Additive for modifying positive electrode material of lithium battery as well as preparation method and application of additive

Abstract

The invention discloses an additive for modifying a lithium battery positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The problems that an existing lithium battery positive electrode material is unstable in air, high in total alkali residue and poor in high-temperature stability, and active lithium is consumed due to long circulation are solved. The expression of the additive is LiaMgbMec( PO4) dYe, Me represents a transition metal element, Y represents an anion, a is greater than 0 and less than or equal to 2, b is greater than 0 and less than or equal to 1.5, c is greater than or equal to 0 and less than or equal to 0.4, d is greater than 0 and less than or equal to 1, and e is greater than or equal to 0 and less than or equal to 0.4. The additive is rich in magnesium, so that the positive electrode material can provide effective structural support during lithium ion intercalation / deintercalation, and high-temperature cycle stability is provided; by doping the transition metal element, irreversible lithium loss caused by formation of an SEI film can be counteracted during intercalation / deintercalation of lithium ions, so that the total capacity and the energy density of the battery are improved; the added anion group can reduce the residual alkali of the positive electrode material and reduce the gas production of the lithium battery under high voltage.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and specifically relates to an additive for modifying anode materials of lithium batteries, and further discloses a preparation method and application thereof. Background Art

[0002] The performance of positive electrode materials directly affects the performance indicators of lithium batteries, so they occupy a core position in lithium batteries. Excessive residual alkali content on the surface of positive electrode materials will have many negative effects on electrochemical performance. The impact of surface alkaline compounds on electrochemical performance is mainly reflected in the increase of irreversible capacity loss and the deterioration of cycle performance. When the de-lithiated positive electrode material is subjected to high temperature, its crystal structure will undergo a series of changes, which will release heat and some highly active oxygen in the process, and the active oxygen will oxidize the electrolyte to produce a large amount of gas.

[0003] In addition, the positive electrode materials of lithium-ion batteries continuously extract and insert lithium ions during operation, during which the transition metal plates slide, leading to structural degradation and oxygen evolution, triggering a series of side reactions including volume strain, microcrack generation, and electrolyte side reactions. Moreover, a long-term challenge facing lithium-ion batteries is the consumption of active lithium and the formation of a solid electrolyte interface (SEI). This will lead to irreversible lithium loss in the initial cycle and gradually further deplete the active lithium in subsequent cycles. Although pre-lithiation has been shown to effectively compensate for this loss by introducing additional active lithium into the battery, previous studies have focused on offsetting the initial lithium loss and often ignore the continuous lithium consumption throughout the cycle.

[0004] In response to the problems of traditional lithium-ion positive electrode materials such as air instability, high total alkali residue, poor high temperature stability, and active lithium consumption caused by long cycles. In recent years, a variety of positive electrode materials have been developed, and transition metal elements are more often doped into positive electrode materials to maintain the single crystal or polycrystalline structure of positive electrode materials during circulation and improve the stability of positive electrode materials. For the total alkali residue, high temperature stability and lithium supplementation of positive electrode materials, coating additives are often used to reduce the total alkali residue of positive electrode materials and maintain high temperature stability.

[0005] For example, Chinese patent CN118507694A discloses a high-power ternary positive electrode material, which includes a core layer and a boron coating layer and a silicon coating layer sequentially coated on the outer surface of the core layer. By coating the surface of the ternary positive electrode material with a boron coating layer and controlling the amount of boron added and the sintering temperature, boron migrates and enters the interior of the ternary positive electrode material to form shallow boron doping. At the same time, as the boron in the boron coating layer migrates to the interior of the ternary positive electrode material, the thickness of the boron coating layer decreases, so that the low-thickness boron coating layer can not only improve the conductivity of the positive electrode material, but also play a role in leveling the surface depressions of the material, thereby improving the stability, rate performance and cycle performance of the positive electrode material.

[0006] As disclosed in Chinese Patent CN118419984A, a cathode lithium supplement additive can effectively isolate Li

[0007] , from direct contact with the environment, reduce the residual alkali amount on the material surface, thereby significantly reducing the agglomeration phenomenon of the slurry during the homogenization process, and thus reducing the manufacturing difficulty.

