CN116053619A - Low-residual-alkali positive electrode lithium supplementing agent and preparation method and application thereof - Google Patents

Low-residual-alkali positive electrode lithium supplementing agent and preparation method and application thereof Download PDF

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CN116053619A
CN116053619A CN202310070598.0A CN202310070598A CN116053619A CN 116053619 A CN116053619 A CN 116053619A CN 202310070598 A CN202310070598 A CN 202310070598A CN 116053619 A CN116053619 A CN 116053619A
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positive electrode
lithium
supplementing agent
residual
low
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谢芳
杨雪
郑奇
张帅帅
尹雪晗
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Shandong Haike Innovation Research Institute Co Ltd
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Abstract

The invention provides a low residual alkali positive electrode lithium supplementing agent, a preparation method and application thereof, belongs to the technical field of lithium ion batteries, and can solve the problems of difficult homogenate coating, reduced conductivity, aggravated electrolyte side reaction and the like caused by high alkali number of the lithium supplementing agent. The alkali number of the low-residual-alkali positive electrode lithium supplementing agent is less than or equal to 5%, and the low-residual-alkali positive electrode lithium supplementing agent comprises lithium supplementingA core body and a hydrophobic isolation layer, wherein the molecular formula of the lithium supplementing agent core body is Li x M y N 1‑y O z Wherein M and N are each one of elements Fe, co, ni, mn, cu, V, mo, ti, al, and M and N are different elements, x=2 to 6, y=0.5 to 1, and z=2 to 4; the hydrophobic isolation layer is LiF. According to the invention, the lithium ion battery electrolyte is used for soaking the lithium supplementing material at low temperature, so that the residual alkali on the surface layer of the material reacts with the electrolyte in situ, and the residual alkali on the surface is converted into a component LiF beneficial to a battery system, thereby realizing the purpose of reducing the base number; the coating layer obtained by the liquid phase reaction is more uniform and compact; the preparation process is green and environment-friendly, and the energy consumption is low.

Description

Low-residual-alkali positive electrode lithium supplementing agent and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a low-residual-alkali positive electrode lithium supplementing agent, and a preparation method and application thereof.
Background
With the continuous development of lithium ion battery technology, the performance development of the existing commercial lithium ion battery system almost reaches the limit, and the improvement of energy density is still a serious issue in the future battery development. During the first cycle of a lithium ion battery, the formation of a negative electrode SEI film consumes about 7-10% of active lithium, meaning Li extracted from the positive electrode material + Part is irreversibly consumed, and loss of lithium results in reduced battery capacity, reduced coulombic efficiency, and poor cycle performance. When a negative electrode material having a high specific capacity, such as alloys of silicon, tin, oxides of silicon oxide, tin oxide, and amorphous carbon negative electrode is used, li is further consumed by the negative electrode material, particularly a silicon-based negative electrode material + The consumption of the positive lithium source will be further exacerbated, resulting in a first pass low coulombic efficiency.
In order to further improve the energy density of the lithium ion battery, the active lithium supplementation becomes an effective means for solving the problem, and currently existing lithium supplementation methods are positive electrode lithium supplementation and negative electrode lithium supplementation. Because the lithium supplement of the negative electrode involves the use of active metals such as lithium powder, lithium foil and the like, the activity is too high to be stably stored for a long time, so that the operation difficulty and the production risk are increased; the anode lithium supplementing is simple and easy to operate, a small amount of anode lithium supplementing agent can be added in the homogenizing process of preparing the anode plate, and the supplementing can be realized in the formation stageThe lithium supplementing process is safe, has good compatibility with the existing battery manufacturing process, and has wide commercial application prospect. The positive electrode lithium-supplementing agents currently studied and reported are of a wide variety, wherein Li 5 FeO 4 The theoretical 867mAh/g and the proper lithium removal voltage range are considered to be the lithium supplement agent with the best lithium supplement effect at present due to the higher specific capacity. However, in practical application, the existing lithium supplementing additive has some defects, and the defects are that the alkalinity of the material is high and the homogenate coating process is unstable; poor air compatibility with water and CO 2 The quality change occurs to generate lithium compound impurities, so that the alkali content is further increased, the coating difficulty is increased, the performance of the material is reduced, and the polarization is increased; meanwhile, the higher alkali content and electrolyte undergo side reactions, which cause abnormal gas production and excessive gas production during formation, and the swelling phenomenon easily occurs during high-temperature storage, so that the material capacity is reduced and the safety problem is caused.
