CN116487591A

CN116487591A - Positive electrode lithium supplementing additive and preparation method and application thereof

Info

Publication number: CN116487591A
Application number: CN202310118756.5A
Authority: CN
Inventors: 张顺心; 万远鑫; 孔令涌; 裴现一男
Original assignee: Foshan Defang Chuangjie New Energy Technology Co ltd; Qujing Defang Chuangjie New Energy Technology Co ltd; Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Current assignee: Foshan Defang Chuangjie New Energy Technology Co ltd; Qujing Defang Chuangjie New Energy Technology Co ltd; Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Priority date: 2023-02-01
Filing date: 2023-02-01
Publication date: 2023-07-25

Abstract

The application provides a positive electrode lithium supplementing additive, a preparation method and application thereof, wherein the positive electrode lithium supplementing additive comprises the following components: a lithium-rich oxide and a high entropy oxide present in the positive electrode lithium-compensating additive in any one of three ways: (1) The high entropy oxide is fully blended in the lithium-rich oxide; (2) The high entropy oxide is fully bonded to the outer surface layer of the lithium-rich oxide; (3) The high entropy oxide is partially blended in the lithium-rich oxide and partially bonded to the outer surface layer of the lithium-rich oxide. The positive electrode lithium supplementing additive is prepared by mixing and/or combining high-entropy oxide materials on the surface of lithium-rich oxide, so that gas generated during charging of the lithium-rich oxide can be reduced, migration of electrons and ions of electrode materials is facilitated, and rate performance, stability and corrosion resistance are improved.

Description

Positive electrode lithium supplementing additive and preparation method and application thereof

Technical Field

The application relates to the technical field of lithium ion batteries, in particular to a positive electrode lithium supplementing additive, a preparation method and application thereof.

Background

In a lithium ion battery, li is first inserted due to low initial coulombic efficiency of the anode material ⁺ Will permanently consume Li from the positive electrode ⁺ To form SEI film while Li as an energy transmission medium in a full cell ⁺ Provided by the positive electrode material and the electrolyte only, a decrease in the reversible capacity and energy density of the battery is caused. It has been proposed to add a supplemental agent to a lithium ion battery to compensate for lithium consumed by the negative electrode at the time of initial operation, thereby improving capacity and energy density.

Using lithium ferrite (Li) ₅ FeO ₄ ) The equal-repair agent is used for positive electrode repair, and a certain amount of Li is added in the preparation of positive electrode slurry ₅ FeO ₄ The lithium supplementing agent is needed without changing the production process of the lithium ion battery, and the stability of the electrode material, the electrolyte and the whole battery is not greatly adversely affected. At the same time Li ₅ FeO ₄ The lithium-supplementing agent has the advantages of low production cost, no toxicity, high gram capacity and unique advantages. The method belongs to an inverse fluorite structure, pbca space group and has simple synthesis process. At present Li ₅ FeO ₄ The problem with such lithium-compensating agents is that some gases are generated during charge and discharge, for example: o (O) ₂ 、CO ₂ CO and H ₂ Etc. For large-scale industrial production, li needs to be reduced ₅ FeO ₄ And generating gas during charging and discharging of the lithium supplementing agent so as to inhibit adverse effects during charging and discharging.

Disclosure of Invention

In view of this, an object of the present application is to provide a positive electrode lithium-supplementing additive, which adopts a high-entropy oxide material to blend or/and combine with the surface of a lithium-rich oxide, so as to reduce the gas generated during charging of the lithium-rich oxide, facilitate the migration of electrons and ions of the electrode material, and improve the rate capability, stability and corrosion resistance.

Another object of the present application is to provide a method for preparing a positive electrode lithium supplement additive.

It is yet another object of the present application to provide a lithium-rich positive electrode.

It is still another object of the present application to provide a secondary battery.

To achieve the above object, an embodiment of a first aspect of the present application provides a positive electrode lithium supplementing additive, including:

lithium-rich oxides;

a high entropy oxide present in the positive electrode lithium supplement additive in any one of three ways:

(1) The high entropy oxide is fully blended in the lithium-rich oxide;

(2) The high entropy oxide is fully bonded to the outer surface layer of the lithium-rich oxide;

(3) The high entropy oxide is partially blended in the lithium-rich oxide and partially bonded to the outer surface layer of the lithium-rich oxide.

In some embodiments of the present application, the high entropy oxide has the chemical formula (M1) _a M2 _b M3 _c ...Mi _j )O _k Wherein: m1, M2, M3 in the M element. a, b, c..j is the stoichiometric coefficient of each M element, and a+b+c+ … +j=1, meaning that the sum of the stoichiometric coefficients of all M elements is 1; i is more than or equal to 5 and less than or equal to 10, k is more than or equal to 2 and less than or equal to 8.

In some embodiments of the present application, the lithium-rich oxide has the chemical formula Li _ɑ Q _β T _ε O _γ Wherein alpha is more than or equal to 2 and less than or equal to 8,0.1, beta is more than or equal to 3, epsilon is more than or equal to 0 and less than or equal to 3, gamma is more than or equal to 1 and less than or equal to 6,Q, and the transition metal is the 4 th or 5 th periodOne or more of the genera, T is one or more of a main group metal element or a 4 th period transition metal.

In some embodiments of the present application, the high entropy oxide is discontinuously or continuously coated on the outer surface of the lithium-rich oxide when the high entropy oxide is fully or partially bonded to the outer surface of the lithium-rich oxide.

In some embodiments of the present application, the positive electrode lithium-compensating additive further comprises an encapsulating material; when the high-entropy oxide is fully or partially combined with the outer surface layer of the lithium-rich oxide, the packaging material and the high-entropy oxide fully or partially combined with the surface of the lithium-rich oxide are mutually mixed to form a coating layer, and the coating layer is coated on the outer surface of the lithium-rich oxide.

In some embodiments of the present application, the positive electrode lithium-compensating additive further comprises an encapsulating material; the packaging material is coated on the outer surface of the lithium-rich oxide and/or the high-entropy oxide.

In some embodiments of the present application, the encapsulation material comprises at least one layer of an isolation encapsulation material, an ion conductor encapsulation material, an electronic conductor encapsulation material.

In some embodiments of the present application, the high entropy oxide, which is fully or partially bound to the lithium-rich oxide surface, comprises 1-10% by mass of all coating materials.

In some embodiments of the present application, the total thickness of the portion other than the lithium-rich oxide surface is between 5-200 nm.

