WO2023134589A1 - Positive electrode lithium supplementing agent, and preparation method therefor and use thereof - Google Patents

Abstract

The embodiments of the present application provide a positive electrode lithium supplementing agent, comprising a particle body, wherein the particle body comprises a lithium compound of a sulfoselenide of a transition metal, and the average chemical formula of the lithium compound of a sulfoselenide of a transition metal is LixMSySe2-y, where 1 < x ≤ 4, 0 < y < 2, and M represents the transition metal. When active lithium ions are de-intercalated from the positive electrode lithium supplementing agent, the decomposition voltage is low and no gas is produced, a high lithium supplementing capacity can be provided, and the delithiated product does not affect the performance of a positive electrode of a battery. The embodiments of the present application further provide a method for preparing the positive electrode lithium supplementing agent, a positive electrode sheet of a battery, an electrochemical battery, and an electronic device.

Description

Positive electrode lithium supplement and its preparation method and application

This application claims the priority of the Chinese patent application with the application number 202210031227.7 and the application title "Positive electrode lithium supplement and its preparation method and application" submitted to the China Patent Office on January 12, 2022, the entire content of which is incorporated by reference in this application.

technical field

The embodiment of the present application relates to the field of battery technology, in particular to a positive electrode lithium supplement and its preparation method and application.

Background technique

With the development of economy and technology, industries such as portable electronic devices (mobile phones, tablet computers, notebook computers, etc.), drones, and electric vehicles are in urgent need of energy storage devices with higher energy density and longer cycle life. In order to make lithium-ion batteries, an energy storage device, meet the above requirements, the industry usually takes measures to pre-add lithium-supplementing agents that can provide active lithium to the lithium-ion battery system to compensate for the irreversible effect of the negative electrode on the active lithium during the first charging process of the battery. loss.

At present, the solutions for replenishing lithium for batteries can be mainly divided into positive electrode lithium replenishment and negative electrode lithium replenishment. The negative electrode lithium supplement material itself has great safety hazards, and it is difficult to be compatible with the preparation process of the negative electrode sheet, which hinders its commercial application. Although the common positive electrode lithium supplement materials are usually compatible with the preparation process of the positive electrode sheet, they still cannot meet the requirements of high lithium supplement capacity, low gas production, and low residue side effects.

Contents of the invention

In view of this, the embodiment of the present application provides a positive electrode lithium supplementing agent, which has a low delithiation decomposition voltage and high lithium supplementation capacity, and does not produce gas when it delithiates active lithium ions, and the ionic conductivity of the delithiated product is high, which does not affect The performance of the positive electrode of the battery.

Specifically, the first aspect of the embodiment of the present application provides a positive electrode lithium supplement agent, the positive electrode lithium supplement agent includes a particle body, the particle body includes a lithiated transition metal sulfur selenide, and the transition metal sulfur selenide The average chemical formula of lithium selenide is Li _x MS _y Se _2-y , wherein 1<x≤4, 0<y<2, and M represents a transition metal.

The positive electrode lithium replenishing agent has good conductivity, its delithiation decomposition voltage is low, and it can be decomposed in the formation stage of the battery cell to produce more active lithium ions (that is, the actual lithium replenishment capacity is high), which can supplement the battery in the first charge. The irreversible consumption of active lithium by the negative electrode in the process is beneficial to improve the energy density and cycle performance of the battery; in addition, it does not produce gas during delithiation, and the solid residue after delithiation has high ion conductivity, which will not increase the cell impedance , does not affect the rate performance of the battery. Therefore, the positive electrode lithium replenishing agent can supplement the loss of active lithium for the battery without affecting other performances of the battery, and better improve the energy density of the battery.

In the embodiment of the present application, the particle body includes a compound of the general formula Li _x MS _y Se _2-y , as well as M, Li ₂ S and Li ₂ Se. Among them, M, Li ₂ S and Li ₂ Se can be obtained by partial decomposition of the compound Li _x MS _y Se _2-y . Different from M, Li ₂ S and Li ₂ Se that are simply mixed, these substances in the positive lithium replenishing agent are closely combined at this time. If they are in nanometer-level contact, they can release lithium ions during the formation stage of the battery and transform into transition The metal sulfur selenium compound can avoid the decomposition and gas generation of Li ₂ S in the simple mixture of M, Li ₂ S and Li ₂ Se.

In some embodiments of the present application, the particle body further includes a compound having the general formula LiMS _y Se _2-y . The structural stability of LiMS _y Se _2-y is high.

In the embodiments of the present application, M may include one or more of Cr, Ti, V, Co, Fe, Ni, Mn, and Nb.

In the embodiment of the present application, the surface of the particle body also has a coating layer. The presence of the coating layer can endow the positive electrode lithium supplement with good air stability and processability.

The second aspect of the embodiment of the present application also provides a preparation method of a positive electrode lithium supplement, including:

Mixing transition metal sources, sulfur sources, and selenium sources, ball milling and sintering to prepare transition metal sulfoselenides;

The sulfoselenide compound of the transition metal is lithiated to obtain a positive electrode lithium supplement; wherein, the positive electrode lithium supplement includes a particle body, and the particle body includes a lithium compound of a transition metal sulfur selenide, and the transition metal The average chemical formula of the lithiated sulfur selenide is Li _x MS _y Se _2-y , where 1<x≤4, 0<y<2, and M represents a transition metal.

The preparation method of the positive electrode lithium supplement provided in the second aspect of the embodiment of the present application has a simple process, high efficiency and environmental protection, and can be produced on a large scale.

The third aspect of the embodiment of the present application also provides a battery positive pole piece, the battery positive pole piece contains the positive lithium replenishing agent as described in the first aspect of the embodiment of the present application. The electrode sheet containing the positive electrode lithium supplement can be used to provide an electrochemical battery with high energy density and long cycle life.

In some embodiments of the present application, the positive electrode sheet of the battery includes a current collector and a positive electrode material layer disposed on the current collector, and the positive electrode material layer includes a positive electrode active material, as described in the first aspect of the embodiment of the present application. Positive electrode lithium supplement, and binder. In the production process of the positive electrode sheet of the battery, the introduction of the above-mentioned positive electrode lithium supplementing agent will not cause the positive electrode slurry forming the positive electrode material layer to jelly, and it is easier to coat to obtain a film layer with high flatness.

In some embodiments of the present application, the positive electrode sheet of the battery includes a current collector, a positive electrode material layer and a lithium replenishing agent layer sequentially arranged on the current collector, wherein the positive electrode material layer contains a positive electrode active material, a binder and a conductive agent, the lithium supplementing agent layer contains the positive electrode lithium supplementing agent, a binder and a conductive agent.

