Positive electrode material, secondary battery, and electric device

Abstract

The invention provides a positive electrode material, a secondary battery and a power utilization device, the positive electrode material comprises a substrate and a coating layer coating at least part of the surface of the substrate, and the substrate comprises a spinel structure manganese-rich oxide; the coating layer comprises an element M and an element N, the element M comprises at least one of W, Mo, Te, Sb, Ru and P, and the element N comprises at least one of Nb and Ta. The positive electrode material is stable in structure, and the reversible capacity retention rate of the obtained secondary battery in the using process is high.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a cathode material, a secondary battery, and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application range of secondary batteries, they have been widely used in energy storage power systems such as hydro, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of secondary batteries, higher requirements have been put forward for their performance.

[0003] As an important component of the battery, the cathode material is closely related to the battery performance. However, cathode materials such as manganese-rich materials are prone to oxygen loss, and the stability of the cathode material is poor, which affects the battery performance. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a stable and novel cathode material, a secondary battery using the cathode material, and an electrical device.

[0005] To achieve the above object, a first aspect of the present application provides a cathode material, which includes a matrix and a coating layer covering at least a part of the surface of the matrix, the matrix includes a spinel-structured manganese-rich oxide; the coating layer includes M element and N element, the M element includes at least one of W, Mo, Te, Sb, Ru, P, and the N element includes at least one of Nb, Ta. By providing the above coating layer, the cathode material of the present application can not only stabilize the oxygen on the surface of the matrix but also obtain excellent acid corrosion resistance, thereby improving the stability of the cathode material, and further improving the reversible capacity retention rate of the secondary battery during use.

[0006] In some embodiments, the coating layer includes an M element-containing compound and an N element-containing compound; the M element-containing compound includes an M-X chemical bond; and / or, the N element-containing compound includes an N-X chemical bond; wherein, X represents at least one of halogen, O, C, N, and S; optionally, X represents at least one of halogen and O. Thus, on the one hand, the risk of oxygen loss of the matrix can be effectively reduced, and on the other hand, the acid in the electrolyte can be blocked from contacting the matrix, thereby stabilizing the cathode material.

[0007] In some embodiments, when the M element includes at least one of W, Mo, Te, Sb, and Ru, the coating layer includes at least one of a halide, an oxide, a carbide, a nitride, or a sulfide of the M element; when the M element includes P, the coating layer includes at least one of phosphoric acid, metaphosphoric acid, polyphosphoric acid, pyrophosphoric acid, halogenated phosphoric acid, and salts formed therefrom; and / or, the coating layer includes at least one of a halide, an oxide, a carbide, a nitride, or a sulfide of the N element. Thus, on the one hand, the risk of oxygen loss from the substrate can be effectively reduced, and on the other hand, the acid in the electrolyte can be blocked from contacting the substrate, thereby stabilizing the cathode material.

[0008] In some embodiments, the M element includes at least Te and / or P; optionally, the M element includes at least P. Te and / or P can form stronger chemical bonds with halogens, O, C, N, S, etc., and can more effectively stabilize the oxygen on the surface of the substrate. Further, P can also form strongly bonded composite compounds with other M and N elements, which can further improve the stability of the coating layer and enhance its protection of the substrate.

[0009] In some embodiments, in the cathode material, the content of the M element is 0.01% to 4% by mass; and / or, the content of the N element is 0.01% to 4% by mass; and / or, the total content of the M element and the N element is 0.05% to 5% by mass. Thus, it is more conducive for the coating layer to play the role of stabilizing the surface oxygen and improving the acid corrosion resistance.

[0010] In some embodiments, the coating layer further includes the B element and / or the Si element, and in the cathode material, the content of the B element and / or the Si element is 0.01% to 1% by mass. In some embodiments, the coating layer includes borate and / or silicate. The B element and / or the Si element in the coating layer can both form strong bonds with the substrate and form strong bonds with the N element, thereby improving the bond between the coating layer and the substrate and the bond within the coating layer. In addition, by setting the content of the B element and / or the Si element between 0.01% and 1% by mass, it can not only improve the bond between the coating layer and the substrate and within the coating layer, but also improve the function of the coating layer in stabilizing the surface oxygen and improving the acid corrosion resistance.

[0011] In some embodiments, the coating layer further includes a Z element with an electronegativity less than that of the M element or the N element. Optionally, the Z element includes at least one of Li, Na, and K; in the positive electrode material, the content of the Z element is 0.01% to 1% by mass. By making the coating layer include the above-mentioned alkaline Z element, the Z element can preferentially combine with the acid in the electrolyte, thereby further reducing the possibility of acid damage to the positive electrode material and improving the stability of the battery system. In addition, by setting the content of the Z element in the positive electrode material between 0.01% and 1% by mass, it can both combine with the acid and ensure the stable surface oxygen of the coating layer and improve the acid corrosion resistance.

[0012] In some embodiments, in the positive electrode material, the content of the coating layer is 0.05% to 10% by mass. Thus, it can not only improve the stability of the battery system through the coating layer but also take into account the kinetics and energy density of the battery. In some embodiments, the content of the coating layer is 0.5% to 5.5% by mass, whereby the initial discharge specific capacity of the positive electrode material can be maintained at a relatively high level.

[0013] In some embodiments, the coating layer includes a first coating layer covering at least a part of the surface of the matrix and a second coating layer covering at least a part of the surface of the first coating layer. The first coating layer includes the M element, and the second coating layer includes the N element. Since the compound containing the M element can stabilize the oxygen on the surface of the matrix, and the compound containing the N element has excellent acid corrosion resistance, by arranging the M element in the inner layer of the coating layer and the N element in the outer layer of the coating layer in contact with the electrolyte, oxygen can be stabilized and acid corrosion resistance can be improved in a targeted manner, thereby improving the stability of the positive electrode material.

[0014] In some embodiments, the first coating layer and the second coating layer further contain B element and / or Si element. Thereby, the bonding force between the first coating layer and the second coating layer can be improved, thereby improving the stability of the positive electrode material.

[0015] In some embodiments, the coating layer further includes a third coating layer located between the first coating layer and the second coating layer. The third coating layer includes B element and / or Si element. Thereby, the bonding force between the first coating layer and the second coating layer can be improved, thereby improving the stability of the positive electrode material.

