CN115588734A - Composite lithium supplement agent and preparation method thereof - Google Patents
Composite lithium supplement agent and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a composite lithium supplementing agent, which is carbon-coated transition metal-doped lithium borate and/or carbon-coated transition metal-doped lithium thioborate. The composite lithium supplement agent has high theoretical decomposition capacity and ion transmission performance, and is beneficial to improving the rate capability of a battery; the composite lithium supplement agent with two decomposition mechanisms is prepared by regulating and controlling the doping elements and the proportion and carbon coating, so that the electronic conductivity of the material is obviously improved, and the decomposition potential is effectively reduced; and lithium can be supplemented as required by regulating and controlling the charging voltage according to different decomposition reactions. The composite lithium supplement agent prepared by the invention has good air stability and moisture resistance, and is compatible with the existing battery preparation process. And the material has good chemical stability and high safety, and is suitable for industrial large-scale preparation.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a composite lithium supplement agent and a preparation method thereof.
Background
With the continuous propulsion of traffic electrification, electric vehicles have come to the golden period of development. However, the new energy automobile is limited by the current power battery technology development level, the endurance mileage of the new energy automobile is relatively short, and the battery life is limited, so that the improvement of the energy density and the extension of the service life of the power battery become key scientific problems which need to be solved urgently. On the one hand, researchers are working on developing new material systems, such as high nickel anodes, silicon-based cathodes, and the like. On the other hand, the failure mechanism of the lithium ion battery is deeply researched, and a corresponding solution is provided. At present, domestic famous enterprises have already laid out a high-energy-density battery system based on a high-nickel ternary anode matched with a silicon oxide or nano-silicon cathode, and strive for energy density to break through 350Wh/kg. However, the silicon-based negative electrode undergoes severe volume expansion during charging and discharging, resulting in pulverization of particles and continuous destruction of a solid electrical cut-off film, resulting in greater irreversible lithium loss, thereby causing the battery to exhibit lower first-turn coulombic efficiency. Meanwhile, due to the consumption of active lithium on the negative electrode side, the positive electrode is in a lithium-deficient state for a long time and then generates irreversible phase change, which all cause the energy density of the battery to be lower than the theoretical energy density of the material. Therefore, the development of a lithium supplement agent for improving the coulomb efficiency of the first circle of the battery and compensating the lithium loss in the long-cycle process is a key technology for improving the energy density of the battery
The existing lithium supplement agents comprise lithium-rich materials, decomposable lithium salts and some binary lithium-containing compounds, and although a great deal of research verifies the lithium supplement effect of the materials, a mature lithium supplement product which can be applied in a large scale is still not found at present.
CN110867584B discloses a ternary lithium-rich material Li 5 MO 4 Although the theoretical specific capacity is high, the air stability is poor and the capacity is short in the airThe exposure of the material can have a detrimental effect on the electrochemical properties of the material. And because the decomposition products of the materials contain transition metal oxides, the energy density of a battery system can be reduced, and the side reaction of the electrolyte can be continuously catalyzed, so that the battery fails. CN112951620B discloses a coating-layer-modified lithium nitride as a lithium supplement agent, which improves the water resistance of the lithium nitride to a certain extent and improves the compatibility of the lithium nitride with a battery preparation process. However, the method still does not solve the problems of strong intrinsic reducibility and poor chemical stability of the lithium nitride, and the method uses an organic solvent to treat the lithium nitride, which may bring potential environmental pollution.
At present, although the academic community has conducted extensive research on a positive electrode lithium supplement agent, a negative electrode pre-lithiation method and some novel lithium supplement methods, no lithium supplement method can meet the actual requirements of current battery production, and a lithium supplement agent which is high in theoretical specific capacity, good in air stability and simple in preparation process is still lacking in the market. Therefore, the development of a novel composite lithium supplement agent is very important for improving the coulomb efficiency of the first circle of the battery, effectively improving the energy density of the battery and prolonging the service life of the battery.
Disclosure of Invention
In order to solve the technical problems, the invention provides a novel composite lithium supplement agent and a preparation method and application thereof. The composite lithium supplement agent prepared by carbon coating and transition metal doping has two lithium removal mechanisms, can be applied to long-acting lithium supplement in a lithium ion battery, effectively improves the electronic conductivity of the material, reduces the decomposition potential of the material, and realizes high-efficiency lithium supplement of the lithium ion battery.
