ With Li + The radius is similar. Due to the high degree of cation mixing, in Li + When Ni is extracted from lithium-containing metal oxides, 2+ Will occupy Li + The position in the lattice. Limiting the content of nickel to the above range can make enough Ni 2+ Occupy Li + The position in the lattice promotes the lithium-containing metal oxide to reduce its lattice thickness, so that it transforms from a layered structure to a spinel / rock salt phase structure, thereby increasing the Li + The embedded impedance makes the Li + It can no longer be transferred back to the lithium-containing metal oxide through discharge.

[0054] In some embodiments, the mass percentage of the lithium-containing metal oxide in the positive electrode active material is 1%-5%. For example, the mass percentage of the lithium-containing metal oxide in the positive electrode active material can be 1%, 1.5%, 2%, 2.6%, 3%, 3.3%, 4%, 4.7%, 5%, etc., or a range consisting of any two of the above values, for example, it can be 1%-3.3%, 1.5%-2.6%, 2.6%-3.3%, 1.5%-4.7%, 3.3%-5%, etc. In the positive electrode active material, the lithium-containing metal oxide acts as a lithium supplement. Controlling the mass percentage of the lithium-containing metal oxide within the above range can not only not affect the lithium-containing phosphate from playing the role of the positive electrode active material, but also play the role of lithium supplement.

[0055] In some embodiments, the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is ≤ 1. For example, the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide may be 0.3, 0.5, 0.6, 0.7, 0.73, 0.8, 0.86, 0.9, 0.94, 1.0, etc., or a range formed by any two of the above values, for example, 0.3-0.5, 0.5-0.8, 0.5-0.73, 0.7-0.86, 0.94-1.0, etc. As described above, the larger the R value, the higher the degree of ordering of the hexagonal unit cell of the lithium-containing metal oxide, the closer it is to the ideal hexagonal structure, and the more complete the crystal structure. Generally, an R value greater than 1.20 indicates that the lithium-containing metal oxide has a good layered structure, which is conducive to the diffusion of lithium ions, while when the R value is less than or equal to 1.2, it indicates that the degree of cation mixing in the layered positive electrode material is high, and the lithium ion deintercalation of the material is hindered. Further limiting the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide to the above range can further improve the effect of the lithium-containing metal oxide as a lithium supplement, that is, it can further improve the cycle performance of the secondary battery.

[0056] [Positive electrode]

[0057] The secondary battery provided in the embodiment of the present application, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on the current collector, and the positive electrode film layer includes the positive electrode active material as described above. Optionally, the mass percentage of the positive electrode active material in the positive electrode film layer is 90%-97%. For example, the percentage of the mass of the positive electrode active material in the positive electrode film layer can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, etc., or a range composed of any two of the above values, for example, it can be 90%-91%, 91%-93%, 92%-95%, 94%-97%, etc. As mentioned above, the positive electrode active material is a decisive factor in the electrochemical performance of the lithium battery, directly determines the energy density and reliability of the battery, and thus affects the comprehensive performance of the battery. The embodiment of the present application controls the mass percentage of the positive electrode active material within the above range, which can improve the energy density of the secondary battery and thus improve the cycle performance of the secondary battery.

[0058] The positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may be an aluminum foil.

[0059] The positive electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.

[0060] As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, conductive carbon black (Super P, SP), graphene and carbon nanofibers.

