CN111668470A - Positive electrode lithium supplement material and preparation method and application thereof - Google Patents

Positive electrode lithium supplement material and preparation method and application thereof Download PDF

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CN111668470A
CN111668470A CN202010567299.4A CN202010567299A CN111668470A CN 111668470 A CN111668470 A CN 111668470A CN 202010567299 A CN202010567299 A CN 202010567299A CN 111668470 A CN111668470 A CN 111668470A
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lithium
positive electrode
supplement material
lithium supplement
battery
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黄杰
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Beijing Wuke Qingneng Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a positive electrode lithium supplement material, a preparation method and application thereof, wherein the average chemical formula of the positive electrode lithium supplement material is SiO2∙ bLi, b is more than 0 and less than or equal to 4.2, and the grain diameter D50In the range of 0 < D50Less than or equal to 1 mu m, the preparation method of the lithium supplement material comprises the step of adding SiO in a certain gas atmosphere2The lithium ion-supplementing material can be added into positive pole slurry to be mixed or independently prepared into slurry in the process of preparing the positive pole piece, and the slurry is attached to the prepared positive pole piece to form a lithium-supplementing coating. The lithium supplement material of the invention has high stability and high specific capacity in PVDF dissolved N-methyl pyrrolidone solution, and no gas release in the process of releasing lithiumThe method has the advantages of no safety problem caused by the dissolution of transition metal, no change of the current mainstream preparation process of the positive plate, the diaphragm and the battery when the method is applied to the battery, high stability, low cost, high battery core safety performance and the like.

Description

Positive electrode lithium supplement material and preparation method and application thereof
Technical Field
The invention relates to a positive electrode lithium supplement material and a preparation method and application thereof, belonging to the technical field of lithium ion batteries.
Background
With the increasing demand of electronic equipment for miniaturization and long standby and the increasing demand of electric vehicles for battery endurance, improving the energy density of lithium ion batteries is always the most central problem in the industry and the academia while keeping the battery performance unchanged or acceptable in change.
In the first charging process of the lithium ion battery, a passivation layer, namely a solid electrolyte interface film (SEI) film for short, is formed on the surface of a negative electrode. The formation of the SEI film consumes a part of lithium, and causes a loss of lithium that can be recycled in the battery, thereby reducing the capacity of the battery, resulting in a decrease in the first efficiency. In addition, materials of silicon (theoretical specific capacity of 4200mAh/g), silicon oxygen and silicon carbon are high-capacity novel negative active materials, and the first coulombic efficiency of the materials is far lower than that of a positive material, so that a large amount of lithium ions are consumed, and the reversible capacity of the battery is far lower than the theoretical value. Therefore, the concept of "lithium supplement" is developed to compensate for the loss of lithium.
The lithium supplement method in the prior art mainly comprises the steps of supplementing lithium to a positive electrode and supplementing lithium to a negative electrode. The lithium supplement of the negative electrode is that the surface of the negative electrode is directly covered with a lithium foil so that the negative electrode material and lithium are in direct chemical contact or the negative electrode is pre-embedded with lithium ions through electrochemical reaction before a battery assembly area, and the irreversible consumption of the first week is compensated; for example, in patent CN1830110A, the process of lithium supplement by using a negative electrode is complicated, the equipment cost is high, the production environment is severe, and uniformity is difficult to control, resulting in poor consistency of the battery, and a certain distance is left in practical production application. The currently adopted method for supplementing lithium to the positive electrode is to add a positive electrode lithium supplementing material in the preparation process of positive electrode slurry, the existing production process is not required to be changed, new equipment is not required to be additionally developed, and the uniform lithium supplementing effect can be achieved on the premise of not increasing the cost, so that the positive electrode lithium supplementing technology is widely concerned; li doped with conductive metals, as in patent CN107863567A2The lithium replenishing effect can be achieved by preparing the lithium replenishing material of the positive electrode from O powder, and the battery capacity is further improved, but in the practical use of the lithium replenishing material of the positive electrode in the patent, due to Li2The reaction of trace amounts of water in O (which reacts with water to produce LiOH, a strong base) and N-methylpyrrolidone (NMP) tends to decompose and deactivate PVDF, leading to coagulation of the positive electrode slurry, failure to coat, and failure to coat even if coated in a very harsh, anhydrous environmentLi of rim body2O can lead to incomplete decomposition in the process of first charging and lithium supplementing, and gas can still be generated in the using process of the battery, so that the safety problem caused by the expansion and the rupture of the battery is caused.