The invention solves the technical problems through the following technical scheme:
a composite lithium supplementing agent is carbon-coated transition metal doped lithium borate and/or carbon-coated transition metal doped lithium thioborate.
In the composite lithium supplement agent, the molar ratio of Li to B is 1-5:1. lithium borate/thioborate exist in various forms, e.g. lithium borate is Li 2 B 4 O 7 ，LiBO 2 ，Li 4 B 2 O 5 ，Li 3 BO 3 ，Li 5 BO 4 And lithium thioborate is Li 2 B 2 S 5 ，Li 3 BS 3 And the like. Theoretically, the higher the content of lithium in the lithium supplement agent is, the higher the lithium supplement efficiency is. However, if the lithium content is too high, the air stability of the material is deteriorated, and lithium carbonate is easily generated on the surface. On the other hand, the increase of the lithium content can cause the increase of residual alkali on the surface of the material, and the lithium content is easy to react with the PVDF as a binder in the pulping preparation process, thereby causing gelation. Therefore, lithium borate/lithium thioborate is preferably Li in view of the comprehensive consideration of the fact that the lithium supplementing effect of lithium batteries and the raw material and production costs can be practically solved, and the industrial applicability of the manufacturing process 3 BO 3 /Li 3 BS 3 In the form of (a).
Further, the thickness of the carbon coating layer is 1-10nm, preferably 2-5nm.
Further, the transition metal-doped lithium borate is expressed by the chemical formula Li x M a B y O z Transition metal doped lithium borate is expressed by the chemical formula Li x M a B y S z Wherein x is between 2 and 5, y is between 1 and 4, z is between 2 and 7, a is between 0.01 and 1, preferably 01 to 0.5, and the values of x, y, z and a satisfy the conservation of charge of the compound. The transition metal is at least one of Al, ti, mn, fe, co, ni and Cu.
In a preferred embodiment of the present invention, the transition metal-doped lithium borate is Li 3-2x M x BO 3 The transition metal doped lithium thioborate is Li 3-2x M x BO 3 (ii) a The transition metal M is at least one of Al, ti, mn, fe, co, ni and Cu; x is 0.01 to 1, preferably 0.05 to 0.1.
Lithium borate and/or lithium thioborate are/is used as a lithium supplement agent, and lithium removal is an oxygen anion redox reaction mechanism. In the formation stage, most irreversible capacity loss is contributed by the oxygen anion redox reaction corresponding to the extraction of lithium, and the oxygen release which is difficult to avoid can be removed by methods such as reserving an air bag and the like. After doping with a proper amount of transition metal element M, the mechanism of delithiation is not only the redox reaction of oxygen anions, but also the redox mechanism of transition metal cations. The lithium removal is accompanied by the valence state change of the transition metal, the volume expansion change is small, and no gas is generated. This feature can be used to achieve on-demand lithium replenishment during battery cycling. After the battery is circulated for a certain number of cycles, aiming at the capacity attenuation caused by the loss of active lithium, the lithium ions in the lithium supplement agent can be effectively released by adjusting the charging voltage interval, and the capacity of the electrode material is recovered. According to the invention, through a double lithium removal mechanism of the lithium supplement additive, the first-loop coulombic efficiency of the battery can be effectively improved, and meanwhile, lithium supplement as required is realized by regulating and controlling voltage in the battery circulation process, so that the circulation stability of the battery is improved.
The transition metal doped lithium borate is taken as Li 3-2x M x BO 3 For example, during battery operation, the decomposition process of the lithium supplement additive includes (i) a transition metal cation valence mechanism, and (ii) an oxygen anion valence mechanism. Two different decomposition potentials are corresponded during the charging process.
i)
ii)xLiMBO 3 →xLi + +xMBO 3 ++xe -
The transition metal doped lithium thioborate is taken as Li 3-2x M x BS 3 For example, during battery operation, the decomposition process of the lithium supplement additive includes: (i) A transition metal cation valence transition mechanism, and (ii) an oxygen anion valence transition mechanism.
iii)
iv)xLiMBS 3 →xLi + +xMBS 3 ++xe -
Wherein the corresponding decomposition potentials of reactions i) and iii) are from 4.0 to 4.5V (Vs, li) + Li), reactions ii) and iv) corresponding to decomposition potentials of 4.5-4.7V (Vs, li) + /Li)。
The second purpose of the invention is to provide a preparation method of the composite lithium supplement agent, which comprises the following steps:
(S1) a lithium source, a lithium source and a boron source, optionally, a sulfur source is also added, the transition metal source is uniformly mixed in a solvent, the solvent is evaporated to dryness, and the mixture is mechanically ground and calcined in an inert atmosphere to obtain transition metal doped lithium borate and/or transition metal doped lithium thioborate;
and (S2) crushing the material obtained in the step (S1), uniformly mixing the crushed material with a carbon source, and calcining the mixture in an inert atmosphere to obtain carbon-coated transition metal-doped lithium borate and/or transition metal-doped lithium thioborate, namely the composite lithium supplement agent.