Chinese patent No. CN114709391a discloses a positive electrode lithium-supplementing agent containing a coating layer, wherein the core is LFMO (M-doped lithium ferrite), and the shell is alumina; the problem of higher gas production ratio when lithium ferrite is used as a positive electrode lithium supplementing agent is solved by doping metal for modification; by coating the surface of the lithium supplementing agent active material with an alumina coating layer, the residual alkali amount on the surface of the material is reduced, and agglomeration in the positive electrode slurry is avoided, so that the safety of the lithium ion battery is affected. Although the lithium supplementing agent can improve the air stability of the lithium supplementing material to a certain extent, specific examples of the lithium supplementing agent show that residual alkali on the surface layer of the material is coated inside the material, is not friendly to electrolyte, and reduces the conductivity of the material.
Chinese patent No. CN115295772A discloses a lithium-rich composite material, a preparation method and application thereof. The lithium-rich composite material comprises a core body and a compact hydrophobic layer coated on the core body, the core body comprises a lithium-rich material, and the compact hydrophobic layer comprises a polyanion type electrochemical active material, wherein the lithium-rich composite material contains the compact hydrophobic layer, has high compactness, low residual alkali content and high chemical stability in contact with electrolyte, but the formation of the coating layer requires secondary high-temperature treatment, so that the energy consumption is increased, and the operation complexity is increased.
However, although the above positive electrode lithium supplementing agent improves the homogenization stability and air stability by incorporating a hydrophobic coating layer or an isolating layer to contain residual alkali inside the material, the following disadvantages still exist: residual alkali still exists in the material, contacts with electrolyte when the battery works, catalyzes side reaction of the electrolyte, increases gas production and deteriorates battery performance; almost all cladding schemes require secondary high temperature sintering, resulting in secondary growth of the nuclear material and increased energy consumption.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a low residual alkali positive electrode lithium supplementing agent, a preparation method and application thereof, and solves the problems of difficult homogenate coating, reduced conductivity, aggravated electrolyte side reaction and the like caused by high alkali number of the lithium supplementing agent; the dense LiF coating can isolate water and CO in the air 2 The air stability of the material is improved, and the increase of the base number in the processes of material storage, transportation, tabletting and the like is inhibited; meanwhile, the LiF coating layer can passivate the active surface of the lithium supplementing agent, reduce side reaction of materials and electrolyte, reduce formation gas production, reduce high-temperature storage gas production and improve battery performance.
In order to achieve the above purpose, the present invention provides a low residual alkali positive electrode lithium supplementing agent, which adopts the following technical scheme: the alkali number of the low-residual-alkali positive electrode lithium supplementing agent is less than or equal to 5%, the low-residual-alkali positive electrode lithium supplementing agent comprises a lithium supplementing agent core body and a hydrophobic isolation layer, wherein the molecular formula of the lithium supplementing agent core body is Li x M y N 1-y O z Wherein M and N are each one of elements Fe, co, ni, mn, cu, V, mo, ti, al, and M and N are different elements, x=2 to 6, y=0.5 to 1, and z=2 to 4; the hydrophobic isolation layer is LiF.
The invention also provides a preparation method of the low residual alkali positive electrode lithium supplementing agent, which comprises the following steps:
s1, dissolving a lithium source, an M source and an N source in water to prepare uniform gel, and spray-drying to prepare precursor powder;
s2, sintering the precursor at a high temperature under inert gas to obtain a positive electrode lithium supplementing agent;
and S3, fully and uniformly stirring the positive electrode lithium supplementing agent and the electrolyte in a reaction kettle, filtering the electrolyte after keeping constant temperature for a period of time, leaching to remove the residual lithium salt on the surface layer of the lithium supplementing agent by using a non-aqueous organic solvent, and drying to obtain the low-residual-alkali positive electrode lithium supplementing agent.
Preferably, the lithium source is at least one of an oxide, hydroxide, peroxide, inorganic salt, and organic salt of lithium.
Preferably, the M source is at least one of an oxide, hydroxide, sulfate, chlorate, and nitrate of M; the N source is at least one of oxide, hydroxide, sulfate, chlorate, nitrate and phosphate.
Preferably, the inert gas is at least one of nitrogen, argon and helium.