[0016] In some embodiments, the chemical formula of the spinel-structured manganese-rich oxide is: A x T y Mn 2-y O 4-k, where x is from 0.8 to 2.2, y is from 0 to 1, k is from -0.1 to 0.5, A includes at least one of Li, Na, K, and Mg, and T includes at least one of Ni, Co, Fe, Al, Cr, Y, La, Ce, B, Si, the said M, and the said N. In some embodiments, where y is from 0.01 to 0.8, the said T includes T3, T4, and T5; wherein, the said T3 includes at least one of Ni and Fe, the said T4 includes at least one of P, B, and Si, and the said T5 includes at least one of Ta and Nb. For the spinel-structured manganese-rich oxide, its surface is extremely prone to oxygen loss, resulting in the dissolution of Mn, and its acid corrosion resistance is poor. Moreover, its average charge and discharge voltage is relatively high, which is more likely to cause the oxidation of the electrolyte to produce acid and corrode it. Therefore, by forming the above coating layer on the surface of the spinel-structured manganese-rich oxide, its stability can be greatly improved.

[0017] In some embodiments, the chemical formula of the spinel-structured manganese-rich oxide includes Li x1 Na x2 T1 y1 T2 y2 Mn 2-y1-y2 O 4-k , where x1 + x2 = 0.9 to 1.2, x2 = 0 to 0.5, y1 = 0.2 to 0.7, y2 = 0 to 0.2, k = -0.1 to 0.5, T1 includes at least one of Ni, Co, and Fe, and T2 includes at least one of Al, Cr, Y, La, Ce, B, Si, the said M, and the said N. This spinel-structured manganese-rich oxide has a relatively large charge and discharge capacity above 4.5V, improving the energy density of the battery. However, the problem of acid production at high voltage is more significant, and the effect of improving the stability of the battery system by forming the above coating layer on its surface is more remarkable.

[0018] In some embodiments, the volume average particle size Dv50 of the positive electrode material is from 1 μm to 20 μm. Thus, the positive electrode material has better processability, and at the same time, it can better balance the kinetics of the battery and reduce the occurrence of side reactions.

[0019] The second aspect of the present application provides a secondary battery, including a positive electrode tab, the positive electrode tab includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material of the first aspect of the present application. The secondary battery of the present application has excellent storage performance.

[0020] The third aspect of the present application provides an electrical device, including the secondary battery of the second aspect of the present application. Description of the Drawings

[0021] Figure 1XRD patterns of the positive electrode materials of Example 6 and Comparative Example 1 of the present application.

[0022] Figure 2 is Figure 1 a partial enlarged view of.

[0023] Figure 3 Schematic diagram of a battery cell according to an embodiment of the present application.

[0024] Figure 4 is Figure 3 exploded view of a battery cell according to an embodiment of the present application shown in.

[0025] Figure 5 Schematic diagram of a battery module according to an embodiment of the present application.

[0026] Figure 6 Schematic diagram of a battery pack according to an embodiment of the present application.

[0027] Figure 7 is Figure 6 exploded view of a battery pack according to an embodiment of the present application shown in.

[0028] Figure 8 Schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0029] Explanation of reference numerals:

[0030] 1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly Detailed Description of the Embodiments

[0031] Hereinafter, embodiments of the positive electrode material, secondary battery, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0032] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are understood to be contemplated as well. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is just an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0034] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0035] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0036] If there is no special instruction, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0037] If there is no special instruction, the numerical values of the various parameters mentioned in this application can be measured using various common testing methods in the art. For example, they can be measured according to the testing methods given in this application.

[0038] If not otherwise specified, in the present application, the term "active ions" refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0039] For current manganese-rich materials, when they are used in batteries, their surfaces are usually prone to oxygen loss, resulting in the dissolution of Mn and the like. In response to this, there are reports proposing to stabilize surface oxygen by providing a coating layer on the surface of the material. However, when the material is used in batteries, there is still the problem of Mn dissolution, and the improvement of battery performance is not sufficient.

[0040] Based on this, the present application proposes a positive electrode material, a secondary battery and an electrical device, wherein the positive electrode material includes a substrate and a coating layer covering at least a portion of the surface of the substrate, the substrate includes a spinel structure manganese-rich oxide, the coating layer includes an M element and an N element, the M element includes at least one of W, Mo, Te, Sb, Ru, and P, and the N element includes at least one of Nb and Ta. In the present application, the coating layer includes the M element and the N element, which can be understood as: the coating layer includes a compound having the M element and a compound having the N element.

[0041] In view of the problem that the surface of the spinel structure manganese-rich positive electrode material is easy to lose oxygen, the coating layer of the positive electrode material of the present application contains the M element, which can be stably present in the coating layer in the form of a compound. On the one hand, the substrate surface oxygen can be kept from being lost by coating the substrate and maintained on the substrate surface. On the other hand, at least part of the compound with the M element can be bonded with the substrate surface oxygen to further achieve the effect of stabilizing the surface oxygen. In addition, it has been found that the average charge and discharge voltage of the battery using manganese-rich materials is high, which easily causes the electrolyte to be oxidized to produce acid, thereby corroding the positive electrode, thereby accelerating the dissolution of Mn. In view of this, the coating layer of the positive electrode material of the present application also contains the N element, and the compound with the N element has excellent acid corrosion resistance, reducing the risk of the positive electrode material being corroded by acid. As a result, the positive electrode material of the present application has excellent stability, can reduce the attenuation of the reversible capacity of the battery during use, and improve the reversible capacity retention rate of the secondary battery during use.

[0042] In some embodiments, the coating layer comprises an M-containing compound and an N-containing compound; the M-containing compound comprises an MX chemical bond; and / or the N-containing compound comprises an NX chemical bond; wherein X represents at least one of halogen, O, C, N and S, and optionally, X represents at least one of halogen and O. wherein halogen represents any one of fluorine, chlorine, bromine and iodine.

[0043] The M-element-containing compounds mentioned in this application include M-X chemical bonds, and the N-element-containing compounds include N-X chemical bonds, which can be characterized by X-ray photoelectron spectroscopy. The M element and N element mentioned in this application can be characterized by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0044] In this application, the M element and the X element can form strong M-X chemical bonds, and the chemical bonds are not easily broken, thereby improving the stability of the coating layer and the stability of the cathode material. In addition, the N element and the X element can form strong N-X chemical bonds, with strong acid and corrosion resistance, which can block the acid in the electrolyte from contacting the substrate. Thus, the structural stability of the cathode material can be improved. Since when X is a halogen or an O element, the strength of the M-X and N-X chemical bonds is stronger, which is more beneficial to protecting the oxygen on the substrate surface, thereby realizing a more stable structure of the cathode material.

