Positive electrode active material and preparation method therefor, positive electrode sheet, battery, and electric device

Abstract

The present application discloses a positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery, and an electric device. The positive electrode active material comprises: Li1+xAaBbMmMn2-a-b-mO4-y, wherein A comprises at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B comprises at least one of Ni, Al, Co or Fe, M comprises at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, and -0.5≤y≤1.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical equipment

[0001] Priority information

[0002] This application claims priority and benefits of patent application 202310729217.5 filed with the State Intellectual Property Office of China on June 19, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0004] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0005] Spinel oxides are commonly used as positive electrode active materials in secondary batteries. However, existing secondary batteries containing spinel oxides have difficulty balancing capacity and cycle life.

[0006] Public content

[0007] In view of the technical problems existing in the background technology, the present application provides a positive electrode active material, aiming to solve the problems of low capacity and short cycle life of batteries containing the positive electrode active material.

[0008] In order to achieve the above-mentioned object, the first aspect of the present application provides a positive electrode active material, wherein the positive electrode active material comprises: Li 1+x A a B b M m Mn 2-a-b-m O 4-y ,

[0009] Among them, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1.

[0010] The present application includes at least the following beneficial effects: in the positive electrode active material of the present application, controlling the amount of x, that is, the amount of excess Li in the positive electrode active material, is conducive to forming a sufficient amount of tetragonal spinel in the positive electrode active material, thereby improving the capacity of the positive electrode active material; element A is an element that easily forms an oxide containing a Li spinel structure, and the atomic radius of element A is large, which reduces the oxygen octahedral gap and inhibits Li from entering the Mn position. In addition, A will preferentially enter the Mn position, fill the Mn position, stabilize the octahedral gap, and thus inhibit Li from entering the Mn position, so the doping element A and the above-mentioned a range are Within the range of x and a, the formation of spinel with excess Li can be promoted, which is beneficial for the phase state of part of the positive electrode active material to be tetragonal spinel, so that more Li is retained in the Li position, the active Li is increased to exert its capacity, and the capacity of the positive electrode active material is improved; in addition, within the range of the above x and a, the positive electrode active material also includes cubic spinel, and the cubic spinel has strong stability, so that the positive electrode active material has excellent stability. The positive electrode active material contains a sufficient amount of tetragonal spinel and part of the cubic spinel, which improves the capacity of the battery containing it, and the battery has excellent cycle performance. The radius of element B is comparable to that of Mn, and it can be dispersed at the Mn site. Its low valence state can promote the valence state of Mn to rise, and promote Mn to become +4 valence, thereby inhibiting the Jan-Taylor effect of the positive electrode active material and improving the capacity of the positive electrode active material. Element M can form a strong bond with oxygen, stabilize the positive electrode active material, especially the oxygen atoms on the surface of the grains, reduce surface side reactions, reduce side reactions between the positive electrode active material and the electrolyte, reduce oxygen loss in the positive electrode active material, reduce Mn dissolution, and improve the capacity of the positive electrode active material. At the same time, the positive electrode active material has excellent cycle performance.

[0011] In some embodiments of the present application, A includes at least one of Ca, Sc, Ti, V, Cr, or Y. Thus, the capacity and stability of the positive electrode active material can be improved, the capacity of the battery containing the positive electrode active material can be improved, and the battery has excellent cycle performance.

[0012] In some embodiments of the present application, A includes at least one of Sc, V, or Y. Thus, the capacity and stability of the positive electrode active material can be improved, the capacity of the battery containing the positive electrode active material can be improved, and the battery has excellent cycle performance.

[0013] In some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions: 0.2≤x≤0.6, optionally 0.2≤x≤0.4; 0.01≤a≤0.4, optionally 0.05≤a≤0.3; 0.01≤b≤1, optionally 0.1≤b≤0.7; 0.001≤m≤0.2, optionally 0.01≤m≤0.1. Thus, batteries containing the positive electrode active material have excellent capacity and cycle life.

[0014] In some embodiments of the present application, 1≤x / a≤10, and may be 2≤x / a≤7. Thus, within the above x / a range, the positive electrode active material can be promoted to maximize its capacity while reducing the capacity reduction caused by excessive A element, thereby increasing the capacity of the battery containing it and achieving excellent cycle performance.

[0015] In some embodiments of the present application, 0.001≤a+b+m≤1, optionally, 0.3≤a+b+m≤0.7. Thus, within the above range of a+b+m, the positive electrode active material maintains a spinel phase, and a battery containing the positive electrode active material exhibits excellent capacity and cycle life.

[0016] In some embodiments of the present application, the positive electrode active material further comprises a 1+x A a B b M m Mn 2-a-b-m O 4-y An alkaline coating on at least part of the surface. The alkaline coating can increase the pH of the positive electrode active material and neutralize the acid generated by electrolyte oxidation, thereby reducing corrosion damage to the positive electrode active material, improving the stability of the positive electrode active material, and increasing the capacity of the battery containing it, while also having excellent cycle performance.

[0017] In some embodiments of the present application, the alkaline coating layer includes D g+ d Z h+ z O 2- t Q - q , wherein D comprises at least one of Li, Na, K, Be, Mg, or Ca, Z comprises at least one of B, Si, P, or As, Q comprises at least one of F, Cl, Br, or I, g = 1 or 2, h = 3, 4, or 5, 1.5 ≤ (t + q) / z ≤ 5, and 0 ≤ q / t ≤ 2. Thus, the above-mentioned substance is a salt of a strong base and a weak acid, exhibiting alkalinity but not excessively high, and exhibiting good compatibility with the positive electrode active material itself and excellent ion conductivity, enabling the positive electrode active material to maximize its capacity. Batteries containing the substance have excellent capacity and cycle life.

[0018] In some embodiments of the present application, the mass percentage of the alkaline coating layer in the positive electrode active material is 0.3%-5%, and optionally 1%-3%. Therefore, when the mass percentage of the alkaline coating layer is within the above range, the battery containing it has excellent capacity and cycle life.

[0019] In some embodiments of the present application, the charge capacity of the positive electrode active material at 2.9V accounts for 10%-30% of the total charge capacity, and optionally 15%-25%. Thus, the ratio of the charge capacity at 2.9V to the total charge capacity is within the above range, which ensures that the content of tetragonal spinel in the positive electrode active material is within a suitable range. The excess Li at the Li position can just compensate for the loss of active Li when the positive electrode active material is used in the battery. At the same time, the structure of the positive electrode active material is relatively stable, and the battery containing the positive electrode active material has excellent capacity and cycle life.

[0020] In some embodiments of the present application, the pH value of the saturated aqueous solution of the positive electrode active material at 25° C. is 9-11.5, optionally 10-11. Within the above pH range, the acid generated by electrolyte oxidation can be neutralized, thereby reducing corrosion damage to the positive electrode active material, improving the stability of the positive electrode active material, and increasing the capacity of the battery containing the positive electrode active material, while also having excellent cycle performance.