The fourth aspect of the embodiment of the present application also provides an electrochemical cell, including a positive electrode, a negative electrode, a separator and an electrolyte between the positive electrode and the negative electrode, wherein the positive electrode is the The positive electrode sheet of the battery described in the third aspect of the application embodiment. The electrochemical cell has high energy density and long cycle life.

The fifth aspect of the embodiment of the present application further provides an electronic device, and the electronic device includes the electrochemical cell as described in the fourth aspect of the embodiment of the present application.

The electronic equipment may be various consumer electronic products, such as mobile phones, tablet computers, notebook computers, smart wearable products, etc., and may also be mobile devices, such as electric vehicles.

Description of drawings

Fig. 1 is a schematic structural view of the electrochemical cell provided in the examples of the present application.

FIG. 2 is a schematic structural view of the positive electrode sheet of the battery provided in an embodiment of the present application.

Fig. 3 is a schematic structural diagram of a positive electrode sheet of a battery provided in another embodiment of the present application.

FIG. 4 is a schematic structural diagram of an electronic device provided by an embodiment of the present application.

FIG. 5 is another schematic structural diagram of an electronic device provided by an embodiment of the present application.

Fig. 6 shows the X-ray diffraction (XRD) characterization results of the positive lithium supplement Li _x CrSSe and its precursor CrSSe in Example 1 of the present application.

FIG. 7 is the charge-discharge curve of the first cycle of the half-cell in Example 1 of the present application.

Fig. 8 is the charge-discharge curve of the first cycle of the half-cell of Comparative Example 1.

FIG. 9 is the charge-discharge curve of the half-cell of Comparative Example 2 (ie, a simple LiFePO ₄ button cell).

Fig. 10 is the charge and discharge curve of the half-cell of Example 2 (a button cell in which LiFePO ₄ is mixed with a positive electrode lithium supplement).

Detailed ways

Embodiments of the present application are described below with reference to the drawings in the embodiments of the present application.

As shown in FIG. 1 , FIG. 1 is a schematic structural diagram of an electrochemical cell 100 provided in an embodiment of the present application, and the electrochemical cell 100 may specifically be a lithium secondary battery. The lithium secondary battery includes a positive electrode 101, a negative electrode 102, a separator 103, an electrolyte 104, and corresponding communication accessories and circuits. Among them, the positive electrode 101 and the negative electrode 102 can deintercalate active metal ions (for lithium secondary batteries, the active metal ions are lithium ions) to realize energy storage and release: driven by an external circuit, the active metal ions are extracted from the positive electrode, Migrate to the negative electrode through the electrolyte 104 and the separator 103 to realize battery charging; when an external electrical load is connected, the active metal ions escape from the negative electrode and migrate back to the positive electrode to carry out the discharge process.

All the active lithium in a Li-ion battery is provided by the cathode material. However, during the first charging process of lithium-ion batteries, the formation of solid electrolyte interphase (SEI film) on the surface of the negative electrode and other chemical side reactions in the subsequent charge-discharge cycle will consume active lithium ions, resulting in the reversible capacity of the battery. loss and decrease in energy density. In order to improve the energy density of lithium-ion batteries, a common solution in the industry is to add lithium supplements to the positive electrode of the battery. Commonly used positive lithium supplements generally include binary lithium-containing compounds, ternary lithium-containing compounds, or organic lithium salts, etc. . Among them, Li ₂ NiO ₂ , Li ₆ CoO ₄ and other ternary lithium-containing compounds have low theoretical lithium supplement capacity, and the ion and electronic conductivity of the residue after lithium supplement is poor, which is not conducive to the performance of battery rate performance. Lithium oxalate (Li ₂ C ₂ O ₄ ), Li ₂ C ₃ O ₅ and other organolithium salts have moderate theoretical specific capacity, but their prominent disadvantages are high decomposition voltage and limited actual lithium supplementation capacity. Li ₂ O, LiF, Li ₂ S, Li ₃ N and other binary lithium-containing compounds have high theoretical specific capacity, but due to their own poor electronic conductivity, their decomposition voltage is also high, and the gas produced by their decomposition It will affect the cycle performance and safety performance of the battery. In view of this, the embodiment of the present application provides a positive electrode lithium supplement that can take into account the properties of good conductivity, low decomposition voltage, high lithium supplement capacity, and no gas production during delithiation.

Specifically, the positive electrode lithium supplement agent provided in the embodiment of the present application, the positive electrode lithium supplement agent includes a particle body, the particle body includes a lithium compound of a transition metal sulfur selenide, and the average chemical formula of the transition metal sulfur selenide lithium compound is Li _x MS _y Se _2-y , wherein, 1<x≤4, 0<y<2, and M represents a transition metal.

The positive electrode lithium replenishing agent has good conductivity, its delithiation decomposition voltage is low, and it can be decomposed in the formation stage of the battery cell to produce more active lithium ions (that is, the actual lithium replenishment capacity is high), which can supplement the battery in the first charge. The irreversible consumption of active lithium by the negative electrode in the process is conducive to improving the energy density and cycle performance of the battery. In addition, the delithiation reaction formula of the cathode lithium supplement is: Li _x MS _y Se _2-y -e ^- → MS _y Se _2-y +xLi ⁺ . The lithium replenishing agent does not produce gas during delithiation, thus avoiding various gas production problems (for example, it is not necessary to increase the volume of the vent bag in the battery manufacturing process, and it also avoids the gas generated by the delithiation of common positive electrode lithium supplements. Partially dissolved in the electrolyte to increase the degree of side reactions in the electrolyte), and the residue after removing the active lithium is mainly the transition metal sulfur selenium compound MS _y Se _2-y , which has high ion conductivity and will not Increasing the impedance of the cell will not affect the rate performance of the battery, nor will it increase the risk of electrolyte gas production. Therefore, the positive electrode lithium replenishing agent can supplement the loss of active lithium for the battery without affecting other performances of the battery, and better improve the energy density of the battery.

In the present application, in the particle body, the molar ratio of Li element to M element is in the range of greater than 1-4. That is, the value range of x is: 1<x≤4. At this time, the lithium supplementing capacity of the particle body of the positive electrode lithium supplementing agent is relatively high. In some embodiments, x can be 2, 2.5, 3, 3.5 or 4, etc. In some embodiments of the present application, y may be 0.2, 0.5, 1, 1.5, 1.8, etc.

In the present application, the particle body can be obtained by lithiation of transition metal sulfoselenide. In some embodiments of the present application, the particle body includes a compound of the general formula Li _x MS _y Se _2-y .

In some embodiments of the present application, the particle body includes a compound of the general formula Li _x MS _y Se _2-y , and M, Li ₂ S and Li ₂ Se. Among them, M, Li ₂ S and Li ₂ Se can be obtained by partial decomposition of Li _x MS _y Se _2-y . In the present application, regardless of whether Li _x MS _y Se _2-y is partially decomposed or not decomposed, the average chemical formula of the particle body is Li _x MS _y Se _2-y .