Although the positive electrode lithium supplement has the advantages of simple process, low price, high safety and the like, the lithium supplement material has higher requirement on the environment and is easy to react with moisture, carbon dioxide and the like in the air to cause the capacity reduction of the lithium supplement material, or the lithium supplement material is incompletely decomposed in the formation process of the battery and is continuously decomposed to generate gas in the subsequent use process, so that the battery has the safety problem; in addition, some positive electrode lithium supplement materials can react with polyvinylidene fluoride (PVDF) dissolved in N-methyl pyrrolidone (NMP) in the positive electrode slurry mixing process, so that the PVDF as a binder is inactivated, and the subsequent battery process cannot be prepared; most of the capacity of the conventional anode lithium supplement material is low (<500mAh/g), so that the lithium supplement effect is not obvious.
In summary, the following technical problems exist in the prior art:
1. the lithium is directly supplemented by the metal lithium, and the common method is to supplement partial metal lithium powder on the surface of the negative electrode, because the activity of the lithium powder is too high, the danger is very high; in addition, an ultrathin lithium foil is rolled on the surface of the negative electrode so as to supplement lithium, but the lithium supplementing process is complicated and high in cost, and the uniformity of the lithium supplementing is difficult to control, so that the consistency of the battery is poor, and the practical production and application are difficult;
2. the lithium supplement capacity of a plurality of anode lithium supplement materials is not high enough, generally 250-570mAh/g, and the capacity of the anode lithium supplement materials needs to be improved;
3. the first cycle of lithium removal of the positive electrode lithium supplement material is incomplete, and the gas production risk exists in the use process, so that no gas is generated in the use process;
4. part of the positive electrode lithium supplement material can react with water in NMP during slurry mixing to produce alkali, so that PVDF is subjected to reduction inactivation;
5. part of the positive electrode lithium supplement material contains transition metal, the transition metal is dissolved in the battery charging and discharging process, and the transition metal is precipitated at the negative electrode to form transition metal dendrite, so that great potential safety hazard is brought to the battery, for example, the lithium supplement material Li5FeO4During charging and dischargingIn the process, the risk of iron precipitation exists at the negative electrode, so that great safety problems are brought to the battery.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a positive electrode lithium supplement material and a preparation method and application thereof, the positive electrode lithium supplement material has the characteristics of high stability and high specific capacity in an N-methylpyrrolidone solution dissolved by PVDF, no gas release in the lithium release process and no safety problem caused by transition metal dissolution, and when the positive electrode lithium supplement material is applied to a battery, the current mainstream preparation processes of a positive plate, a diaphragm and the battery can not be changed, so that the positive electrode lithium supplement material has the advantages of high stability, low cost, high battery cell safety performance and the like.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a positive electrode lithium supplementing material with average chemical formula of SiO2∙ bLi, wherein b is in the range of 0 < b < 4.2.
Further, the particle diameter D of the positive electrode lithium supplement material50In the range of 0 < D50≤1μm。
Preferably, D is50D is within the range of 10 to50Less than or equal to 500nm, further preferably, D50Range 20 < D50≤50nm。
The preparation method of the anode lithium supplement material comprises the step of adding SiO in one or more gas atmospheres of carbon dioxide, inert gas and vacuum2Uniformly mixing the powder with metallic lithium physically and then carrying out heat treatment to obtain SiO2∙bLi。
The preparation method of the anode lithium supplement material comprises the step of adding SiO in one or more gas atmospheres of carbon dioxide, inert gas or vacuum2Uniformly mixing the powder with metallic lithium physically and then carrying out heat treatment to obtain SiO2∙ bLi after the reaction, SiO2∙ bLi are passivated in an atmosphere of one or more of dry gas, carbon dioxide, oxygen.