[0045] In some embodiments, when the above-mentioned M element includes at least one of W, Mo, Te, Sb, and Ru, the above-mentioned coating layer includes at least one of halides, oxides, carbides, nitrides, or sulfides of the M element. When the above-mentioned M element includes P, the above-mentioned coating layer includes at least one of phosphoric acid, metaphosphoric acid, polyphosphoric acid, pyrophosphoric acid, halogenated phosphoric acid, and salts formed by them. In addition, the above-mentioned coating layer includes at least one of halides, oxides, carbides, nitrides, or sulfides of the above-mentioned N element. Thus, on the one hand, the risk of oxygen loss from the substrate can be effectively reduced, and on the other hand, the acid in the electrolyte can be blocked from contacting the substrate, thereby stabilizing the cathode material.

[0046] In some embodiments, the above-mentioned M element includes at least Te and / or P; optionally, the above-mentioned M element includes at least P. Te and / or P can form stronger chemical bonds with halogens, O, S, etc., and can more effectively stabilize the oxygen on the substrate surface, further improving the stability of the cathode material; in addition, P can also form strongly bonded composite compounds with other M and N elements, such as Te3(PO4)4 and Li2Te(PO4)2, further improving the stability of the coating layer, thereby further improving the stability of the cathode material.

[0047] In some embodiments, M is P and Te, or M is P and W, or M is P and Mo, or M is P and Sb, or M is P and Ru, or M is P, Te, and W, or M is P, Te, and Mo, or M is P, Te, and Sb, or M is P, Te, and Ru, or M is P, W, and Mo, or M is P, W, and Sb, or M is P, W, and Ru, or M is P, Sb, and Ru, or M is P, Te, W, and Mo, or M is P, Te, W, and Sb, or M is P, Te, W, and Ru, or M is P, Te, Mo, and Sb, or M is P, Te, Mo, and Ru, or M is P, Te, W, Mo, and Sb, or M is P, Te, W, Mo, and Ru, or M is P, Te, W, Mo, Sb, and Ru.

[0048] In some embodiments, in the above-mentioned cathode material, the content of the above-mentioned M element is 0.01% to 4% by mass; and / or, the content of the above-mentioned N element is 0.01% to 4% by mass; and / or, the total content of the above-mentioned M element and the above-mentioned N element is 0.05% to 5% by mass. By setting the contents of M and N within the above ranges, it is more helpful for the coating layer to play the role of stabilizing surface oxygen and improving acid corrosion resistance.

[0049] In some embodiments, the above-mentioned coating layer further includes B and / or Si. In the present application, the coating layer including B and / or Si can be understood as the coating layer containing a compound having the B element and / or a compound having the Si element. The chemical formula can be, for example, M b + a N d+ c Z f+ e T h+ g Q j+ i X m- l , where a*b + c*d + e*f + g*h + i*j = l*m, i > 0, b, d, f, h, j, m respectively represent the valence states of the corresponding M, N, Z, T, Q, X, and are all integers from 1 to 6. M is at least one of W, Mo, Te, Sb, Ru, P, N is at least one of Nb, Ta, Z is an element with an electronegativity less than M and N, such as at least one of Li, Na, K, T is at least one of Ni, Co, Fe, Al, Cr, Y, La, Ce, Q is at least one of B, Si, X represents at least one of halogen, O, C, N, and S, and optionally, the X represents at least one of halogen and O. In some embodiments, the above-mentioned coating layer contains borate and / or silicate.

[0050] The boron element in the borate and / or the silicon element in the silicate can not only form strong chemical bonds with the matrix but also form strong chemical bonds with the N element, thereby improving the bonding between the coating layer and the matrix and the bonding inside the coating layer.

[0051] In some embodiments, in the above-mentioned cathode material, the content of the B element and / or the Si element is 0.01% by mass to 1% by mass. By setting the content of the boron element and / or the silicon element between 0.01% and 1% by mass, it can not only improve the bonding between the coating layer and the matrix and inside the coating layer but also improve the stable surface oxygen of the coating layer and the acid corrosion resistance.

[0052] In some embodiments, the above-mentioned coating layer further includes a Z element whose electronegativity is less than the above-mentioned M element or the above-mentioned N element. Optionally, the above-mentioned Z element is at least one of Li, Na, and K. In the present application, the coating layer including the Z element can be understood as the coating layer containing a compound having the Z element. For example, it can include one or more of the compounds with the chemical formula M b+ a N d+ c Z f+ e T h+ g Q j+ i X m- l where a*b + c*d + e*f + g*h + i*j = l*m, e > 0, and the definitions of other symbols are the same as above.

[0053] In the present application, by further including the alkaline Z element in the coating layer, the Z element can preferentially bind to the acid in the electrolyte, thereby realizing the consumption of the acid in the electrolyte, reducing the content of the acid in the electrolyte from the source, further reducing the possibility of the acid damaging the structure of the cathode material, and improving the stability of the cathode material.

[0054] In some embodiments, in the above-mentioned cathode material, the content of the above-mentioned Z is 0.01% by mass to 1% by mass. By making the content of Z in the cathode material within the above range, it can neutralize the acid in the electrolyte while not destroying the stability of the coating layer.

[0055] It should be noted that the element content in the present application can be measured by conventional means such as X-ray diffraction analysis (XRD), Raman spectroscopy analysis (Raman), energy spectrum analysis (EDS), inductively coupled plasma optical emission spectrometry (ICP-OES), etc.

[0056] In some embodiments, in the above-mentioned positive electrode material, the content of the above-mentioned coating layer is 0.05% to 10% by mass. Thus, the stability of the battery system can be improved through the coating layer, and the kinetics and energy density of the battery can be taken into account. Preferably, the content of the above-mentioned coating layer is 0.5% to 5.5% by mass. Thus, the initial discharge specific capacity of the positive electrode material can be maintained at a relatively high level.

[0057] In some embodiments, the thickness of the above-mentioned coating layer is 1 nm to 200 nm. By setting the thickness of the coating layer between 1 nm and 200 nm, the kinetics and energy density of the battery can be taken into account. The structure and thickness of the coating layer mentioned in this application can be tested by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0058] In some embodiments, the above-mentioned coating layer includes a first coating layer covering at least part of the surface of the above-mentioned matrix and a second coating layer covering at least part of the surface of the above-mentioned first coating layer. The above-mentioned first coating layer includes the above-mentioned M element, and the above-mentioned second coating layer includes the above-mentioned N element.