[0021] In some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions:

[0022] The volume average particle size D of the positive electrode active material v 50 is 1μm-30μm, optional is 2μm-10μm;

[0023] The BET specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-5m 2 / g, optional 0.2m 2 / g-2m 2 / g;

[0024] The tap density of the positive electrode active material is 1.5 g / cm 3 -3.0g / cm 3 , optional 2g / cm 3 -2.5g / cm 3 .

[0025] Therefore, when the volume average particle size D of the positive electrode active material v 50. When at least one of the BET specific surface area and the tap density is within the above range, the conduction distance of ions in the positive electrode active material is small and the surface side reactions are few, which promotes the positive electrode active material to exert its gram capacity and improves the capacity of the battery containing it. At the same time, the battery has excellent cycle performance.

[0026] A second aspect of the present application provides a method for preparing a positive electrode active material, comprising:

[0027] LiA a B b M m Mn2-a-b-m O 4-y Mixed with a first lithium source and subjected to a first sintering to obtain a positive electrode active material, the positive electrode active material comprising: Li 1+x A a B b M m Mn 2-a-b-m O 4-y ,

[0028] Among them, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1.

[0029] Therefore, the positive electrode active material prepared in this application is a spinel structure LiA a B b M m Mn 2-a-b-m O 4-y On the basis of LiA a B b M m Mn 2-a-b-m O 4-y Li is supplemented in the electrolyte, so that excess Li enters the Li site, so that the obtained positive electrode active material contains sufficient tetragonal spinel and part of cubic spinel, has excellent capacity and stability, improves the capacity of the battery containing it, and at the same time the battery has excellent cycle performance.

[0030] In some embodiments of the present application, the first sintering temperature is 300-600° C. At the above temperature, the positive electrode active material is promoted to include both tetragonal spinel and cubic spinel, thereby increasing the capacity of the battery containing the same and having excellent cycle performance.

[0031] In some embodiments of the present application, the LiA a B b M m Mn 2-a-b-m O 4-y The following steps are used to obtain the lithium source: a second lithium source, a source A, a source B, a source M and a source Mn are mixed, and a second sintering is performed to obtain LiA a B b M m Mn 2-a-b-m O 4-y .

[0032] In some embodiments of the present application, the present invention further comprises: mixing the positive electrode active material with an alkaline material, performing a third sintering, and a B b M m Mn 2-a-b-m O 4-y A basic coating is formed on at least a portion of the surface.

[0033] In a third aspect, the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect.

[0034] The fourth aspect of the present application provides a battery comprising the positive electrode sheet according to the third aspect of the present application, thereby having excellent capacity and cycle life.

[0035] A fifth aspect of the present application provides an electrical device comprising the battery described in the fourth aspect.

[0036] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0038] FIG1 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0039] FIG2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0040] FIG3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0041] FIG4 is an exploded view of FIG3 ;

[0042] FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source;

[0043] FIG6 is an XRD spectrum of the positive electrode active materials of Example 1 and Comparative Example 1 of the present application;

[0044] FIG7 is a first-cycle charging curve diagram of the button-type half-cells of Example 1 and Comparative Example 1 of the present application.

[0045] Description of reference numerals:

[0046] 1: Secondary battery; 2: Battery module; 3: Battery pack; 4: Upper case; 5: Lower case. DETAILED DESCRIPTION

[0047] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0048] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0049] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0050] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0052] With the technological advancements and increasing demand for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy sector, are experiencing rapid research development. Lithium-ion batteries offer a compact size and weight, making them easy to carry and use. Their high specific energy content allows for greater energy storage capacity, and they exhibit no memory effect, requiring no full discharge and recharge. Therefore, lithium-ion batteries hold broad application prospects.

[0053] Spinel-structured oxides have high voltage, good overcharge resistance, easy preparation and low cost, making them one of the popular positive electrode active materials for lithium-ion batteries.

[0054] However, existing spinel oxides have the following problems: On the one hand, excess lithium in spinel oxides easily enters the Mn site, rendering the excess lithium inactive. Furthermore, the lithium in neighboring Li sites also loses activity, resulting in lithium loss. On the other hand, existing spinel oxides are mostly cubic spinels. Even if tetragonal spinels exist, the content of tetragonal spinels is insufficient, resulting in the easy loss of active lithium in the positive electrode active material. This loss of active lithium reduces the capacity of the spinel oxides.

[0055] In the present application, the amount of x, that is, the amount of excess Li in the positive electrode active material, is controlled to supplement active lithium and promote the formation of a sufficient amount of tetragonal spinel, thereby improving the capacity of the positive electrode active material. The positive electrode active material is doped with element A and its doping amount is controlled. The atomic radius of element A is large, which reduces the oxygen octahedral gap and inhibits Li from entering the Mn position. In addition, A will preferentially enter the Mn position (oxygen octahedral gap), fill the Mn position, stabilize the octahedral gap, and thus inhibit Li from entering the Mn position. Therefore, doping element A within the above-mentioned range of a can promote The formation of spinel with excess Li is beneficial to the phase state of part of the positive electrode active material being tetragonal spinel, so that more Li is retained in the Li position, the active Li is increased to exert its capacity, and the capacity of the positive electrode active material is improved; in addition, within the range of the above-mentioned x and a, the positive electrode active material also includes cubic spinel, so that the positive electrode active material has excellent stability, and the positive electrode active material contains a sufficient amount of tetragonal spinel and part of the cubic spinel, which improves the capacity of the battery containing it, and the battery has excellent cycle performance.

[0056] The positive electrode active material disclosed in the embodiments of the present application is suitable for secondary batteries, and the battery disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include but are not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles and spacecraft, etc.

[0057] In a first aspect, the present application proposes a positive electrode active material, wherein the positive electrode active material comprises: Li 1+x A a B b M m Mn2-a-b-m O 4-y ,

[0058] Among them, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1.

[0059] The present application includes at least the following beneficial effects: in the positive electrode active material of the present application, first, the amount of x, i.e., the amount of excess Li in the positive electrode active material, is controlled to supplement active lithium, promote the formation of a sufficient amount of tetragonal spinel in the positive electrode active material, and improve the capacity of the positive electrode active material; secondly, for the excess Li, doping element A and controlling its doping amount can promote the positive electrode active material to form more Li-excess spinel LMO, which is beneficial for the phase state of part of the positive electrode active material to be tetragonal spinel, so that the excess Li is as much as possible. The active Li in the positive electrode active material is retained at the Li position, thereby increasing the active Li in the positive electrode active material and improving the capacity of the positive electrode active material. Finally, since the tetragonal spinel is unstable and has poor reversibility, within the range of the above-mentioned x and a, the positive electrode active material also includes some cubic spinel. The cubic spinel has strong stability. By controlling x and a, the positive electrode active material contains a sufficient amount of tetragonal spinel and some cubic spinel at the same time. The joint action of x and a improves the capacity of the battery containing it, and the battery has excellent cycle performance.