[0007] As disclosed in Chinese Patent CN118431478A, a cathode lithium supplement agent and its preparation method are provided. The cathode lithium supplement agent includes a core and a coating layer covering the core; the core includes modified lithium-rich nickelate, and the expression is: Li2Ni 1-x-y A x B y M z O 2-z ; wherein, 0 < x ≤ 0.1, 0 < y ≤ 0.1, 0 < z ≤ 0.1; element A and element B each independently include at least one of La, Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y, and Al, and the coating layer includes lithium oxide and carbide; lithium oxide and carbide each independently contain element A and element B; the carbide has oxygen vacancies. This cathode lithium supplement agent has the advantages of good air stability, low surface residual alkali content, and low gas generation amount, which is beneficial to improving the safety, cycle stability, and battery capacity of lithium-ion batteries.

[0008] As disclosed in Chinese Patent CN118579857A, a method for recycling waste power lithium battery recycling materials into lithium-rich manganese-based cathode materials is provided. The cathode material powder obtained by pretreatment is subjected to carbothermal reduction calcination. Carbothermal reduction reduces the waste ternary nickel cobalt manganese cathode material into a mixture of nickel, cobalt, lithium carbonate, and manganese oxide for ammonia leaching, then a precursor is prepared by a one-step sol-gel method, and finally Zr 4+ cations and F - anions are added by ball milling, and then a Zr- and F-doped recycled lithium-rich manganese-based cathode material is obtained by calcination. The introduction of double doping increases the lattice spacing beneficial to the ion insertion process, increases the oxygen vacancy formation energy, and improves the ion diffusion kinetics and structural stability.

[0009] As disclosed in Chinese Patent CN114220951B, a cathode lithium supplement additive and its preparation method, a cathode sheet, and a lithium-ion battery are provided, including a core material and an outer layer material covering at least a part of the outer surface of the core material. The core material is an oxide of lithium, and the outer layer material is a lithium compound. The lithium compound contains a non-metal element, and the non-metal element includes one or more of phosphorus, sulfur, or selenium elements. It has a higher specific capacity and more de-lithiation potentials, making it easier for lithium ions to be embedded and de-embedded, having better electrical conductivity, and better lithium supplement effect.

[0010] In summary, there is currently no comprehensive solution to the problems of lithium-ion battery positive electrode materials being unstable in the air, high total alkali residue, poor high-temperature stability, and active lithium consumption due to long cycles. Summary of the invention

[0011] In view of this, the object of the present invention is to provide an additive for modifying a positive electrode material of a lithium battery and a preparation method and application thereof.

[0012] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are as follows.

[0013] An additive for modifying the positive electrode material of lithium batteries, expressed as Li a Mg b Me c (PO4) d Y e ;

[0014] Wherein, Me represents a transition metal element, the type of Me is greater than or equal to 0, Y represents an anion, the type of Y is greater than or equal to 0;

[0015] Among them, 0<a≤2, 0<b≤1.5, 0≤c≤0.4, 0<d≤1, 0≤e≤0.4.

[0016] Preferably, the transition metal element includes but is not limited to one or more of Al, V, Co, Cu, Nb, Mo, and Ti.

[0017] Preferably, the anion includes but is not limited to Cl - 、F - 、NO3 - 、SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- PO4 3- PO3 3- 、P2O7 4- One or more of .

[0018] Preferably, a is 0.6 to 1; b is 0.5 to 1.5, c is 0 to 0.3, d is 0.4 to 0.8, and e is 0 to 0.3;

[0019] More preferably, a is 0.7 to 0.9; b is 0.7 to 1.2, c is 0.1 to 0.2, d is 0.5 to 0.7, and e is 0.1 to 0.2.

[0020] The present invention also provides a method for preparing the additive for modifying the positive electrode material of a lithium battery, the steps of which are as follows:

[0021] S1: According to Li a Mg b Me c (PO4) d Y e The raw materials are taken according to the stoichiometric ratio of each element, and a lithium source, a magnesium source, a Me source, and a phosphorus source are mixed to obtain a mixed material;

[0022] S2: calcining the mixture to obtain Li a Mg b Me c (PO4) d Y e additive;

[0023] S3: Li a Mg b Me c (PO4) d Y e The additive and the dispersant are mixed, and the obtained slurry is vacuum dried and sieved to obtain the additive for modifying the positive electrode material of the lithium battery.