In some embodiments of the present application, the portion other than the surface of the lithium-rich oxide accounts for 1-10% of the mass of the positive electrode lithium-supplementing additive.

In some embodiments of the present application, the high entropy oxide has a porosity of between 1-50%.

To achieve the above object, a second aspect of the present application provides a method for preparing a positive electrode lithium-supplementing additive, including:

selecting low-valence oxides of metal elements in the high-entropy oxide as raw materials, and performing heating treatment in an air atmosphere to obtain the high-entropy oxide;

and ball-milling the high-entropy oxide and the lithium-rich oxide, and sintering to obtain the lithium-rich oxide coated by the high-entropy oxide.

To achieve the above objective, an embodiment of a third aspect of the present application provides a lithium-rich positive electrode, which includes the positive electrode lithium supplement additive of the embodiment of the present application, or the positive electrode lithium supplement additive prepared by the method for preparing the positive electrode lithium supplement additive of the embodiment of the present application.

To achieve the above object, a fourth aspect of the present application provides a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode is the lithium-rich positive electrode of the embodiments of the present application.

The positive electrode lithium supplementing additive provided by the embodiment of the application has the beneficial effects that:

1. the high-entropy oxide material is mixed or/and combined on the surface of the lithium-rich oxide, the multielement synergistic effect and the inherent complex surface of the high-entropy oxide material can provide nearly continuous adsorption energy, active oxygen, CO and the like generated by the lithium-rich oxide can be well absorbed, the effect of inhibiting the gas generated by the lithium-rich oxide is achieved, and the gas generated during charging of the lithium-rich oxide is reduced.

2. The highly disordered and distorted crystal lattice of the high-entropy oxide material can generate a large number of defects in the electrode material, is favorable for migration of electrons and ions, and has a certain improvement on the rate capability of the lithium-rich oxide.

3. The high entropy oxide material can maintain a stable structure even under extreme use conditions due to the high entropy effect of thermodynamics and the delayed diffusion effect of dynamics, so that the corrosion of trace HF in electrolyte to lithium-rich oxide and the performance degradation caused by the corrosion are well prevented.

4. The electronic structure and the production cost of the high-entropy oxide (HEO) can be regulated and controlled by changing the stoichiometric ratio, and the method is beneficial to industrial production.

Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.

Drawings

The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

fig. 1 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to an embodiment of the present application (high entropy oxide is bonded to the surface of lithium-rich oxide and fully coated).

Fig. 2 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (high entropy oxide is bonded to the surface of lithium-rich oxide and semi-coated).

Fig. 3 is a schematic structural diagram of a positive electrode lithium-compensating additive (high entropy oxide blended in lithium-rich oxide) according to yet another embodiment of the present application.

Fig. 4 is a schematic structural diagram of a positive electrode lithium-compensating additive according to yet another embodiment of the present application (high entropy oxide is partially incorporated into the lithium-rich oxide and partially bound to the lithium-rich oxide surface).

Fig. 5 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (high entropy oxide is bonded to the surface of lithium-rich oxide and is discontinuously coated).

Fig. 6 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (a packaging material and a high-entropy oxide are mixed as a coating layer to coat the surface of a lithium-rich oxide).

Fig. 7 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (a lithium-rich oxide surface is fully coated with a high entropy oxide and an encapsulating material in order).

Fig. 8 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (a lithium-rich oxide surface is semi-coated with a high entropy oxide and an encapsulating material in order).

Fig. 9 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (the encapsulating material coats the surface of the lithium-rich oxide and the high-entropy oxide, and the high-entropy oxide discontinuously coats the lithium-rich oxide).

Fig. 10 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (an encapsulating material coats a surface of a lithium-rich oxide and a high-entropy oxide, which is blended in the lithium-rich oxide).

Fig. 11 is a schematic structural diagram of a positive electrode lithium-supplementing additive according to another embodiment of the present application (the encapsulating material coats the surface of the lithium-rich oxide and the high-entropy oxide, which is partially mixed in the lithium-rich oxide and partially serves as the coating material).

Reference numerals:

1-lithium-rich oxide; 2-high entropy oxide; 3-packaging material.

Detailed Description

Embodiments of the present application, examples of which are illustrated in the accompanying drawings, are described in detail below. The embodiments described below by referring to the drawings are exemplary and intended for the purpose of explaining the present application and are not to be construed as limiting the present application.

In the application, the disclosure of numerical ranges includes disclosure of all values and further sub-ranges within the entire range, including endpoints and sub-ranges given for these ranges.

In the application, the related raw materials, equipment and the like are all raw materials and equipment which can be self-made by commercial paths or known methods unless specified otherwise; the methods involved, unless otherwise specified, are all conventional.

The positive electrode lithium supplementing additive comprises a lithium-rich oxide 1 and a high-entropy oxide 2, wherein the high-entropy oxide 2 exists in the positive electrode lithium supplementing additive in any one of the following three modes:

(1) The high entropy oxide is fully incorporated into the lithium-rich oxide (as shown in fig. 3);

(2) The high entropy oxide is fully bound to the outer surface layer of the lithium-rich oxide (as shown in fig. 1, 2 and 5);

(3) The high entropy oxide is partially incorporated into the lithium-rich oxide and partially bound to the outer surface layer of the lithium-rich oxide (as shown in fig. 4).

The positive electrode lithium supplementing additive adopts the high-entropy oxide material to blend or/and combine on the surface of the lithium-rich oxide, so that gas generated during charging of the lithium-rich oxide can be reduced, migration of electrons and ions of the electrode material is facilitated, and rate performance, stability and corrosion resistance are improved.

In some embodiments of the present application, the high entropy oxide has the chemical formula (M1 _a M2 _b M3 _c ...Mi _j )O _k Wherein: m1, M2, M3 in the M element. a, b, c..j is the stoichiometric coefficient of each M element, and a+b+c+ … +j=1, meaning that the sum of the stoichiometric coefficients of all M elements is 1; i is more than or equal to 5 and less than or equal to 10, k is more than or equal to 2 and less than or equal to 8. In this application, the elements selected by M1, M2, and M3..mi are different from each other, and the values of a, b, and c..j may be the same or different. As non-limiting examples, the values of i include, but are not limited to, 5, 6, 7, 8, 9, or 10, and the values of k include, but are not limited to, 2, 3, 4, 5, 6, 7, or 8. In the application, M1, M2 and M3 in the M element of the high-entropy oxide are selected, so that the M element can share the same atomic site, and cations are arranged in disorder, so that the system tends to form a single-phase solid solution structure; the value of i is in the range, so that the material can keep high enough entropy, and the system can maintain a disordered structure; if the material entropy is less than 5, the material entropy is not high enough and the material entropy can become a mid-entropy oxide; if the amount is more than 10, the stability of the system will be deteriorated; since the kind and valence of the M element are different, the value of k varies within the above range.