Preferably, the electrolyte comprises a solvent and lithium salt, wherein the solvent is a carbonate solvent, and the mass concentration of the lithium salt is 0.1% -5%.
Preferably, the nonaqueous organic solvent is at least one of carbonates, ethers, sulfones, amides, and lower alkanes.
Preferably, the high-temperature sintering temperature in the step S2 is 600-1000 ℃ and the sintering time is 2-40h; and S3, the constant temperature is 25-45 ℃ and the constant temperature time is 0.5-6h.
Preferably, in the step S3, the mass ratio of the positive electrode lithium supplementing agent to the electrolyte is 1 (10-100), and the mass ratio of the positive electrode lithium supplementing agent to the nonaqueous organic solvent is 1 (2-20).
The invention also provides application of the low-residual-alkali positive electrode lithium supplementing agent, wherein the low-residual-alkali positive electrode lithium supplementing agent is used for preparing a lithium ion battery, and the addition amount of the low-residual-alkali positive electrode lithium supplementing agent is 0.5-5% of the mass ratio of positive electrode active materials in the lithium ion battery.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) According to the invention, the lithium ion battery electrolyte is used for soaking the lithium supplementing material at low temperature, so that the residual alkali on the surface layer of the material reacts with the electrolyte in situ, and the residual alkali on the surface is converted into a component LiF beneficial to a battery system, thereby realizing the purpose of reducing the base number; the coating layer obtained by the liquid phase reaction is more uniform and compact; the preparation process is green and environment-friendly, and the energy consumption is low.
(2) The invention converts the residual alkali on the surface into LiF in situ, does not increase the ratio of inert substances of the battery and does not reduce the gram capacity of the material; the compact and uniform LiF has the function of isolating air, does not increase the base number any more in the storage and use processes, can improve the lithium ion transmission rate, improve the lithium removal efficiency, passivate the surface of a material, improve the compatibility with electrolyte, reduce the gas production and improve the high-temperature storage and cycle performance of the battery.
Drawings
FIG. 1 is a flow chart of the preparation of a low residual alkali positive electrode lithium-supplementing agent according to an embodiment of the present invention;
fig. 2 is an SEM image of the low residual alkali positive electrode lithium-compensating agent provided in example 1 of the present invention.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a low-residual-alkali positive electrode lithium supplementing agent, wherein the alkali number of the low-residual-alkali positive electrode lithium supplementing agent is less than or equal to 5%, an electrochemical titration method is used for alkali number test, and the specific steps are as follows: and (3) dissolving the alkali on the surface layer of the material by using methanol, filtering, and titrating the filtrate by using an acid standard solution.
The invention relates to a low residual alkali positive electrode lithium supplementing agent, which comprises a lithium supplementing agent nucleus body and a hydrophobic isolation layer, wherein the nucleus body is a pure product of lithium M acid lithium and a doped coating modified product taking the pure product as a main body, and the molecular formula is Li x M y N 1-y O z Wherein M and N are each one of the elements Fe, co, ni, mn, cu, V, mo, ti, al and M and N are different elements, x=2-6, y=0.5-1, z=2-4, preferably M is selected from Fe orNi, N is selected from Al or Cu; the hydrophobic isolation layer is LiF.
The preparation method of the low-residual-alkali positive electrode lithium supplementing agent comprises the following steps:
s1, dissolving a lithium source, an M source and an N source in water to prepare uniform gel, and spray-drying by using a spray dryer to prepare precursor powder;
s2, sintering the precursor at a high temperature under inert gas to obtain a positive electrode lithium supplementing agent;
and S3, fully and uniformly stirring the positive electrode lithium supplementing agent and the electrolyte in a reaction kettle, filtering the electrolyte after keeping constant temperature for a period of time, leaching to remove residual lithium salt on the surface layer of the lithium supplementing agent by using a non-aqueous organic solvent, and drying to obtain the low-residual-alkali positive electrode lithium supplementing agent.
