Lithium replenishing additive and preparation method therefor, positive electrode slurry, and battery

Abstract

Disclosed in the present application are a lithium replenishing additive and a preparation method therefor, a positive electrode slurry and a battery. The lithium replenishing additive comprises: an inner core, the inner core satisfying the chemical formula LixM1yM21-yO6, wherein 6≤x≤8, 0<y<1, M1 is at least one of Zr, Nb, Sb, Bi, Ru, Ta, Sn, Hf, Ir, Pr, Pt and Np, and M2 is at least one of W, Ge, Ca, Ce, K and Ta; and a coating layer, the coating layer being at least provided on part of the surface of the inner core, the coating layer comprising a lithium-containing metal oxide and a carbon material, and the lithium-containing metal oxide satisfying the chemical formula LiaMbOc, wherein 1.8≤a≤2, 0.7≤b≤1.1, 2.8≤c≤3 and M comprises Ti and / or Zr. The lithium replenishing additive exhibits a diffraction peak intensity S1 relative to an X-ray within the 2θ diffraction angle of 20.1°-20.3° and exhibits a diffraction peak intensity S2 relative to the X-ray within the 2θ diffraction angle of 17°-17.3°, S1 / S2 being 0.02-0.05.

Description

Lithium supplement agent, its preparation method, positive electrode slurry and battery Technical Field

[0001] The present disclosure relates to the technical field of batteries, and specifically, to a lithium supplement agent, its preparation method, positive electrode slurry and battery. Background Art

[0002] During the first charging process of a lithium-ion battery, a solid electrolyte interface film (SEI) is formed at the negative electrode interface, resulting in irreversible loss of the battery's capacity, and further causing a decrease in the energy density of the lithium-ion battery. The capacity loss during the formation of the SEI film can be effectively alleviated through lithium supplement technology. There are mainly two ways of lithium supplement technology: lithium supplement on the positive electrode side and lithium supplement on the negative electrode side. Among them, the lithium supplement technology on the negative electrode side requires the use of metallic lithium materials, which has problems such as complex processes and high environmental requirements. The lithium supplement technology on the positive electrode side has higher safety and compatibility, and higher feasibility. However, there are still many problems in the actual production and application of the lithium supplement technology on the positive electrode side, which need to be further solved.

[0003] Application Content

[0004] In the first aspect of the present application, a lithium supplement agent is proposed, including: a core, the core satisfying the chemical formula Li x M1 y M2 1-y O6, where 6 ≤ x ≤ 8, 0 < y < 1, M1 is at least one of Zr, Nb, Sb, Bi, Ru, Ta, Sn, Hf, Ir, Pr, Pt, Np, and M2 is at least one of W, Ge, Ca, Ce, K, Ta; a coating layer, the coating layer being at least located on a part of the surface of the core, the coating layer including a lithium-containing metal oxide and a carbon material, where the lithium-containing metal oxide satisfies the chemical formula Li a M b O c , where 1.8 ≤ a ≤ 2, 0.7 ≤ b ≤ 1.1, 2.8 ≤ c ≤ 3, M includes Ti and / or Zr. Among them, the peak intensity of the diffraction peak of the X-ray of the lithium supplement agent at a 2θ diffraction angle of 20.1° - 20.3° is S1, and the peak intensity of the diffraction peak of the X-ray of the lithium supplement agent at a 2θ diffraction angle of 17° - 17.3° is S2, and S1 / S2 is 0.02 - 0.05. Thus, the lithium supplement agent has a high lithium supplement capacity, a high lithium ion migration rate, and excellent processing performance.

[0005] In some embodiments, the mass fraction of the lithium-containing metal oxide in the lithium supplement agent is 0.01% - 0.1%, and / or, the mass fraction of the carbon material in the lithium supplement agent is 0.01% - 0.5%. Thus, the lithium supplement agent has a high lithium supplement capacity.

[0006] In some embodiments, the unit cell parameters of the core satisfy a=b, a≠c, wherein c / a is 2 to 3. This can increase the lithium ion migration rate of the lithium supplement.

[0007] In some embodiments, a is 0.4 nm to 0.7 nm, and c is 1.4 nm to 1.6 nm. This can further increase the lithium ion migration rate of the lithium supplement.

[0008] In some embodiments, the core has a Dv50 particle size of 1 μm to 10 μm, and / or the coating layer has a thickness of 50 nm to 500 nm. Thus, the coating layer can improve the storage performance and conductivity of the lithium supplement, thereby helping the lithium supplement to fully exert its lithium supplementation capacity.