[0059] Since the compound containing the M element can stabilize the oxygen on the surface of the matrix, and the compound containing the N element has acid corrosion resistance, therefore, setting the M element in the inner layer of the coating layer can specifically stabilize the oxygen on the surface of the matrix, and setting the N element in the outer layer of the coating layer in contact with the electrolyte can specifically act on the acid in the electrolyte and improve the acid corrosion resistance.

[0060] In some embodiments, the first coating layer can be an oxide or phosphate, silicate, borate containing the M element (such as W, Mo, Te, Sb, Ru); the second coating layer can be an oxide, fluoride, phosphate, fluorophosphate containing the N element (Ta or Nb).

[0061] In some embodiments, the above-mentioned first coating layer and the above-mentioned second coating layer further contain B element and / or Si element.

[0062] Since the B element and / or Si element can form chemical bonds with the M element and the N element, by setting the first coating layer and the second coating layer to contain the B element and / or Si element, the bonding force between the first coating layer and the second coating layer can be improved, thereby improving the stability of the positive electrode material.

[0063] In some embodiments, the thickness of the above-mentioned first coating layer is 0.5 nm to 150 nm, and the thickness of the above-mentioned second coating layer is 0.5 nm to 150 nm. Thus, the kinetics and the energy density of the battery can be taken into account, and the electrical performance of the battery can be improved.

[0064] In some embodiments, the above-mentioned coating layer further includes a third coating layer located between the first coating layer and the second coating layer, and the third coating layer includes B and / or Si. In some embodiments, the third coating layer may be a weak acid strong base salt containing Si or B, for example, it may be Li2SiO3 or Li3BO3.

[0065] In this application, by providing a third coating layer containing B and / or Si between the first coating layer and the second coating layer, the adhesion between the first coating layer and the second coating layer can be improved, thereby enhancing the stability of the cathode material.

[0066] In this application, the elemental distribution of the first coating layer, the second coating layer, and the third coating layer mentioned can be tested by cross-section polishing (CP) and energy spectrometer. The thickness and structure of the first coating layer, the second coating layer, and the third coating layer mentioned in this application can be tested by scanning electron microscope or transmission electron microscope.

[0067] In some embodiments, the thickness of the above-mentioned third coating layer is 0.5 nm to 100 nm. By setting the thickness of the third coating layer between 0.5 nm and 100 nm, the kinetics and energy density of the battery can be taken into account.

[0068] In some embodiments, the above-mentioned matrix includes but is not limited to spinel-structured manganese-rich oxides. For example, it may also include layered-structured oxides, olivine-structured active materials, etc. These cathode materials have the advantages of high voltage, low cost, and stable bulk structure, but are limited by their intolerance to acid and easy oxygen loss at high voltages.

[0069] Spinel-structured manganese-rich oxides have characteristics such as a high voltage plateau and small strain during charge and discharge compared to conventional layered-structured oxides and olivine-structured active materials. They are materials with low cost, high energy density, and excellent charge and discharge reversibility. However, the surface of spinel-structured manganese-rich oxides is more prone to oxygen loss, resulting in Mn dissolution. The dissolved Mn deposits on the surface of the negative electrode to passivate the SEI film, causing hindrance to the lithium deintercalation from the graphite negative electrode, and further leading to rapid attenuation of the battery capacity. In addition, due to the relatively high average charge and discharge voltages of spinel manganese-rich materials, for example, the average charge and discharge voltage of spinel LiMn2O4 is 4.0 V vs Li / Li + , spinel LiNi 0.5 Mn 1.5 O4's average charge and discharge voltage is 4.7 V vs Li / Li + , spinel Li4Mn5O 12The upper charging voltage is > 4.3V, and the electrolyte is easily oxidized to produce acid at high voltages. The acid can corrode the spinel-rich manganese active material, further accelerating the dissolution of Mn. Therefore, by providing the above coating layer on the surface of the spinel-rich manganese active material, its surface can be stabilized, greatly improving the performance of the secondary battery using the spinel-rich manganese active material.

[0070] The spinel structure, layered structure, and olivine structure mentioned in this application can be analyzed and characterized by an X-ray diffractometer (XRD).

[0071] In some embodiments, the chemical formula of the spinel-structured manganese-rich oxide is: A x T y Mn 2-y O 4-k , where x is 0.8 to 2.2, y is 0 to 1, k is -0.1 to 0.5, A is at least one of Li, Na, K, Mg, and T includes at least one of Ni, Co, Fe, Al, Cr, Y, La, Ce, B, Si, the above M, and the above N. In some embodiments, the above A x T y Mn 2-y O 4-k In the formula, y is 0.01 to 0.8, and the above T includes T3, T4, and T5; wherein, the T3 includes at least one of Ni and Fe; the T4 includes at least one of P, B, and Si; the T5 includes at least one of Ta and Nb.

[0072] In some embodiments, the chemical formula of the spinel-structured manganese-rich oxide includes Li x1 Na x2 T1 y1 T2 y2 Mn 2-y1-y2 O 4-k , where x1 + x2 = 0.9 to 1.2, x2 = 0 to 0.5, y1 = 0.2 to 0.7, y2 = 0 to 0.2, k = -0.1 to 0.5, T1 includes at least one of Ni, Co, and Fe, and T2 includes at least one of Al, Cr, Y, La, Ce, B, Si, the above M, and the above N.

[0073] In some embodiments, a carbon coating layer can also be formed on at least a part of the surface of the above positive electrode material, that is, on at least a part of the surface of the coating layer. The carbon includes one or more of amorphous carbon, graphite, acetylene black, carbon nanotubes, etc. The thickness of the above carbon coating layer can be 1 to 50 nm. Relative to the total mass of the above positive electrode material, the mass ratio of the above carbon coating layer is 0.05 mass% to 2 mass%.

[0074] The carbon coating layer is beneficial to improving the electronic conductivity of the cathode material, thereby facilitating the conduction of electrons. The carbon coating layer is coated on the surface of the cathode material, which is beneficial for the battery to obtain excellent rate performance and impedance characteristics. In addition, the carbon coating layer can also isolate the electrolyte from the cathode material, further reducing the contact between the acid in the electrolyte and the cathode material, and improving the stability of the cathode material.

[0075] It should be understood that the coating layer in the present application on the surface of the substrate can be a full coating structure or a partial coating structure, such as an island coating. The coating layer in the present application can be single-layer or multi-layer. Among them, the coating form of each coating layer can be the same or different. For example, the multi-layer coating layers can all be full coating structures or all be island coating structures, or some layers are full coating structures and the other part of the layers are island coating structures.