Wherein the lithium source is at least one of lithium oxide, hydroxide, peroxide, inorganic salt and organic salt, and preferably the lithium source is Li 2 O、LiOH、Li 2 CO 3 、LiNO 3 、Li 2 C 2 O 4 、CH 3 At least one of COOLi; more preferably, the lithium source is LiNO 3 . The M source is at least one of oxide, hydroxide, sulfate, chlorate and nitrate of M; preferably, the M source is Fe 2 O 3 、Fe 3 O 4 、FeC 2 O 4 、Fe(NO 3 ) 3 ·9H 2 O、FeCl 3 、FeSO 4 、NiO、Ni(NO 3 ) 2 、Ni 2 SO 4 、NiCl 3 At least one of (a) and (b); more preferably, the M source is Fe (NO 3 ) 3 ·9H 2 O or Ni (NO) 3 ) 2 . The N source is at least one of oxide, hydroxide, sulfate, chlorate, nitrate and phosphate; preferably, the N source is Al 2 O 3 Aluminum trichloride, aluminum sulfate, alum, cuCl 2 、CuSO 4 ·5H 2 O、Cu(NO 3 ) 2 At least one of (a) and (b); more preferably, the N source is aluminum sulfate or CuSO 4 ·5H 2 O. The inert gas is at least one of nitrogen, argon and helium; preferably, the inert gas is nitrogen.
The preparation of the electrolyte is carried out in a glove box, and the electrolyte comprises a solvent and lithium salt, wherein the solvent is a carbonate solvent, and preferably the solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; the preferred lithium salt is LiPF 6 ，LiPF 6 The mass concentration of (2) is 0.1% -5%. The non-aqueous organic solvent is at least one of carbonates, ethers, sulfones, amides and low-carbon alkanes; preferably, the nonaqueous organic solvent is a carbonate solvent, and is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate; more preferably, the nonaqueous organic solvent is dimethyl carbonate.
The high-temperature sintering temperature in the step S2 is 600-1000 ℃ and the sintering time is 2-40h. The constant temperature in the step S3 is 25-45 ℃ and the constant temperature time is 0.5-6h.
The mass ratio of the positive electrode lithium supplementing agent to the electrolyte in the step S3 is 1:10-100, the mass ratio of the positive electrode lithium supplementing agent to the nonaqueous organic solvent is 1:2-20, the preparation of the low-residual-alkali positive electrode lithium supplementing agent in the step S3 is carried out in a drying room, and a microporous filter is arranged at the outlet of a reaction kettle used in the step S3.
The application of the low-residual-alkali positive electrode lithium supplementing agent is used for preparing a lithium ion battery, preferably for preparing a positive electrode of the lithium ion battery, wherein the addition amount of the low-residual-alkali positive electrode lithium supplementing agent is 0.5-5% of the mass ratio of positive electrode active materials in the lithium ion battery. The lithium ion battery also comprises a current collector, a negative electrode, a diaphragm and electrolyte. Wherein the positive electrode active material is LiCoO 2 、LiFePO 4 At least one of NCM, preferably, the positive electrode active material is NCM811; the negative electrode active material is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon carbon and silicon oxygen; preferably, the negative electrode active material is a silicon oxygen negative electrode.
In order to more clearly and in detail describe the low residual alkali positive electrode lithium supplementing agent, the preparation method and the application thereof provided by the embodiment of the invention, the following description is made with reference to specific embodiments. The specific examples described herein are intended to be illustrative of the invention and are not intended to be limiting. Unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional unless otherwise specified.
Example 1
Preparing a positive electrode lithium supplementing agent matrix: according to formula Li 5 Fe 0.98 Al 0.02 O 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O and Al 2 (SO 4 ) 3 To ensure the purity of the sintered material, liNO 3 Excess 5%; adding all the materials into water, heating and stirring to form uniform gel, spray drying by a spray dryer to obtain precursor powder, maintaining the temperature of the obtained precursor powder at 850 ℃ in nitrogen atmosphere for 2h, and cooling in a furnace to obtain Li 5 Fe 0.98 Al 0.02 O 4 ；
Preparing 1% of electrolyte: in a glove box, weighing ethylene carbonate and ethylmethyl carbonate according to the mass fraction of 3:7, storing for 24 hours at the low temperature of 0 ℃, and adding LiPF with the mass fraction of 1 percent 6 Standby;
preparing a low residual alkali positive electrode lithium supplementing agent: in a drying room, weighing the solid material and the electrolyte according to the mass ratio of 1:50, adding the solid material and the electrolyte into a reaction kettle with a microporous filter at an outlet, stirring at 45 ℃ for 0.5h, filtering out the electrolyte, then adding dimethyl carbonate with the mass 10 times of that of the solid material, stirring and leaching, and vacuum drying the obtained solid material at 80 ℃ to obtain the low-residual-alkali positive electrode lithium supplementing agent, wherein fig. 2 is an SEM (scanning electron microscope) graph of the low-residual-alkali positive electrode lithium supplementing agent.