As one possible example, in some embodiments of the present application, the high entropy oxide has the chemical formula ((M1) _a M2 _b M3 _c M4 _d M5 _e M6 _f ) O), wherein: wherein: m1, M2, M3, M4, M5 and M6 in M elements are any one of Mg, al, ti, V, cr, mn, fe, co, ni, cu, zn, Y, zr, nb, mo, hf, ta, W, and the selected elements of M1, M2, M3, M4, M5 and M6 are different; a. b, c, d, e, f is the stoichiometric coefficient of each M element, and a+b+c+d+e+f=1, representing that the sum of the stoichiometric coefficients of all M elements is 1; a. b, c, d, e, f are all 0.05-0.35, and a, b, c, d, e, f may be the same or different.

In some embodiments of the present application, the lithium-rich oxide has the chemical formula Li _ɑ Q _β T _ε O _γ Wherein alpha is more than or equal to 2 and less than or equal to 8,0.1 and less than or equal to beta is more than or equal to 3, epsilon is more than or equal to 0 and less than or equal to 3, gamma is more than or equal to 1 and less than or equal to 6,Q, and comprises one or more of transition metals of the 4 th or 5 th period such as K, ca, sc, ti, V, cr, mn, fe, co, ni, cu, zn, ga, ge, ru, sr, Y, zr, nb, mo, tc, ru, rh, pd, ag, cd, in, sn, sb, and T comprises one or more of main group metal elements such as Li, na, K, rb, cs, fr, be, mg, ca, sr, ba, ra, al, ga, in, ti, ge, sn, pb, sb, bi, po, or transition metals of the 4 th period such as Sc, ti, V, cr, mn, fe, co, ni, cu, zn. In the chemical general formula of the lithium-rich oxide, the value of alpha comprises, but is not limited to, 2, 3, 4, 5, 6, 7 or 8, the value of beta comprises, but is not limited to, 0.1, 0.5, 1.5, 2, 2.5 or 3, the value of epsilon comprises, but is not limited to, 0.01, 0.1, 0.5, 1, 1.5, 2, 2.5 or 3, and the value of gamma comprises, but is not limited to, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6, and the like. In the chemical general formula of the lithium-rich oxide, Q and T are respectively selected from the metal elements, so that the material structure can be stabilized, and meanwhile, voltage attenuation is reduced; the values of alpha, beta, epsilon and gamma are in the range, so that the stability of the material structure during charge and discharge can be ensured; and if the values of alpha, beta, epsilon and gamma exceed the ranges, the structure is easy to collapse during charge and discharge, and the electrochemical performance of the material is affected.

In the present application, "admixed in the lithium-rich oxide" includes, but is not limited to, homogeneous mixing of the high entropy oxide with the lithium-rich oxide, heterogeneous mixing of the high entropy oxide with the lithium-rich oxide in any form, high entropy oxide being admixed in the core site of the lithium-rich oxide, and the like. In some embodiments of the present application, when the high entropy oxide is fully blended in the lithium-rich oxide, the mass ratio of the high entropy oxide to the lithium-rich oxide is 1-10:99-90. As non-limiting examples, when the high entropy oxide is fully blended in the lithium rich oxide, the mass ratio of the high entropy oxide to the lithium rich oxide includes, but is not limited to, 2:98, 4:96, 6:94, 8:92, etc. When the high-entropy oxide is fully mixed in the lithium-rich oxide, the mass ratio of the high-entropy oxide to the lithium-rich oxide is in the range, so that gas generated during charging of the lithium-rich oxide can be reduced, the migration of electrons and ions of the electrode material is facilitated, and the rate performance, the stability and the corrosion resistance are improved; beyond the above range, the high entropy oxide ratio is too low to remove gas, and when the ratio is too high, the electrochemical performance is seriously affected.

In the present application, the binding of the high-entropy oxide to the surface of the lithium-rich oxide means that the high-entropy oxide exists on the outer surface layer of the lithium-rich oxide, and the existence form of the high-entropy oxide is not limited.

In some embodiments of the present application, the high entropy oxide is discontinuously or continuously coated on the outer surface of the lithium-rich oxide when the high entropy oxide is fully or partially bound to the outer surface of the lithium-rich oxide. Here, the term "partially bonded to the outer surface of the lithium-rich oxide" refers to the case where the "high entropy oxide is partially incorporated into the lithium-rich oxide and partially bonded to the surface of the lithium-rich oxide" described above. The high-entropy oxide is discontinuously coated on the outer surface of the lithium-rich oxide, including but not limited to the case that the high-entropy oxide continuously coats part of the outer surface of the lithium-rich oxide (as shown in fig. 2, 8 and 11), the case that the high-entropy oxide intermittently coats part of the outer surface of the lithium-rich oxide (as shown in fig. 5 and 9), and the like, and the coating area of the high-entropy oxide on the lithium-rich oxide is not limited and can be 50%, 60%, 70%, 80% or 90%. The continuous coating of the high-entropy oxide on the outer surface of the lithium-rich oxide refers to the case where the high-entropy oxide is continuous and coats the entire outer surface of the lithium-rich oxide (as shown in fig. 1, 4 and 7). In the present application, the oxygen content in the gas generated during charging of the lithium-rich oxide is a major proportion, so that it is critical to reduce oxygen release during charging of the lithium-rich oxide. The larger the coating area of the high-entropy oxide on the outer surface of the lithium-rich oxide, the larger the specific surface area of the high-entropy oxide material as a coating material, and the better the adsorption performance of the high-entropy oxide material on the gas generated when the lithium-rich oxide is charged.

In some embodiments of the present application, to further improve the compactness and conductivity of the entire coating layer of the lithium-rich core material, the positive electrode lithium-supplementing additive further comprises an encapsulating material 3, as shown in fig. 6-11.