[0009] In some embodiments, the core comprises Li8Zr 0.9 W 0.1 O6、Li7Nb 0.8 Ta 0.2 O6、Li7Sb 0.9 Ta 0.1 O6、 Li7Ru 0.7 W 0.2 Ce 0.1 O6、Li8Sn 0.9 Ca 0.1 O6、Li8Hf 0.7 W 0.2 Ca 0.1 O6、Li8Ir 0.6 W 0.2 Ce 0.2 O6、Li8Pr 0.5 W 0.3 Ca 0.2 O6、Li8Pt 0.7 W 0.2 Ca 0.1 At least one of O6. Thus, the lithium replenishing capacity of the lithium replenishing agent can be effectively increased and the decomposition potential of the lithium replenishing agent can be reduced.

[0010] In some embodiments, the graphitization degree of the carbon material is greater than or equal to 60%, thereby further improving the conductivity of the lithium supplement.

[0011] In a second aspect of this application, a method for preparing the aforementioned lithium supplement agent is provided, comprising: performing a first sintering process on a lithium source, an M1 source, and an M2 source in an oxygen-containing atmosphere to obtain a core; and performing a second sintering process on the core, the M source, and a carbon source in an inert atmosphere to form a coating layer on at least a portion of the surface of the core, thereby obtaining the lithium supplement agent. Thus, the aforementioned lithium supplement agent with superior lithium supplement performance can be prepared by a simple method.

[0012] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxide; and / or the M1 source includes at least one of M1 oxide, M1 chloride, M1 nitrate, and M1 hydroxide; and / or the M2 source includes at least one of M2 oxide, M2 chloride, M2 nitrate, and M2 hydroxide. This facilitates the formation of a core with a high lithium replenishment capacity.

[0013] In some embodiments, the temperature of the first sintering treatment is 700° C.-1200° C., and the time of the first sintering treatment is 8 hours-24 hours, thereby facilitating the acquisition of pure-phase core particles with a moderate particle size.

[0014] In some embodiments, the M source includes at least one of zirconium propoxide, zirconium oxide, zirconium nitrate, zirconyl chloride, lithium zirconate, zirconium chloride, titanium oxide, titanium tetrachloride, titanium nitrate, and titanium alkoxide; and / or the carbon source includes at least one of glucose, starch, sucrose, and graphite. This facilitates the formation of a lithium-containing metal oxide on the surface of the core.

[0015] In some embodiments, the temperature of the second sintering treatment is 400° C.-800° C., and the time of the second sintering treatment is 6 hours-10 hours, thereby facilitating the formation of lithium-containing metal oxide and carbon material in the coating layer.

[0016] In some embodiments, the method further comprises: before the second sintering process, mixing the core, the M source, and the carbon source in a solvent and performing a drying process, thereby helping to improve the coating uniformity of the coating layer.

[0017] In some embodiments, the solvent includes at least one of ethanol and isopropanol; and / or the drying process includes at least one of spray drying, freeze drying, and flash drying. This helps to improve the coating uniformity of the coating layer.

[0018] In a third aspect of the present application, a positive electrode slurry is provided, comprising the aforementioned lithium supplement, or a lithium supplement prepared using the aforementioned method. Thus, the positive electrode slurry has all the features and advantages of the aforementioned lithium supplement and method for preparing the lithium supplement, and no further details are given here.

[0019] In some embodiments, the viscosity of the positive electrode slurry is 1000 mPa·s-8000 mPa·s, which is beneficial for improving the processing performance of the positive electrode slurry.

[0020] In a fourth aspect, the present application provides a battery comprising a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located at least on one side of the positive electrode current collector, wherein the positive electrode active material layer is prepared using the aforementioned positive electrode slurry. Thus, the battery has all the features and advantages of the aforementioned positive electrode slurry, which will not be further elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] FIG1 is a scanning electron microscope image of the lithium supplement agent of Example 1 of the present application;

[0023] FIG2 is an X-ray diffraction diagram of the lithium supplement agent of Example 1 and Comparative Example 5 of the present application;