Different from M, Li ₂ S and Li ₂ Se that are simply mixed, these substances in the positive electrode lithium replenishing agent are closely combined at this time, such as nano-level contacts, M, Li ₂ S and Li ₂ Se can be used in the battery cell In the formation stage, lithium ions are removed and transformed into sulfur-selenium compounds of transition metals. The delithiation reaction formula is: M+Li ₂ Se+Li ₂ S-4e ^- →MS _y Se _2-y +4Li ⁺ . It can be seen that even if Li _x MS _y Se _2-y is decomposed to a certain extent, its decomposition products can still undergo the delithiation reaction together without producing gas, avoiding the Li ₂ S, or the simple physical mixture of M and Li ₂ S In the mixture with Li ₂ Se, Li ₂ S decomposes to produce gas, and correspondingly avoids the problem that the SO ₂ and other gases generated by the decomposition of Li ₂ S affect the cycle and safety performance of the battery.

In some embodiments of the present application, the particle body further includes a compound having the general formula LiMS _y Se _2-y . The compound LiMS _y Se _2-y has high structural stability and can also contribute a certain lithium supplementary capacity. At this time, the particle body includes a compound of the general formula Li _x MS _y Se _2-y (x≠1), as well as M, Li ₂ S and Li ₂ Se, and the compound LiMS _y Se _2-y . Wherein, the compound LiMS _y Se _2-y is transformed by the compound (x≠1) of Li _x MS _y Se _2-y .

In the present application, M is selected from transition metal elements. In the embodiment of the present application, M may include one or more of chromium Cr, titanium Ti, vanadium V, cobalt Co, iron Fe, nickel Ni, manganese Mn, and niobium Nb, but is not limited thereto. When the expression "multiple" is involved in the present application, "multiple" means two or more.

In some embodiments of the present application, the surface of the particle body also has a doping layer. This doping layer may comprise the material of the particle body, but doping elements have been introduced therein. Exemplarily, the doped layer may contain a Li _x MS _y Se _2-y compound containing a doping element. Wherein, the doping element can be a non-metallic element, such as one or more of nitrogen N, phosphorus P, carbon C, boron B; it can also be a transition metal element/metal element different from M, such as molybdenum Mo, tungsten One or more of W, zirconium Zr, silver Ag, copper Cu, tin Sn, antimony Sb, aluminum Al, magnesium Mg, calcium Ca, etc.; of course, co-doping of the above two types of elements is also possible. The presence of doping elements can further improve the structural stability of the compound Li _x MS _y Se _2-y , ensure its good stability in air, and facilitate its smooth addition to the positive electrode system. In some embodiments, the doping elements are preferably the above-mentioned non-metallic elements.

In some embodiments of the present application, the surface of the particle body also has a coating layer. Wherein, the material of the coating layer may be a material with ion conductivity, so that it will not affect the release of active lithium in the subsequent particle body. In some embodiments, the surface of the particle body may include the above-mentioned doped layer and cladding layer in sequence. Specifically, the material of the cladding layer may include at least one of inorganic carbon materials, organic polymers, inert oxides, and the like. The coating layer material has good stability in the air, is not easy to absorb water or oxygen, etc., and is not highly alkaline. The positive electrode lithium supplement agent with the coating layer can have good air stability and processability, and the positive electrode supplement After the particle body of the lithium agent is delithiated, the remaining coating layer material will not increase the risk of gas production in the battery electrolyte.

Specifically, for the inorganic carbon material, one or more of graphite, graphene, carbon nanotube, carbon fiber, carbon black, pyrolytic carbon, etc. can be cited, but not limited thereto. For organic polymers, examples include parylene and its derivatives, polyacrylates such as polymethyl methacrylate (PMMA), polyolefins such as polyethylene (PE), and polystyrene; for inert oxides, examples include Silica, oxides of metal elements from the first main group to the third main group (such as alumina, magnesia, barium oxide, etc.), non-catalytically active transition metal oxides (such as titanium dioxide, zinc oxide, zirconia, tin, etc.). Wherein, when the coating layer is an inorganic carbon material, the conductivity of the positive electrode lithium supplementing agent can also be improved. Most of the cladding layers can be formed by mixing the raw materials of the cladding layer materials with the positive electrode lithium replenishing agent and then performing heat treatment.

In the embodiment of the present application, the thickness of the cladding layer may be in the range of 3 nm-1000 nm, for example, may be in the range of 5 nm-500 nm. The thickness of the coating layer can be adjusted according to the size of the positive electrode lithium supplement. The appropriate thickness of the coating layer can not only ensure that the positive electrode lithium supplement has good processing performance, but also avoid the influence of excessive thickness on the timely release and increase of active lithium. battery impedance.

In some embodiments of the present application, the mass of the coating layer may account for 0.01wt%-10wt% of the mass of the positive electrode lithium supplement. The lower mass ratio enables the coating layer to have better air stability and processability in improving the positive electrode lithium supplementation agent, without reducing the lithium supplementation specific capacity of the overall material too much.

The above-mentioned positive electrode lithium supplement agent provided in the examples of the present application has a high actual lithium supplement capacity, no gas is produced after delithiation, and the residue after delithiation does not affect the performance of the positive electrode of the battery, which can well improve the energy density and cycle performance of the battery wait.

Correspondingly, the embodiment of the present application also provides a preparation method of the above-mentioned positive electrode lithium supplementing agent, the preparation method is simple in process, easy to operate, efficient and environmentally friendly, and can be produced on a large scale. The preparation method may specifically include:

S01, ball milling a transition metal source, a sulfur source, and a selenium source to obtain a mixture, and sintering the mixture to obtain a transition metal sulfur selenide;

S02, performing lithiation on the sulfur selenide compound of the transition metal to obtain a positive electrode lithium supplement; wherein, the positive electrode lithium supplement includes a particle body, and the particle body includes a lithium compound of a transition metal sulfur selenide, and the The average chemical formula of the lithiated transition metal sulfoselenide is Li _x MS _y Se _2-y , wherein 1<x≤4, 0<y<2, and M represents a transition metal.

In step S01, the transition metal source can be one or more of transition metal simple substance, oxide, hydroxide, salt, etc.; the sulfur source can be S and alkali metal sulfides (such as Li ₂ S, Na ₂ S, K ₂ S); the selenium source can be one or more of Se, Li ₂ Se, Na ₂ Se, K ₂ Se. In some embodiments of the present application, at least one of the sulfur source and the selenium source includes a corresponding compound of an alkali metal, which makes it easier to obtain the precursor of the lithium supplement agent.