[0024] Preferably, in step S1, the lithium source is any combination of one or more of lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, lithium hydroxide, lithium fluoride, and lithium phosphate;

[0025] More preferably, the lithium source is any combination of one or more of lithium carbonate, lithium acetate, lithium hydroxide and lithium fluoride.

[0026] Preferably, in step S1, the magnesium source is any combination of one or more of magnesium carbonate, magnesium nitrate, magnesium chloride, magnesium phosphate, magnesium acetate, magnesium hydroxide, and magnesium fluoride;

[0027] More preferably, the magnesium source is any combination of one or more of magnesium carbonate, magnesium phosphate, magnesium acetate and magnesium hydroxide.

[0028] Preferably, in step S1, the phosphorus source is any combination of one or more of diammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, lithium phosphate, magnesium phosphate, and phosphorus pentoxide;

[0029] More preferably, the phosphorus source is any combination of one or more of diammonium phosphate, ammonium phosphate, lithium phosphate and magnesium phosphate.

[0030] Preferably, in step S1, the Me source is any combination of one or more of Me oxide, Me hydroxide, Me fluoride, Me phosphate, Me sulfate, Me nitrate, Me acetate, and Me carbonate;

[0031] More preferably, the Me source is any combination of one or more of Me oxide, Me fluoride, Me acetate and Me phosphate.

[0032] Preferably, in step S1, a ball mill is used for mixing, the mixing speed is 50 to 400 r / min, and the mixing time is 0.5 to 4 h;

[0033] More preferably, the mixing speed is 100 to 300 r / min, and the mixing time is 1 to 3 h;

[0034] Particularly preferably, the mixing speed is 100-300 r / min, and the mixing time is 1.5-2.5 h.

[0035] Preferably, in step S2, the calcination temperature is 500-1200°C, the calcination time is 1-20h, and the heating rate is 1-20°C / h;

[0036] More preferably, the calcination temperature is 700-1000°C, the calcination time is 4-16h, and the heating rate is 5-15°C / h;

[0037] Particularly preferably, the calcination temperature is 800-900° C., the calcination time is 8-12 h, and the heating rate is 8-12° C. / h.

[0038] Preferably, in step S3, the dispersant is any combination of one or more of deionized water, ethanol, isopropanol, ketone, acetone, ethyl acetate, dimethylformamide and N-methylpyrrolidone;

[0039] More preferably, the dispersant is any combination of one or more of deionized water, ethanol, ethyl acetate, dimethylformamide and N-methylpyrrolidone.

[0040] Preferably, in step S3, a ball mill is used for mixing, the ball mill speed is 200 to 800 r / min, and the mixing time is 2 to 10 h;

[0041] More preferably, the mixing speed is 300-700 r / min, and the mixing time is 4-8 h;

[0042] More preferably, the mixing speed is 400-600 r / min, and the mixing time is 5-7 h.

[0043] Preferably, in step S3, the vacuum drying temperature is 60 to 160° C., and the vacuum drying time is 2 to 72 hours;

[0044] More preferably, the vacuum drying temperature is 80 to 140° C., and the vacuum drying time is 10 to 48 hours;

[0045] Particularly preferably, the vacuum drying temperature is 100-120° C., and the vacuum drying time is 18-36 hours.

[0046] The present invention also provides the use of the above-mentioned additive for modifying lithium battery positive electrode materials in lithium battery positive electrode materials, mixing 0.1wt% to 5wt% of the additive for lithium battery positive electrode materials with the lithium battery positive electrode materials, sintering, crushing and sieving in an oxygen atmosphere to obtain a ternary positive electrode material.

[0047] Preferably, the lithium battery positive electrode material comprises one or more arbitrary combinations of a ternary positive electrode material, a ternary positive electrode material precursor, lithium cobaltate, a lithium cobaltate precursor, lithium manganate, a lithium manganate precursor, lithium iron phosphate, a lithium iron phosphate precursor, lithium iron manganese phosphate, and a lithium iron manganese phosphate precursor.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The additive for modifying the positive electrode material of a lithium battery provided by the present invention can synergistically improve the problems of instability of lithium ion positive electrode materials in the air, high total alkali residue, poor high temperature stability, and active lithium consumption caused by long cycles. The additive is rich in magnesium, which can provide effective structural support for the positive electrode material during lithium ion embedding / de-embedding and provide high temperature cycle stability. The additive doped with transition metal elements can offset the irreversible lithium loss caused by the formation of SEI film during lithium ion embedding / de-embedding, so as to improve the total capacity and energy density of the battery. The addition of anionic groups can reduce the residual alkali of the positive electrode material and reduce the gas production of lithium batteries under high voltage.