Further, the metal lithium and SiO2The mixing molar ratio of (3) is not less than 0 and not more than 4.2.
Wherein, reactant SiO2Mixing with metallic lithium to obtainSiO2∙ bLi, the chemical reaction equation is:
8.4Li+2SiO2→Li4SiO4+Li4.4Si、
31Li+8SiO2→4Li4SiO4+Li15Si4、
8.4Li+5SiO2→2Li2Si2O5+Li4.4si or
16.8Li+7SiO2→2Li2Si2O5+Li4SiO4+2Li4.4At least one of Si.
Preferably, the metal lithium is mixed with SiO2The mixing molar ratio of (A) to (B) is 3-4.2: 1.
Preferably, the inert gas is argon; the mixing method comprises one or more of three-dimensional mixing, ball milling and stirring, and the mixing temperature is 0-500 ℃.
Specifically, the structure of the positive electrode lithium supplement material comprises a core and a coating layer, wherein the core is an alloy formed by silicon and lithium, and the coating layer is a compound formed by silicon, oxygen and lithium or unreacted SiO2One or two of them.
Further, the lithium metal is one or more of lithium powder, lithium foil or lithium ingot.
Further, the temperature of the heat treatment is 200-1100 ℃, and the heat treatment time is 0.01-24 h.
Preferably, the temperature of the heat treatment is 220-600 ℃, and the time of the heat treatment is 6-8 h.
Further, the passivation temperature is 60-550 ℃, and the passivation time is 1min-8 h.
Preferably, the passivation temperature is 250-350 ℃, and the passivation time is 10-25 min.
The application of the positive electrode lithium supplement material in the preparation of the positive plate is that the positive electrode lithium supplement material is added into positive electrode slurry as a lithium supplement additive to be mixed, and is attached to an aluminum foil in a dipping, coating and/or spraying mode to prepare the positive plate.
Specifically, the positive active substance, the conductive agent, the binder, the lithium supplement additive and NMP are mixed and stirred together to prepare homogenate, then the homogenate is coated on an aluminum foil current collector, and the pole piece is prepared by baking, rolling and slicing for storage and standby.
Further, the positive active material of the positive electrode slurry includes, but is not limited to, lithium cobaltate (LiCoO)2) Lithium nickelate (LiNiO)2) Lithium manganate (LiMnO)2) Lithium iron phosphate (LiFePO)4) Lithium nickel cobaltate (LiMn)xNiyCo1-x-yO2) Lithium nickel cobalt manganese oxide (LiNi)xMn2-xO4) Lithium nickel cobalt aluminate (LiAl)xNiyCo1-x-yO2) Any one or more of nickel lithium manganate and lithium-rich cathode materials, 0<x<1,0<y<1,0<x+y≤1。
The application of the positive electrode lithium supplement material in the preparation of the positive plate is that the positive electrode lithium supplement material is independently prepared into slurry and is attached to the prepared positive plate in a dipping, coating and/or spraying manner to form a lithium supplement coating.
Compared with the prior art, the invention has the beneficial effects that:
1. the anode lithium supplement material has the characteristic of high stability in dry air and a N-methylpyrrolidone solution in which PVDF is dissolved, and is prepared by using a chemical average formula SiO in the process of first-week charging and lithium release2∙ bLi the process of releasing lithium is SiO2The process of lithium removal has no gas release and no participation of transition metal, so that the risk of precipitation of the transition metal is avoided, the safety of the battery cell is high, and the SiO is used as the material2And a high theoretical specific capacity of a compound of lithium: (>600mAh/g), so the lithium supplement material has high specific capacity and has larger development space.