[0076] The morphology of the coating layer mentioned in the present application can be directly observed in the microscope image of the cross-section (for example, using a cross-section polisher) (for example, a scanning electron microscope image with a magnification of 1000 times).

[0077] In some embodiments, the carbon coating layer can be formed by means such as gas-phase carbon coating, liquid-phase carbon coating, or solid-phase carbon coating.

[0078] In some embodiments, by adjusting the composition and synthesis process, the above coating layer is a fast lithium-ion conductor or a fast lithium-ion conductor is introduced into the above coating layer. The fast lithium-ion conductor can be, for example, one or more of LiAlTi2(PO4)3, LiTa(PO4)2, LiTaO3, LiNbO3, LiAlO2, LiTiO3, LiZrO3, LiYO2, etc.

[0079] The fast lithium-ion conductor can achieve rapid conduction of Li ions, thereby improving the rate performance of the cathode material. When the fast lithium-ion conductor can stably exist in the electrolyte, it can further isolate the electrolyte and reduce side reactions, thereby improving the long-term use performance of the battery.

[0080] In some embodiments, when the coating layer is single-layer, the fast lithium-ion conductor can be mixed and coated with the coating layer; when the coating layer includes a first coating layer and a second coating layer, the fast lithium-ion conductor can be located between the first coating layer and the second coating layer. There is no particular limitation on the type of the fast lithium-ion conductor, and substances well-known in the art can be used. For example, the fast lithium-ion conductor can be lithium aluminum titanium phosphate (LATP).

[0081] In some embodiments, the particles of the above cathode material are single crystals or pseudo single crystals. Here, the pseudo single crystal refers to a secondary particle containing only a few or a dozen grains. Thus, the coating layer can be made more uniform and dense.

[0082] In some embodiments, the volume average particle size Dv50 of the above-mentioned positive electrode material is 1 μm to 20 μm. The volume average particle size Dv50 of the positive electrode material refers to the particle size of the positive electrode material after being coated with a coating layer and a carbon coating layer. By setting the volume average particle size Dv50 of the positive electrode material between 1 μm and 20 μm, the positive electrode material has excellent processing performance, and at the same time can better balance the kinetics of the battery and reduce the side reactions of the battery.

[0083] In the present application, the volume average particle size of the positive electrode material has the meaning well-known in the art, which represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be measured by referring to GB / T 19077-2016 and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0084] Taking the matrix as spinel-rich manganese oxide as an example, the preparation method of the positive electrode material in the present application will be described below.

[0085] (1) Preparation method of spinel-rich manganese oxide positive electrode material

[0086] It includes the following steps: mixing the A source, the T source and the Mn source evenly, and heating up to 600 °C to 1300 °C, and keeping warm for 5 h to 30 h in an air atmosphere to obtain spinel-rich manganese oxide. Among them, the A source, the T source and the Mn source can be one or more of oxides, hydroxides, basic oxides, carbonates, bicarbonates, basic carbonates, nitrates, oxalates, sulfates, etc. containing one or more of A, T and Mn.

[0087] (2) Preparation method of positive electrode material with a single-layer coating layer

[0088] It includes the following steps: mixing the M source, the N source with the spinel-rich manganese oxide prepared in the above (1) evenly (optionally, the B source and / or the Si source can also be added), and then heating up to 200 °C to 1000 °C, and keeping warm for 0.5 h to 20 h in an air atmosphere to obtain a positive electrode material with a single-layer coating layer.

[0089] The M source can be one or more of oxides, hydroxides, basic oxides, carbonates, bicarbonates, basic carbonates, nitrates, oxalates, sulfates, etc. containing the M element. The N source can be one or more of oxides, hydroxides, basic oxides, carbonates, bicarbonates, basic carbonates, nitrates, oxalates, sulfates, etc. containing the N element. The B source can be one or more of oxides, hydroxides, borates, silicates containing the B element. The Si source can be one or more of oxides, hydroxides, borates, silicates containing the Si element.

[0090] (3) Preparation method of cathode material with double-layer coating

[0091] It includes the following steps: First, mix the M source (optionally, B source and / or Si source can also be added) with the spinel manganese-rich oxide prepared in the above (1) evenly, then heat up to 200°C to 1000°C, and keep it warm for 0.5 h to 20 h in an air atmosphere to obtain a semi-finished product; Second, mix the N source (optionally, B source and / or Si source can also be added) with this semi-finished product evenly, then heat up to 200°C to 1000°C, and keep it warm for 0.5 h to 20 h in an air atmosphere to obtain the cathode material with double-layer coating.

[0092] (4) Preparation method of cathode material with triple-layer coating

[0093] It includes the following steps: First, mix the M source with the spinel manganese-rich oxide prepared in the above (1) evenly, then heat up to 200°C to 1000°C, and keep it warm for 0.5 h to 20 h in an air atmosphere to obtain semi-finished product 1; Second, mix the B source and / or Si source with the above semi-finished product 1 evenly, then heat up to 200°C to 1000°C, and keep it warm for 0.5 h to 20 h in an air atmosphere to obtain semi-finished product 2; Finally, mix the N source with semi-finished product 2 evenly, then heat up to 200°C to 1000°C, and keep it warm for 0.5 h to 20 h to obtain the finished product, and obtain the cathode material with triple-layer coating.

[0094] In one embodiment of the present application, a secondary battery is provided.

[0095] The term "secondary battery" mentioned herein refers to a battery cell, a battery module or a battery pack. The following will be described separately.

[0096] Generally, a battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and de-embedded back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is arranged between the positive electrode plate and the negative electrode plate, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0097] Positive electrode sheet

[0098] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the cathode material of the first aspect of the present application.

[0099] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0100] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0101] In some embodiments, the positive electrode film layer may optionally further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0102] In some embodiments, the positive electrode film layer may optionally further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the above components for preparing the positive electrode plate, such as positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0104] Negative electrode sheet

[0105] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0106] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] In some embodiments, when the battery cell is a lithium-ion battery, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0109] In some embodiments, the negative electrode film layer may also optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0110] In some embodiments, the negative electrode film layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the negative electrode film layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0112] In some embodiments, the negative electrode plate may be prepared by the following method: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0113] Electrolyte

[0114] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of the electrolyte in this application, and it can be selected according to requirements.

[0115] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0116] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0117] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0118] In some embodiments, the electrolytic solution may optionally further include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain performances of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0119] Separator

[0120] In some embodiments, the battery cell further includes a separator. There is no particular limitation on the type of the separator in this application, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0121] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the separator is a multi-layer composite thin film, the materials of each layer can be the same or different, without particular limitation.