[0050] The preparation method provided by the present invention has low cost of raw materials, simple synthesis process and conditions, easy implementation, and environmentally friendly characteristics, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some specific implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 Scanning electron microscopy (SEM) of the additive for the lithium battery positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0054] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0055] Example 1

[0056] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0057] (1) 2.4 mol of lithium acetate, 1 mol of magnesium phosphate, 0.1 mol of cobalt trioxide, and 1 mol of ammonium dihydrogen phosphate were added into a ball mill for mixing at a mixing speed of 100 r / min for 1.5 h.

[0058] (2) The obtained mixture was calcined in a muffle furnace at a calcination temperature of 860°C, a heating rate of 10°C / h, and a calcination time of 10 h.

[0059] (3) adding the calcined mixture and anhydrous ethanol into a ball mill for ball milling at a mixing speed of 500 r / min for a mixing time of 6 h, and drying the obtained slurry at 100° C. in vacuum for 10 h, and sieving to obtain the modified lithium battery positive electrode material additive Li 0.8 MgCo 0.07 PO4.

[0060] Example 2

[0061] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0062] (1) 1.8 mol of lithium acetate, 1 mol of magnesium acetate, 0.1 mol of titanium dioxide, and 2 mol of ammonium dihydrogen phosphate were added into a ball mill for mixing at a mixing speed of 100 r / min for a mixing time of 1.5 h.

[0063] (2) The obtained mixture was calcined in a muffle furnace at a calcination temperature of 860°C, a heating rate of 10°C / h, and a calcination time of 10 h.

[0064] (3) adding the calcined mixture and anhydrous ethanol into a ball mill for ball milling at a mixing speed of 500 r / min for a mixing time of 6 h, and drying the obtained slurry at 100° C. in vacuum for 10 h, and sieving to obtain the modified lithium battery positive electrode material additive Li 1.8 MgTi 0.1 PO4.

[0065] Example 3

[0066] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0067] (1) 0.8 mol of lithium acetate, 1 mol of magnesium hydroxide, 0.05 mol of aluminum oxide, and 1 mol of ammonium hydrogen phosphate were added into a ball mill for mixing at a mixing speed of 100 r / min for a mixing time of 1.5 h.

[0068] (2) calcining the obtained mixture in a muffle furnace at a calcination temperature of 860° C., a heating rate of 10° C. / h, and a calcination time of 10 h;

[0069] (3) adding the calcined mixture and anhydrous ethanol into a ball mill for ball milling at a mixing speed of 500 r / min for a mixing time of 6 h, and drying the obtained slurry at 100° C. in vacuum for 10 h, and sieving to obtain the modified lithium battery positive electrode material additive Li 0.8 MgAl 0.1 PO4.

[0070] Example 4

[0071] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0072] (1) 2.4 mol of lithium acetate, 1 mol of magnesium phosphate, 0.1 mol of cobalt trioxide, and 1 mol of ammonium dihydrogen phosphate were added into a ball mill for mixing at a mixing speed of 100 r / min for 1.5 h.

[0073] (2) The obtained mixture was calcined in a muffle furnace at a calcination temperature of 860°C, a heating rate of 10°C / h, and a calcination time of 10 h.

[0074] (3) adding the calcined mixture and deionized water into a ball mill for ball milling at a mixing speed of 500 r / min for a mixing time of 6 h, and drying the obtained slurry at 100° C. in vacuum for 10 h, and sieving to obtain the modified lithium battery positive electrode material additive Li 0.8 MgCo 0.07 PO4.

[0075] Example 5

[0076] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0077] (1) Add 2 mol of lithium acetate, 1 mol of magnesium acetate, and 2 mol of ammonium dihydrogen phosphate into a ball mill for mixing at a speed of 100 r / min for 1.5 h.