[0061] As an example, the binder can be one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0062] As an example, other optional auxiliary agents include, but are not limited to, one or more combinations of acids, dispersants, surfactants, chelating agents, etc. The acid in the auxiliary agent may be an inorganic acid and / or an organic acid, and the inorganic acid in the auxiliary agent includes, but is not limited to, one or more combinations of hydrochloric acid, nitric acid, sulfuric acid, perchloric acid, chloric acid, etc., and the organic acid in the auxiliary agent preferably includes, but is not limited to, one or more combinations of 2,4,6-trinitrophenol, 2,4,6-trinitrobenzoic acid, trifluoroacetic acid, trichloroacetic acid, methanesulfonic acid, benzenesulfonic acid, KMD acid, etc. The dispersant may include, but is not limited to, one or more combinations of water, ethanol, acetone, propanol, isopropanol, methanol, n-butanol, acetonitrile, tetrahydrofuran, ether dichloromethane, chloroform, dimethyl sulfoxide, dimethylformamide, etc. The surfactant may include, but is not limited to, one or more combinations of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyethylene glycol, polyethylene oxide, polyacrylamide or carboxymethyl cellulose, polyvinyl pyrrolidone, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, etc. The chelating agent may be a combination of one or more of, including but not limited to, nitrilotriacetic acid, 1,2-cyclohexanediaminetetraacetic acid, ethylenediaminetetraacetic acid, citric acid, malic acid, oxalic acid, acetic acid, salicylic acid, and the like.

[0063] [Negative electrode]

[0064] In a secondary battery, a negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0065] The negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector may be a copper foil.

[0066] The specific type of negative electrode active material is not limited, and active materials known in the art that can be used for the negative electrode of a secondary battery can be used, and those skilled in the art can choose according to actual needs. As an example, the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials and tin-based materials. Silicon-based materials can be selected from one or more of elemental silicon, silicon oxide compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. These materials can all be obtained commercially.

[0067] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicon-based material.

[0068] The negative electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.

[0069] As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0070] As an example, the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0071] As examples, other optional additives may be thickeners and dispersants (eg, carboxymethylcellulose sodium, CMC-Na), and PTC thermistor materials.

[0072] [Electrolyte]

[0073] The secondary battery may include an electrolyte that conducts ions between the positive electrode and the negative electrode. The electrolyte may include an electrolyte salt and a solvent.

[0074] As an example, the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0075] As an example, the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl 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), n-propyl acetate (PA), methyl propionate (MP), ethyl propionate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (MP), ethyl propionate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (MP), ethyl propionate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (MP), ethyl propionate (EPC), butylene carbonate (BC), butylene carbonate (BC), butylene carbonate (BC), butylene carbonate (BC), butylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (PA), methyl propionate (MP), ethyl propionate (EPC), butylene carbonate (BC), butylene carbonate (BC), butylene carbonate (BC), butylene carbonate (FEC), butylene carbonate (MF), butylene carbonate ( One or more of propyl propionate (EP), propyl propionate (n-PropylPropionate, PP), methyl butyrate (Methyl ButyrateMB), ethyl butyrate (Ethyl Butyrate, EB), 1,4-butyrolactone (1,4-Butyrolactone, GBL), tetramethylene sulfone (SF), dimethyl sulfone (MethylSulfone, MSM), methyl ethyl sulfone (Methyl Ethyl Sulfone, EMS) and diethyl sulfone (Diethyl Sulfone, ESE).

[0076] In some embodiments, the electrolyte further includes additives, such as additives that 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, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.

[0077] The embodiment of the present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1 The secondary battery 5 is a square structure as an example.

[0078] In some embodiments, the secondary battery may include an outer package for packaging the positive electrode sheet, the negative electrode sheet, and the electrolyte, with the separator facing the positive electrode sheet.

[0079] 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. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0080] In some embodiments, reference Figure 2 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 can be covered on the opening to close the receiving cavity.

[0081] The preparation method of the secondary battery 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 secondary battery. 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. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0082] Figure 3 4 is an example of a battery module. Figure 5In the battery module 4, the plurality of secondary batteries 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 secondary batteries 5 may be fixed by fasteners.

[0083] The battery module 4 may further include a housing having a housing space in which the plurality of secondary batteries 5 are housed.

[0084] 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.

[0085] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 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. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0086] [Secondary battery]

[0087] A secondary battery is a battery that can be used again after being discharged by recharging to activate the active materials. Usually, a secondary battery includes a positive electrode, a negative electrode, a separator and an electrolyte. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to play an isolation role. The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.