[0024] FIG3 is a charge and discharge curve diagram of a battery made with the lithium supplement agent of Example 1 of the present application. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present application in detail. Examples of the embodiments are shown in the accompanying drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0026] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0027] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0028] In the description of this application, regardless of whether the word "about" or "approximately" is used, all numbers disclosed herein are approximate values. The value of each number may vary by less than 10% or by a reasonable difference considered by a person skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0029] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0031] The positive electrode side lithium replenishers in the related art include binary lithium-containing compounds, such as Li2O, Li2O2, Li3N, and ternary lithium-containing compounds, such as Li2NiO2, Li6CoO4, Li5FeO4, etc. Binary lithium-containing compounds have poor stability in the atmospheric environment and are difficult to be applied in industrial applications. Ternary lithium-containing compounds are more stable than binary lithium-containing compounds, but ternary lithium-containing compounds also have the disadvantages of strong surface alkalinity and high decomposition potential. Specifically, when the lithium replenisher is added to the positive electrode slurry, the strong alkaline surface of the lithium replenisher will cause the occurrence of lithium precipitation reaction, which will increase the alkalinity of the positive electrode slurry, causing the viscosity of the positive electrode slurry to increase significantly or even form a jelly-like slurry, which cannot meet the coating requirements; when the decomposition potential of the lithium replenisher is too high, a higher voltage needs to be applied during the first charging process of the battery to fully release the lithium replenishment capacity in the lithium replenisher. When the voltage applied during the first charging process is too high, the positive electrode active material in the positive electrode active material layer will undergo irreversible structural changes, resulting in a decrease in the lithium deintercalation sites of the positive electrode active material and a decrease in the energy density of the battery; when the voltage applied during the first charging process is too low, the lithium replenishing capacity of the lithium replenisher cannot be fully utilized, and the lithium replenishing effect of the lithium replenisher is poor.

[0032] In this application, by optimizing the elemental composition of the lithium supplement core, on the basis of the ternary lithium supplement, the lithium ion migration rate of the lithium supplement core is further improved by adding doping elements. Specifically, the lithium supplement core satisfies the chemical formula Li x M1 y M2 1-yO6, where 6 ≤ x ≤ 8 and 0 < y < 1. Among them, the ternary lithium-containing compound containing element M1 has a relatively high theoretical capacity, which can effectively improve the lithium supplementation capacity of the lithium supplement. Element M2 can provide a relatively smaller lithium supplementation capacity compared with element M1, but it has a larger ionic radius than element M1. After doping with element M2, the interlayer spacing between the inner core and the layered structure can be increased, which helps the rapid insertion and extraction of lithium ions. Therefore, the lithium supplement inner core has a high lithium supplement capacity, a high lithium supplementation capacity, and a high lithium ion migration rate. Further, since the alkaline surface of the aforementioned lithium supplement inner core may cause problems such as gelation of the positive electrode slurry, a coating layer is formed on the surface of the aforementioned lithium supplement inner core. The coating layer includes a lithium-containing metal oxide and a carbon material. Among them, the lithium-containing metal oxide in the coating layer can effectively inhibit the reaction between the inner core and moisture, carbon dioxide, etc. in the air to generate impurities such as lithium hydroxide or lithium carbonate. However, the conductivity of the lithium-containing metal oxide is poor. By adding an appropriate amount of carbon material to the coating layer, the conductivity of the coating layer can be effectively improved, thereby improving the surface electron conductivity of the lithium supplement and improving the lithium ion and electron transport channels of the lithium supplement.

[0033] When the lithium supplement has a characteristic diffraction peak for X-rays within the 2θ diffraction angle range of 20.1° - 20.3°, it indicates that the lithium-containing metal oxide in the coating layer is in a tetragonal phase structure (110 crystal plane). When the lithium supplement has a characteristic diffraction peak for X-rays within the 2θ diffraction angle range of 17° - 17.3°, it indicates that the lithium supplement inner core is in a hexagonal phase structure (101 crystal plane). Further, when the peak intensity of the diffraction peak of the lithium supplement for X-rays within the 2θ diffraction angle range of 20.1° - 20.3° is S1, and the peak intensity of the diffraction peak of the lithium supplement for X-rays within the 2θ diffraction angle range of 17° - 17.3° is S2, and when S1 / S2 is 0.02 - 0.05, the phase ratio between the hexagonal phase structure lithium supplement inner core and the tetragonal phase structure coating layer is relatively appropriate. At this time, the hexagonal phase structure inner core has a high lithium ion migration rate, which is beneficial to the full extraction of lithium ions in the inner core; the lithium-containing metal oxide with a tetragonal phase structure not only has high structural stability, can effectively inhibit the reaction between the inner core and moisture, carbon dioxide, etc. to generate impurities, but also has good lithium insertion and extraction characteristics, so that the surface coating layer jointly formed by the lithium-containing metal oxide and the carbon material has a small impact on the lithium supplementation performance of the inner core, effectively improving the lithium ion and electron transport channels of the lithium supplement.