[0060] The unit cell of the tetragonal system has the shape of a square column, and the unit cell parameters are a=b≠c, α=β=γ=90°; while the cubic system has four cube diagonal direction triple axis characteristic symmetry elements, and its unit cell parameters are a=b=c, α=β=γ=90°. In the embodiment of the present application, Li 1+x A a B b M m Mn 2-a-b-m O 4-y A sufficient amount of tetragonal spinel can provide a large amount of active lithium, while cubic spinel has good stability. The two complement each other, making the positive electrode active material have a high active lithium content and strong stability, thereby improving the capacity of the positive electrode active material and at the same time, the positive electrode active material has excellent cycle performance.

[0061] It should be noted that the phase state of the positive electrode active material in the present application can be characterized by XRD. Specifically, the peak at 33° in the XRD spectrum represents tetragonal spinel.

[0062] It is understood that in the embodiments of the present application, when the battery is charged, some lithium in the tetragonal spinel in the positive electrode active material is preferentially released and converted into cubic spinel. Therefore, when the battery is charged to a positive electrode potential greater than 3.0V, the positive electrode contains no or very little tetragonal spinel. When the battery is discharged again to a positive electrode potential of 2.5V, the tetragonal spinel is restored.

[0063] In some embodiments of the present application, A includes at least one of Ca, Sc, Ti, V, Cr, or Y. These doping elements preferentially enter the Mn site, filling it and stabilizing the octahedral interstices. This in turn inhibits Li from entering the Mn site, allowing the positive electrode active material to contain a sufficient amount of tetragonal spinel, increasing active Li and improving the capacity of the positive electrode active material. In other embodiments of the present application, A includes at least one of Sc, V, or Y.

[0064] In some embodiments of the present application, the charging capacity of the positive electrode active material at 2.9V accounts for 10%-30% of the total charging capacity. For example, the charging capacity of the positive electrode active material at 2.9V accounts for 10%-30% of the total charging capacity. For example, the charging capacity of the positive electrode active material at 2.9V accounts for 10%-30%, 11%-29%, 12%-28%, 13%-27%, 14%-26%, 15%-25%, 16%-24%, 17%-23%, 18%-22%, 19%-21%, etc.

[0065] Specifically, the ratio of the charging capacity of the positive electrode active material at 2.9V to the total charging capacity is proportional to the content of tetragonal spinel in the positive electrode active material. At this 2.9V potential, the active Li of the positive electrode active material comes from tetragonal spinel, that is, the greater the ratio of the charging capacity of the positive electrode active material at 2.9V to the total charging capacity, the higher the content of tetragonal spinel in the positive electrode active material, and the more active lithium can be provided. When the ratio of the charging capacity of the positive electrode active material at 2.9V to the total charging capacity is within this range, the excess Li at the Li position in the positive electrode active material is sufficient to make up for the loss of active Li when it is used in the battery. At the same time, the positive electrode active material contains an appropriate amount of cubic spinel, which has a stable structure, improves the capacity of the positive electrode active material, and has excellent cycle performance, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance. In other embodiments of the present application, the above-mentioned positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the embodiment, the charging capacity of the positive electrode active material at 2.9V accounts for 15%-25% of the total charging capacity.

[0066] It is understood that the “total charge capacity” refers to the total capacity of a battery containing the positive electrode active material of the embodiment of the present application from the start to the end of charging, that is, the charge capacity of the battery from 0V to 4.35V.

[0067] It is understood that the "ratio of the charge capacity of the positive electrode active material at 2.9V to the total charge capacity" in this application has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by the following method:

[0068] In a battery using the positive electrode active material of the embodiment of the present application as the positive electrode and Li as the negative electrode, the battery is charged to 4.35V at a constant current rate of 0.1C, and the proportion of the charging capacity of 2.8-3.1V to the total charging capacity is calculated.

[0069] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the above, x can be 0.1<x≤1.1, for example, 0.15≤x≤1.05, 0.18≤x≤1, 0.2≤x≤0.9, 0.3≤x≤0.8, 0.4≤x≤0.7, 0.5≤x≤0.6, etc. Thus, x represents the excess Li in the positive electrode active material. As x increases, the active Li in the positive electrode active material increases, and the capacity of the positive electrode active material increases. When x is within the above range, the structural instability of the positive electrode active material caused by excessive Li content can be reduced, and excessive Li entering the Mn site can be reduced. In addition, excess Li also promotes the formation of tetragonal spinel, so that there is a sufficient amount of tetragonal spinel and part of cubic spinel in the positive electrode active material, thereby improving the capacity of the positive electrode active material and having excellent cycle performance. In other embodiments of the present application, 0.2≤x≤0.6, for example, 0.2≤x≤0.4.

[0070] It should be noted that the ratio of each element in the positive electrode active material in the present application refers to the ratio of each element in the positive electrode active material before the positive electrode active material is made into a positive electrode sheet and assembled into a battery for formation. Those skilled in the art will understand that in the positive electrode sheet, battery or electrical device, due to the formation and circulation processes, some elements will be consumed. Even if the measured element ratio of the positive electrode active material is not within the above range, it should fall within the scope of the present application. For example, batteries appearing on the market usually undergo cyclic aging after assembly of the battery. As a result, the lithium content in the positive electrode active material is less than 1+x. At the same time, if the positive electrode sheet and the negative electrode sheet use a lithium supplement, after the battery undergoes the formation and circulation processes, the measured lithium content in the positive electrode active material will be greater than 1+x.

[0071] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the formula, a can be 0.001≤a≤0.5, for example, 0.001≤a≤0.5, 0.005≤a≤0.5, 0.1≤a≤0.5, 0.15≤a≤0.45, 0.2≤a≤0.4, 0.25≤a≤0.35, 0.25≤a≤0.3, etc. Specifically, the positive electrode active material includes the A element at this content, which can promote the formation of spinel with excessive Li, which is beneficial for the phase state of part of the positive electrode active material to be tetragonal spinel, so that more Li is retained in the Li position, increasing the active Li to exert its capacity, and improving the capacity of the positive electrode active material. In other embodiments of the present application, the above-mentioned positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y Here, a can be 0.01≤a≤0.4, for example, 0.05≤a≤0.3.

[0072] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the formula, b can be 0≤b≤1, for example, 0≤b≤0.9, 0.1≤b≤0.9, 0.2≤b≤0.8, 0.3≤b≤0.7, 0.4≤b≤0.6, etc. Specifically, the B element is comparable to the radius of Mn and can be dispersed to the Mn position, and its low valence state can promote the valence state of Mn to rise, and promote Mn to become +4 valence, thereby inhibiting the Jan-Taylor effect of the positive electrode active material and improving the capacity of the positive electrode active material. The doping amount b of the B element is within the above range, so that the positive electrode active material has a spinel structure, and can slow down the structural decay of the positive electrode active material and the dissolution of the Mn element, thereby improving the capacity of the positive electrode active material. At the same time, its cycle performance is excellent, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance. In other embodiments of the present application, the above-mentioned positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the equation, b can be 0.01≤b≤1, for example, 0.1≤b≤0.7.