Example 2
Preparing a positive electrode lithium supplementing agent matrix: according to formula Li 5 FeO 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O, liNO to ensure the purity of the sintered material 3 Excess 5%; adding all the above materials into water, heating and stirring to obtain uniform gel, spray drying to obtain precursor powder, and collecting the precursorPreserving the temperature of the powder in a nitrogen atmosphere at 900 ℃ for 1h, and cooling the powder along with a furnace to obtain Li 5 FeO 4 ；
Preparing 2% of electrolyte: in a glove box, weighing propylene carbonate and dimethyl carbonate according to the mass fraction of 2:8, storing at a low temperature of 0 ℃ for 24 hours, and adding LiPF with the mass fraction of 2 percent 6 Standby;
preparing a low residual alkali positive electrode lithium supplementing agent: and (3) weighing the solid material and the electrolyte in a drying room according to the mass ratio of 1:30, adding the solid material and the electrolyte into a reaction kettle with a microporous filter at an outlet, stirring for 2 hours at 30 ℃, filtering out the electrolyte, adding dimethyl carbonate with the mass which is 20 times that of the solid material, stirring and leaching, and vacuum-drying the obtained solid material at 80 ℃ to obtain the low-residual-alkali positive electrode lithium supplementing agent.
Example 3
Preparing a positive electrode lithium supplementing agent matrix: according to formula Li 5 FeO 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O, liNO to ensure the purity of the sintered material 3 Excess 5%; adding all the materials into water, heating and stirring to form uniform gel, spray drying by a spray dryer to obtain precursor powder, maintaining the temperature of the obtained precursor powder at 800 ℃ in nitrogen atmosphere for 5h, and cooling in a furnace to obtain Li 5 FeO 4 ；
Preparing 0.5% of electrolyte: in a glove box, weighing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate according to the mass fraction of 3:2:5, storing for 24 hours at the low temperature of 0 ℃, and adding LiPF with the mass fraction of 0.5 percent 6 Standby;
preparing a low residual alkali positive electrode lithium supplementing agent: and (3) weighing the solid material and the electrolyte according to the mass ratio of 1:100 in a drying room, adding the solid material and the electrolyte into a reaction kettle with a microporous filter at an outlet, stirring for 6 hours at 25 ℃, filtering out the electrolyte, adding dimethyl carbonate with the mass 2 times of that of the solid material, stirring and leaching, and vacuum-drying the obtained solid material at 80 ℃ to obtain the low-residual-alkali positive electrode lithium supplementing agent.
Example 4
Preparing a positive electrode lithium supplementing agent matrix: according to formula Li 2 Ni 0.95 Cu 0.5 O 2 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Ni(NO 3 ) 2 、CuSO 4 ·5H 2 O, liNO to ensure the purity of the sintered material 3 An excess of 10%; adding all the substances into water, heating and stirring to obtain a uniform solution, spray drying by a spray dryer to obtain precursor powder, preserving the heat of the obtained precursor powder at 850 ℃ in nitrogen atmosphere for 10h, and cooling along with a furnace to obtain Li 2 Ni 0.95 Cu 0.5 O 2 ；
Preparing 2% of electrolyte: in a glove box, weighing propylene carbonate and dimethyl carbonate according to the mass fraction of 2:8, storing at a low temperature of 0 ℃ for 24 hours, and adding LiPF with the mass fraction of 2 percent 6 Standby;
preparing a low residual alkali positive electrode lithium supplementing agent: and (3) weighing the solid material and the electrolyte in a drying room according to the mass ratio of 1:30, adding the solid material and the electrolyte into a reaction kettle with a microporous filter at an outlet, stirring for 2 hours at 30 ℃, filtering out the electrolyte, adding dimethyl carbonate with the mass which is 20 times that of the solid material, stirring and leaching, and vacuum-drying the obtained solid material at 80 ℃ to obtain the low-residual-alkali positive electrode lithium supplementing agent.