[0034] In the first aspect of the present application, the present application proposes a lithium supplement, including: an inner core, and the inner core satisfies the chemical formula Li x M1 y M2 1-yO6, where 6 ≤ x ≤ 8, 0 < y < 1, M1 is at least one of Zr, Nb, Sb, Bi, Ru, Ta, Sn, Hf, Ir, Pr, Pt, Np; a coating layer, the coating layer is at least located on a part of the surface of the core, the coating layer includes a lithium-containing metal oxide and a carbon material, where the lithium-containing metal oxide satisfies the chemical formula Li a M b O c , where 1.8 ≤ a ≤ 2, 0.7 ≤ b ≤ 1.1, 2.8 ≤ c ≤ 3, M includes Ti and / or Zr. Among them, the peak intensity of the X-ray diffraction peak of the lithium supplement agent at a 2θ diffraction angle of 20.1° - 20.3° is S1, and the peak intensity of the X-ray diffraction peak of the lithium supplement agent at a 2θ diffraction angle of 17° - 17.3° is S2, and S1 / S2 is 0.02 - 0.05. Thus, the aforementioned lithium supplement agent has a high lithium supplement capacity and a high lithium ion migration rate. Among them, there is a stable tetragonal phase structure coating layer on the surface of the hexagonal phase structure core. When the ratio of S1 to S2 meets the aforementioned limit, the coating layer can effectively improve the stability of the core, reduce the increase in the viscosity of the positive electrode slurry caused by the alkalinity on the surface of the core during the use of the lithium supplement agent, and has better processing performance. When the aforementioned lithium supplement agent is applied to the lithium supplement technology on the positive electrode side, during the charging process of the battery, the lithium supplement agent can be fully decomposed and release active lithium ions to supplement the loss of active lithium caused by the formation of the SEI film, achieving the effect of improving the energy density and cycle life of the lithium battery.

[0035] As an example, x can be 6, 6.5, 7, 7.5 or 8.

[0036] As an example, y can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9.

[0037] As an example, a can be 1.8, 1.9 or 2.

[0038] As an example, b can be 0.7, 0.8, 0.9, 1 or 1.1.

[0039] As an example, c can be 2.8, 2.9 or 3.

[0040] As an example, S1 / S2 can be 0.02, 0.03, 0.04 or 0.05.

[0041] The "diffraction peak intensity ratio" herein has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be obtained by performing phase and crystal structure analysis using an automated X-ray diffractometer at an operating voltage of 40 kV, an operating current of 250 mA, continuous scanning at a scan rate of 4° / min, a step size of 0.02°, and a scanning angle range of 10°-80°.

[0042] In some embodiments, the mass fraction of the lithium-containing metal oxide in the lithium supplement agent is 0.01%-0.1%, and / or the mass fraction of the carbon material in the lithium supplement agent is 0.01%-0.5%.

[0043] As an example, the mass fraction of the lithium-containing metal oxide in the lithium supplement may be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%.

[0044] When the mass fraction of the lithium-containing metal oxide in the lithium supplement is within the above range, the lithium-containing metal oxide in the coating layer can take advantage of its ultra-high ion conductivity and inhibit the reaction of the core with moisture, carbon dioxide, etc., thereby preventing the formation of an impurity layer on the surface of the core.

[0045] As an example, the mass fraction of the carbon material in the lithium supplement may be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0046] When the mass fraction of the carbon material in the lithium supplement agent is within the above range, the carbon material in the coating layer can effectively improve the conductivity of the coating layer, thereby improving the surface electronic conductivity of the lithium supplement agent, improving the transmission channels of lithium ions and electrons of the lithium supplement agent, and having little effect on the lithium supplement capacity of the lithium supplement agent.

[0047] In some embodiments, the unit cell parameters of the core satisfy a=b, a≠c, wherein c / a is 2 to 3. This can increase the lithium ion migration rate of the lithium supplement.

[0048] As an example, c / a can be 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.

[0049] When the unit cell parameters of the inner core satisfy a=b, a≠c, the inner core is a hexagonal crystal system. The characteristic symmetry of the hexagonal crystal system determines that the basis vector characteristics corresponding to the hexagonal crystal cell are that the two minor axes are perpendicular to the main axis, the two minor axis basis vectors are equal in size, and the angle between the minor axes is 120°, that is, its unit cell parameters are a=b≠c, α=β=90°, γ=120°. At this time, the unit cell is a layered structure. Then, by matching elements with different chemical valence states and designing unbalanced charges in the transition metal layer, it is helpful to form lithium ion layer vacancies, thereby realizing rapid transport and efficient utilization of lithium ions.

[0050] In some embodiments, a is 0.4 nm to 0.7 nm, and c is 1.4 nm to 1.6 nm. This can further increase the lithium ion migration rate of the lithium supplement.

[0051] As an example, a may be 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, 0.65 nm, or 0.7 nm.

[0052] As an example, c may be 1.4 nm, 1.45 nm, 1.5 nm, 1.55 nm, or 1.6 nm.