2. The invention discloses a positive electrode lithium supplement material which is made of SiO2By reaction with Li to obtain SiO2Because of the insulator and poor electron conductivity, it is used as the lithium-supplementing material particle D50In the range of 0 to 1 μm, further optimizing D5010nm-500nm, otherwise lithium cannot be completely and effectively removed. The small particles have the advantage that when the lithium-supplementing cathode material is used, most of the lithium-supplementing cathode materialThe spacing between the positive electrode particle gaps has no or little effect on the bulk energy density of the cell, and secondly, SiO2The specific content of medium oxygen/silicon is higher than that of silicon and silicon monoxide, SiO2And the content of lithium silicon compounds in Li is high, the capacity of the lithium ion battery cathode material in the usable range (voltage range of 0-0.8V for lithium battery) of the lithium ion battery is lower than 60%, most of the capacity is above 0.8Vvs. Li, and the lithium ion battery cathode material is difficult to directly use as a cathode in practical use, but the lithium-intercalated compound is directly used as a lithium-supplementing cathode material, the voltage working range is 2-4.5V, the intercalated lithium can be basically removed, and the more the voltage is above 0.8Vvs. Li, the more stable the material mixing process is.
3. The anode lithium supplement material is SiO2And compounds of lithium, in which SiO2After heat treatment with metallic lithium, silicon, oxygen and lithium form compounds and unreacted SiO2Is coated with an alloy of silicon and lithium to form a common coating layer for the surface and bulk phases of the above compounds, due to SiO2The specific content of the medium oxygen/silicon is higher than that of silicon and silicon monoxide, so that compounds formed by silicon, oxygen and lithium elements are more than lithium, silicon and silicon monoxide, the coating surface of the lithium-silicon alloy is more sufficient, the content of the lithium-silicon alloy is less, the stability of the lithium supplement positive electrode additive in NMP and air is improved, and in the material mixing process, collision among particles causes the breakage of the coating layer on the surface, but the coating layer in the bulk phase still exists, so that the stability is greatly improved.
4. According to the positive electrode lithium supplement material provided by the invention, active lithium ions brought by the battery are irreversible active lithium ions, the lithium supplement material can be used for removing higher lithium capacity in the charging voltage range of the battery, reversible lithium capacity is not basically available in the discharging voltage range of the battery, in the first charging process of the battery, the irreversible lithium ions of the lithium supplement material can be used for compensating the active lithium ions consumed by the positive electrode active material for forming an SEI film, but the lithium supplement material does not insert or inserts few lithium ions in the discharging process.
5. When the anode lithium supplement material is applied to a battery, the current main preparation process of an anode plate, a diaphragm and the battery can be not changed, the anode lithium supplement material is added during anode slurry mixing so as to prepare the anode plate, or the anode lithium supplement material is independently used as a main material to be mixed with a conductive agent and a bonding agent to form slurry, and then the slurry is attached to the prepared anode plate to form a lithium supplement layer.
6. According to the positive electrode lithium supplement material disclosed by the invention, no matter the positive electrode lithium supplement material is distributed between positive electrode active materials or on the surface of a positive electrode piece, after a lithium battery is assembled, when an electrolyte fully infiltrates the positive electrode active materials and the lithium supplement material, lithium ions in the positive electrode lithium supplement material can be released under the action of charging, the lithium ions enter the electrolyte and are finally embedded into a negative electrode or form SEI (solid electrolyte interphase), the loss of reversible lithium in the battery is reduced, the capacity of the battery is improved, because the cut voltages of batteries of different systems are inconsistent, after the first-cycle charging is finished, partial active lithium in the positive electrode lithium supplement material is still not completely extracted, the principle of the positive electrode lithium supplement material is consistent with that of the positive electrode material, and the active lithium is not.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIG. 1 is a first cycle charge and discharge curve chart of example 1 and comparative example 1 of the present invention;
FIG. 2 is a graph showing the first-week charge and discharge curves of example 2 of the present invention and comparative example 2.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Firstly, the method comprises the following steps: preparation of anode lithium-supplement material
Example 1:
preparing a positive electrode lithium supplement material: the molar ratio of the components is 3: 1 weighing a certain amount of lithium powder and D50SiO of 20nm2Ball-milling for 9h at 350r/min in a ball-milling device in an argon protective atmosphere, then placing the mixture of the two into a tube furnace in the argon protective atmosphere, heating the tube furnace to 480 ℃ at the heating rate of 5 ℃/min, keeping the temperature at the constant temperature for 8h, then naturally cooling, then placing the product into a muffle furnace, heating to 250 ℃ at the heating rate of 5 ℃/min in a dry room (the dew point is less than-45 ℃) and keeping the temperature for 25min for passivation, thus obtaining the lithium supplement material A of the lithium ion battery anode material.