The preparation of the mixture can be obtained by ball milling after mixing the transition metal source, the sulfur source and the selenium source. Wherein, the rotational speed of the ball mill may be 400-1600r/min, specifically 500, 800, 1000, 1200 or 1500r/min. A higher ball milling speed is conducive to the lattice reconstruction between the various raw materials, and facilitates the sintering to obtain the precursor-transition metal sulfur selenide compound for forming lithium supplementation agent. In some embodiments, the rotational speed of the ball mill may be 800-1500 r/min. Wherein, the time of ball milling may be 5 min-300 min, specifically 20 min, 30 min, 60 min, 120 min, 180 min, 200 min, 240 min, etc. In addition, the ball-to-material ratio in the ball milling process can be in the range of (1-30):1. Higher ball-to-material ratio can achieve better lattice reconstruction.

Among them, the sintering treatment can help the ball-milled mixture to re-grow crystals and eliminate lattice defects. Wherein, the sintering temperature may be 700-1000° C., specifically 750, 800, 850, 900 or 950° C. and the like. The holding time during sintering can be 8h-24h, specifically 10, 12, 16, 18 or 20h. The sintering treatment can be performed under an inert atmosphere, and the inert atmosphere can be argon, helium or the like. Further, since the temperature increase rate is too fast to generate greater stress on the interface between the phases, in the embodiment of the present application, the temperature increase rate is controlled at 1-5° C./min during the sintering process.

In some embodiments of the present application, the above-mentioned mixture is obtained by ball milling after mixing transition metal element, sulfur element, alkali metal sulfide, and selenium element. Further, when the alkali metal in the alkali metal sulfide is not lithium (M' is not Li), after sintering, it also includes: performing a displacement reaction with iodine simple substance to obtain a transition metal sulfur selenide compound. The reaction equations involved are:

1) M' ₂ S+(2y-1)S+2(2-y)Se+2M==2M'MS _y Se _2-y ;

2) 2M'MS _y Se _2-y + I ₂ == 2MS _y Se _2-y + 2M'I;

M' represents an alkali metal element. The unreacted elemental iodine can be washed away by solvents such as acetonitrile and acetone.

In step S02, the lithiation method includes one or more of electrochemical lithiation, organic lithiation reagent lithiation, and metal lithium lithiation. Among them, electrochemical lithiation is usually to put the material to be lithiated into a tablet and place the lithium source in the electrolyte, and separate them through a diaphragm, and the two are electrically connected through an external circuit, and the lithiation to be lithiated can be realized when the power is turned on. Lithium supplementation of materials. Among them, the lithium source is generally a self-supporting lithium plate, a lithium-coated metal sheet, or a lithium foil attached to other thin film substrates. Lithiation using an organic lithiation reagent can specifically be to place the material to be lithiated in an organic lithiation reagent, and the lithium ions in the organic lithiation reagent will come out and be embedded in the material to be lithiated to realize its lithiation. . The organic lithiation reagent is generally an aryl lithiation reagent, specifically one or more of naphthalene lithium, anthracene lithium, phenanthrene lithium, biphenyl lithium, and the like. The metal lithium used for lithiation can be one or more of lithium powder, lithium foil, molten lithium liquid, and the like. Among them, lithium powder and lithium foil are generally pressed together with the material to be lithiated, and molten lithium liquid is generally mixed with the material to be lithiated (for example, cast into the material to be lithiated) to realize the lithiation of the latter. Among them, adjusting the parameters of the lithiation process (such as lithiation time, etc.) can realize the regulation of the subscript x in the particle body of the lithium supplementing agent.

In some embodiments of the present application, after the above-mentioned lithiation, some post-processing, such as doping, surface coating, etc., can also be performed on the obtained particle body. Among them, doping and surface coating usually involve heat treatment. The surface coating of the particle body is used as an example below. After the above step S02, the following step S03 is included.

S03, mixing the particle body and the raw material for the coating layer to form a coating layer on the surface of the particle body.

Wherein, the raw material of the cladding layer can be directly selected from the cladding layer material, and can also be selected from various raw materials of the synthetic cladding layer material. If the raw materials for the synthesis of the cladding layer material are selected, the precursor of the cladding layer material is generally formed on the surface of the particle body of the positive electrode lithium supplementing agent, and further heat treatment is required to promote the transformation of the precursor into the cladding layer material, and improve the bonding force with the particle body. The method for forming the coating layer includes one or more of ball milling, mechanical stirring, mechanical fusion, coating, spray drying, vapor deposition, and thermal decomposition. Wherein, the coating method may specifically include one or a combination of drip coating, brush coating, spray coating, dip coating, blade coating, and spin coating. Vapor deposition methods include physical vapor deposition (such as vapor deposition, magnetron sputtering, vacuum thermal deposition, etc.), chemical vapor deposition, atomic layer deposition, and the like. The construction method of the cladding layer can be selected according to the specific material.

The cladding material is as described earlier in this application. Among them, inorganic carbon materials such as graphite, carbon nanotubes, and carbon fibers are suitable for coating by ball milling, and appropriate heat treatment can also be performed after ball milling. The cladding layer made of pyrolytic carbon is especially suitable for construction by thermal decomposition. Specifically, the organic carbon source can be mixed with the positive electrode lithium supplement (for example, grinding, or a gaseous carbon source) for heat treatment to make the organic carbon The source heat decomposes into an inorganic conductive carbon layer. Organic polymers can be coated by coating method, spray drying method, etc. Some organic polymers (such as parylene and its derivatives) are more suitable to be constructed by chemical vapor deposition with high density and good adhesion cladding. The inert oxide can be coated by coating method, spray drying method, vapor deposition method, etc.

The embodiment of the present application also provides a battery positive pole piece, the battery positive pole piece contains the above-mentioned positive electrode lithium replenishing agent in the embodiment of the present application. The positive pole piece of the battery may be as shown in FIG. 2 or FIG. 3 .

In some embodiments of the present application, referring to FIG. 2, the positive electrode sheet 101 of the battery includes a current collector 1011 and a positive electrode material layer 1012' disposed on the current collector 1011. The positive electrode material layer 1012' includes a positive electrode active material, an embodiment of the present application The above-mentioned positive electrode lithium replenishing agent, and a binder. In some embodiments, the anode material layer 1012' further includes a conductive agent. The positive electrode sheet shown in FIG. 2 can be formed by coating the positive electrode slurry containing the above-mentioned positive electrode lithium supplementing agent, positive electrode active material, binder and optional conductive agent on the current collector 1011, followed by drying and pressing.

Wherein, the mass ratio of the mass of the positive lithium supplement to the sum of the mass of the positive lithium supplement and the positive active material may be 1%-10%. The appropriate mass proportion of the positive electrode lithium supplement can provide enough active lithium for the positive electrode sheet without reducing the specific capacity of the positive electrode sheet, thereby ensuring an effective increase in the energy density of the battery. In some embodiments, the mass proportion can be specifically 2%, 3%, 5%, 7.5%, 9% and so on.