[0122] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0123] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0124] In some embodiments, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0125] The present application has no particular limitation on the shape of the battery cell, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 is a battery cell 5 with a square structure as an example.

[0126] In some embodiments, referring to Figure 4 , the outer packaging can include a housing 51 and a top cover assembly 53. Among them, the housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0127] In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0128] Figure 5 is a battery module 4 as an example. Referring to Figure 5 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0129] Optionally, the battery module 4 can further include a housing with a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0130] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0131] Figure 6 and Figure 7 is a battery pack 1 as an example. Referring to Figure 6 and Figure 7, a 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 be covered on the lower box body 3 to 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.

[0132] In addition, the present application also provides an electric device, and the electric device includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electric device or as the energy storage unit of the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0133] As the electric device, the secondary battery, battery module or battery pack can be selected according to its usage requirements.

[0134] Figure 8 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for this electric device, a battery pack or a battery module can be adopted.

[0135] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be used as the power source.

[0136] Embodiment

[0137] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0138] Embodiment 1

[0139] Preparation of the matrix: According to the target component LiNi 0.5 Mn 1.5 O4, weigh the Li2CO3 and Ni 0.25 Mn 0.75 (OH)2 powders in corresponding stoichiometric ratios, mix them evenly, heat them to 900 °C in an air atmosphere, keep them at this temperature for 10 hours, and then cool them to room temperature to obtain the spinel-structured manganese-rich oxide LiNi 0.5 Mn 1.5 O4.

[0140] Preparation of the positive electrode material: Mix the above spinel-structured manganese-rich oxide LiNi 0.5 Mn 1.5 O4 with the M source TeO2 and the N source Ta2O5 in a mass ratio of 97.53:1.25:1.22 and mix them evenly so that the mass fractions of Te and Ta elements in the positive electrode material are each 1 mass%, and then heat up to 500 °C in an air atmosphere and keep it for 5 h to obtain a positive electrode material with a single-layer coating containing Te and Ta.

[0141] Testing of the phase and content of the coating layer

[0142] Referring to the general rules of X-ray diffraction analysis method in JIS K 0131-1996, measure the XRD diffraction peaks of the positive electrode material, and analyze that the main phase forms of each coating element are TeO2 and Ta2O5. The proportion of the total mass of each phase in the positive electrode material (the sum of the masses of TeO2 and Ta2O5, that is, the mass of the coating layer) is 2.5%, which is basically consistent with the theoretical value converted based on the mass fractions of Te and Ta elements.

[0143] Preparation of secondary battery

[0144] Preparation of the positive electrode sheet: Mix the above-obtained positive electrode material with conductive carbon black (Super P) and PVDF in a weight ratio of 96:2.5:1.5, add an appropriate amount of solvent N-methylpyrrolidone (NMP), and stir evenly to obtain a positive electrode slurry. Coat the positive electrode slurry on an aluminum foil, and dry it after coating to obtain a positive electrode sheet. The loading amount of the positive electrode material on one side of the positive electrode current collector is 0.016 g / cm 2 .

[0145] Preparation of the negative electrode sheet: Mix the negative electrode active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96:1:1:2 in an appropriate amount of solvent deionized water and stir well to form a uniform negative electrode slurry; uniformly coat the negative electrode slurry on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, obtain a negative electrode sheet. The loading amount of the negative electrode active material on one side of the negative electrode current collector is 0.007 g / cm 2 .

[0146] Electrolyte: A solution containing 1 mol / L LiPF6 and ethylene carbonate and methyl trifluoroethyl carbonate mixed evenly in a mass ratio of 1:1.

[0147] Separator: A polypropylene film with a thickness of 12 μm.

[0148] Place the prepared positive electrode sheet, separator, and negative electrode sheet in order, with the separator in the middle of the positive electrode sheet and the negative electrode sheet to play an isolation role, process and form, package with an aluminum-plastic bag, inject electrolyte, and perform formation after encapsulation to obtain a secondary battery.

[0149] Performance test

[0150] 1. Initial discharge specific capacity test of the positive electrode material

[0151] 1) At 25 °C, charge the secondary battery at a constant current of 0.33C until the voltage reaches 4.9V, and then charge it at a constant voltage of 4.9V until the current reaches 0.05C;

[0152] 2) Let it stand for 5 min;

[0153] 3) Discharge the secondary battery at a constant current of 0.33C until the voltage reaches 3.0V.

[0154] The discharge capacity in step 3) is the first-cycle discharge capacity C0 of the lithium-ion battery. Divide the first-cycle discharge capacity C0 by the mass of the positive electrode material in the secondary battery, which is the initial discharge specific capacity C of the positive electrode material. a .

[0155] 2. 40 °C full charge storage performance test

[0156] 1) At 25 °C, charge the secondary battery at a constant current of 0.33C until the voltage reaches 4.9V, and then charge it at a constant voltage of 4.9V until the current reaches 0.05C;

[0157] 2) After placing the secondary battery at 40 °C for 100 days, take it out and let it stand for 24 h until the overall temperature of the battery drops to room temperature;

[0158] 3) At 25 °C, discharge the battery at a constant current of 0.33C until the voltage reaches 3.0V, and then perform one charge to 100% and discharge to 0%, and extract the discharge capacity value C n ;

[0159] 4) Divide C n by the initial value C0, which is the reversible capacity retention rate of the battery stored at 40 °C for 100 days.

[0160] 3. 40 °C full charge storage Mn dissolution amount test

[0161] 1) Disassemble the secondary battery that has completed 100-day storage and tested C n in the above step 2, disassemble the negative electrode sheet, and soak and clean the negative electrode sheet with dimethyl carbonate (DMC) until the white foreign matter on the surface of the negative electrode sheet no longer decreases, and then dry the electrode sheet.

[0162] 2) Refer to EPA 6010D - 2014 Inductively Coupled Plasma Atomic Emission Spectrometry to measure the negative electrode sheet obtained in the above step 1), and calculate the content of Mn element after deducting the weight of the current collector copper foil.

[0163] The Mn content obtained in step 2) is the content of Mn dissolved from the spinel - structured manganese - rich oxide in the battery and deposited on the negative electrode.

[0164] Example 2 - 16

[0165] As shown in Table 1 - 1, adjust the types of M source and N source, and make the mass ratios of M element and N element in the positive electrode material be the values shown in Table 1 - 1. In addition, prepare the positive electrode material according to a method similar to that of Example 1 and assemble it into a soft - package battery.