[0053] The "lattice parameter" in this application has a well-known meaning in the art and can be measured using instruments and methods well-known in the art. For example, the lattice parameter can be obtained by X-ray diffraction testing.

[0054] In some embodiments, the core has a Dv50 particle size of 1 μm to 10 μm, and / or the coating layer has a thickness of 50 nm to 500 nm. Thus, the coating layer can improve the storage performance and conductivity of the lithium supplement, thereby helping the lithium supplement to fully exert its lithium supplementation capacity.

[0055] As an example, the Dv50 particle size of the core can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm.

[0056] As an example, the thickness of the coating layer may be 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0057] In some embodiments, the core comprises Li8Zr 0.9 W 0.1 O6、Li7Nb 0.8 Ta 0.2 O6、Li7Sb 0.9 Ta0.1 O6、Li7Ru 0.7 W 0.2 Ce 0.1 O6、Li8Sn 0.9 Ca 0.1 O6、Li8Hf 0.7 W 0.2 Ca 0.1 O6、Li8Ir 0.6 W 0.2 Ce 0.2 O6、Li8Pr 0.5 W 0.3 Ca 0.2 O6、Li8Pt 0.7 W 0.2 Ca 0.1 At least one of O6. Thus, the lithium replenishing capacity of the lithium replenishing agent can be effectively increased and the decomposition potential of the lithium replenishing agent can be reduced.

[0058] When the core of the lithium supplement agent includes the aforementioned substances, the core has a higher lithium supplement capacity and a higher lithium supplement agent capacity.

[0059] As an example, Li8Zr 0.9 W 0.1 The theoretical capacity of O6 is 883mAh / g, Li7Nb 0.8 Ta 0.2 The theoretical capacity of O6 is 790mAh / g, Li7Sb 0.9 Ta 0.1 The theoretical capacity of O6 is 704mAh / g, Li7Ru 0.7 W 0.2 Ce 0.1 The theoretical capacity of O6 is 764mAh / g, Li8Sn 0.9 Ca 0.1 The theoretical capacity of O6 is 793mAh / g, Li8Hf 0.7 W 0.2 Ca 0.1 The theoretical capacity of O6 is 650mAh / g, Li8Ir 0.6 W 0.2 Ce 0.2 The theoretical capacity of O6 is 624mAh / g, Li8Pr 0.5 W 0.3 Ca 0.2 The theoretical capacity of O6 is 733mAh / g, Li8Pt 0.7 W 0.2 Ca 0.1 The theoretical capacity of O6 is 619 mAh / g.

[0060] In some embodiments, the graphitization degree of the carbon material is greater than or equal to 60%, thereby further improving the conductivity of the lithium supplement.

[0061] When the graphitization degree of the carbon material is within the aforementioned range, the closer the internal structure of the carbon material is to ideal graphite, the better the conductive performance.

[0062] In the second aspect of the present application, the present application proposes a method for preparing the aforementioned lithium supplement, thereby, the aforementioned lithium supplement with better lithium supplement performance can be prepared by a simple method. Specifically, the method for preparing the lithium supplement may include:

[0063] S100: The lithium source, M1 source, and M2 source are subjected to a first sintering treatment in an oxygen-containing atmosphere.

[0064] In some embodiments, in this step, the M1 and M2 sources are mixed evenly with the lithium source according to the amount ratio of the substance in the chemical formula, and sintered in an oxygen-containing atmosphere to obtain a lithium ion battery having the chemical formula Li x M1 y M2 1-y O6 lithium supplement core, where 6≤x≤8, 0 <y<1。

[0065] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxide.

[0066] In some embodiments, the M1 source includes at least one of an oxide of M1, a chloride of M1, a nitrate of M1, and a hydroxide of M1.

[0067] In some embodiments, the M2 source includes at least one of an oxide of M2, a chloride of M2, a nitrate of M2, and a hydroxide of M2.

[0068] In some embodiments, the temperature of the first sintering treatment is 700° C.-1200° C., and the time of the first sintering treatment is 8 hours-24 hours, thereby facilitating the acquisition of pure-phase core particles with a moderate particle size.

[0069] As an example, the temperature of the first sintering process may be 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C.

[0070] As an example, the time of the first sintering process may be 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0071] When the temperature and time of the first sintering treatment are within the aforementioned range, it is conducive to the formation of a hexagonal phase structure core, and the physical phase structure is highly stable, with less impurities, and the particle size of the formed core particles is moderate.

[0072] In some embodiments, the oxygen-containing atmosphere can be an oxygen-containing atmosphere such as oxygen or air.

[0073] S200: The core, M source and carbon source are subjected to a second sintering process in an inert atmosphere.