In the positive electrode sheet shown in Fig. 2, the mass of the positive electrode lithium supplementing agent accounts for 0.5%-15% of the mass of the positive electrode material layer 1012'. This mass ratio can ensure that the battery made through the positive electrode sheet 101 of the battery has a higher capacity during the first charge and discharge and multiple non-first charge and discharge processes, so that the battery has a higher energy density and a longer battery life. cycle life. In some embodiments, the mass proportion may be 2%-10%, further may be 5%-10%. Wherein, the mass of the binder may account for 0.5%-10% of the mass of the positive electrode material layer 1012'. The mass of the conductive agent may account for 0.5%-10% of the mass of the positive electrode material layer 1012'.

In other embodiments of the present application, referring to FIG. 3 , the positive electrode sheet 101 of the battery includes a current collector 1011 and a positive electrode material layer 1012 and a lithium replenishing agent layer 1013 sequentially arranged on the current collector 1011, wherein the positive electrode material layer 1012 contains a positive electrode Active materials, binders, and conductive agents, and the lithium-replenishing agent layer 1013 contain the above-mentioned positive electrode lithium-replenishing agent, binder, and conductive agent in the embodiment of the present application.

The positive electrode sheet shown in FIG. 3 can be prepared by the following steps: firstly coat the conventional positive electrode slurry on the current collector 1011, dry it to form the positive electrode material layer 1012, and then coat the positive electrode material layer 1012 on the positive electrode material layer 1012. The lithium supplement layer 1013 is obtained after the slurry of the lithium agent, the battery agent and the binder is dried. It can also be understood that the positive electrode sheet provided by this embodiment is equivalent to the positive electrode sheet in the prior art plus the lithium-supplementing agent layer 1013 on its surface. As mentioned above, in the positive electrode sheet shown in FIG. 3 , the mass ratio of the mass of the positive lithium supplement to the sum of the mass of the positive lithium supplement and the positive active material can also be 1%-10%.

The above-mentioned current collector 1011 can be referred to as a positive electrode current collector, which includes but is not limited to metal foil, alloy foil or metallized film, and its surface can be etched or roughened to form a secondary structure, which is convenient for the positive electrode material layer effective contact. Exemplary metal foil materials may be aluminum foil, carbon-coated aluminum foil, or aluminized film, and exemplary alloy foil materials may be stainless steel foil, aluminum alloy foil, or carbon-coated stainless steel foil.

The above-mentioned positive electrode active material, binder, and conductive agent can be conventional choices in the field of batteries. Among them, the positive electrode active material may include but not limited to lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobaltate, lithium manganate, lithium nickel manganate, nickel cobalt manganese (NCM ), nickel cobalt aluminum (NCA), etc. at least one. Binders may specifically include, but are not limited to, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyacrylate, styrene-butadiene rubber (SBR), carboxyl One or more of sodium methylcellulose (CMC) and sodium alginate, etc. The conductive agent may specifically include, but not limited to, one or more of acetylene black, Ketjen black, Supper P conductive carbon black, graphite, graphene, carbon nanotubes, carbon fibers, amorphous carbon, and the like.

In the positive pole piece of the battery provided in the embodiment of the present application, since the above-mentioned positive lithium replenishing agent is included, the positive pole piece can be used to provide an electrochemical battery with high energy density and long cycle life.

The embodiment of the present application also provides an electrochemical battery, which includes the above-mentioned positive electrode sheet of the battery. The structure of the electrochemical cell can be as described above in FIG. 1 . The electrochemical battery may be a secondary battery, which has high cycle performance and high safety. Specifically, the secondary battery may be specifically a lithium secondary battery.

Wherein, the negative electrode 102 may include a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, a binder and an optional conductive agent. Among them, the negative electrode current collector includes but not limited to metal foil, alloy foil or metallized film, and its surface can be etched or roughened to form a secondary structure to facilitate effective contact with the negative electrode material layer. Exemplary metal foil materials may be copper foil, carbon-coated copper foil, or copper-plated film, and exemplary alloy foil materials may be stainless steel foil, copper alloy foil, and the like. The negative electrode active material includes, but is not limited to, one or more of lithium titanate, lithium metal (lithium element or lithium alloy), carbon-based materials, silicon-based materials, tin-based materials, and the like. Among them, carbon-based materials can include graphite (such as natural graphite, artificial graphite), non-graphitized carbon (soft carbon, hard carbon, etc.); silicon-based materials can include elemental silicon, silicon-based alloys, silicon oxides, and silicon-carbon composite materials One or more of them; tin-based materials may include one or more of simple tin, tin alloys, etc. The separator 103 can be a polymer separator, non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP and three-layer PP/PE /PP and other diaphragms. The electrolyte solution 104 includes a lithium salt and a solvent, and the solvent may include one or more of carbonate solvents, carboxylate solvents, and ether solvents.

The electrochemical battery of the embodiment of the present application can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers, digital cameras, and other wearable electronic devices or mobile electronic devices, such as drones, electric products such as bicycles and electric vehicles to improve the performance of the products.

The embodiment of the present application also provides an electronic device including the above electrochemical cell. The electronic equipment can include various consumer electronic products, such as mobile phones, tablet computers, notebook computers, mobile power supplies, portable computers, and other wearable or mobile electronic equipment, TV sets, DVD players, video recorders, camcorders , radios, tape recorders, stereos, record players, CD players, home office equipment, home electronic health care equipment and automobiles and other electronic products. It should be noted that when the above-mentioned electrochemical battery is applied to an electronic device, it can be accommodated in the electronic device in the form of a battery pack. Generally, the battery pack includes a plurality of battery modules (a single battery module can include multiple electrochemical cells mentioned above) and the battery management system that manages them.

In some implementations, referring to FIG. 4 , the embodiment of the present application provides an electronic device 200, which includes a casing 201, electronic components (not shown in FIG. 4 ) contained in the casing 201, and a battery 202. The battery 202 provides power for the electronic device 200, and the battery 202 includes the electrochemical battery 100 described above in the embodiment of the present application. The housing 201 may include a front cover assembled on the front side of the terminal and a rear case assembled on the rear side, and the battery 202 may be fixed inside the rear case. The electronic device shown in FIG. 4 is usually a small portable electronic device, such as a mobile phone.

In other implementations, referring to FIG. 5, the embodiment of the present application provides an electronic device 300, which can be a variety of mobile devices for loading, transportation, assembly, disassembly, security, etc., and can be in various forms vehicle. Specifically, the electronic device 300 may include a car body 301 , a moving assembly 302 , and a driving assembly. The driving assembly includes a motor 303 and a battery 304 , and the battery 304 includes the above-mentioned electrochemical battery 100 provided in the embodiment of the present application. Wherein, the moving component 302 may be a wheel. The battery 304 can be a battery pack containing the above-mentioned electrochemical battery 100, which is accommodated at the bottom of the vehicle body and electrically connected to the motor 303, so that the electrochemical battery 100 can supply power to the motor 303, and the motor 303 provides power to drive electronic equipment The movement component 302 of 300 moves.