Example 2:
preparing a positive electrode lithium supplement material: weighing a certain amount of lithium foil and D according to the molar ratio of 4.2:150Is 50nm SiO2And putting the mixture into a three-dimensional mixer in an argon protective atmosphere, performing ball milling for 8h at 600r/min, then performing vacuum sealing on the mixture in a quartz tube, putting the quartz tube into a muffle furnace, heating to 450 ℃ at a heating rate of 3 ℃/min, keeping the temperature for 6h at a constant temperature, and then naturally cooling to obtain the lithium supplement material B of the lithium ion battery anode material.
Example 3:
preparing a positive electrode lithium supplement material: the molar ratio of the components is 3.5: 1 weighing a certain amount of lithium ingot and D50SiO of 25nm2And putting the mixture into a 200 ℃ high-temperature mixer in the argon protection atmosphere for mixing for 7h at a speed of 500r/min, then putting the mixture into a tubular furnace in the argon protection atmosphere, heating the tubular furnace to 660 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 6h at a constant temperature, then naturally cooling, putting the product into the tubular furnace, introducing a mixed gas with the purity of oxygen and carbon dioxide of 1:1, heating to 350 ℃ at a heating rate of 3 ℃/min, keeping the temperature for 10min, and passivating to obtain the lithium supplement material C of the lithium ion battery anode material.
II, secondly: test of
1. Positive electrode preparation test
(1) Preparing a positive electrode
Positive electrode, carbon black conductive agent (super-P), Carbon Nanotube (CNT), and polyvinylideneVinyl fluoride (PVDF) and a positive electrode lithium supplement material are mixed according to the weight ratio of 96-a: 1: 1: 2: weighing the mass ratio of a (a is more than or equal to 0 and less than or equal to 2, when the positive electrode lithium supplement material exists, a is 2, otherwise a is 0), adding a proper amount of NMP, stirring at a high speed for 40 minutes to obtain uniform positive electrode slurry, coating the uniform positive electrode slurry on an aluminum foil with the thickness of 12um, drying and rolling, and then punching into a wafer with the diameter of phi 14 mm. The positive electrode surface capacity is 3mAh/cm2。
(2) State of the different cathode preparation processes
Table 1 states of different positive electrode preparation processes
Figure BDA0002548312010000071
Figure BDA0002548312010000081
As can be seen from table 1, when the lithium supplement material lithium oxide is added during the mixing of the positive electrode slurry, the solution of the lithium supplement material lithium oxide in NMP of PVDF is unstable, and a reaction phenomenon occurs, which causes a phenomenon that the slurry is in jelly state, so that the positive electrode plate cannot be prepared. Different anode slurries without adding the anode lithium supplement material and with the anode lithium supplement material are good flowing slurries, and the jelly phenomenon does not occur even if the anode lithium supplement material is independently prepared into the slurries, so that the anode lithium supplement material has high stability, can not influence the mixing of the anode slurries, and can adapt to the mixing of different anode active substances.
2. Button cell test
(1) Assembling the button cell: at 1.0mol/L LiPF6The electrolyte is EC + DEC (volume ratio of 1:1) +2 vol.% VC +3 vol.% FEC, the surface capacity of a 450 mu m Li plate or surface is 3.3mAh/cm2The silicon-oxygen-carbon negative electrode with the first week efficiency of 86 +/-1 percent is a counter electrode, the Cellgard-2400 type polypropylene membrane is a diaphragm, and the diaphragm is assembled into a button cell in a glove box filled with argon.