[0088] The secondary battery provided in the application embodiment includes a lithium battery, whose active ions are lithium ions. The lithium ions are embedded and released back and forth between the positive electrode plate and the negative electrode plate, thereby realizing the charging and discharging process.

[0089] In the related art, the operating voltage range of the secondary battery whose positive electrode active material is a lithium-containing metal oxide is 2.8V-4.4V, and the voltage platform is about 3.2V. The operating voltage range of the lithium iron phosphate battery is 2V-3.8V, and the voltage platform is about 3.7V. Therefore, the lithium-containing metal oxide can only be activated and delithiated by increasing the charging voltage. However, increasing the charging voltage may cause side reactions at the electrode, resulting in increased electrode interface impedance, increased polarization, and affecting the performance of the battery cell. In addition, with this strategy, the negative electrode can only be replenished with lithium when charging and activation are performed within the above-mentioned activation voltage range, and it is impossible to continuously replenish lithium during each charge and discharge process. Furthermore, in order to stabilize the structure of the lithium-containing metal oxide, the precursor is generally modified by doping modification, coating modification, structural improvement, etc., which will increase the manufacturing cost and difficulty.

[0090] The secondary battery provided by the embodiment of the present application includes the positive electrode active material as described above, which includes a lithium-containing phosphate and a lithium-containing metal oxide.

[0091] In some embodiments, the input voltage of the secondary battery is 2.0 V-3.8 V. Compared with the secondary battery in the related art whose positive electrode active material is a lithium-containing metal oxide, the secondary battery provided in the embodiment of the present application can continuously replenish lithium during each charge and discharge process at an input voltage between 2.0 V and 3.8 V, without the need to increase the charging voltage to replenish lithium.

[0092] In any embodiment of the present application, the charging temperature of the secondary battery is 30-45°C. If the charging temperature is too high, excessive charging and discharging of the secondary battery will cause damage to the positive and negative electrodes. For example, collapse will cause the lithium ions to be unable to be inserted into the negative electrode during charging, or cause some of the lithium ions in the negative electrode to no longer be released, thereby shortening the life of the secondary battery. If the charging temperature is too low, the lithium replenishment speed of the lithium battery is slow. Within the above temperature range, the charging efficiency of the lithium battery is high and the charging time is short. At the same time, the lithium replenishment effect is good, which can also improve the reliability and life of the battery.

[0093] [Device]

[0094] The present application also provides an electrical device, which includes the secondary battery of the present application. The battery cell, battery module or battery pack can be used as a power source for the device, or as an energy storage unit for the device. The device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer), 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), an electric train, a ship and a satellite, and an energy storage system.

[0095] The device can select battery cells, battery modules or battery packs according to its usage requirements.

[0096] In any embodiment of the present application, the electrical device also includes a temperature regulator, which is used to adjust the ambient temperature of the secondary battery to 30-45°C. If the charging temperature is too high, excessive charging and discharging of the secondary battery will cause damage to the positive and negative electrodes. For example, collapse will cause the lithium ions to be unable to be inserted into the negative electrode during charging, or cause some of the lithium ions in the negative electrode to no longer be released, thereby shortening the life of the secondary battery. If the charging temperature is too low, the lithium replenishment speed of the lithium battery is slow. Within the above temperature range, the charging efficiency of the lithium battery is high and the charging time is short. At the same time, the lithium replenishment effect is good, which can also improve the reliability and life of the battery.

[0097] Figure 6 The power consumption device 6 is taken as an example. The power consumption device 6 may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device 6's requirements for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.

[0098] As another example, the electric device 6 may be a mobile phone, a tablet computer, or a notebook computer. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0099] The beneficial effects of the present application are further illustrated below in conjunction with embodiments.