[0073] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the formula, m can be 0≤m≤0.2, such as 0.001≤m≤0.2, 0.01≤m≤0.15, 0.05≤m≤0.12, 0.06≤m≤0.1, 0.07≤m≤0.09, etc. Thus, the element M at this content can form a strong bond with oxygen, stabilize the positive electrode active material, especially the oxygen atoms on the surface of the grains, reduce surface side reactions, reduce side reactions between the positive electrode active material and the electrolyte, reduce oxygen loss of the positive electrode active material, reduce Mn dissolution, and improve the capacity of the positive electrode active material. At the same time, its cycle performance is excellent, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance. In other embodiments of the present application, the above-mentioned positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the equation, m can be 0.001≤m≤0.2, for example, 0.01≤m≤0.1.

[0074] It can be understood that in the embodiments of the present application, the lower limit of b and m is 0, which means that b and m may not be present in the positive electrode active material.

[0075] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the equation, y can be -0.5≤y≤1, for example, -0.5≤y≤0.9, -0.4≤y≤0.8, -0.3≤y≤0.7, -0.2≤y≤0.6, -0.1≤y≤0.5, 0≤y≤0.4, 0.1≤y≤0.3, etc.

[0076] It should be noted that in the positive electrode sheet, battery or electrical device, due to the battery cycle and other processes, the positive electrode active material may release oxygen from the lattice, resulting in the loss of oxygen in the positive electrode active material. Therefore, the measured oxygen content 4-y in the positive electrode active material may be less than 4. In addition, there are many cases where the positive electrode active material is oxygen-rich, such as the dissolution of Mn, the entry of Li into the Mn position, and the presence of a portion of Li4Mn5O in the positive electrode active material. 12 phase, therefore, the measured oxygen element content 4-y in the positive electrode active material may be greater than 4.

[0077] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In the formula, x / a can be 1≤x / a≤10, such as 1≤x / a≤9, 2≤x / a≤8, 3≤x / a≤7, 4≤x / a≤6, etc. Specifically, the larger the x, the better the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y The more excess Li there is, the easier it is for Li to enter the Mn site, and the more doping element A is needed to inhibit Li from entering the Mn site and promote Li to stay in the Li site. Within the above x / a range, the capacity of the positive electrode active material is increased, and its cycle performance is excellent, thereby increasing the capacity of the battery containing it, and the battery has excellent cycle performance. In other embodiments of the present application, the above positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y In this case, x / a can be 2≤x / a≤7.

[0078] In some embodiments of the present application, the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y The contents of A, B and M satisfy the following relationship: 0.001≤a+b+m≤1, for example, 0.001≤a+b+m≤0.9, 0.01≤a+b+m≤0.9, 0.1≤a+b+m≤0.9, 0.2≤a+b+m≤0.8, 0.3≤a+b+m≤0.7, 0.4≤a+b+m≤0.6, etc. Thus, a+b+m represents the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O 4-y The amount of doping elements in the positive electrode active material is within the range of the sum of the contents of A, B and M, which can significantly inhibit the Jan-Taylor effect of the positive electrode active material, making the positive electrode active material a spinel structure, and improving the positive electrode active material Li 1+x A a B b M m Mn 2-a-b-m O4-y The structural stability of the positive electrode active material Li is improved, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance. 1+x A a B b M m Mn 2-a-b-m O 4-y In the equation, we can take 0.3≤a+b+m≤0.7.

[0079] In some embodiments of the present application, the positive electrode active material further comprises a 1+x A a B b M m Mn 2-a-b-m O 4-y At least part of the surface of the alkaline coating. During the battery charge and discharge cycle, the electrolyte is easily oxidized to produce acid (such as HF). The alkaline coating can reduce the replacement of active Li by the acidified electrolyte, especially reducing Li 1+x A a B b M m Mn 2-a-b-m O 4-y The excess Li in the positive electrode is replaced, thereby reducing the loss of active Li; the alkaline coating layer can also neutralize part of the acid, reduce the corrosion and damage of the acid on the surface of the positive electrode active material, and improve the capacity of the positive electrode active material. At the same time, its cycle performance is excellent, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance.

[0080] It is understood that the basic coating layer refers to the coating on the Li 1+x A a B b M m Mn 2-a-b-m O 4-y The alkaline substance on the outer surface of the particle may have a pH value of 7.5-13. For example, the pH value of the alkaline coating layer may be 7.5-12.5, 8-12, 8.5-11.5, 9-11, 9.5-10.5, etc. For example, the alkaline coating layer may include a strong base and a weak acid salt.

[0081] It is understood that the positive electrode active material also includes the Li 1+x A a B b M m Mn 2-a-b-m O 4-y At least part of the surface alkaline coating, including Li 1+x A a B b M mMn 2-a-b-m O 4-y The surface of the 1+x A a B b M m Mn 2-a-b-m O 4-y The entire surface of the substrate is covered with an alkaline coating layer.

[0082] In some embodiments of the present application, Li 1+x A a B b M m Mn 2-a-b-m O 4-y The entire surface of the positive electrode is covered with an alkaline coating layer, which acts to isolate the electrolyte, reduce the loss of active lithium, reduce the corrosion and damage of the surface of the positive electrode active material, and improve the capacity and cycle performance of the positive electrode active material, thereby improving the capacity of the battery containing it, and the battery has excellent cycle performance.

[0083] In some embodiments of the present application, the alkaline coating layer includes D g+ d Z h+ z O 2- t Q - q , specifically, D g+ d Z h+ z O 2- t Q - q It is a strong base weak acid salt, wherein D includes at least one of Li, Na, K, Be, Mg or Ca, Z includes at least one of B, Si, P or As, Q includes at least one of F, Cl, Br or I, g=1 or 2, h=3, 4 or 5, 1.5≤(t+q) / z≤5, 0≤q / t≤2. For example, 1.5≤(t+q) / z≤4.5, 2≤(t+q) / z≤4, 2.5≤(t+q) / z≤3.5, etc., (t+q) / z represents the number of anions that the core element Z needs to match, 0.1≤q / t≤1.9, 0.5≤q / t≤1.5, 1≤q / t≤1.5, etc., q / t represents the amount of elements substituted at the O position. Specifically, the above-mentioned alkaline coating layer can increase the pH value of the material. The above-mentioned D g+ d Z h+ z O 2- t Q - qIt is alkaline, but not too alkaline; in addition, D g+ d Z h+ z O 2- t Q - q It has good compatibility with positive electrode active materials and excellent ion conductivity, which increases the capacity of positive electrode active materials. At the same time, it has excellent cycle performance, thereby increasing the capacity of the battery containing it, and the battery has excellent cycle performance.

[0084] In some embodiments of the present application, D g+ d Z h+ z O 2- t Q - q It can include small molecule weak acid and strong base salts, such as lithium phosphate, sodium phosphate, lithium borate, sodium borate, lithium silicate, sodium silicate, etc. It can also include polymers, such as lithium polyphosphate (Li n+2 P n O 3n+1 ).