(2) And (3) button cell testing:
a. the test method of the cobalt acid lithium battery comprises the following steps: connecting the button cell with a blue test instrument at room temperature, and when metal lithium is used as a negative electrode, setting the cell to perform constant-current and constant-voltage charge-discharge circulation at a current of 0.1C/0.1C, wherein the charge cut-off voltage is 4.45V, the charge cut-off current is 0.01C, and the discharge cut-off voltage is 2.75V, and standing for 10 min; when using silicon-oxygen-carbon as cathode, the charge cut-off voltage is 4.35V, and the rest of the test procedure is the same.
Testing method of NCM811 ternary battery: connecting the button cell with a blue test instrument at room temperature, adopting metal lithium as a cathode, setting the cell to perform constant-current and constant-voltage charge-discharge circulation at a current of 0.1C/0.1C, wherein the charge cut-off voltage is 4.25V, the charge cut-off current is 0.01C, the discharge cut-off voltage is 2.8V, and standing for 10 min.
c. The test method of the lithium iron phosphate battery comprises the following steps: connecting the button cell with a blue test instrument at room temperature, adopting metal lithium as a cathode, setting the cell to perform constant-current and constant-voltage charge-discharge circulation at a current of 0.1C/0.1C, wherein the charge cut-off voltage is 3.6V, the charge cut-off current is 0.01C, and the discharge cut-off voltage is 2.75V, and standing for 10 min.
d. The testing method of the positive electrode lithium-supplement material battery comprises the following steps: the button cell is connected with a blue light tester at room temperature, metal lithium is used as a negative electrode, the cell is set to carry out constant-current constant-voltage charging at a current of 0.1 ℃, the charging cut-off voltage is 4.45V, the button cell is placed for 10min, constant-current constant-voltage discharging is carried out at a current of 0.1 ℃, and the discharging cut-off voltage is 2.75V.
The above tests involve the following calculation:
specific charge capacity is charge capacity/mass of positive electrode active material;
specific discharge capacity is discharge capacity/mass of positive active material;
first coulombic efficiency (first cycle discharge capacity/first cycle charge capacity) 100%;
TABLE 2 different Pole piece test data
Figure BDA0002548312010000091
Table 2 shows the test data of different electrode plates, in this table, the specific charge capacity of the electrode plate containing only the lithium supplement material a and not containing the positive active material in the comparative battery example 3 is 510.6mAh/g at 0V-4.45V, and the specific discharge capacity is 0 at 4.45V-2.75V, which is identical to the charge-discharge range of the positive electrode material, which indicates that the lithium ion released from the lithium supplement material a does not re-embed in the discharge range, and the released active lithium ion can be used to compensate the loss of the lithium ion in the charge-discharge process of the lithium battery.
Fig. 1 is a first cycle charge and discharge graph of a battery example 1 and a battery comparative example 1, wherein the positive electrode sheet of the battery example 1 contains a lithium supplement material a, and the battery comparative example 1 is different from the battery example 1 in that the battery comparative example 1 does not contain the lithium supplement material. As can be seen from table 2, the specific first charge capacity of the battery example 1 containing the positive electrode lithium supplement material a is 201.4mAh/g, while the specific first charge capacity of the battery comparative example 1 not containing the lithium supplement material is only 190.6mAh/g, which is significantly lower than that of the battery example 1, which indicates that the active lithium in the lithium supplement material a is substantially released, the first lithium removal capacity of the battery is significantly improved, and additional active lithium ions are provided, which also indicates from the side that the positive electrode lithium supplement material a has a coating layer on the bulk phase and the surface, and the active lithium in the positive electrode lithium supplement material a can be well protected.