[0078] (2) The obtained mixture was calcined in a muffle furnace at a calcination temperature of 860°C, a heating rate of 10°C / h, and a calcination time of 10 h.

[0079] (3) The calcined mixture and anhydrous ethanol are added to a ball mill for ball milling at a mixing speed of 500 r / min and a mixing time of 6 h. The obtained slurry is vacuum dried at 100° C. for 10 h and sieved to obtain the modified lithium battery positive electrode material additive Li2MgPO4.

[0080] Example 6

[0081] The preparation method of an additive for modifying a positive electrode material of a lithium battery described in this embodiment comprises the following steps:

[0082] (1) 0.8 mol of lithium acetate, 1 mol of magnesium hydroxide, 0.05 mol of aluminum oxide, and 1 mol of ammonium hydrogen phosphate were added into a ball mill for mixing at a speed of 100 r / min for 1.5 h.

[0083] (2) The obtained mixture was calcined in a muffle furnace at a calcination temperature of 860°C, a heating rate of 10°C / h, and a calcination time of 10 h.

[0084] (3) adding anhydrous ethanol to the calcined mixture for ball milling at a ball mill speed of 400 r / min for 5 h, and vacuum drying the obtained slurry at 100° C. for 10 h, and sieving to obtain the modified lithium battery positive electrode material additive Li 0.8 MgAl 0.1 PO4.

[0085] Example 7

[0086] The application of an additive for modifying a positive electrode material of a lithium battery described in this embodiment in a positive electrode material of a lithium ion battery comprises the following steps:

[0087] (1) 100g of Ni 0.65 Co 0.07 Mn 0.28 The (OH)2 ternary precursor was mixed with 0.5 g of the additive prepared in Example 1 in a mixer;

[0088] (2) The obtained mixture is placed in a muffle furnace, sintered at 880° C. for 10 h in an oxygen atmosphere, and then crushed using an ultrafine grinder and sieved to obtain a magnesium phosphate-lithium modified ternary positive electrode material.

[0089] Comparative Example 1

[0090] 100g of Ni 0.65 Co 0.07 Mn 0.28 The (OH)2 ternary precursor was placed in a muffle furnace and sintered at 880°C for 10 hours in an oxygen atmosphere. It was then crushed using an ultrafine grinder and sieved to obtain an unmodified ternary positive electrode material.

[0091] The test results of the physical characteristics of the additives for modifying the positive electrode materials of lithium batteries prepared in the above Examples 1 to 6 are shown in Table 1 below.

[0092] Table 1 Physical characteristics test results of additives of Examples 1 to 6

[0093]

[0094] It can be seen that the physical characteristics of the additives used to modify the positive electrode materials of lithium batteries in Examples 1 to 6 were tested.

[0095] The results of Example 1 and Example 4 show that with the addition of an organic dispersant, a lithium battery positive electrode material additive with a smaller particle size and a larger specific gravity can be obtained.

[0096] The results of Example 2 and Example 5 show that the physical characteristics of the additives for the positive electrode materials of lithium batteries can be affected by doping with transition metal ions.

[0097] The results of Example 3 and Example 6 show that by adjusting the ball milling parameters, positive electrode material additives with different requirements can be obtained.

[0098] In addition, by comparing Examples 1, 2, and 3, it is found that different transition metal doping will affect the material characteristics of the additive for the positive electrode material of the lithium battery, and introducing it into the positive electrode material can improve the stability of the positive electrode material to a certain extent.

[0099] The physical characteristics test results of the lithium magnesium phosphate modified ternary positive electrode material prepared in the above Example 7 and the unmodified ternary positive electrode material prepared in Comparative Example 1 are shown in Table 2 below.

[0100] Table 2 Physical characteristics test results of positive electrode materials of Example 7 and Comparative Example 1

[0101] Test items Example 7 Comparative Example 1 Total alkali 4829 5265 <![CDATA[Li2CO3]]> 2860 2350 LiOH 1277 1890 PH 11.44 11.59 DSC thermal stability temperature (℃) 289 267

[0102] The physical characteristic test results provided in the above-mentioned Example 7 and Comparative Example 1 indicate that the additives provided by the present invention can synergistically improve the problems of lithium-ion positive electrode materials such as instability in air, high total alkali residue, and poor high-temperature stability.