[0166] Comparative Example 1

[0167] Prepare the positive electrode material according to a method similar to that of Example 1 and assemble it into a soft - package battery, with the only difference being that no coating layer is set.

[0168] Figure 1 is the XRD pattern of the positive electrode materials of Comparative Example 1 and Example 6 above. Figure 2 is Figure 1 a partial enlarged view of Figure 1 and Figure 2 The XRD patterns in

[0169] Comparative Example 2

[0170] Prepare the positive electrode material according to a method similar to that of Example 1 and assemble it into a soft - package battery, with the only difference being that an Al source is used when preparing the coating layer to obtain a single - layer coating layer containing Al element.

[0171] Comparative Example 3

[0172] Prepare the positive electrode material according to a method similar to that of Example 1 and assemble it into a soft - package battery, with the only difference being that only the M source is added when preparing the coating layer to obtain a single - layer coating layer containing M element and no N element.

[0173] Comparative Example 4

[0174] Prepare the positive electrode material according to a method similar to that of Example 1 and assemble it into a soft - package battery, with the only difference being that only the N source is added when preparing the coating layer to obtain a single - layer coating layer containing N element and no M element.

[0175] Comparative Example 5

[0176] The cathode material was prepared in a method similar to that of Example 1 and assembled into a soft-pack battery, except that an M source and a Ti source were added during the preparation of the coating layer to form a coating layer containing M element and Ti element.

[0177] Comparative Example 6

[0178] The cathode material was prepared in a method similar to that of Example 1 and assembled into a soft-pack battery, except that an N source and a Zr source were added during the preparation of the coating layer to form a coating layer containing N element and Zr element.

[0179] The elements of the coating layer in the cathode materials prepared in the above Examples 1-19 and Comparative Examples 1-6 and the content of the coating layer measured based on XRD are shown in Tables 1-1 and 1-2 below, and the test results of their soft-pack batteries are shown in Table 2 below.

[0180] Table 1-1:

[0181]

[0182] Table 1-2

[0183]

[0184] Among them, " / " in Table 1 indicates non-existence.

[0185] Table 2:

[0186]

[0187] It can be seen from the results in Table 2 above that compared with Comparative Example 1 (cathode material without coating layer), the cathode materials of Examples 1 to 16 form a coating layer containing M element and N element on the surface of the matrix, improving the reversible capacity retention rate after 100 days of full charge storage at 40 °C and greatly reducing the Mn dissolution amount. Moreover, the initial discharge specific capacity of the cathode material remains at a level basically the same as that of Comparative Example 1 (cathode material without coating layer).

[0188] Although a coating layer was formed in Comparative Examples 2 to 6, since it did not contain both M element and N element, Mn dissolution could not be fully inhibited, and the reversible capacity retention rate after 100 days of full charge storage at 40 °C was poor.

[0189] Examples 17-23

[0190] As shown in Table 3, the contents of M element and N element were adjusted. Except for this, the cathode material was prepared in a method similar to that of Example 1 and assembled into a soft-pack battery, and the test results of its soft-pack battery are shown in Table 4 below.

[0191] Table 3:

[0192]

[0193]

[0194] Table 4:

[0195]

[0196] From the results of Table 3 and Table 4 above, it can be seen that compared with Comparative Examples 1-6, in Examples 17-23, by making the content of element M in the coating layer be 0.01% to 4% by mass and the content of element N be 0.01% to 4% by mass, the reversible capacity retention rate at 40 °C full charge for 100D is improved, and the Mn dissolution amount is reduced. Among them, although the initial discharge specific capacity of the positive electrode material in Examples 20, 21, and 23 is reduced compared with the comparative examples, it still belongs to the normal value range. Moreover, since the reversible capacity retention rates of Examples 20, 21, and 23 are greatly improved, all greater than 94%, far higher than the comparative examples (all lower than 80%), therefore, the reversible capacity after 100 days of storage is higher than that of the comparative examples. For example, the reversible capacity after 100 days of storage in Example 23 is approximately 119×94.2% = 112 mAh / g, while the reversible capacity after 100 days of storage in Comparative Example 6 is approximately 132×79.5% = 105 mAh / g.

[0197] Examples 24 - 28

[0198] The positive electrode material was prepared by a method similar to that of Example 1 and assembled into a soft-pack battery, except that at least one of B source, Si source, and Z source was further added when preparing the coating layer to obtain a coating layer containing B, Si, or Z element. For details, please refer to Table 5.

[0199] The coating layer elements in the positive electrode materials prepared in the above Examples 24 - 28 are shown in Table 5 below, and the test results of the soft-pack batteries are shown in Table 6 below.

[0200] Table 5:

[0201]

[0202]

[0203] Among them, " / " in Table 5 indicates non-existence.

[0204] Table 6:

[0205]

[0206] As can be seen from the results of Table 5 and Table 6 above, by introducing element B or element Si into the coating layer containing element M and element N, the dissolution of Mn can be further reduced. In addition, by introducing element Z into the coating layer containing element M and element N, it can improve the stable surface oxygen of the coating layer and the acid corrosion resistance, further reduce the dissolution of Mn, and improve the reversible capacity retention rate of the battery system.

[0207] Example 29

[0208] The matrix of spinel-structured manganese-rich oxide was prepared by a method similar to that of Example 1. Then, the spinel-structured manganese-rich oxide LiNi 0.5 Mn 1.5 O4 and the M source TeO2 were mixed evenly according to a mass ratio of 97.5:1.3 and heated to 500 °C in an air atmosphere and held for 3 h to obtain a coated semi-finished product. Then, the coated semi-finished product and the N source Ta2O5 were mixed evenly according to a mass ratio of 98.8:1.2 and heated to 500 °C in an air atmosphere and held for 3 h to obtain a first coating layer of TeO2 and a second coating layer of Ta2O5. The total content of the coating layer was 2.5% by mass. Then, a soft-pack battery was assembled by the same method as in Example 1, as shown in Table 7 for details.

[0209] Examples 30 - 33

[0210] The cathode material was prepared by a method similar to that of Example 29 and assembled into a soft-pack battery, with the difference only being that the coating materials used for the first coating layer and the second coating layer were different, as shown in Table 7 for details.