[0085] In some embodiments, in the positive electrode active material, the mass proportion of the alkaline coating layer is 0.3%-5%. For example, the mass proportion of the alkaline coating layer can be 0.3%-4.5%, 0.5%-4%, 1%-3.5%, 1.5%-3%, 2%-2.5%, etc. Specifically, in the positive electrode active material, the mass proportion of the alkaline coating layer is within the above range, which can play a good protective role on the positive electrode active material, while reducing the hindrance of the transmission of lithium ions caused by excessive coating, thereby increasing the capacity of the positive electrode active material, and its cycle performance is excellent, thereby increasing the capacity of the battery containing it, and the battery has excellent cycle performance. In other embodiments of the present application, in the positive electrode active material, the mass proportion of the alkaline coating layer is 1%-3%.

[0086] In some embodiments of the present application, the pH value of the saturated aqueous solution of the positive electrode active material at 25°C is 9-11.5. For example, the pH value of the saturated aqueous solution of the positive electrode active material at 25°C can be 9-11.2, 9.2-11, 9.5-10.8, 9.8-10.5, 9.9-10, etc. When the pH value of the saturated aqueous solution of the positive electrode active material at 25°C is within the above range, it can neutralize part of the acid produced by oxidation of the electrolyte, reduce the corrosion and damage of the acid on the surface of the positive electrode active material, and at the same time reduce the deterioration of the processing performance of the positive electrode active material caused by excessive alkalinity, thereby increasing the capacity of the positive electrode active material and having excellent cycle performance, thereby increasing the capacity of the battery containing it and having excellent cycle performance. In other embodiments of the present application, the pH value of the saturated aqueous solution of the positive electrode active material is 10-11.

[0087] Specifically, the "pH value of a saturated aqueous solution of a positive electrode active material at 25°C" in this application has a well-known meaning in the art and can be measured using instruments and methods well-known in the art. For example, it can be obtained by the following method:

[0088] The positive electrode active material and pure water were mixed in a mass ratio of 1:9, magnetically stirred for 30 minutes, and then placed in a constant temperature water bath at 25°C for 1.5 hours. The pH value of the mixture was then tested according to GB / T 9724-2007.

[0089] In some embodiments of the present application, the volume average particle size D of the positive electrode active material is v 50 is 1 μm-30 μm, for example, the volume average particle size D of the positive electrode active material v 50 can be 1 μm-29 μm, 3 μm-25 μm, 5 μm-23 μm, 10 μm-20 μm, 13 μm-15 μm, etc. In other embodiments of the present application, the volume average particle size D of the positive electrode active material is v 50 is 2μm-10μm.

[0090] In this application, the volume average particle size D v 50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, for example, with reference to the standard GB / T 19077-2016, and is measured using a laser particle size analyzer (such as Malvern Master Size 3000).

[0091] In some embodiments of the present application, the BET specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-5m 2 / g, for example, the BET specific surface area of ​​the positive electrode active material can be 0.1m 2 / g-4.5m 2 / g,0.5m 2 / g-4m 2 / g,1m 2 / g-3.5m 2 / g,1.5m 2 / g-3m 2 / g,2m 2 / g-2.5m 2 In other embodiments of the present application, the BET specific surface area of ​​the positive electrode active material is 0.2 m 2 / g-2m 2 / g.

[0092] In this application, the "BET specific surface area of ​​the positive electrode active material" has a meaning well known in the art and can be measured using instruments and methods well known in the art. For example, it can be obtained by the following method: using a US Microscope multi-station fully automatic BET specific surface area and pore analyzer GeminiVII2390, approximately 7g of sample is placed in a 9cc long tube with a bulb, degassed at 200°C for 2 hours, and then placed in a main unit for testing to obtain the BET (specific surface area) data of the positive electrode active material.

[0093] In some embodiments of the present application, the tap density of the positive electrode active material is 1.5 g / cm 3 -3.0g / cm 3 For example, the tap density of the positive electrode active material can be 1.5 g / cm 3 -2.8g / cm 3 , 1.8g / cm 3 -2.5g / cm 3 , 2.0g / cm 3 -2.3g / cm 3 In some other embodiments of the present application, the tap density of the positive electrode active material is 2 g / cm 3 -2.5g / cm 3 .

[0094] In this application, tap density refers to the mass per unit volume of the powder in the container after being tapped under specified conditions. The tap density of the positive electrode active material can be determined by the following method:

[0095] Place the weighed positive electrode active material into the graduated cylinder of the vibrating device and secure the cylinder to the support. Rotate the cam, and the directional rod drives the support up and down, striking the anvil. Vibrate at 250 ± 15 vibrations per minute for 12 minutes. Measure the volume of the positive electrode active material in the graduated cylinder. The ratio of the positive electrode active material mass to volume is the tap density of the positive electrode active material.

[0096] The calculation formula of tap density is: ρbt=m0 / V

[0097] Where, ρbt is the tap density, g / cm 3

[0098] m0——mass of positive electrode active material, g

[0099] V - the volume of the positive electrode active material after compaction (the volume of the measuring cup), cm 3 .

[0100] Specifically, when the volume average particle size D of the positive electrode active material of the present application is v 50. When at least one of the BET specific surface area and the tap density is within the above range, the conduction distance within the positive electrode active material is small and the surface side reactions are few, which promotes the positive electrode active material to exert its gram capacity and improves the capacity of the battery containing it. At the same time, the battery has excellent cycle performance.

[0101] The second aspect of the present application provides a method for preparing the positive electrode active material according to the first aspect, comprising:

[0102] S100: LiA a B b M m Mn 2-a-b-m O 4-y Mixed with a first lithium source and subjected to a first sintering to obtain a positive electrode active material, the positive electrode active material comprising: Li 1+x A a B b M m Mn 2-a-b-m O 4-y ,

[0103] Wherein, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1

[0104] Use LiA a B b M m Mn 2-a-b-m O 4-y Mixed with the first lithium source and sintered, the spinel structure of LiA a B b M m Mn 2-a-b-m Supplementing Li on the basis of O4 makes it easy for excess Li to enter the Li site, which is beneficial to the formation of sufficient tetragonal spinel in the positive electrode active material and improves the capacity of the positive electrode active material.

[0105] In some embodiments of the present application, the above-mentioned LiA a B b M m Mn 2-a-b-m O 4-y The first lithium source and the first lithium source are placed in a muffle furnace in an air atmosphere for a first sintering, and then cooled to room temperature and mechanically crushed to obtain a positive electrode active material, wherein the temperature of the first sintering is 300°C-600°C. For example, the temperature of the first sintering can be 300°C-590°C, 320°C-550°C, 350°C-500°C, 380°C-480°C, 350°C-450°C, 380°C-400°C, etc. Controlling the first sintering temperature within the above range is conducive to forming a sufficient amount of tetragonal spinel in the positive electrode active material, and is conducive to obtaining a positive electrode active material containing a sufficient amount of tetragonal spinel and a portion of cubic spinel, thereby improving the capacity and stability of the positive electrode active material, thereby improving the capacity of the battery containing the same, and the battery has excellent cycle performance.