[0103] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0104] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An additive for modifying a positive electrode material of a lithium battery, characterized in that: The expression is Li a Mg b Me c (PO4) d Y e ; Wherein, Me represents a transition metal element, the type of Me is greater than or equal to 0, Y represents an anion, the type of Y is greater than or equal to 0; Among them, 0<a≤2, 0<b≤1.5, 0≤c≤0.4, 0<d≤1, 0≤e≤0.

4.

2. The additive for modifying the positive electrode material of a lithium battery according to claim 1, characterized in that: The transition metal element includes one or more of Al, V, Co, Cu, Nb, Mo, and Ti.

3. The additive for modifying the positive electrode material of a lithium battery according to claim 1, characterized in that: The anions include Cl - 、F - 、NO3 - 、SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- PO4 3- PO3 3- 、P2O7 4- One or more of .

4. The additive for modifying the positive electrode material of a lithium battery according to claim 1, characterized in that: The a is 0.6 to 1, b is 0.5 to 1.5, c is 0 to 0.3, d is 0.4 to 0.8, and e is 0 to 0.

3.

5. The method for preparing the additive for modifying the positive electrode material of a lithium battery according to any one of claims 1 to 4, characterized in that: Here are the steps: S1: According to Li a Mg b Me c (PO4) d Y e The raw materials are taken according to the stoichiometric ratio of each element, and a lithium source, a magnesium source, a Me source, and a phosphorus source are mixed to obtain a mixed material; S2: calcining the mixture to obtain Li a Mg b Me c (PO4) d Y e additive; S3: Li a Mg b Me c (PO4) d Y e The additive and the dispersant are mixed, and the obtained slurry is vacuum dried and sieved to obtain the additive for modifying the positive electrode material of the lithium battery.

6. The method for preparing the additive for modifying the positive electrode material of a lithium battery according to claim 5, characterized in that: In step S1, the lithium source is any combination of one or more of lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, lithium hydroxide, lithium fluoride, and lithium phosphate; The magnesium source is any combination of one or more of magnesium carbonate, magnesium nitrate, magnesium chloride, magnesium phosphate, magnesium acetate, magnesium hydroxide, and magnesium fluoride; The Me source is any combination of one or more of Me oxide, Me hydroxide, Me fluoride, Me phosphate, Me sulfate, Me nitrate, Me acetate, and Me carbonate; The phosphorus source is any combination of one or more of diammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, lithium phosphate, magnesium phosphate, and phosphorus pentoxide.

7. The method for preparing the additive for modifying the positive electrode material of a lithium battery according to claim 5, characterized in that: In step S1, a ball mill is used for mixing, the mixing speed is 50 to 400 r / min, and the mixing time is 0.5 to 4 h; In step S2, the calcination temperature is 500-1200° C., the calcination time is 1-20 h, and the heating rate is 1-20° C. / h; In step S3, a ball mill is used for mixing, the mixing speed is 200-800 r / min, and the mixing time is 2-10 h; the vacuum drying temperature is 60-160° C., and the vacuum drying time is 2-72 h.

8. The method for preparing the additive for modifying the positive electrode material of a lithium battery according to claim 5, characterized in that: In step S3, the dispersant is any combination of one or more of deionized water, ethanol, isopropanol, ketone, acetone, ethyl acetate, dimethylformamide and N-methylpyrrolidone.

9. Use of the additive for modifying the positive electrode material of a lithium battery according to any one of claims 1 to 4 in the positive electrode material of a lithium battery, characterized in that: 0.1 wt% to 5 wt% of the additive of the lithium battery positive electrode material is mixed with the lithium battery positive electrode material, sintered in an oxygen atmosphere, crushed, and sieved to obtain a ternary positive electrode material.

10. Use of the additive for modifying the positive electrode material of a lithium battery according to claim 9 in the positive electrode material of a lithium battery, characterized in that: The lithium battery positive electrode material includes any combination of one or more of a ternary positive electrode material, a ternary positive electrode material precursor, lithium cobaltate, a lithium cobaltate precursor, lithium manganate, a lithium manganate precursor, lithium iron phosphate, a lithium iron phosphate precursor, lithium iron manganese phosphate, and a lithium iron manganese phosphate precursor.

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