Fig. 2 is a first-cycle charge-discharge graph of battery example 2 and battery comparative example 2, which can better show the lithium supplementing effect of the lithium supplementing material of the present invention because the batteries in both examples are full batteries. As can be seen from Table 2, the first-week charge capacity of the battery of example 2 was 197.1mAh/g, and the first-week discharge capacity was 168.5 mAh/g; the first-week charge capacity of the battery comparative example 2 was 186.3mAh/g, and the first-week discharge capacity was 160.2 mAh/g; it can be seen that the battery of comparative example 2 has a low first discharge capacity because active lithium ions are all derived from the positive active material in the full battery and are limited, and a portion of the active lithium ions are consumed to form an SEI film during charging and a portion of the lithium ions inserted into the negative electrode cannot be completely extracted. The reason why the reversible discharge capacity of the battery in example 2 is obviously higher than that of the battery in comparative example 2 is that the lithium supplement material A is added into the battery in example 2, and the extra active lithium ions can be provided to compensate the lithium ions consumed by the participation of SEI formation. In addition, comparing the specific discharge capacity of the battery in the cycle 50 th cycle of the battery example 2 and the battery comparative example 2, it can be seen that the specific discharge capacity of the battery in the example 2 with the lithium supplement material a added into the positive electrode is obviously higher than that of the battery without the lithium supplement material, the lithium supplement effect of the lithium supplement material a is shown, and the lithium supplement material a has no negative influence on the performance of the positive electrode material of the battery.
The above embodiment is tested by assembling the button lithium battery, and the material of the invention has the same effect when being applied to different types of lithium batteries such as soft package lithium batteries, aluminum shell lithium batteries, steel shell lithium batteries, cylindrical lithium batteries and the like, and is not repeated herein.
In summary, the lithium ion supplement additive of the present invention has an excellent lithium supplement effect, and is applied to a battery for lithium supplement, the specific addition amount needs to be optimally designed according to the lithium ion demand of the battery and the lithium ion amount actually provided by the lithium ion supplement additive, rather than being added randomly, and when the addition amount is too small, the lithium ion provided to the battery cannot meet the battery demand, so the lithium supplement effect is not particularly obvious.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Other technical features than those described in the specification are known to those skilled in the art, and are not described herein in detail in order to highlight the innovative features of the present invention.

Claims (9)

1. The anode lithium supplement material is characterized in that the chemical formula of the anode lithium supplement material is SiO2∙ bLi, wherein b is in the range of 0 < b < 4.2.
2. According to claim 1The positive electrode lithium supplement material is characterized in that the particle diameter D of the positive electrode lithium supplement material50In the range of 0 < D50≤1μm。
3. The method for preparing a positive electrode lithium supplement material according to claim 1 or 2, wherein SiO is added in one or more of carbon dioxide, inert gas and vacuum2Uniformly mixing the powder with metallic lithium physically and then carrying out heat treatment to obtain SiO2∙ bLi, respectively; or: in one or more of carbon dioxide, inert gas or vacuum atmosphere, SiO2Uniformly mixing the powder with metallic lithium physically and then carrying out heat treatment to obtain SiO2∙ bLi after the reaction, SiO2∙ bLi are passivated in an atmosphere of one or more of dry gas, carbon dioxide, oxygen.
4. The method for preparing the lithium supplementing material for the positive electrode according to claim 3, wherein the metal lithium and SiO are2The mixing molar ratio of (3) is not less than 0 and not more than 4.2.
5. The method for preparing the lithium supplementing material for the positive electrode according to claim 3, wherein the metallic lithium is one or more of lithium powder, lithium foil or lithium ingot.
6. The method as claimed in claim 3, wherein the heat treatment temperature is 200-1100 deg.C, and the heat treatment time is 0.01-24 h.
7. The preparation method of the positive electrode lithium supplement material according to claim 3, wherein the passivation temperature is 60-550 ℃, and the passivation time is 1min-8 h.
8. Use of the positive electrode lithium supplement material according to any one of claims 1 to 2 in the production of a positive electrode sheet.
9. The application of the positive electrode lithium supplement material as claimed in claim 8, wherein the positive electrode lithium supplement material is added into the positive electrode slurry to be mixed, and is attached to the aluminum foil in a dipping, coating and/or spraying manner to form a positive electrode sheet; or: and independently preparing the positive electrode lithium supplement material into slurry, and attaching the slurry to the prepared positive electrode plate in a dipping, coating and/or spraying manner to form a lithium supplement coating.
CN202010567299.4A 2020-06-19 2020-06-19 Positive electrode lithium supplement material and preparation method and application thereof Pending CN111668470A (en)

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