The electronic device provided in the embodiment of the present application uses the electrochemical battery provided in the embodiment of the present application to supply power for it, which can meet the requirements of various electronic devices for high energy density and long cycle life of the battery, and improve the use experience and market competition of electronic devices force.

The embodiments of the present application will be further described below in terms of multiple embodiments.

Example 1

A preparation of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Cr at a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere, wherein the ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature to obtain the product NaCrSSe;

Then add NaCrSSe and _I2 into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove the unreacted _I2 acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed _I2 simple substance, The precursor CrSSe was obtained after vacuum drying.

The chemical reaction formula involved above is: Na ₂ S+S+2Se+2Cr=2NaCrSSe; 2NaCrSSe+I ₂ =2CrSSe+2NaI.

(2) Lithiation:

Add the above-mentioned CrSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, carry out the lithiation reaction for 20 minutes, and obtain the lithiated product, and then centrifuge the lithiated product, and use a solvent After repeated cleaning, the positive lithium supplement agent can be obtained. The average chemical formula of the particle body of the positive electrode lithium supplement agent is Li _3.5 CrSSe, which specifically includes the following substances: Li _3.5 CrSSe and LiCrSSe, Li ₂ S, Li ₂ Se and Cr.

A preparation of a lithium-ion half battery, comprising:

1) Preparation of battery positive pole piece:

Add the above-mentioned positive electrode lithium replenishing agent, binder-polyvinylidene fluoride (PVDF), conductive agent-acetylene black into N-methylpyrrolidone (NMP) according to the weight ratio of 8:1:1, and stir evenly to obtain the positive electrode Slurry: coating the positive electrode slurry on the aluminum foil of the positive electrode current collector, drying, rolling, and cutting to obtain the positive electrode sheet;

2) Battery assembly: use the above-mentioned positive pole piece as the positive pole, the lithium metal sheet as the negative pole, the diaphragm as celgard2400, and the electrolyte as ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dicarbonate of 1mol/L LiPF ₆ A mixed solution of methyl ester (DMC); assembled in an argon-filled glove box to obtain a lithium-ion half-cell.

The half battery of embodiment 1 is carried out the starting voltage of charging for the first time to be open circuit voltage (Open Circuit Voltage, OCV), about 1.3V, constant current charging (40mA/g), charging cut-off voltage is 4.2V; The initial voltage of the first discharge is 4.2V, the constant current charge (40mA/g), the discharge cut-off voltage is 2.5V.

Example 2

A preparation of a lithium-ion half battery, comprising:

Positive electrode sheet production: the positive electrode active material-lithium iron phosphate (LiFePO ₄ ), the positive electrode lithium supplement prepared in Example 1, the binder-polyvinylidene fluoride (PVDF), the conductive agent-acetylene black according to the ratio of 74:6 : Add the weight ratio of 10:10 into N-methylpyrrolidone (NMP), stir evenly to obtain the positive electrode slurry; coat the positive electrode slurry on the positive electrode current collector aluminum foil, dry, roll, and cut Afterwards, the positive electrode sheet is obtained;

According to the half-cell fabrication method described in Example 1, the above-mentioned positive pole piece was assembled into a lithium-ion half-cell.

Carry out charge-discharge cycle test to the half-battery of embodiment 2, wherein, charging initial voltage is OCV, is about 2.3V, 0.1C constant current charging, charging cut-off voltage is 4.2V; The initial voltage when discharging is 4.2V, 0.1C constant current charging, the cut-off voltage is 2.7V.

In order to highlight the beneficial effects of the present application, comparative examples 1 and 2 are provided.

Comparative example 1

The precursor of the lithium-supplementing agent CrSSe prepared in Example 1 was used to replace the positive electrode lithium-supplementing agent, and the positive electrode sheet and the half-cell were fabricated according to the method described in Example 1, and the half-cell of Comparative Example 1 was tested for the first time according to the test conditions of Example 1. charging and discharging.

Comparative example 2

A lithium-ion half-battery, which differs from Example 2 in that no positive electrode lithium supplement is introduced, and the weight ratio of positive electrode active material, binder, and conductive agent is 80:10:10. According to the test conditions of Example 2, the half-cell of Comparative Example 2 was subjected to a charge-discharge cycle test.

Fig. 6 is an X-ray diffraction (XRD) characterization result of the particle body of the positive electrode lithium supplementing agent in Example 1 of the present application - Li _3.5 CrSSe and its precursor CrSSe. It can be seen from Figure 6 that the crystal structure of the precursor CrSSe changed significantly after lithiation, and the characteristic peaks of CrSSe disappeared. In the lithium supplementary agent obtained after lithiation, Cr, Li ₂ S, Li ₂ Se, The characteristic peak of LiCrSSe indicates that part of Li _3.5 CrSSe is decomposed, and the lithium supplement contains Cr, Li ₂ S, Li ₂ Se and LiCrSSe.

Fig. 7 and Fig. 8 are the first cycle charge and discharge curves of the half-cell of Example 1 and the half-cell of Comparative Example 1, respectively. It can be seen that the lithium supplementing agent whose average chemical formula is Li _3.5 CrSSe in Example 1 shows a higher delithiation capacity (>460mAh/g) at a charge cut-off voltage of 4.2V, and its lithium intercalation capacity is lower, less than 40mAh/g. g, can be ignored. It can be calculated that the lithium supplementing agent can provide a lithium supplementation capacity (i.e., irreversible capacity)>420mAh/g; while the CrSSe before lithiation used in Comparative Example 1 has a negligible delithiation capacity (<15mAh/g), It shows that the lithiated Li _3.5 CrSSe as a lithium supplement additive can have a high lithium supplement capacity within the normal working potential range of the battery.

Figure 9 is the charge-discharge curve of the half-cell of Comparative Example 2 (i.e., a simple _LiFePO4 button cell), and Figure 10 is the charge-discharge curve of the half-cell of Example 2 (a coin cell in which _LiFePO4 is mixed with positive lithium supplements) , The dotted line in Figure 9 and Figure 10 represents the first charge-discharge cycle. It can be seen from Figures 9-10 that the first charge specific capacity of the LiFePO ₄ positive electrode in Comparative Example 2 is only 160mAh/g, while the first charge specific capacity of the LiFePO ₄ positive electrode after adding a certain lithium supplement is as high as 199.6mAh/g, which is It shows that the actual lithium supplement capacity of the lithium supplement agent of Example 1 is above 450mAh/g. In addition, in the subsequent charge-discharge cycles, the charge-discharge curves of the half-battery of Example 2 and the half-cell of Comparative Example 2 are basically the same, and the specific capacity of the battery of Example 2 is more stable, which shows that the positive electrode supplement provided by the present application The lithium agent plays a good role in lithium supplementation, and has no side effects on the battery cycle performance.