[0106] In some embodiments of the present application, the first sintering time is 5 hours to 50 hours. For example, the first sintering time can be 5 hours to 45 hours, 10 hours to 40 hours, 15 hours to 35 hours, 20 hours to 30 hours, etc.

[0107] In some embodiments of the present application, the LiA a B b M m Mn 2-a-b-m O 4-y The following steps are used to obtain:

[0108] S1000: Mix the second lithium source, A source, B source, M source and Mn source, and perform a second sintering to obtain LiA a B b M m Mn 2-a-b-m O 4-y

[0109] In some embodiments of the present application, the second lithium source, A source, B source, M source and Mn source are mixed and placed in a muffle furnace in an air atmosphere for a second sintering, and then cooled to room temperature and mechanically crushed to obtain LiA a B b M m Mn 2-a-b-m O 4-y, wherein the second sintering temperature is 700-1100°C, for example, the second sintering temperature can be 700-1000°C, 750-950°C, 800-900°C, etc., and the second sintering time is 5h-50h, for example, the second sintering time can be 5h-45h, 10h-40h, 15h-35h, 20h-30h, etc. Under the above second sintering conditions, spinel structured LiA a B b M m Mn 2-a-b-m O 4-y .

[0110] It should be noted that the Li source, A source, B source, M source and Mn source in this application are conventional materials in the field, and those skilled in the art can select them according to actual conditions. For example, the Li source can include at least one of Li2CO3, LiHCO3, LiOH, Li2O2, Li2O, Li2NO3, Li2C2O4, Li3PO4, Li2SO4, and Li3BO3; the A source can include at least one of the carbonate, hydroxide, oxide, nitrate, oxalate, phosphate, sulfate, and borate of A; the B source can be Including at least one of B carbonate, hydroxide, oxide, nitrate, oxalate, phosphate, sulfate, and borate; the M source may include at least one of M carbonate, hydroxide, oxide, nitrate, oxalate, phosphate, sulfate, and borate; the Mn source may include at least one of Mn2O3, Mn3O4, MnO, MnO2, MnCO3, Mn(HCO3)2, Mn(OH)2, MnNO3, MnC2O4, Mn3(PO4)2, MnSO4, and Mn3(BO3)2.

[0111] It should be noted that if the positive electrode active material does not include the B element and / or the M element, then in the process of preparing the positive electrode active material, accordingly, no B source and / or M source is added.

[0112] In some embodiments of the present application, the method for preparing the positive electrode active material further includes:

[0113] S200: Mix the positive electrode active material with the alkaline material and perform the third sintering. a B b M m Mn 2-a-b-m O 4-y At least part of the surface is covered with an alkaline coating

[0114] The alkaline material and Li 1+x A a B b M m Mn 2-a-b-mO 4-y Mixing to achieve coating and protection. The third sintering can enhance the alkaline coating layer and Li 1+x A a B b M m Mn 2-a-b-m O 4-y The bonding force promotes the comprehensiveness of the coating and improves the protective effect of the alkaline coating layer.

[0115] In some embodiments of the present application, the temperature of the third sintering is 200°C-700°C, for example, the third sintering temperature can be 200°C-650°C, 250°C-600°C, 300°C-550°C, 350°C-500°C, 400°C-450°C, etc. Within the above third sintering temperature range, the alkaline coating layer and Li 1+x A a B b M m Mn 2-a-b-m O 4-y The bonding force promotes comprehensive coating and improves the protective effect of the alkaline coating layer.

[0116] In some embodiments of the present application, the third sintering time is 1 hour to 10 hours. For example, the third sintering time can be 1 hour to 9 hours, 2 hours to 8 hours, 3 hours to 7 hours, 4 hours to 6 hours, etc.

[0117] In a third aspect, the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect.

[0118] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0119] 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 include at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0120] The positive electrode active material includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material prepared by the method described in the second aspect.

[0121] The positive electrode active material layer may also optionally include a conductive agent and a binder. The conductive agent is used to improve the conductivity of the positive electrode active material layer, and the binder is used to firmly bond the positive electrode active material and the binder to the positive electrode current collector. This application does not specifically limit the types of conductive agent and binder, and they can be selected according to actual needs.

[0122] 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; the binder may include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA).

[0123] These materials are all commercially available.

[0124] The fourth aspect of the present application provides a battery comprising the positive electrode sheet according to the third aspect of the present application, thereby having excellent capacity and cycle life.

[0125] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0126] It can be understood that the battery proposed in this application is a lithium-ion battery.

[0127] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[0128] [Negative electrode]

[0129] In a battery, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0130] 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.

[0131] The specific type of the negative electrode active material is not limited, and active materials that can be used for the negative electrode of the battery known in the art 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. The silicon-based material may include one or more of elemental silicon, silicon oxide compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. These materials can all be obtained through commercial channels.

[0132] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicon-based material.

[0133] The negative electrode active material layer may also optionally include a binder, a conductive agent, and other optional auxiliary agents.

[0134] As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] As an example, the binder may include 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).

[0136] As examples, other optional additives may include thickening and dispersing agents (eg, sodium carboxymethyl cellulose CMC-Na), and PTC thermistor materials.

[0137] [Electrolyte]

[0138] The electrolyte solution may include an electrolyte salt and a solvent.

[0139] As an example, the electrolyte salt may include 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).

[0140] As an example, the solvent may include 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).

[0141] In some embodiments, the electrolyte further includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives capable of improving 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.

[0142] [Isolation film]

[0143] As the above-mentioned isolation membrane, the present application has no special restrictions and any known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0144] The embodiment of the present application has no particular limitation on the shape of the battery, which can be cylindrical, square or any other shape. FIG1 shows a square battery 1 as an example.

[0145] In some embodiments, the battery may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0146] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0147] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The number of electrode assemblies in a battery can include one or more, which can be adjusted according to needs.

[0148] In some embodiments, the outer packaging of the battery may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0149] The outer packaging of the battery may also include a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0150] In some embodiments, batteries may be assembled into a battery module. The battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0151] Figure 2 shows an example battery module 2. Referring to Figure 2 , within the battery module 2, multiple batteries 1 may be arranged sequentially along the length of the battery module 2. Of course, any other arrangement is also possible. Furthermore, the multiple batteries 1 may be secured together using fasteners.

[0152] The battery module 2 may further include a housing having a housing space, wherein the housing space accommodates a plurality of batteries 1. In some embodiments, the battery modules may 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.

[0153] Figures 3 and 4 illustrate an example battery pack 3. Referring to Figures 3 and 4 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 4 and a lower case 5. The upper case 4 can be placed over the lower case 5 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0154] In a fifth aspect, the present application provides an electrical device comprising the battery described in the fourth aspect. Specifically, the battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0155] FIG5 shows an example of an electric device, which includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0156] As another example, electric devices may include mobile phones, tablet computers, and laptop computers. These electric devices are generally required to be lightweight and thin, and may use batteries as power sources.