In some embodiments of the present application, when the high-entropy oxide is fully or partially bound to the outer surface layer of the lithium-rich oxide, the encapsulation material and the high-entropy oxide fully or partially bound to the surface of the lithium-rich oxide are mixed together to form a coating layer, and the coating layer is coated on the outer surface of the lithium-rich oxide. Here, mainly for the case where the aforementioned high-entropy oxide 2 exists in the positive electrode lithium-supplementing additive in any one of the modes (2) and (3), when the "high-entropy oxide is fully bonded to the outer surface layer of the lithium-rich oxide", it may be mixed with each other with the encapsulating material to form a coating layer together, as shown in fig. 6, so that the gas generated when the lithium-rich oxide is charged and discharged can be sufficiently absorbed; when the high-entropy oxide is partially mixed in the lithium-rich oxide and is partially combined with the outer surface layer of the lithium-rich oxide, the high-entropy oxide combined with the surface of the lithium-rich oxide and the packaging material are mutually mixed to form a coating layer, so that a good inhibition effect on gas production can be kept, and meanwhile, the limitation on the requirement of coating is reduced, thereby being beneficial to reducing the experiment cost.

In other embodiments of the present application, the encapsulating material coats the outer surface of the lithium-rich oxide and the high entropy oxide. Here, the case where the aforementioned high-entropy oxide 2 exists in the positive electrode lithium-supplementing additive in either one of the modes (1) and (3), and the case where the aforementioned high-entropy oxide 2 exists in the positive electrode lithium-supplementing additive in the form of only coating the surface of the lithium-rich oxide portion in the mode (2) are mainly aimed at. When the high-entropy oxide is fully blended into the lithium-rich oxide, as described above, the high-entropy oxide can be uniformly mixed with the lithium-rich oxide or non-uniformly mixed in any form, and the encapsulating material coats the outer surfaces of the lithium-rich oxide and the high-entropy oxide, as shown in fig. 10, so that the experimental cost of the coating can be reduced, and the high-entropy oxide has a good inhibition effect on gas production; when all the high-entropy oxide is combined on the surface of the lithium-rich oxide, but only part of the outer surface of the lithium-rich oxide is coated, at the moment, the packaging material is partially coated on the outer surface of the high-entropy oxide and partially coated on the outer surface of the lithium-rich oxide, as shown in fig. 9, so that the lithium ion migration rate and the electron conductivity of the lithium-rich material can be ensured; when the high-entropy oxide is partially mixed in the lithium-rich oxide and partially combined with the outer surface layer of the lithium-rich oxide, the encapsulation material is partially coated on the outer surface of the high-entropy oxide and partially coated on the outer surface of the lithium-rich oxide, as shown in fig. 11, so that the electron transmission rate of the lithium-rich oxide and the high-entropy oxide can be improved.

In still other embodiments of the present application, the encapsulation material coats the outer surface of the lithium-rich oxide. The method mainly aims at the situation that the high-entropy oxide exists in the positive electrode lithium supplementing agent in the mode (1) and is mixed with the lithium-rich oxide inner core part, and at the moment, the packaging material is coated on the outer surface of the lithium-rich oxide, so that good conductivity and protection effect of the lithium-rich oxide can be ensured, and meanwhile, the high-entropy oxide is mixed with the lithium-rich oxide inner core, and the effect of inhibiting gas production is obvious.

In still other embodiments of the present application, the encapsulation material coats the outer surface of the high entropy oxide. The method mainly aims at the situation that the high-entropy oxide coats the whole outer surface of the lithium-rich oxide or is partially coated but the coating areas of the packaging materials are overlapped, and at the moment, the high-entropy oxide is fully coated on all the outer surfaces of the lithium-rich oxide due to the fact that the lithium-rich oxide is positioned at the inner core position, so that the packaging materials are coated on the outer surfaces of the high-entropy oxide (shown in fig. 7 and 8), gas production can be well restrained, and meanwhile, the packaging materials on the outermost layers can also provide good conductivity. As a possible example, as shown in fig. 3, the second coating layer 3 is completely overlapped with the coating region of the first coating layer 1, the first coating layer 2 is completely coated on the outer surface of the lithium-rich oxide 1, and the second coating layer 3 is completely coated on the outer surface of the first coating layer 2.

In some embodiments of the present application, the encapsulation material includes, but is not limited to, at least one layer of an isolation encapsulation material, an ion conductor encapsulation material, an electronic conductor encapsulation material. Wherein the isolation packaging material comprises one or more of ceramic, high molecular polymer and carbon material, preferably carbon material. The electronic conductor encapsulation material includes, but is not limited to, at least one of a carbon material, a conductive polymer, or a conductive oxide, preferably a carbon material. The ion conductor encapsulation material includes, but is not limited to, at least one of perovskite type, NASICON type, garnet type, or polymer type solid state electrolytes. As one possible example, the encapsulation material is a carbon material, including, but not limited to, one or more of graphite, amorphous carbon, hard carbon, carbon nanotubes, graphene sheets, as the encapsulation material.

In some embodiments of the present application, the high entropy oxide, which is fully or partially bound to the lithium-rich oxide surface, comprises 1-10% by mass of all coating materials. That is, in this application, when the coating material located on the outer surface of the lithium-rich oxide contains both the high-entropy oxide and the encapsulating material, the high-entropy oxide as the coating material of the lithium-rich oxide accounts for 1 to 10% by mass of all the coating materials, regardless of the aforementioned coating forms. As non-limiting examples, the high entropy oxide, which is fully or partially bound to the lithium-rich oxide surface, comprises, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., by mass of all coating materials. The mass ratio of the high-entropy oxide fully or partially combined on the surface of the lithium-rich oxide to all the coating materials is within the range, so that good lithium ion migration rate and electron conductivity and inhibition effect on gas production can be maintained; if the lithium ion mobility is less than 1%, the lithium ion mobility is too slow, and the rate capability is affected; if the amount is more than 10%, the electron conductivity is lowered, and the electrochemical performance is affected.

In some embodiments of the present application, the total thickness of the portion other than the lithium-rich oxide surface is between 5-200 nm. The part other than the surface of the lithium-rich oxide refers to a coating layer which is the outer surface of the lithium-rich oxide; when the coating layer is only high-entropy oxide, the coating layer is the high-entropy oxide used as a coating material; when the coating layer contains both high entropy oxide and packaging material, the coating layer is the high entropy oxide and the packaging material as the coating material. As non-limiting examples, the total thickness of the portion other than the lithium-rich oxide surface includes, but is not limited to, 5nm, 25nm, 50nm, 75nm, 100nm, 125nm, 150nm, 175nm, 200nm, or the like. The total thickness of the part outside the surface of the lithium-rich oxide is in the range, so that the lithium-rich oxide can be protected from being corroded by electrolyte under the condition of not affecting the electrochemical performance, and the gas production inhibiting effect is good; less than 5nm, the insufficient gas production capacity is inhibited, and the protection capacity for the lithium-rich oxide is weakened; if the thickness of the coating layer is larger than 200nm, the migration rate of lithium ions of the lithium-rich oxide can be reduced, and the repairing effect is affected.