[0100] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0101] 1. Preparation of secondary batteries

[0102] 1. Preparation of negative electrode

[0103] Preparation of negative electrode: Graphite: sodium carboxymethyl cellulose CMC: conductive carbon SP: binder SBR are mixed in water at a ratio of 96:1:1:2 and stirred at high speed to obtain a slurry with a solid content of 53%. The weight of the obtained slurry is controlled to 0.209g / 1540.25mm 2 Evenly coated on 10μm thick copper foil. After the slurry on the copper foil is fully dried in an environment with an average temperature of 85℃, the density is controlled to be 1.7g / cc for cold pressing to obtain a negative electrode sheet with a thickness of 0.1694mm, which is then cut into 97mm width for standby use.

[0104] 2. Preparation of positive electrode

[0105] Lithium iron phosphate LFP: lithium metal oxide NCM622 with an R value of 1.2: binder PVDF: conductive carbon SP are stirred evenly in a NMP solution at a ratio of 97:1:1:1 to obtain a slurry with a solid content of 62%. The weight of the obtained slurry is controlled to 0.45g / 1540.25mm 2 Evenly coated on 15μm thick aluminum foil. After the slurry on the aluminum foil is fully dried in an environment with an average temperature of 85℃, the density is controlled to be 2.6g / cc for cold pressing to obtain a positive electrode sheet with a thickness of 0.2384mm, which is then cut into 100mm width for standby use.

[0106] 3. Secondary battery assembly

[0107] The 7μm separator was cut into 106mm width, and a winding needle with a circumference of 322mm was used to wind the positive and negative electrodes and separator to obtain a dry battery cell. Then 1M LiPF6 was injected as lithium salt, and the electrolyte with a solvent ratio of EC / DMC / PC of 1:1:1 was obtained to obtain a 169.9Ah secondary battery.

[0108] 4. Charging method

[0109] The charging and discharging cycle is performed between the working voltage of 2V-3.8V.

[0110] The preparation methods of the secondary batteries of Examples 2-8 and Comparative Examples 1-5 are similar to those of the secondary battery of Example 1, except that the types and addition ratios of the lithium-containing metal oxides are different, and the cycle temperatures are different. For Examples 6 / 11 / 16 and Comparative Example 3, the molar ratio of NCM622 to NCA622 is 1:1.

[0111] See Table 1 for details.

[0112] 2. Battery performance test

[0113] Battery cycle performance (cycles):

[0114] At 25°C, the secondary battery prepared in the embodiment and the comparative example is charged at a constant current of 1C to a charge cut-off voltage V1, then charged at a constant voltage to a current ≤ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage V2, left to stand for 5 minutes. This is a charge and discharge cycle. The battery is tested for cyclic charge and discharge according to this method until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery at 25°C.

[0115]

[0116]

[0117] As can be seen from Table 1, compared with Comparative Examples 1-3, the mass ratio of lithium-containing metal oxide added in Examples 1-26 is 1%-20% and the R value is less than or equal to 1.2, the lithium supplementation effect is good, and the cycle performance of the secondary battery is good.

[0118] Example 7 is compared with Example 1, Example 8 is compared with Example 2, Example 9 is compared with Example 3, Example 10 is compared with Example 4, and Example 11 is compared with Example 6. When the value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is ≤1, the lithium replenishing effect is good and the cycle performance of the secondary battery is good.

[0119] Compared with Examples 7-8 and 17, when the lithium-containing metal oxide accounts for 1% to 5% by mass of the positive electrode active material, Examples 12-16 have good lithium replenishment effects and good cycle performance of the secondary battery.

[0120] Compared with Example 18, Examples 8, 19 and 20 show that when the molar ratio of nickel element to all metal elements except lithium element in the lithium-containing metal oxide is greater than or equal to 50%, the lithium supplementation effect is good and the cycle performance of the secondary battery is good.