[0157] 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 drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0158] Example 1

[0159]

【Li 1.4 Sc 0.1 Mn 1.9 O4 preparation]

[0160] Li2O3, Sc2O3 and Mn3O4 (the molar ratio of Li, Sc and Mn is 1:0.1:1.9) are mixed evenly, and then the temperature is increased to 850℃ (the second sintering temperature) in a muffle furnace at a heating rate of 5℃ / min. After sintering for 10 hours, the temperature is naturally cooled to room temperature to obtain LiSc 0.1 Mn 1.9 O4.

[0161] LiSc 0.1 Mn 1.9 O4 and Li (molar ratio 1:0.4) were mixed and sintered at 450℃ (first sintering temperature) for 15h and then naturally cooled to room temperature to obtain the positive electrode active material Li 1.4 Sc 0.1 Mn 1.9 O4.

[0162]

Preparation of positive electrode sheet

[0163] The Li 1.4 Sc 0.1 Mn 1.9 O4, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dispersed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5 and stirred to mix evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode aluminum foil collector, and after drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0164]

Preparation of negative electrode sheet

[0165] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0166] Preparation of electrolyte

[0167] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7 to obtain a mixed solvent, and then LiPF6 was dissolved in the mixed solvent and stirred to obtain an electrolyte.

[0168]

Isolation film

[0169] Glass fiber is used as the isolation membrane.

[0170] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.

[0171] The secondary batteries containing the positive electrode active materials of Examples 2-26 are the same as those of Example 1 except for the different parameters (see Table 1).

[0172] Example 27

[0173] [Li with alkaline coating on the surface 1.4 Sc 0.1 Mn 1.9 O4 preparation]

[0174] Li2O3, Sc2O3 and Mn3O4 (the molar ratio of Li, Sc and Mn is 1:0.1:1.9) are mixed evenly, and then the temperature is increased to 850℃ (the second sintering temperature) in a muffle furnace at a heating rate of 5℃ / min. After sintering for 10 hours, the temperature is naturally cooled to room temperature to obtain LiSc 0.1 Mn 1.9 O4.

[0175] LiSc 0.1 Mn 1.9 O4 and Li (molar ratio 1:0.4) were mixed and sintered at 450℃ (first sintering temperature) for 15h and then cooled naturally to room temperature to obtain Li 1.4 Sc 0.1Mn 1.9 O4.

[0176] The alkaline material and Li 1.4 Sc 0.1 Mn 1.9 O4 was mixed evenly according to the coating mass ratio, and then the temperature was raised to 500°C and kept for 5 hours to obtain the positive electrode active material.

[0177]

Preparation of positive electrode sheet

[0178] The positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) prepared above are dispersed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5 and stirred and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode aluminum foil current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0179]

Preparation of negative electrode sheet

[0180] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0181] Preparation of electrolyte

[0182] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7 to obtain a mixed solvent, and then LiPF6 was dissolved in the mixed solvent and stirred to obtain an electrolyte.

[0183]

Isolation film

[0184] Glass fiber is used as the isolation membrane.

[0185] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.

[0186] The secondary batteries containing the positive electrode active materials of Examples 28-32 are the same as those of Example 27 except for the different parameters (see Table 1).

[0187] The secondary battery containing the positive electrode active material of Example 33 is the same as that of Example 1 except for the different parameters (see Table 1).

[0188] Comparative Example 1

[0189]

【Li 1.4 Preparation of Mn2O4

[0190] Li2O3 and Mn2O3 (the molar ratio of Li to Mn is 1.4:2) are mixed in the agate mill of a planetary ball mill, and the raw materials are ground at a speed of 600r / min. Then, the temperature is increased to 850℃ (the second sintering temperature) in a muffle furnace at a heating rate of 5℃ / min. After sintering for 10h, the temperature is naturally cooled to room temperature to obtain the positive electrode active material Li 1.4 Mn2O4.

[0191]

Preparation of positive electrode sheet

[0192] The Li 1.4 Mn2O4, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) are stirred and mixed in a weight ratio of 60:5:5:30 to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode aluminum foil collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0193]

Preparation of negative electrode sheet

[0194] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0195] Preparation of electrolyte

[0196] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7 to obtain a mixed solvent, and then LiPF6 was dissolved in the mixed solvent and stirred to obtain an electrolyte.

[0197]

Isolation film

[0198] Glass fiber is used as the isolation membrane.

[0199] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.

[0200] Comparative Example 2

[0201]

【Li 1.4 Sc 0.6 Mn 1.4 O4 preparation]

[0202] Li2O3, Sc2O3 and Mn2O3 (the molar ratio of Li, Sc and Mn is 1:0.6:1.4) are mixed evenly, and then the temperature is increased to 850℃ (the second sintering temperature) at a heating rate of 5℃ / min in a muffle furnace. After sintering for 10 hours, the temperature is naturally cooled to room temperature to obtain black LiSc 0.6 Mn 1.4 O4.

[0203] LiSc 0.1 Mn 1.9 O4 and Li (molar ratio 1:0.4) were mixed and sintered at 450℃ (first sintering temperature) for 15h and then naturally cooled to room temperature to obtain the positive electrode active material Li 1.4 Sc 0.6 Mn 1.4 O4.

[0204]

Preparation of positive electrode sheet

[0205] The Li 1.4 Sc 0.6 Mn 1.4 O4, conductive agent carbon black and binder polyvinylidene fluoride (PVDF) are dispersed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5 and stirred to mix evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode aluminum foil collector, and after drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0206]

Preparation of negative electrode sheet

[0207] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0208] Preparation of electrolyte

[0209] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7 to obtain a mixed solvent, and then LiPF6 was dissolved in the mixed solvent and stirred to obtain an electrolyte.

[0210]

Isolation film

[0211] Glass fiber is used as the isolation membrane.

[0212] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried secondary battery. After vacuum packaging, standing, formation, and shaping processes, a secondary battery is obtained.

[0213] The compositions of the positive electrode active materials in the batteries of Examples 1-33 and Comparative Examples 1-2 of the present application are shown in Table 1.

[0214] Table 1

[0215] In Table 1, “ / ” indicates that no addition was made.

[0216] Performance testing:

[0217] 1. XRD diagram of the positive electrode active material. The positive electrode active materials of Example 1 and Comparative Example 1 were subjected to XRD diagrams, and FIG6 was obtained.

[0218] 2. Test of the proportion of the 2.9V charging capacity of the positive electrode active material to the total charging capacity:

[0219] Taking Example 1 as an example, in a battery using the positive electrode active material of Example 1 as the positive electrode and Li as the negative electrode, the battery was charged to 4.35 V at a constant current rate of 0.1 C. The charging curves of Example 1 and Comparative Example 1 are shown in FIG7 . The proportion of the charging capacity at 2.8-3.1 V to the total charging capacity was calculated, and the results are shown in Table 1.