Further, in the step (S1), the lithium source includes lithium carbonate (Li) 2 CO 3 ) Lithium hydroxide monohydrate (LiOH. H) 2 O), lithium nitrate (LiNO) 3 ) Lithium acetate (CH) 3 COOLi), lithium sulfide (Li) 2 S) at least one of; the transition metal source is a salt of a transition metal, such as an oxalate, nitrate, halide, or the like, of the transition metal M. A lithium source, boric acid and/or thioboric acid, the transition metal source being used in an amount sufficient for Li 3-2x M x BO 3 And/or Li 3-2x M x BS 3 And (4) finishing.
Further, in the steps (S1) and (S2), the inert atmosphere is one or a mixture of nitrogen and argon in any proportion; the calcining temperature of the step (S1) is 600-800 ℃, and the calcining time is 6-10h; the calcining temperature of the step (S2) is 500-700 ℃, and the calcining time is 2-4h. And step (S2) is to carbonize organic matters, and the lithium supplement agent is melted away when the temperature is too high, so that the original carbon coating appearance is lost.
Further, in the step (S2), the carbon source is an organic carbon source and/or an inorganic carbon source; the organic carbon source comprises at least one of organic acid and polysaccharide, the organic acid comprises at least one of citric acid, oxalic acid and malic acid, and the polysaccharide comprises at least one of glucose, sucrose and fructose; the inorganic carbon source comprises at least one of graphite oxide, single-layer graphene oxide and carbon nanotubes (hydroxyl multi-walled carbon nanotubes, fluorinated carbon nanotubes, single-walled carbon nanotubes and the like). The adding amount of the carbon source is 5-10% of the mass of the material obtained in the step (S1). The addition amount of the carbon source is too small, the lithium supplement agent has poor conductivity, the decomposition voltage is increased, and the lithium supplement effect cannot be effectively exerted in the conventional charge-discharge voltage circulation process, so that the capacity of the battery is reduced; the excessive carbon source consumption reduces the content of active substances of the pole piece and the volume energy density of the battery.
Further, the carbon source is an organic carbon source and a graphite carbon source according to a mass ratio of 90-95:5-10 of compound carbon source. Graphitized carbon such as graphite oxide can be attached to the lithium supplement using an organic component such as citric acid, so that the uniform coating of the material is most effective. The composite system of the organic carbon source and the inorganic carbon source can effectively improve the overall electronic conductivity and reduce the decomposition voltage of the lithium supplement agent by introducing the graphite carbon source with higher graphitization degree. Because the graphite carbon source and the lithium supplement material lack strong interaction, a single graphite carbon source is difficult to form a uniform coating layer on the surface of the lithium supplement agent. Organic matters in the composite lithium supplementing system, such as citric acid, have reducibility, can interact with oxygen-containing functional groups on the surface of graphite oxide, and simultaneously form acid-base action with residual alkali on the surface of a lithium supplementing material, so that strong connection between a carbon layer and a lithium supplementing agent is established. In the high-temperature calcination process, the carbon material is uniformly attached to the surface of the lithium supplement agent, and a uniform carbon coating layer is obtained after calcination.
Further, in the step (S2), the crushing method is not particularly limited, and in one embodiment of the present invention, the high energy ball milling method is performed at a ball-to-material ratio of 5:1 to 30:1, the ball milling speed is 300rpm-700rpm, and the ball milling time is 2h-20h.
The third purpose of the invention is to provide a lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte; the positive electrode contains the composite lithium supplement agent.
Further, in the positive electrode, the composite lithium supplement agent accounts for 5-15wt%, preferably 10-15wt%, such as 12.5wt% of the positive electrode active material. The positive active material is well known in the art and includes, but is not limited to, lithium iron phosphate, lithium cobaltate, CNM ternary positive electrode material, and the like.