Comparative example 1
According to formula Li 5 Fe 0.98 Al 0.02 O 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O and Al 2 (SO 4 ) 3 To ensure the purity of the sintered material, liNO 3 Excess 5%; adding all the materials into water, heating and stirring to form uniform gel, spray drying by a spray dryer to obtain precursor powder, maintaining the temperature of the obtained precursor powder at 850 ℃ in nitrogen atmosphere for 2h, and cooling in a furnace to obtain Li 5 Fe 0.98 Al 0.02 O 4 。
Comparative example 2
According to formula Li 5 FeO 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O, liNO to ensure the purity of the sintered material 3 Excess 5%;adding all the materials into water, heating and stirring to form uniform gel, spray drying by a spray dryer to obtain precursor powder, maintaining the temperature of the obtained precursor powder at 900 ℃ in nitrogen atmosphere for 1h, and cooling in a furnace to obtain Li 5 FeO 4 。
Comparative example 3
According to formula Li 5 FeO 4 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Fe(NO 3 ) 3 ·9H 2 O, liNO to ensure the purity of the sintered material 3 Excess 5%; adding all the materials into water, heating and stirring to form uniform gel, spray drying by a spray dryer to obtain precursor powder, maintaining the temperature of the obtained precursor powder at 800 ℃ in nitrogen atmosphere for 5h, and cooling in a furnace to obtain Li 5 FeO 4 。
Comparative example 4
According to formula Li 2 Ni 0.95 Cu 0.5 O 2 The corresponding mole ratios of the elements are respectively weighed LiNO 3 、Ni(NO 3 ) 2 、CuSO 4 ·5H 2 O, liNO to ensure the purity of the sintered material 3 An excess of 10%; adding all the substances into water, heating and stirring to obtain a uniform solution, spray drying by a spray dryer to obtain precursor powder, preserving the heat of the obtained precursor powder at 850 ℃ in nitrogen atmosphere for 10h, and cooling along with a furnace to obtain Li 2 Ni 0.95 Cu 0.5 O 2 。
Base number test
The positive electrode lithium-compensating agent products of examples 1 to 4 and comparative examples 1 to 4 were dissolved in methanol at a ratio of solid to liquid=1:20, the solid material was filtered after stirring for 10min, the filtrate was transferred to a titration cup, electrochemical titration was performed with a hydrochloric acid standard solution of 0.1M, and the sum of the two points of jump was taken as the total base number, and the test results are shown in table 1.
TABLE 1 results of surface residual alkali for examples 1-4 and comparative examples 1-4
Test sample Total base number
Example 1 0.52
Example 2 0.66
Example 3 0.80
Example 4 1.01
Comparative example 1 6.35
Comparative example 2 7.83
Comparative example 3 9.30
Comparative example 4 12.03
As is clear from Table 1, the total base number of examples 1 to 4 employing the technical scheme of the present invention is significantly reduced as compared with comparative examples 1 to 4, indicating that the technical scheme of the present invention is very effective in reducing residual base on the surface of the lithium-supplementing agent.
Battery performance test
To further demonstrate the effectiveness of the low residual alkali positive electrode lithium supplement of the present invention, the positive electrode lithium supplement of example 1 and comparative example 1 was added to a pouch cell for formation gas production test and cycle test, wherein the positive electrode was commercial NCM811, the negative electrode was commercial silica, the cell capacity was 2.0Ah, the formation cutoff voltage was 4.4V, the cycle voltage range was 2.8V-4.2V, and the formation gas production, the capacity retention after 100 cycles of 0.5C/1C, and the gas expansion were tested, respectively, in which the formation gas production test method was a drainage method for testing the gas volume of the pouch cell after formation of the pouch cell, and the gas expansion test method was a method for measuring the peak thickness variation before and after cycling of the pouch cell. The test data are shown in table 2.