In some embodiments of the present application, the portion of the lithium-rich oxide other than the surface comprises 1-10% by mass of the positive electrode lithium-compensating additive. The portions other than the surface of the lithium-rich oxide are explained as described above, and will not be described in detail herein. As a non-limiting example, the mass ratio of the portion other than the surface of the lithium-rich oxide to the positive electrode lithium-supplementing additive includes, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and the like. The mass ratio of the part except the surface of the lithium-rich oxide to the positive electrode lithium-supplementing additive is in the range, so that the gas production is inhibited, and meanwhile, the good electrochemical performance is maintained; less than 1%, insufficient gas production is suppressed; if the content is more than 10%, the lithium supplementing effect of the positive electrode supplementing and treating agent is affected, and the electrochemical performance of the positive electrode is reduced.

In some embodiments of the present application, when the high entropy oxide is partially blended into the lithium-rich oxide, partially bound to the lithium-rich oxide surface, the mass ratio of the high entropy oxide blended in the lithium-rich oxide to the high entropy oxide bound to the lithium-rich oxide surface (in some cases, it may be understood that the high entropy oxide is the coating material) includes, but is not limited to, 30:70, 20:80, 35:65, 25:75, etc. The mass ratio of the high-entropy oxide blended in the lithium-rich oxide to the high-entropy oxide combined on the surface of the lithium-rich oxide is in the range, so that the gas production can be kept to have a good inhibition effect, and the limitation on the coating requirement is reduced; beyond the above range, the effect of suppressing gas production is insufficient.

In some embodiments of the present application, the high entropy oxides each have a porosity of between 1-50%. The high entropy oxide herein refers to all the high entropy oxides referred to in the present application, including the aforementioned high entropy oxides blended with lithium-rich oxides and the high entropy oxides as coating materials. As non-limiting examples, the porosities of the high entropy oxides all include, but are not limited to, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. The high-entropy oxide has the porosity in the range, so that the high-entropy oxide can well adsorb gas and infiltrate electrolyte; if the content is less than 1%, the adsorption effect is insufficient, and the ion transmission rate is also reduced; if the content is more than 50%, the structure of the oxide is unstable, and the oxide is easy to damage during subsequent ball milling and sintering.

The preparation method of the positive electrode lithium supplementing additive comprises the following steps:

s101, selecting low-valence oxides of metal elements in the high-entropy oxide as raw materials, and performing heat treatment in an air atmosphere to obtain the high-entropy oxide.

The chemical formula of the high entropy oxide is (M1) _a M2 _b M3 _c ...Mi _j )O _k Wherein: m1, M2, M3 in the M element. a, b, c..j is the stoichiometric coefficient of each M element, and a+b+c+ … +j=1, meaning that the sum of the stoichiometric coefficients of all M elements is 1; i is more than or equal to 5 and less than or equal to 10, k is more than or equal to 2 and less than or equal to 8.

In some embodiments of the present application, after mixing the suboxides of M1, M2, M3..mi in proportions, heating in an air atmosphere at 600-900 ℃ for 4-10 hours to obtain the high entropy oxide (M1) _a M2 _b M3 _c ...Mi _j )O _k A material.

In some embodiments of the present application, the temperature at which the suboxides of M1, M2, M3..mi are heated in an air atmosphere after being mixed in proportions includes, but is not limited to, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, or the like, as non-limiting examples. The heating temperature is in the range, so that the elements can be uniformly diffused, and the powder is not seriously grown; if the temperature is less than 600 ℃, the sintering temperature is too low, the element diffusion rate is too slow, the system is uneven, and more impurities are easy to generate; if the temperature is higher than 900 ℃, the sintering temperature is too high, so that the material particles are seriously grown up, even agglomeration is caused, and the coating effect is affected. .

In some embodiments of the present application, the time to heat in an air atmosphere after mixing the suboxides of M1, M2, M3. The heating time is in the range, so that the elements can be uniformly diffused, and the powder is not seriously grown; if the sintering time is less than 4 hours, the sintering time is insufficient, the element diffusion is uneven, and more impurities are easy to generate; if the sintering time is longer than 10 hours, the particle size of the material is too large, agglomeration is seriously caused, and the coating effect is affected.

In some embodiments of the present application, the heating treatment may be performed in a tube furnace, rotary furnace, box furnace, roller kiln, pusher kiln, fluidized bed, or the like.

And S102, ball milling the high-entropy oxide and the lithium-rich oxide, and sintering to obtain the lithium-rich oxide coated by the high-entropy oxide.

In the method, the high-entropy oxide and the lithium-rich oxide are subjected to ball milling and then sintering, so that the high-entropy oxide and the lithium-rich oxide are uniformly dispersed by ball milling, and element diffusion is carried out between the high-entropy oxide and the lithium-rich material surface by sintering, so that a stable coating layer is formed.

In some embodiments of the present application, to prevent contamination of lithium-rich oxides and high entropy alloys with oxygen and moisture in the air, ball milling is performed in an oxygen-free environment.

In some embodiments of the present application, the ball milling speed includes, but is not limited to, 15-35Hz. As non-limiting examples, ball milling speeds include, but are not limited to, 15Hz, 20Hz, 25Hz, 30Hz, 35Hz, etc. The ball milling adopts a bidirectional mode ball milling, and the ball milling time is 4-6h. As non-limiting examples, ball milling times include, but are not limited to, 4h, 4.5h, 5h, 5.5h, 6h, or the like. The ball milling speed and the ball milling time are selected within the above ranges, so that the ball milling speed and the ball milling time can be fully and uniformly mixed; beyond the above range, too slow or too short a ball milling speed may result in uneven mixing, and too fast or too long a ball milling speed may cause the coated high entropy oxide to be ball milled off.