[0121] Compared with Examples 8, 25 and 26, when the charging temperature is 30-45°C, Examples 21-24 have good lithium replenishing effect and good cycle performance of the secondary battery.

[0122] In summary, the positive electrode active material provided in the embodiment of the present application includes a lithium-containing phosphate and a lithium-containing metal oxide. Among them, the lithium-containing metal oxide includes a lithium-containing metal oxide, and the mass percentage of the lithium-containing metal oxide in the positive electrode active material is 1%-20%. The value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is ≤1.2. Li + When released from lithium-containing metal oxides, lithium-containing metal oxides easily transform from a layered structure to a spinel / rock salt phase structure, which can increase the Li + The embedding impedance affects its lithium embedding ability, that is, the Li + Therefore, lithium-containing metal oxides with high cation mixing have low capacity retention, which can remove lithium during each charge and discharge process, making Li + It is irreversibly released and transferred to the negative electrode to supplement the active lithium. Therefore, during the cycle, the active lithium of the battery can be continuously supplemented without increasing the charging voltage, thereby improving the cycle performance of the secondary battery.

[0123] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A positive electrode active material, characterized in that: including lithium-containing phosphates and lithium-containing metal oxides; Wherein, the lithium-containing metal oxide accounts for 1%-20% by mass of the positive electrode active material; The X-ray diffraction spectrum of the lithium-containing metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the diffraction peak of the (003) crystal plane and the diffraction peak of the (104) crystal plane satisfy: I(003) / I(104)≤1.2, wherein I(003) represents the intensity of the diffraction peak of the (003) crystal plane, and I(104) represents the intensity of the diffraction peak of the (104) crystal plane.

2. The positive electrode active material according to claim 1, characterized in that The lithium-containing phosphate includes a compound with the molecular formula Li x A y Me a M b P 1-c X c Y z and its modified compounds, where 0 < x ≤ 1.3, 0 ≤ y < 1.3, and 0.9 ≤ x + y ≤ 1.3, 0 < a ≤ 1.5, 0 ≤ b ≤ 0.7, 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 at least one of lithium iron phosphate and lithium vanadium phosphate; Optionally, the lithium-containing phosphate includes LiFePO4, LiNiPO4, LiCoPO4, LiV 0.67 PO4, LiMnPO4, LiMn 0.2 Fe 0.8 PO4 and LiMn 0.5 Fe 0.5 One or more of PO4.

3. The positive electrode active material according to claim 1 or 2, characterized in that The lithium-containing metal oxide includes a molecular formula of Li d Ni g Co h R k Q j O r T 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; Q includes one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb; T includes one or more of N, F, S, and Cl; Optionally, the lithium-containing metal oxide includes at least one of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide; Optionally, the lithium-containing 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 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.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that In the lithium-containing metal oxide, the molar ratio of nickel element to all metal elements except lithium element is greater than or equal to 50%.

5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The lithium-containing metal oxide accounts for 1% to 5% of the positive electrode active material by mass.

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that The value of the XRD diffraction peak I(003) / I(104) of the lithium-containing metal oxide is ≤1.

7. A positive electrode sheet, characterized in that: It comprises a current collector and a positive electrode film layer arranged on the current collector, wherein the positive electrode film layer comprises the positive electrode active material according to any one of claims 1 to 6, and optionally, the positive electrode active material accounts for 90%-97% of the mass of the positive electrode film layer.

8. A secondary battery, characterized in that: Comprising the positive electrode sheet as described in claim 7.

9. The secondary battery according to claim 8, characterized in that The input voltage of the secondary battery is 2.0V-3.8V.

10. The secondary battery according to claim 8 or 9, characterized in that: The charging temperature of the secondary battery is 30-45°C.

11. An electrical device, characterized in that: Comprising the secondary battery as claimed in any one of claims 8 to 10.

12. The electrical device according to claim 11, characterized in that: The device also includes a temperature regulator, which is used to adjust the ambient temperature of the secondary battery to 30-45°C.

Images