Table 2 the cycle performance and the gassing ratio of the soft pack battery cells of the added example 1 and the comparative example 1
Test sample Formation gas yield Capacity retention rate for 100 cycles Gas expansion rate of 100-cycle battery
Example 1 0.8mL 92.3％ 0.5％
Comparative example 1 3.5mL 60.5％ 7.3％
As can be seen from table 2, compared with the lithium supplement agent of comparative example 1 which is not treated by the electrolyte, the passivation of the lithium supplement agent of example 1 by the electrolyte treatment has lower formation gas yield than that of comparative example 1, the 100-cycle capacity retention rate is obviously superior to that of comparative example 1, and the gas expansion rate of the 100-cycle battery is obviously smaller than that of comparative example 1, so that the application of the low-residual-alkali positive electrode lithium supplement agent of the invention to a lithium battery can obviously improve the battery performance of the lithium battery.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (10)

1. The low-residual-alkali positive electrode lithium supplementing agent is characterized in that the alkali number of the low-residual-alkali positive electrode lithium supplementing agent is less than or equal to 5%, the low-residual-alkali positive electrode lithium supplementing agent comprises a lithium supplementing agent core body and a hydrophobic isolation layer, wherein the molecular formula of the lithium supplementing agent core body is Li x M y N 1-y O z Wherein M and N are each one of elements Fe, co, ni, mn, cu, V, mo, ti, al, and M and N are different elements, x=2 to 6, y=0.5 to 1, and z=2 to 4; the hydrophobic isolation layer is LiF.
2. The method for preparing the low residual alkali positive electrode lithium supplementing agent according to claim 1, comprising the following steps:
s1, dissolving a lithium source, an M source and an N source in water to prepare uniform gel, and spray-drying to prepare precursor powder;
s2, sintering the precursor at a high temperature under inert gas to obtain a positive electrode lithium supplementing agent;
and S3, fully and uniformly stirring the positive electrode lithium supplementing agent and the electrolyte in a reaction kettle, filtering the electrolyte after keeping constant temperature for a period of time, leaching to remove the residual lithium salt on the surface layer of the lithium supplementing agent by using a non-aqueous organic solvent, and drying to obtain the low-residual-alkali positive electrode lithium supplementing agent.
3. The method for producing a low residual alkali positive electrode lithium-supplementing agent according to claim 2, wherein the lithium source is at least one of an oxide, a hydroxide, a peroxide, an inorganic salt, and an organic salt of lithium.
4. The method for preparing a low residual alkali positive electrode lithium supplementing agent according to claim 2, wherein the M source is at least one of an oxide, hydroxide, sulfate, chlorate and nitrate of M; the N source is at least one of oxide, hydroxide, sulfate, chlorate, nitrate and phosphate.
5. The method for preparing a low residual alkali positive electrode lithium supplementing agent according to claim 2, wherein the inert gas is at least one of nitrogen, argon and helium.
6. The method for preparing the low-residual-alkali positive electrode lithium supplementing agent according to claim 2, wherein the electrolyte comprises a solvent and lithium salt, wherein the solvent is a carbonate solvent, and the mass concentration of the lithium salt is 0.1% -5%.
7. The method for preparing a low residual alkali positive electrode lithium supplementing agent according to claim 2, wherein the nonaqueous organic solvent is at least one of carbonates, ethers, sulfones, amides and low-carbon alkanes.
8. The method for preparing a low residual alkali positive electrode lithium supplementing agent according to claim 2, wherein the high temperature sintering temperature in the step S2 is 600-1000 ℃ and the sintering time is 2-40h; and S3, the constant temperature is 25-45 ℃ and the constant temperature time is 0.5-6h.
9. The method for preparing a low residual alkali positive electrode lithium supplementing agent according to claim 2, wherein the mass ratio of the positive electrode lithium supplementing agent to the electrolyte in the step S3 is 1 (10-100), and the mass ratio of the positive electrode lithium supplementing agent to the nonaqueous organic solvent is 1 (2-20).
10. The use of the low-residual-alkali positive electrode lithium supplementing agent according to claim 1, wherein the low-residual-alkali positive electrode lithium supplementing agent is used for preparing a lithium ion battery, and the addition amount of the low-residual-alkali positive electrode lithium supplementing agent is 0.5-5% of the mass ratio of positive electrode active materials in the lithium ion battery.
CN202310070598.0A 2023-01-17 2023-01-17 Low-residual-alkali positive electrode lithium supplementing agent and preparation method and application thereof Pending CN116053619A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117239104A (en) * 2023-11-13 2023-12-15 宁德时代新能源科技股份有限公司 Lithium supplementing additive, positive pole piece, battery and electricity utilization device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117239104A (en) * 2023-11-13 2023-12-15 宁德时代新能源科技股份有限公司 Lithium supplementing additive, positive pole piece, battery and electricity utilization device
CN117239104B (en) * 2023-11-13 2024-03-29 宁德时代新能源科技股份有限公司 Lithium supplementing additive, positive pole piece, battery and electricity utilization device

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