In some embodiments of the present application, sintering is performed in an inert atmosphere including, but not limited to, argon, nitrogen, and the like, at a sintering temperature including, but not limited to, between 500-800 ℃, and for a sintering time including, but not limited to, 3-6 hours. As non-limiting examples, sintering temperatures include, but are not limited to, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, or 800 ℃, etc.; sintering times include, but are not limited to, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, or 6h, etc. The sintering temperature and the sintering time are selected in the above range, so that the high-entropy oxide and the surface of the lithium-rich material can be subjected to element diffusion to form a stable coating layer; when the temperature is too short or too low, the element diffusion is insufficient, the coating effect is affected, and when the temperature is too long or too high, the coating layer is too thick, and the particle size is too large.

In some embodiments of the present application, sintering may be performed in a tube furnace, rotary furnace, box furnace, roller kiln, pusher kiln, fluidized bed, or the like.

In some embodiments of the present application, when the coating material of the positive electrode lithium-compensating additive of the present application further comprises a step of forming the encapsulation material on the surface of the lithium-rich oxide coated with the high entropy oxide, the coating material is further included in the encapsulation material. The forming method of the encapsulation material includes, but is not limited to, at least one of a chemical vapor deposition method (CVD method), a sol-gel method, a solution method, a solid phase method, sintering, and the like.

The lithium-rich positive electrode comprises the positive electrode lithium supplement additive disclosed by the embodiment of the application or the positive electrode lithium supplement additive prepared by the preparation method of the positive electrode lithium supplement additive disclosed by the embodiment of the application.

In some embodiments of the present application, the positive electrode lithium supplement additive in the lithium-rich positive electrode is part of the positive electrode active material, and the positive electrode lithium supplement additive is present in an amount of 0.5 to 15wt% of the total positive electrode active material. As a non-limiting list, the content of the positive electrode lithium supplement additive is 3wt%, 6wt%, 9wt%, 12wt%, or 15wt% of the entire positive electrode active material. The content of the positive electrode lithium supplementing additive is in the range, so that the loss of lithium ions during the first charge and discharge can be supplemented, and meanwhile, the positive electrode can keep good cycle performance; less than 0.5wt%, the lithium supplement agent added is insufficient to supplement the loss in; if the weight of the lithium ion battery is more than 15wt%, the subsequent cycle performance of the positive electrode can be affected by excessive lithium supplementing materials.

In some embodiments of the present application, the positive electrode active material of the lithium-rich positive electrode may further include at least one of a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode active material includes, but is not limited to, one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadium fluorophosphate, lithium titanate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganese iron phosphate. The positive electrode active material can perform intercalation and deintercalation, alloying and dealloying, or plating and exfoliation of lithium. Positive electrode conductive agents include, but are not limited to, one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes. The positive electrode conductive agent is added into the positive electrode active material, so that the conductivity of the electrode material layer can be enhanced, the conductivity of the lithium supplementing material is improved, and the transmission of electrons and ions is facilitated. The positive electrode binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose, and polyacrylic acid.

In some embodiments of the present application, the lithium-rich positive electrode further comprises a current collector, which may optionally comprise aluminum or any other suitable conductive metal foil known to those skilled in the art (such as solid or mesh or cover foil), a metal grid or mesh, or a porous metal. In certain variations, the surface of the current collector may comprise a surface treated (e.g., carbon coated and/or etched) metal foil.

The secondary battery comprises a positive electrode, a negative electrode and a diaphragm, wherein the positive electrode is the lithium-rich positive electrode.

In some embodiments of the present application, the positive electrode tab, separator and negative electrode tab may be processed to form a secondary battery using a lamination process or a winding process. It should be noted that the secondary battery according to the embodiment of the present application includes, but is not limited to, a lithium ion battery.

The negative electrode sheet, electrolyte, separator and the like of the secondary battery in the embodiment of the application are not particularly limited, and can be applied to any battery system.

The secondary battery of the embodiment of the application can be widely applied to the fields of new energy power automobiles, aerospace, electronic products and the like.

The preparation method of the positive electrode lithium supplementing additive, the lithium-rich positive electrode and the secondary battery have the beneficial effects of the positive electrode lithium supplementing additive.

Certain features of the present technology are further illustrated in the following non-limiting examples.

1. Examples and comparative examples

Example 1

As shown in fig. 1, the positive electrode lithium supplement additive of the present embodiment comprises a lithium-rich oxide 1 and a high entropy oxide 2, wherein the lithium-rich oxide 1 is Li ₅ FeO ₄ The high entropy oxide 2 is (CoCrFeNiMnTi) O; the high-entropy oxide 2 is continuously and fully coated on the outer surface of the lithium-rich oxide 1, the high-entropy oxide 2 accounts for 5% of the total mass of the whole positive electrode lithium-supplementing additive, the thickness of the high-entropy oxide 2 is 30nm, and the porosity of the high-entropy oxide 2 is 25%.

The preparation method of the positive electrode lithium supplementing additive of the embodiment comprises the following steps:

(1) Preparing a high entropy oxide material: co, cr, fe, ni, mn, ti six elements are mixed according to 1:1:1:1:1:1 atomic ratio of CoO and Cr ₂ O ₃ 、FeO、NiO、MnO、TiO ₂ Ball milling is carried out for 5 hours under the condition of 30Hz, then the temperature is kept for 8 hours under the atmosphere of air at 950 ℃, and the required high entropy oxide material (CoCrFeNiMnTi) O can be obtained.

(2) Preparing a high entropy oxide coated lithium-rich oxide: (CoCrFeNiMnTi) O and lithium-rich oxide Li ₅ FeO ₄ Ball-milling for 5h at 25Hz under argon atmosphere, and sintering the ball-milled powder at 600 ℃ for 5h under argon atmosphere to obtain the Li coated with the high-entropy oxide material (CoCrFeNiMnTi) O ₅ FeO ₄ 。

The lithium-rich positive electrode of the embodiment comprises a positive electrode current collector and a positive electrode active material coated on the surface of the positive electrode current collector, wherein the positive electrode current collector is aluminum foil, and the positive electrode active material comprises the following components in parts by weight: 93 parts of positive active material lithium iron manganese phosphate, 2 parts of positive lithium supplement additive of the embodiment, 2 parts of positive conductive agent Super P, and 3 parts of positive binder polyvinylidene fluoride.