[0074] In some embodiments, in this step, the M source is uniformly mixed with the core, and then mixed with the carbon source, and then sintered under an inert atmosphere to form a coating layer on at least a portion of the surface of the core to obtain the lithium supplement.

[0075] In some embodiments, the M source includes at least one of zirconium propoxide, zirconium oxide, zirconium nitrate, zirconyl chloride, lithium zirconate, zirconium chloride, titanium oxide, titanium tetrachloride, titanium nitrate, and titanium alkoxide.

[0076] In some embodiments, the carbon source includes at least one of glucose, starch, sucrose, and graphite, thereby facilitating the formation of lithium-containing metal oxide on the surface of the core.

[0077] In some embodiments, the temperature of the second sintering treatment is 400° C.-800° C., and the time of the second sintering treatment is 6 hours-10 hours, thereby facilitating the formation of lithium-containing metal oxide and carbon material in the coating layer.

[0078] As an example, the temperature of the second sintering process may be 400°C, 500°C, 600°C, 700°C, or 800°C.

[0079] As an example, the time of the second sintering process may be 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0080] When the temperature and time of the second sintering treatment are within the aforementioned range, it is helpful to form a tetragonal lithium-containing metal oxide and a carbon material with a high degree of graphitization, and the phase structure is more stable and carbon loss is less.

[0081] In some embodiments, an inert atmosphere is employed during the second sintering process to form the coating layer. This effectively reduces the reaction between the carbon source and the active atmosphere, thereby mitigating carbon loss. For example, a carbon source may be oxidized in an active atmosphere, such as an oxygen-containing atmosphere, to generate carbon dioxide or carbon monoxide gas, which then escapes, causing carbon loss.

[0082] As an example, the inert atmosphere may include a non-oxygen-containing, non-hydrogen-containing atmosphere such as nitrogen or argon.

[0083] In some embodiments, the process further includes mixing the core, the M source, and the carbon source in a solvent and performing a drying process before the second sintering process. This allows the core, the carbon source, and the M source to be fully dispersed in the solvent, facilitating a more uniform mixing of the core, the M source, and the carbon source. Subsequently, the solvent is removed by drying, thereby improving the coating uniformity of the coating layer.

[0084] In some embodiments, the solvent includes at least one of ethanol and isopropanol.

[0085] In some embodiments, the drying process comprises at least one of spray drying, freeze drying, and flash drying.

[0086] In a third aspect of the present application, a positive electrode slurry is provided, comprising the aforementioned lithium supplement, or a lithium supplement prepared using the aforementioned method. Thus, the positive electrode slurry has all the features and advantages of the aforementioned lithium supplement and method for preparing the lithium supplement, and no further details are given here.

[0087] In some embodiments, the viscosity of the positive electrode slurry is 1000 mPa·s-8000 mPa·s, which is beneficial for improving the processing performance of the positive electrode slurry.

[0088] By forming a coating layer on the surface of the lithium supplement agent core, the influence of the alkaline surface of the core on the stability of the slurry is effectively suppressed. When the lithium supplement agent is added to the positive electrode slurry, the strong alkaline surface of the lithium supplement agent will not cause lithium precipitation reaction, thereby effectively alleviating the significant increase in the viscosity of the positive electrode slurry caused by the increase in the alkalinity of the positive electrode slurry, which helps the positive electrode slurry meet the coating requirements.

[0089] As an example, the positive electrode material, lithium supplement, solvent (such as N-methylpyrrolidone), binder (such as polyvinylidene fluoride), and conductive agent (such as carbon black, acetylene black) can be mixed in a mass ratio of 90:2:100:4:4 to obtain the positive electrode slurry.

[0090] In a fourth aspect, the present application provides a battery comprising a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located at least on one side of the positive electrode current collector, wherein the positive electrode active material layer is prepared using the aforementioned positive electrode slurry. Thus, the battery has all the features and advantages of the aforementioned positive electrode slurry, which will not be further elaborated here.

[0091] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0092] Example 1

[0093] (1) Lithium carbonate (lithium source), zirconium dioxide (M1 source), and tungsten oxide (M2 source) were mixed uniformly in a high-speed mixer at a molar ratio of Li:Zr:W=8:0:9:0:1, and sintered at 900°C for 10 h in an air atmosphere to obtain Li8Zr 0.9 W 0.1 The core of O6.