Further, the positive electrode containing the composite lithium supplement agent can be prepared by directly coating slurry containing the composite lithium supplement agent on a positive electrode plate (the slurry comprises the composite lithium supplement agent, a binder and an organic solvent, the proportion of the composite lithium supplement agent to the binder is 80-95, and the solid content of the slurry is 50-70%); the anode material, the composite lithium supplement agent, the conductive agent and the binder can also be prepared into slurry to prepare the working anode plate.
The binder, the conductive agent, and the organic solvent are well known in the art. For example, the binder is selected from at least one of polyvinylidene fluoride, polyacrylonitrile and polyethylene glycol, the conductive agent is selected from at least one of Super P, ketjen black, conductive carbon tube and graphene, and the organic solvent is selected from at least one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO) and N, N-Dimethylformamide (DMF).
In the first charge and discharge process of the lithium ion battery, the anode and the cathode react with an interface to form a stable solid electric cut-off film (SEI) which can irreversibly consume active lithium, so that the first coulomb efficiency is low. And for a silicon-based negative electrode with higher specific capacity, SEI can be continuously reconstructed in the circulation process, so that the consumption of active lithium is further increased. The invention develops a novel composite lithium supplement agent which has different decomposition mechanisms under different voltages and can realize lithium supplement as required by regulating and controlling the potential. The method can improve the coulomb efficiency of the first circle of the high specific energy battery system and prolong the cycle life of the battery.
Compared with the prior art, the invention has the advantages that:
1. the lithium-supplementing agent based on lithium borate and lithium thioborate is prepared, has high theoretical decomposition capacity and ion transmission performance, and is beneficial to improving the rate capability of a battery; and the composite lithium supplement agent with two decomposition mechanisms is prepared by regulating and controlling the doping elements and the proportion and carbon coating. The electronic conductivity of the material is obviously improved, and the decomposition potential of the material is effectively reduced; and lithium can be supplemented as required by regulating and controlling the charging voltage according to different decomposition reactions.
2. The composite lithium supplement agent prepared by the invention has good air stability and moisture resistance, and is compatible with the existing battery preparation process. And the material has good chemical stability and high safety, and is suitable for industrial large-scale preparation.
3. The preparation process is simple to operate, has low requirements on equipment, is favorable for realizing industrialization, and is suitable for large-scale popularization.
Drawings
FIG. 1 is a process flow diagram of the composite lithium supplement of the present invention;
FIG. 2 is a Scanning Electron Micrograph (SEM) of the composite lithium supplement agent of example 1;
FIG. 3 is a Transmission Electron Micrograph (TEM) of the composite lithium supplement agent of example 1;
fig. 4 is a first-turn charge and discharge curve of a full battery assembled by adding a composite lithium supplement in embodiment 1 of the present invention;
FIG. 5 is an X-ray spectroscopy analysis (EDS) of the composite lithium supplement of example 4.
Detailed Description
The present invention will be further described with reference to specific examples, but the present invention is not limited to the specific examples. All proportions in the examples of the present invention are mass ratios unless otherwise specified.
The assembled battery in the following example was a button cell (CR 2032), the positive electrode was lithium nickel cobalt manganese oxide (NCM 622), and the negative electrode was a silicon/graphite composite. The separator type was Celgard 2500, and the electrolyte was 1M lithium hexafluorophosphate (LiPF) 6 ) Dissolved in a mixed solvent of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) in equal volume. And (3) carrying out charge and discharge tests on the assembled battery on a LAND charge and discharge tester, wherein the charge and discharge multiplying power of the 1 st circle is 0.02C (the multiplying power is calculated according to the nominal specific capacity of the used anode material, such as that NCM622 is 180 mAh/g), and the cut-off voltage is 2.5-4.5V. The charge-discharge multiplying power of the 2 rd and 3 rd circles is 0.1C, the charge-discharge multiplying power in the subsequent circulation process is 0.5C, and the cut-off voltage is 2.5-4.3V.