[0220] The testing process for the ratio of the charge capacity of the positive electrode active material 2.9 to the total charge capacity of Example 2-33 and Comparative Example 1-2 is the same as above.

[0221] 3. Battery capacity and cycle life test:

[0222] Taking Example 1 as an example, the secondary battery of Example 1 was charged to 4.25V at a rate of 0.33C, then discharged to 3.0V at 0.33C. The initial discharge capacity divided by the mass of the positive electrode active material was the first cycle capacity (referred to as capacity). This was followed by charging to 4.25V at 1C, then constant voltage charging to 0.05C, then discharging to 3.0V at 1C. This cycle of 1C, 0.05C, and 1C was repeated. The number of repeated charge and discharge cycles was the number of cycles. The total number of cycles when the discharge capacity decayed to 80% of the initial capacity or when the positive electrode active mass decayed to 80 mAh / g (whichever condition was achieved first) was the cycle life. The results are shown in Table 2.

[0223] As can be seen from Figure 6, the positive electrode active material of Example 1 of the present application has a peak at the 33° position (indicated by the dotted line in Figure 6), and it can be seen that it contains tetragonal spinel. Comparative Example 1 does not have a peak at the 33° position, and does not contain tetragonal spinel.

[0224] As can be seen from Figure 7, the proportion of the 2.9V charging capacity content in Example 1 of the present application to the total charging capacity is not 0, which shows that the positive electrode active material contains tetragonal spinel, while the proportion of the 2.9V charging capacity content in Comparative Example 1 to the total charging capacity is 0, which shows that there is no tetragonal spinel in the positive electrode active material of Comparative Example 1.

[0225] The test process of the battery capacity and cycle life of Examples 2-33 and Comparative Examples 1-2 is the same as above, and the results are shown in Table 2. Table 2

[0226] As can be seen from Table 2, in Examples 1 to 33 of the present application, the initial capacity of the secondary batteries is all above 100 mA·h / g, and the capacity and cycle life are excellent. It can be seen that within the above ranges of x and a, the positive electrode active material contains a sufficient amount of tetragonal spinel and a portion of cubic spinel, which improves the capacity of the positive electrode active material and has excellent cycle performance, thereby improving the capacity of the battery containing it and having excellent cycle performance.

[0227] Comparative Example 1 does not contain element A, and the amount a value of element A in Comparative Example 2 is not in the range of 0.001-0.5. Its cycle performance and storage performance are significantly lower than those of the examples of the present application.

[0228] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode active material, wherein: The positive electrode active material includes: Li 1+x A a B b M m Mn 2-a-b-m O 4-y , Among them, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1.

2. The positive electrode active material according to claim 1, wherein A includes at least one of Ca, Sc, Ti, V, Cr or Y.

3. The positive electrode active material according to claim 1 or 2, wherein A includes at least one of Sc, V or Y.

4. The positive electrode active material according to any one of claims 1 to 3, wherein The positive electrode active material satisfies at least one of the following conditions: 0.2≤x≤0.6, which can be 0.2≤x≤0.4; 0.01≤a≤0.4, optional 0.05≤a≤0.3; 0.01≤b≤1, optional 0.1≤b≤0.7; 0.001≤m≤0.2, optionally 0.01≤m≤0.

1.

5. The positive electrode active material according to any one of claims 1 to 4, wherein 1≤x / a≤10, optionally 2≤x / a≤7.

6. The positive electrode active material according to any one of claims 1 to 5, wherein 0.001≤a+b+m≤1, which can be optionally 0.3≤a+b+m≤0.

7.

7. The positive electrode active material according to any one of claims 1 to 6, wherein The positive electrode active material also includes a Li 1+x A a B b M m Mn 2-a-b-m O 4-y A basic coating on at least part of the surface.

8. The positive electrode active material according to claim 7, wherein The basic coating layer comprises D g+ d Z h+ z O 2- t Q - q , wherein D includes at least one of Li, Na, K, Be, Mg or Ca, Z includes at least one of B, Si, P or As, Q includes at least one of F, Cl, Br or I, g=1 or 2, h=3, 4 or 5, 1.5≤(t+q) / z≤5, 0≤q / t≤2.

9. The positive electrode active material according to claim 7 or 8, wherein In the positive electrode active material, the mass proportion of the alkaline coating layer is 0.3%-5%, and can be optionally 1%-3%.

10. The positive electrode active material according to any one of claims 1 to 9, wherein The charging capacity of the positive electrode active material at 2.9V accounts for 10%-30% of the total charging capacity, and can be optionally 15%-25%.

11. The positive electrode active material according to any one of claims 1 to 10, wherein The pH value of the saturated aqueous solution of the positive electrode active material at 25° C. is 9-11.5, and can be optionally 10-11.

12. The positive electrode active material according to any one of claims 1 to 11, wherein The positive electrode active material satisfies at least one of the following conditions: The volume average particle size D of the positive electrode active material v 50 is 1μm-30μm, optional is 2μm-10μm; The BET specific surface area of ​​the positive electrode active material is 0.1 m 2 / g-5m 2 / g, optional 0.2m 2 / g-2m 2 / g; The tap density of the positive electrode active material is 1.5 g / cm 3 -3.0g / cm 3 , optional 2g / cm 3 -2.5g / cm 3 .

13. A method for preparing a positive electrode active material, wherein: include: LiA a B b M m Mn 2-a-b-m O 4-y Mixing with a first lithium source and performing a first sintering to obtain a positive electrode active material, the positive electrode active material comprising: Li 1+x A a B b M m Mr 2-a-b-m O 4-y , Among them, A includes at least one of Ca, Sc, Ti, V, Cr, Sr, Y or Zr, B includes at least one of Ni, Al, Co or Fe, M includes at least one of W, Nb, Sb, P, La, Mo, Ta or Ce, 0.1<x≤1.1, 0.001≤a≤0.5, 0≤b≤1, 0≤m≤0.2, -0.5≤y≤1.

14. The method according to claim 13, wherein: The LiA a B b M m Mn 2-a-b-m O 4-y The following steps are used to obtain the LiA a B b M m Mn 2-a-b-m O 4-y .

15. The method according to claim 13 or 14, wherein: The first sintering temperature is 300°C-600°C.

16. The method according to any one of claims 13 to 15, wherein: The method further comprises: mixing the positive electrode active material with an alkaline material, performing a third sintering, and a B b M m Mn 2-a-b-m O 4-y A basic coating is formed on at least a portion of the surface.

17. A positive electrode sheet, wherein: The positive electrode sheet comprises the positive electrode active material according to any one of claims 1 to 12 or the positive electrode active material prepared by the method according to any one of claims 13 to 16.

18. A battery, wherein: The battery comprises the positive electrode sheet according to claim 17.

19. An electrical device, wherein: Comprising the battery of claim 18.

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