[0094] (2) The zirconium propoxide (M source) and the aforementioned core were weighed in a molar ratio of Zr:W=1:10, and mixed to obtain a first mixture. The first mixture was weighed and mixed with glucose (carbon source) in a mass ratio of 99:1 to obtain a second mixture. The second mixture was added to pure water at a solid content of 50% to obtain a mixture. The mixture was sand-milled at a speed of 2500 rpm for 1 hour in a sand mill, and the obtained mixed slurry was dried in a spray dryer to obtain a powder. The powder was sintered at 800°C in a nitrogen atmosphere to finally obtain a coating layer containing Li2ZrO3 and carbon material, and the core was Li8Zr 0.9 W 0.1 O6 lithium supplement.

[0095] Examples 2-16 and Comparative Examples 1-6 are consistent with Example 1, and the differences are shown in Table 1. In Comparative Example 3, no M2 source is added when the inner core is formed, no M1 source is added when the inner core is formed in Comparative Example 4, no M source is added when the coating layer is formed in Comparative Example 5, and no carbon source is added when the coating layer is formed in Comparative Example 6.

[0096] Table 1

[0097] The parameters of the lithium supplement agents in the aforementioned examples and comparative examples are shown in Table 2:

[0098] Table 2

[0099] The lithium supplement agents in the aforementioned examples and comparative examples were prepared into button batteries, and the preparation method was as follows:

[0100] A lithium supplement material, a conductive agent (acetylene black), and a binder (polyvinylidene fluoride) were mixed in a mass ratio of 90:5:5, coated onto aluminum foil, and dried. The positive electrode was then stamped using a pressure of 100 MPa to form a 12 mm diameter, 120 μm thick electrode. A lithium metal sheet with a diameter of 17 mm and a thickness of 1 mm was used as the negative electrode. A 25 μm thick Celgard 2400 porous membrane was used as the separator. The electrolyte used was 1 mol / L LiPF6, with an equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) as the solvent. The positive electrode, separator, negative electrode, and electrolyte were assembled into 2025-type button cells in an argon glove box with water and oxygen concentrations below 5 ppm.

[0101] The button cells in the aforementioned embodiments and comparative examples were tested as follows. The test results are shown in Table 2:

[0102] Decomposition potential and charge / discharge capacity: The assembled button cell is tested at 3.0V-4.9V and 0.1C rate. The charge specific capacity, discharge specific capacity, and discharge specific energy are read from the test software. The decomposition potential of the lithium supplement agent = discharge specific energy / discharge specific capacity.

[0103] Lithium ion migration rate of the lithium supplement: The assembled button cell is subjected to EIS (Electrochemical Impedance Sensor) testing in an electrochemical workstation, and the lithium ion migration rate of the lithium supplement is obtained from the slope of the straight line segment of the electrochemical impedance graph.

[0104] Table 3

[0105] Test results demonstrate that the coating on the surface of the lithium supplement in Examples 1-16 effectively reduces the increase in positive electrode slurry viscosity caused by the alkalinity of the core surface during use, resulting in excellent processing performance. The lithium supplement exhibited a high initial charge capacity, indicating sufficient lithium ion release during charging. The initial discharge capacity was low, indicating that fewer lithium ions were reinserted into the supplement during discharge, resulting in a better in-situ pre-lithiation effect for lithium batteries.

[0106] Figure 1 is a scanning electron micrograph of the lithium supplement in Example 1, showing a coating layer on the surface of the core. Figure 2 shows that the S1 / S2 ratio of the lithium supplement in Example 1 is 0.03, while the S1 / S2 ratio of the lithium supplement in Comparative Example 5 is 0. Figure 3 is the charge and discharge curve of the button cell in Example 1.

[0107] In Comparative Example 1, the coating layer of the lithium supplement agent contained too little tetragonal lithium-containing metal oxide, which significantly increased the viscosity of the positive electrode slurry. In Comparative Example 2, the coating layer of the lithium supplement agent contained too little tetragonal lithium-containing metal oxide, which significantly increased the viscosity of the positive electrode slurry. The tetragonal lithium-containing metal oxide contained more tetragonal lithium-containing metal oxide, which lowered the viscosity of the positive electrode slurry, but also significantly reduced the lithium supplement capacity of the lithium supplement agent. In Comparative Example 3, the core of the lithium supplement agent did not contain the M2 element, which slowed the lithium ion transmission rate of the core. The core of the lithium supplement agent did not contain the M1 element, which resulted in a low lithium supplement capacity. In Comparative Example 5, the coating layer of the lithium supplement agent did not form a tetragonal lithium-containing metal oxide, which significantly increased the viscosity of the positive electrode slurry. In Comparative Example 6, the coating layer of the lithium supplement agent did not form a carbon material, which resulted in a poor performance of the lithium supplement capacity of the lithium supplement agent.