The secondary battery of the embodiment comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are overlapped between the positive electrode and the negative electrode, and the secondary battery comprises: the positive electrode is the lithium-rich positive electrode of the embodiment; the negative electrode comprises a negative electrode current collector and a negative electrode active material coated on the surface of the negative electrode current collector, wherein the negative electrode current collector is copper foil, and the negative electrode active material comprises the following components in parts by weight: 95 parts of negative electrode active material graphite, 2 parts of negative electrode conductive agent Super P, 0.5 part of thickener carboxymethyl cellulose (CMC) and 2.5 parts of negative electrode binder Styrene Butadiene Rubber (SBR); the diaphragm adopts a Polyethylene (PE) microporous diaphragm; the electrolyte comprises Ethylene Carbonate (EC), ethylmethyl carbonate (DEC) and LiPF ₆ Wherein the volume ratio of the Ethylene Carbonate (EC) to the ethylmethyl carbonate (DEC) is 3:7, liPF ₆ The concentration of (C) was 1mol/L.

The preparation method of the secondary battery of the embodiment comprises the following steps:

1) Preparing a positive electrode: n-methylpyrrolidone, lithium iron phosphate, positive electrode lithium supplement additive, positive electrode conductive agent Super P and positive electrode binder polyvinylidene fluoride are mixed according to a ratio of 100:93:2:2:3, mixing the materials according to the mass ratio, ball milling and stirring to obtain positive electrode slurry, wherein the ball milling time is 60min, the rotating speed is 30Hz, coating the positive electrode slurry on the surface of an aluminum foil, rolling, and vacuum drying overnight at 100 ℃ to obtain the positive electrode plate.

2) Preparing a negative electrode: the negative electrode active material (graphite), a negative electrode conductive agent (conductive carbon black, super P), a thickener (carboxymethyl cellulose, CMC) and a negative electrode binder (styrene butadiene rubber, SBR) are mixed according to the mass ratio of 95:2:0.5:2.5, placing the mixture in deionized water, uniformly mixing to prepare negative electrode slurry, coating the negative electrode slurry on the surface of a current collector copper foil, and obtaining a negative electrode plate after the procedures of drying, rolling and secondary drying.

3) Preparing an electrolyte: mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (DEC) in a volume ratio of 3:7, and adding LiPF ₆ Electrolyte is formed, liPF ₆ The concentration of (C) was 1mol/L.

4) Secondary battery (lithium ion battery) assembly: and assembling the lithium anode, the diaphragm, the electrolyte and the anode in a glove box in an inert nitrogen atmosphere according to the assembling sequence of the lithium anode, the diaphragm, the electrolyte and the anode to obtain the lithium ion battery.

Example 2

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this embodiment, the high-entropy oxide is (MgAlVYCuMo) O.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, during the preparation of the high-entropy oxide in the step (1), the ball milling rate and time are 32Hz and 6h, and the sintering temperature and time of the argon atmosphere in the subsequent step (2) are 900 ℃ and 10h respectively.

Example 3

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this embodiment, the high entropy oxide is (HfNbMoCoNiMn) O.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, during the preparation of the high-entropy oxide in the step (1), the ball milling rate and time are 35Hz and 4 hours, and the sintering temperature and time of the argon atmosphere in the subsequent step (2) are 925 ℃ and 9 hours respectively.

Example 4

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this embodiment, the high entropy oxide is (AlTiCuFeNiMn) O.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, during the preparation of the high-entropy oxide in the step (1), the ball milling rate and time are 40Hz and 4 hours, and the sintering temperature and time of the argon atmosphere in the subsequent step (2) are 975 ℃ and 6 hours respectively.

Example 5

This embodiment is substantially the same as embodiment 1 except that:

as shown in fig. 2, in the positive electrode lithium-supplementing additive of the present embodiment, the high-entropy oxide is continuously and semi-coated on the outer surface of the lithium-rich oxide.

In the preparation method of the positive electrode lithium supplement additive, after the high-entropy oxide and the lithium-rich oxide in the step (1) are mixed, the ball milling rate and time are 30Hz and 3h, and the sintering temperature and time of the argon atmosphere in the subsequent step (2) are 650 ℃ and 3h respectively.

Example 6

This embodiment is substantially the same as embodiment 1 except that:

as shown in fig. 7, the positive electrode lithium-supplementing additive of the present embodiment further includes an encapsulating material 3, wherein the encapsulating material 3 is a carbon layer, and the carbon layer is made of graphite; the packaging material 3 is continuously and fully coated on the outer surface of the high-entropy oxide 2, the packaging material and the high-entropy oxide form a coating layer together, the high-entropy oxide 2 accounts for 80% of the mass ratio of all the coating materials (the high-entropy oxide and the packaging material), and the coating material accounts for 7% of the mass ratio of the positive electrode lithium supplementing additive; the total thickness of the coating layer was 50nm and the porosity of the high entropy oxide 2 was 30%.

In the preparation method of the positive electrode lithium supplement additive of the embodiment, the encapsulating material 3 (graphite) is added in the step (2) when the high-entropy oxide is mixed with the lithium-rich oxide.

Example 7

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this example, the thickness of the high-entropy oxide was 40nm.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, in the step (2), after the high-entropy oxide and the lithium-rich oxide are mixed, the ball milling rate and time are respectively 32Hz and 5h, and the sintering temperature and time of the subsequent argon atmosphere are respectively 625 ℃ and 5h.

Example 8

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this example, the porosity of the high-entropy oxide was 35%.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, in the step (2), after the high-entropy oxide and the lithium-rich oxide are mixed, the ball milling rate and time are 35Hz and 3h, and the sintering temperature and time in the subsequent argon atmosphere are 550 ℃ and 5h.

Example 9

This embodiment is substantially the same as embodiment 1 except that:

in the positive electrode lithium-supplementing additive of this embodiment, as shown in fig. 3, the high-entropy oxide is mixed with the lithium-rich oxide, and the two oxides are uniformly mixed; the mass ratio of the high-entropy oxide to the lithium-rich oxide is 8:92 (i.e., the high-entropy oxide accounts for 8wt% of the positive electrode lithium-supplementing additive), and the porosity of the high-entropy oxide is 32%.

In the preparation method of the positive electrode lithium supplement additive in the embodiment, in the step (2), after the high-entropy oxide and the lithium-rich oxide are mixed, the ball milling rate and time are respectively 37Hz and 4 hours, and the sintering temperature and time in the subsequent argon atmosphere are respectively 650 ℃ and 3.5 hours.

Comparative example 1

This comparative example is substantially the same as example 1 except that:

the positive electrode lithium-supplementing additive of this example does not contain a high entropy oxide.