[0211] Example 34

[0212] The matrix of spinel-structured manganese-rich oxide was prepared by a method similar to that of Example 1. Then, the matrix and the M source Li2Te(BO3)2 containing B were mixed evenly according to a mass ratio of 97:1.3 and heated to 500 °C and held for 2 h to obtain semi-finished product 1. Then, semi-finished product 1 and Li3BO3 were mixed evenly according to a mass ratio of 98.3:0.5 and heated to 500 °C in an air atmosphere and held for 1 h to obtain semi-finished product 2. Then, semi-finished product 2 and the N source LiTa(BO3)2 were mixed evenly according to a mass ratio of 98.8:1.2 and heated to 500 °C in an air atmosphere and held for 3 h to obtain a three-layer coated cathode material with a first coating layer of Li2Te(BO3)2, a third coating layer of Li3BO3, and a second coating layer of LiTa(BO3)2. The total content of the coating layer was 3% by mass. Then, a soft-pack battery was assembled by the same method as in Example 1.

[0213] The coating layer elements in the cathode materials prepared in Examples 29 - 34 above are shown in Table 7 below, and the test results of their soft-pack batteries are shown in Table 8 below.

[0214] Table 7:

[0215]

[0216] In Table 7, " / " indicates the absence of this item; "mass content %" indicates the mass percentage relative to the cathode material (including the matrix and the coating layer).

[0217] Table 8:

[0218]

[0219]

[0220] As can be seen from the results of Table 8 above, compared with the single-layer coating layer in Example 1 above, by setting the M element in the first coating layer and the N element in the second coating layer, the reversible capacity retention rate of 100D at full charge storage at 40 °C can be further improved, and the Mn dissolution amount can be reduced. In Example 34, by further setting an intermediate coating layer containing the B element, compared with Example 33, the reversible capacity retention rate of 100D at full charge storage at 40 °C can be further improved, and the Mn dissolution amount can be further reduced.

[0221] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and the same effect as the technical idea within the scope of the technical solution of the present application are included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A cathode material, characterized in that, It includes a matrix and a coating layer covering at least part of the surface of the matrix. The matrix includes a spinel-structured manganese-rich oxide. The coating layer includes M element and N element. The M element includes at least one of W, Mo, Te, Sb, Ru, and P. The N element includes at least one of Nb and Ta.

2. The positive electrode material according to claim 1, wherein the coating layer includes a compound containing M element and a compound containing N element; the compound containing M element includes an M-X chemical bond; and / or, the compound containing N element includes an N-X chemical bond; wherein the X element includes at least one of halogen, O, C, N, and S.

3. The cathode material according to claim 2, wherein The X element includes at least one of halogen and O.

4. The positive electrode material according to any one of claims 1-3, wherein when the M element includes at least one of W, Mo, Te, Sb, and Ru, the coating layer includes at least one of a halide, an oxide, a carbide, a nitride, or a sulfide of the M element. When the M element is P, the coating layer includes at least one of phosphoric acid, metaphosphoric acid, polyphosphoric acid, pyrophosphoric acid, halogenated phosphoric acid, and salts formed therefrom; and / or, the coating layer includes at least one of a halide, an oxide, a carbide, a nitride, or a sulfide of the N element.

5. The cathode material according to any one of claims 1-4, characterized in that, The M element includes at least Te and / or P.

6. The cathode material according to claim 5, characterized in that, The M element includes at least P.

7. The cathode material according to any one of claims 1-6, characterized in that, In the positive electrode material, the content of the M element is 0.01% by mass to 4% by mass; and / or, the content of the N element is 0.01% by mass to 4% by mass; and / or, the total content of the M element and the N element is 0.05% by mass to 5% by mass.

8. The cathode material according to any one of claims 1-7, characterized in that, The coating layer further includes B element and / or Si element. In the positive electrode material, the content of the B element and / or the Si element is 0.01% by mass to 1% by mass.

9. The cathode material according to claim 8, characterized in that, The coating layer includes borate and / or silicate.

10. The cathode material according to any one of claims 1-9, characterized in that, The coating layer further includes a Z element with an electronegativity less than that of the M element or the N element.

11. The cathode material according to claim 10, wherein The Z element includes at least one of Li, Na, and K.

12. The cathode material according to claim 10 or 11, characterized in that, In the positive electrode material, the content of the Z element is 0.01% by mass to 1% by mass.

13. The cathode material according to any one of claims 1-12, characterized in that, In the positive electrode material, the content of the coating layer is 0.05% by mass to 10% by mass.

14. The cathode material according to claim 13, characterized in that, In the positive electrode material, the content of the coating layer is 0.5% by mass to 5.5% by mass.

15. The cathode material according to any one of claims 1-14, characterized in that, The coating layer includes a first coating layer covering at least part of the surface of the matrix and a second coating layer covering at least part of the surface of the first coating layer. The first coating layer includes the M element. The second coating layer includes the N element.

16. The cathode material according to claim 15, wherein The first coating layer and the second coating layer further contain B element and / or Si element.

17. The cathode material according to claim 15 or 16, characterized in that, The coating layer further includes a third coating layer located between the first coating layer and the second coating layer. The third coating layer includes B element and / or Si element.

18. The positive electrode material according to any one of claims 1-17, wherein the chemical formula of the spinel-structured manganese-rich oxide includes: A x T y Mn 2-y O 4-k Wherein, x is 0.8 to 2.2, y is 0 to 1, and k is -0.1 to 0.5, A includes at least one of Li, Na, K, and Mg, T includes at least one of Ni, Co, Fe, Al, Cr, Y, La, Ce, B, Si, the aforementioned M, and the aforementioned N.

19. The cathode material according to claim 18, characterized in that, Wherein, y is 0.01 to 0.8, The aforementioned T includes T3, T4, and T5; Among them, the aforementioned T3 includes at least one of Ni and Fe; The aforementioned T4 includes at least one of P, B, and Si; The aforementioned T5 includes at least one of Ta and Nb.

20. The cathode material according to claim 18, characterized in that, The chemical formula of the spinel-structured manganese-rich oxide includes Li x1 Na x2 T1 y1 T2 y2 Mn 2-y1-y2 O 4-k ; Wherein, x1 + x2 = 0.9 to 1.2, x2 = 0 to 0.5, y1 = 0.2 to 0.7, y2 = 0 to 0.2, and k = -0.1 to 0.5, T1 includes at least one of Ni, Co, and Fe, T2 includes at least one of Al, Cr, Y, La, Ce, B, Si, the aforementioned M, and the aforementioned N.

21. The cathode material according to any one of claims 1-20, characterized in that, The volume average particle size Dv50 of the positive electrode material is 1 μm to 20 μm.

22. A secondary battery, characterized in that, It includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material according to any one of claims 1 to 21.

23. An electrical device, characterized in that, It includes the secondary battery according to claim 22.

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