[0108] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0109] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0110] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A lithium supplement, wherein: include: a core, said core satisfying the chemical formula Li x M1 y M2 1-y O6, where 6 ≤ x ≤ 8, 0 < y < 1, M1 is at least one of Zr, Nb, Sb, Bi, Ru, Ta, Sn, Hf, Ir, Pr, Pt, Np, and M2 is at least one of W, Ge, Ca, Ce, K, Ta; The coating layer is located at least on a portion of the surface of the core, and the coating layer includes a lithium-containing metal oxide and a carbon material, wherein the lithium-containing metal oxide satisfies the chemical formula Li a M b O c , wherein, 1.8≤a≤2, 0.7≤b≤1.1, 2.8≤c≤3, M includes Ti and / or Zr, The diffraction peak intensity of the lithium supplement agent to X-rays within a 2θ diffraction angle of 20.1°-20.3° is S1, the diffraction peak intensity of the lithium supplement agent to X-rays within a 2θ diffraction angle of 17°-17.3° is S2, and S1 / S2 is 0.02-0.

05.

2. The lithium supplement according to claim 1, wherein The mass fraction of the lithium-containing metal oxide in the lithium supplement agent is 0.01%-0.1%, and / or the mass fraction of the carbon material in the lithium supplement agent is 0.01%-0.5%.

3. The lithium supplement according to claim 1, wherein The unit cell parameters of the core satisfy a=b, a≠c, wherein c / a is 2-3.

4. The lithium supplement according to claim 3, wherein a is 0.4nm-0.7nm, and c is 1.4nm-1.6nm.

5. The lithium supplement according to any one of claims 1 to 4, wherein: The Dv50 particle size of the core is 1 μm-10 μm, and / or the thickness of the coating layer is 50 nm-500 nm.

6. The lithium supplement according to any one of claims 1 to 4, wherein: The core includes Li8Zr 0.9 W 0.1 O6、Li7Nb 0.8 Ta 0.2 O6、Li7Sb 0.9 Ta 0.1 O6、Li7Ru 0.7 W 0.2 Ce 0.1 O6、Li8Sn 0.9 Ca 0.1 O6、Li8Hf 0.7 W 0.2 Ca 0.1 O6、Li8Ir 0.6 W 0.2 Ce 0.2 O6、Li8Pr 0.5 W 0.3 Ca 0.2 O6、Li8Pt 0.7 W 0.2 Ca 0.1 At least one of O6.

7. The lithium supplement according to any one of claims 1 to 4, wherein: The graphitization degree of the carbon material is greater than or equal to 60%.

8. A method for preparing the lithium supplement according to any one of claims 1 to 7, wherein: include: Performing a first sintering treatment on the lithium source, the M1 source, and the M2 source in an oxygen-containing atmosphere to obtain a core; The core, the M source, and the carbon source are subjected to a second sintering treatment under an inert atmosphere to form a coating layer on at least a portion of the surface of the core, thereby obtaining the lithium supplement agent.

9. The method according to claim 8, wherein The lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxide; and / or, The M1 source includes at least one of an oxide of M1, a chloride of M1, a nitrate of M1, and a hydroxide of M1; and / or, The M2 source includes at least one of the oxide of M2, the chloride of M2, the nitrate of M2, the hydroxide of M2, and the like. A sort of.

10. The method according to claim 9, wherein: The temperature of the first sintering treatment is 700° C.-1200° C., and the time of the first sintering treatment is 8 hours-24 hours.

11. The method according to any one of claims 8 to 10, wherein: The M source includes at least one of zirconium propoxide, zirconium oxide, zirconium nitrate, zirconyl chloride, lithium zirconate, zirconium chloride, titanium oxide, titanium tetrachloride, titanium nitrate, and titanium alkoxide; and / or, The carbon source includes at least one of glucose, starch, sucrose and graphite.

12. The method according to claim 11, wherein The temperature of the second sintering treatment is 400° C.-800° C., and the time of the second sintering treatment is 6 hours-10 hours.

13. The method according to claim 8, wherein Also includes: Before the second sintering process, the core, the M source, and the carbon source are mixed in a solvent and dried.

14. The method according to claim 13, wherein: The solvent includes at least one of ethanol and isopropanol; and / or, The drying process includes at least one of spray drying, freeze drying, and flash drying.

15. A positive electrode slurry, wherein: The lithium supplement comprises the lithium supplement according to any one of claims 1 to 7, or the lithium supplement prepared by the method according to any one of claims 8 to 14.

16. The positive electrode slurry according to claim 15, wherein: The viscosity of the positive electrode slurry is 1000 mPa·s-8000 mPa·s.

17. A battery, wherein: The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer at least located on one side of the positive electrode current collector, wherein the positive electrode active material layer is prepared by using the positive electrode slurry according to claim 15 or 16.

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