2. Performance testing

The electrochemical performance of the lithium ion batteries corresponding to the positive electrode lithium supplement additives of the examples and the comparative examples was tested under the following conditions: the assembled battery is placed at room temperature for 6 hours and then subjected to charge and discharge test, the charge and discharge voltage is 2.0-4.3V, and the test temperature is 25 ℃.

The test results are shown in table 1 below:

table 1 results of electrochemical performance tests of lithium ion batteries of examples and comparative examples

As can be seen from table 1, the positive electrode of the present example had improved specific charge capacity and specific discharge capacity at 0.2C, 0.5C, 1C, 2C and 3C, compared with the positive electrode of comparative example 1, and the coulombic efficiency was equal to or higher, and the first-turn gas yield of the lithium-rich oxide was greatly reduced. The multi-element synergistic effect and the inherent complex surface of the high-entropy oxide material can provide near continuous adsorption energy, can well absorb active oxygen, CO and the like generated by the lithium-rich oxide, has the effect of inhibiting the gas generation of the lithium-rich oxide, reduces the gas generated during charging of the lithium-rich oxide, and improves the rate performance of the lithium-rich oxide.

As can be seen from comparative examples 1 to 4, when the high-entropy oxide is continuously and fully coated on the outer surface of the lithium-rich oxide, and the high-entropy oxide content, the porosity and the thickness as the coating layer are all the same, only the high-entropy oxide is different, and in the case of 0.2C, 0.5C, 1C, 2C and 3C, the first-turn gas yield and the rate performance (specific charge capacity, specific discharge capacity, coulombic efficiency) of the lithium-rich oxide are not much different.

As can be seen from comparative examples 1 and 5, in the case that the high-entropy oxide is the same and the high-entropy oxide content, the porosity and the thickness as the coating layer are the same, and only the coating degree of the high-entropy oxide on the lithium-rich oxide is different, the first-turn gas yield of the lithium-rich oxide of example 1 is significantly smaller than that of example 5 in the case of 0.2C, 0.5C, 1C, 2C and 3C, which means that the larger the coating area of the high-entropy oxide on the outer surface of the lithium-rich oxide is, the better the adsorption performance of the lithium-rich oxide on the gas generated when charging the lithium-rich oxide is.

As can be seen from comparative examples 1 and 6, coating the encapsulation material on the surface of the high-entropy oxide has little influence on the first-turn gas yield and rate performance (specific charge capacity, specific discharge capacity, coulombic efficiency) of the lithium-rich oxide.

As can be seen from comparative examples 1 and 7, the first turn gas yield of example 7 is lower than that of example 7, indicating that the thicker the coating thickness, the better the adsorption performance of the gas generated when charging the lithium-rich oxide, with the proper high entropy oxide coating thickness.

As can be seen from comparative examples 1 and 8, the high entropy oxide porosity is improved: under the conditions of 0.2C, 0.5C and 1C, the first-circle gas yield of the lithium-rich oxide is basically equivalent, but under the conditions of 2C and 3C, the first-circle gas yield of the lithium-rich oxide is reduced by more than 10 percent; in the case of 0.2C, 0.5C, 1C, 2C, and 3C, the specific charge capacity and the specific discharge capacity were reduced, and the coulombic efficiency was reduced except for 0.5C.

As can be seen from comparative examples 1 and 9, the high entropy oxide coated on the surface of the lithium-rich oxide has a lower initial gas yield and improved specific charge capacity and specific discharge capacity in the case of 0.2C, 0.5C, 1C, 2C and 3C, compared with the case of mixing the high entropy oxide with the lithium-rich oxide.

The terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., in this application, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.

Claims

1. A positive electrode lithium supplement additive, comprising:

lithium-rich oxides;

(1) The high entropy oxide is fully blended in the lithium-rich oxide;

2. The positive electrode lithium supplement additive according to claim 1, wherein the high entropy oxide has a chemical formula (M1) _a M2 _b M3 _c ...Mi _j )O _k Wherein:

m1, M2, M3 in the M element.

a, b, c..j is the stoichiometric coefficient of each M element, and a+b+c+ … +j=1, meaning that the sum of the stoichiometric coefficients of all M elements is 1;

5≤i≤10，2≤k≤8。

3. The positive electrode lithium supplement additive of claim 1, wherein the lithium-rich oxide has a chemical formula of Li _ɑ Q _β T _ε O _γ Wherein alpha is more than or equal to 2 and less than or equal to 8,0.1 and less than or equal to beta is more than or equal to 3, epsilon is more than or equal to 0 and less than or equal to 3, gamma is more than or equal to 1 and less than or equal to 6,Q, and T is one or more of main group metal elements or 4 th period transition metals.

4. The positive electrode lithium supplement additive according to claim 1, wherein the high entropy oxide is discontinuously or continuously coated on the outer surface of the lithium-rich oxide when the high entropy oxide is fully or partially bonded to the outer surface of the lithium-rich oxide.

5. The positive electrode lithium supplement additive of claim 1, further comprising an encapsulating material;

when the high-entropy oxide is fully or partially combined with the outer surface layer of the lithium-rich oxide, the packaging material and the high-entropy oxide fully or partially combined with the surface of the lithium-rich oxide are mutually mixed to form a coating layer, and the coating layer is coated on the outer surface of the lithium-rich oxide;

or the packaging material is coated on the outer surface of the lithium-rich oxide and/or the high-entropy oxide.

6. The positive electrode lithium supplement additive according to claim 5, wherein the encapsulation material comprises at least one layer of an isolation encapsulation material, an ion conductor encapsulation material, an electron conductor encapsulation material;

And/or, the high entropy oxide fully or partially combined with the surface of the lithium-rich oxide accounts for 1-10% of the mass ratio of all coating materials.

7. The positive electrode lithium-supplementing additive according to any one of claims 1 to 6, wherein a total thickness of a portion other than a surface of the lithium-rich oxide is between 5 and 200 nm;

and/or the part except the surface of the lithium-rich oxide accounts for 1-10% of the mass ratio of the positive electrode lithium-supplementing additive;

and/or the high entropy oxide has a porosity of between 1 and 50%.

8. A method of preparing the positive electrode lithium-compensating additive of any of claims 1 to 7, comprising:

9. A lithium-rich positive electrode comprising the positive electrode lithium-supplementing additive according to any one of claims 1 to 7, or the positive electrode lithium-supplementing additive produced by the production method according to claim 8.

10. A secondary battery comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode is the lithium-rich positive electrode according to claim 9.