Example 3

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Li ₂ S, S, Se, and Cr at a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere. The ball milling speed is 800r/min, and the time is 30min. The material was vacuum-sealed and sintered under an argon atmosphere, wherein the sintering temperature was 900°C, the holding time was 10h, and then cooled to room temperature to obtain the product LiCrSSe;

(2) Lithiation:

The above LiCrSSe powder was added to the ethylene glycol dimethyl ether solution of lithium naphthalene with a concentration of 0.1M, and the lithiation reaction was carried out for 10 minutes to obtain the lithiated product, which was then centrifuged and washed repeatedly with a solvent. The positive electrode lithium supplement can be obtained, and the average chemical formula of the positive electrode lithium supplement is Li _2.5 CrSSe.

Example 4

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Co in a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere. The ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature, and the obtained product is NaCoSSe;

Then NaCoSSe and _I2 were added into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, the unreacted _I2 acetonitrile solution was removed, and the reaction product was washed with acetonitrile to wash away the adsorbed _I2 simple substance, The precursor CoSSe was obtained after vacuum drying.

(2) Lithiation:

Add the above CoSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, carry out the lithiation reaction for 15 minutes, and obtain the lithiated product, and then centrifuge the product, and wash it repeatedly with a solvent , the positive lithium supplement agent can be obtained, and its average chemical formula is Li ₃ CoSSe.

Example 5

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Ti in a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere. The ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 900°C, the holding time is 10h, and then cooled to room temperature, and the obtained product is NaTiSSe;

Then add NaTiSSe and _I2 into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove unreacted _I2 in acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed _I2 simple substance, The precursor TiSSe was obtained after vacuum drying.

(2) Lithiation:

Add the above TiSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, carry out the lithiation reaction for 15 minutes, and obtain the lithiated product, and then centrifuge the product, and wash it repeatedly with a solvent , to obtain a positive electrode lithium supplement, the average chemical formula of which is Li ₃ TiSSe.

Example 6

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and V in a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere, wherein the ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 950°C, the holding time is 8h, and then cooled to room temperature to obtain the product NaVSSe;

Then add NaVSSe and _I2 into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove unreacted _I2 in acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed _I2 simple substance, The precursor VSSe was obtained after vacuum drying.

(2) Lithiation:

Add the above VSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, and carry out the lithiation reaction for 20 minutes to obtain the lithiated product, which is then centrifuged to separate the product and washed repeatedly with a solvent , to obtain a positive electrode lithium supplement, and its average chemical formula is Li _3.5 VSSe.

Example 7

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Mn in a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere, wherein the ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature, and the obtained product is NaMnSSe;

Then add NaMnSSe and _I2 into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove the unreacted _I2 acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed _I2 simple substance, The precursor MnSSe was obtained after vacuum drying.

(2) Lithiation:

Add the above MnSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, carry out the lithiation reaction for 20 minutes, and obtain the lithiated product, which is then centrifuged to separate the product and wash it repeatedly with a solvent , to obtain a positive electrode lithium supplement, and its average chemical formula is Li _3.5 MnSSe.

Example 8

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Cr at a molar ratio of 1:1:2:2, and perform ball milling under an argon atmosphere, wherein the ball milling speed is 600r/min, and the time is 30min. The material is sintered in an argon atmosphere, wherein the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature to obtain the product NaCrSSe;

Then add NaCrSSe and _I2 into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove the unreacted _I2 acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed _I2 simple substance, The precursor CrSSe was obtained after vacuum drying.

(2) Lithiation:

Add the above-mentioned CrSSe powder into the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, and carry out the lithiation reaction for 15 minutes to obtain the lithiated product, which is then centrifuged to separate the product and washed repeatedly with a solvent , to obtain the positive electrode lithium supplement, the average chemical formula of which is Li ₃ CrSSe.

Example 9

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, S, Se, and Cr at a molar ratio of 1:2:1:2, and perform ball milling under an argon atmosphere, wherein the ball milling speed is 600r/min, and the time is 30min. The material is sintered under an argon atmosphere, wherein the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature to obtain the product NaCrS _1.5 Se _0.5 ;

Then add NaCrS _1.5 Se _0.5 and I ₂ into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove the unreacted I ₂ in acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed I ₂ simple substance, the precursor CrS _1.5 Se _0.5 was obtained after vacuum drying.

(2) Lithiation:

The above-mentioned CrS _1.5 Se _0.5 powder was added to the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, and the lithiation reaction was carried out for 20 minutes to obtain the lithiated product, which was then centrifuged and separated, and used The solvent is repeatedly washed to obtain the positive electrode lithium supplement, and its average chemical formula is Li _3.5 CrS _1.5 Se _0.5 .

Example 10

A preparation method of a positive electrode lithium supplement, comprising:

(1) Preparation of lithium supplementation agent precursor:

Mix Na ₂ S, Se, and Cr at a molar ratio of 1:3:2, and perform ball milling under an argon atmosphere. The ball milling speed is 600r/min, and the time is 30min. Carry out sintering under the atmosphere, wherein, the sintering temperature is 800°C, the holding time is 10h, and then cooled to room temperature, the obtained product is NaCrS _0.5 Se _1.5 ;

Then add NaCrS _0.5 Se _1.5 and I ₂ into acetonitrile according to a certain molar ratio, and after fully mixing and reacting under an argon atmosphere, remove the unreacted I ₂ in acetonitrile solution, rinse the reaction product with acetonitrile, and wash away the adsorbed I ₂ simple substance, the precursor CrS _0.5 Se _1.5 was obtained after vacuum drying.

(2) Lithiation:

The above-mentioned CrS _0.5 Se _1.5 powder was added to the ethylene glycol dimethyl ether solution of biphenyllithium with a concentration of 0.1M, and the lithiation reaction was carried out for 20 minutes to obtain the lithiated product, which was then centrifuged and separated, and used The solvent is washed repeatedly to obtain the positive electrode lithium supplement, and its average chemical formula is Li _3.5 CrS _0.5 Se _1.5 .

According to the method described in Example 2, the positive electrode lithium supplements of Examples 3-10 were respectively prepared into positive electrode sheets, and assembled into button batteries, and each button battery was charged and discharged. The voltage range was the corresponding OTC To 4.2V, record the charge-discharge curve, and combine with the half-cell of Comparative Example 2 containing only the positive electrode active material, and calculate the lithium-removing specific capacity of each lithium-supplementing agent. The results are shown in Table 1.

In addition, the positive electrode lithium supplements of the above embodiments were assembled into full batteries, and each assembled full battery was chemically formed to activate the positive and negative active materials inside the battery cell and form a stable SEI on the negative electrode. film, improve battery self-discharge, charge and discharge performance and storage performance. Among them, the assembly process of the full battery is as follows: the graphite pole piece is used as the negative electrode, the diaphragm is celgard2400, and the electrolyte is 1mol/L LiPF ₆ ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC). ) mixed solution; assembled in an argon-filled glove box to obtain a lithium-ion full battery.

The specific process of the formation is as follows: After the full battery is assembled, it is left to stand at a temperature of 25°C for 4 hours, then charged at a constant current rate of 0.05C to 4.2V, and then charged at a constant voltage of 4.2V to a charging current <0.005C. Afterwards, each full battery after formation was subjected to a charge-discharge cycle at 0.2C, with a voltage range of 2.7V to 4.2V, to test its first-cycle Coulombic efficiency, discharge specific capacity, and cycle performance. It should be noted that the first charge here refers to the charge at the time of formation, not the usual first charge after the battery leaves the factory (actually it should be the second charge).

In addition, the present application also provides the performance test results of the LiFePO ₄ full battery (Comparative Example 2) under the same conditions without adding the positive electrode lithium replenishing agent of the embodiment of the present application.

Summary of the test results of the half-cells of each embodiment and comparative example in table 1

Summary of the test results of the full battery of each embodiment and comparative example in table 2

In the above examples of the present application, the average chemical formula is Li _x MS _y Se _2-y lithium replenishing agent, M can be applied to a variety of transition metals, y can take different values, and x can also take different values, which can be controlled by adjusting the lithiation process . From the half-cell data in Table 1, it can be known that the lithium supplementation agent of the embodiment of the present application undergoes irreversible decomposition in the first cycle, and the delithiation specific capacity can exceed 450mAh/g, indicating that the lithium supplementation agent has a high lithium supplementation capacity. After 100 cycles of the installed half-battery, the capacity retention rate is close to that of Comparative Example 2 (half-cell without lithium-supplementing agent), indicating that the lithium-supplementing agent has no obvious side effects on the positive electrode during the cycle and has good compatibility.

From the data of the full battery in Table 2, it can be known that the lithium supplementing agent of the embodiment of the present application is irreversibly decomposed in the first cycle, and the first discharge specific capacity of the full battery is increased from 144mAh/g in the comparative example to more than 155mAh/g, and even up to 160mAh /g, which shows that it can make up for the loss of active lithium in the negative electrode, and there is a part of pre-stored lithium in the negative electrode, thereby improving the cycle performance and energy density of the battery. After 100 cycles, the capacity retention rate of the full battery added with the lithium-supplementing agent of the present application is significantly better than that of the full battery without the lithium-supplementing agent. No other side effects, good compatibility.

In addition, the first-cycle Coulombic efficiency of the full battery in Comparative Example 2 in Table 2 seems to be higher than that of Examples 2-10, which is mainly because the first charge in Table 2 refers to the charge during formation, and the calculation of the cycle capacity retention rate is also based on The formation data is used as a comparison basis. The first-cycle coulombic efficiency of Comparative Example 2 without lithium supplementation is the first effect after the negative electrode and positive electrode are consumed, that is, the loss part is the irreversible active lithium of the positive electrode, and the discharge specific capacity of the second cycle and later is low. , poor cycle performance. However, for the full battery of each embodiment with added lithium supplementing agent, the first cycle (during formation) consumes the active lithium provided by the lithium supplementing agent, and does not consume the positive electrode active material. Although the first effect is low, the second cycle The Coulombic efficiency in the future is not low; and the discharge specific capacity is high, the cycle performance is good, and the energy density of the battery is correspondingly high.

Claims (13)

1. A positive electrode lithium replenishing agent, characterized in that the positive electrode lithium replenishing agent includes a particle body, the particle body includes a lithium compound of a transition metal sulfur selenide, and the average chemical formula of the lithium compound of the transition metal sulfur selenide is is Li _x MS _y Se _2-y , wherein, 1<x≤4, 0<y<2, and M represents a transition metal.
2. The positive electrode lithium supplementing agent according to claim 1, wherein the particle body includes a compound of the general formula Li _x MS _y Se _2-y , and M, Li ₂ S and Li ₂ Se.
3. The positive electrode lithium supplement agent according to claim 2, characterized in that, the particle body also includes a compound with the general formula _{LiMSySe2 -y} .
4. The positive electrode lithium replenishing agent according to any one of claims 1-3, wherein the M includes one or more of Cr, Ti, V, Co, Fe, Ni, Mn, and Nb.
5. The positive electrode lithium supplement agent according to any one of claims 1-4, characterized in that, the surface of the particle body also has a coating layer.
6. A preparation method of a positive electrode lithium supplement, characterized in that the preparation method comprises:

   Mixing transition metal sources, sulfur sources, and selenium sources, ball milling and sintering to prepare transition metal sulfoselenides;

   The sulfoselenide of the transition metal is lithiated to obtain a positive electrode lithium supplement; wherein, the positive electrode lithium supplement includes a particle body, and the particle body includes a lithium compound of a transition metal sulfoselenide, and the transition metal The average chemical formula of the lithiated sulfur selenide is Li _x MS _y Se _2-y , where 1<x≤4, 0<y<2, and M represents a transition metal.
7. A positive pole piece of a battery, characterized in that the positive pole piece of the battery contains the positive lithium replenishing agent according to any one of claims 1-5.
8. The positive electrode sheet of the battery according to claim 7, wherein the positive electrode sheet of the battery comprises a current collector and a positive electrode material layer arranged on the current collector, and the positive electrode material layer includes a positive electrode active material, the Positive electrode lithium supplement, and binder.
9. The positive electrode sheet of the battery according to claim 7, wherein the positive electrode sheet of the battery comprises a current collector, a positive electrode material layer and a lithium replenishing agent layer sequentially arranged on the current collector, wherein the positive electrode material The layer contains positive electrode active material, binding agent and conductive agent, and the lithium supplementing agent layer contains the positive electrode lithium supplementing agent, binding agent and conductive agent.
10. The positive electrode sheet of the battery according to claim 8 or 9, wherein the mass of the positive lithium supplementing agent accounts for 1% of the sum of the mass of the positive lithium supplementing agent and the positive active material -10%.
11. The positive electrode sheet of the battery according to claim 8, wherein the mass of the positive electrode lithium supplementing agent accounts for 0.5%-15% of the mass of the positive electrode material layer.
12. An electrochemical cell, characterized in that it comprises a positive electrode, a negative electrode, and a diaphragm and an electrolyte between the positive electrode and the negative electrode, wherein the positive electrode is as claimed in any one of claims 7-11. The battery positive pole piece described in one item.
13. An electronic device, characterized in that the electronic device has the electrochemical cell as claimed in claim 12.

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