The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
Example 1
(1) LiOH (0.1 mol), H 3 BO 3 And MnC 2 O 4 ·2H 2 O is added according to a molar ratio of 2.9:1:0.05 was dispersed in 100ml of water, heated to 50 ℃ and stirred for 2h to dissolve completely. Evaporating the solvent to dryness at 100 ℃, drying the obtained mixture, mechanically grinding for 15min, and calcining at 600 ℃ for 10h under the atmosphere of argon to obtain manganese-doped lithium borate (Li) 2.9 Mn 0.05 BO 3 )；
(2) Using high-energy ball milling to obtain L in the step (2) 2.9 Mn 0.05 BO 3 The material being mixed with citric acid, li 2.9 Mn 0.05 BO 3 And citric acid in a mass ratio of 100:10, carrying out high-energy ball milling under the following conditions: ball to feed ratio (ratio of grinding balls to mixture) 20:1, the rotating speed of the ball mill is 600rpm, and the ball milling time is 10 hours; and calcining the ball-milled mixture for 5 hours in an argon atmosphere at the calcining temperature of 600 ℃ to obtain the composite lithium supplement agent. . FIG. 2 is an SEM photograph of the composite lithium supplement obtained in example 1, and it can be seen that the particle size of the ball-milled material is 1 to 5 μm. FIG. 3 is a TEM photograph of the composite lithium supplement obtained in example 1.
(3) Taking a composite lithium supplement agent as an additive of a positive electrode material, and mixing the positive electrode material with a ternary positive electrode material NCM622, a conductive agent Super P and a binder PVDF according to a mass ratio of 10:80:10:10 preparing a positive pole piece, and matching the positive pole piece with a silicon/graphite composite negative pole to assemble a button cell for electrochemical test. Fig. 4 is a first-turn charge-discharge curve of the lithium ion battery assembled by the positive electrode sheet obtained in example 1 according to the above method.
Example 2
(1) Mixing Li 2 S, B, S and MnC 2 O 4 ·2H 2 O is added according to a molar ratio of 1.45:1:0.1:0.05 mixing, mechanically grinding for 45min, encapsulating the mixture in a quartz tube under the argon atmosphere, and calcining at 600 ℃ for 10h to obtain manganese-doped lithium thioborate (Li) 2.9 Mn 0.05 BS 3 Abbreviation M 0.05 -LBS)。
(2) Using high energy ball mill to mill M 0.05 LBS mixed with citric acid, M 0.5 LBS to 1-5 μm. Under an argon atmosphere, M 0.05 -the mass ratio of LBS and citric acid is 100:10, ball to feed ratio (ratio of grinding balls to mixture) 20:1, the rotating speed of the ball mill is 600rpm, and the ball milling time is 10h.
(3) Calcining the ball-milled mixture for 2 hours in an argon atmosphere at the calcining temperature of 600 ℃ to obtain the composite lithium supplement agent
(4) Taking the composite lithium supplement agent as an additive of a positive electrode material, and mixing the positive electrode material with NCM622, a conductive agent Super P and a binder PVDF according to the mass ratio of 10:80:10:10 preparing a positive pole piece, and matching the positive pole piece with a silicon/graphite composite negative pole to assemble a button cell for electrochemical test.
Example 3
The rest is the same as example 3, except that LiOH, H in step 1) 3 BO 3 And MnC 2 O 4 ·2H 2 The molar ratio of O is 2.8:1:0.1, the product obtained is Li 2.8 Mn 0.1 BO 3 。
Example 4
The rest is the same as the example 1, except that the doping element in the step 1) is FeC 2 O 4 ·2H 2 O，LiOH，H 3 BO 3 And FeC 2 O 4 ·2H 2 The molar ratio of O is 2.9:1:0.05, the product obtained is Li 2.9 Fe 0.05 BO 3 . Figure 5 is the EDS spectrum of the product obtained.
Example 5
The process is otherwise the same as in example 1, except that in step 2), the mass ratio of citric acid to manganese-doped lithium borate is 5:100.
example 6
The process is otherwise the same as in example 1, except that in step 2), the mass ratio of citric acid to manganese-doped lithium borate is 15:100.
example 7
The process is otherwise the same as in example 1, except that in step 2), the mass ratio of citric acid to manganese-doped lithium borate is 3:100.
example 8
The rest is the same as example 1, except that the carbon sources added in step 2) are citric acid and graphite oxide according to a mass of 95:5 mixture of Li 2.9 Mn 0.05 BO 3 And the mass ratio of the carbon source to the carbon source is 100:10.
example 9
The process is the same as example 1 except that the carbon sources added in step 2) are citric acid and graphite oxide in a mass ratio of 90:10 mixture of Li 2.9 Mn 0.05 BO 3 And the mass ratio of the carbon source to the carbon source is 100:10.
example 10
The same as example 1 except that the carbon source added in step 2) was graphite oxide.
Comparative example 1
NCM622, a conductive agent Super P, and a binder PVDF according to the mass ratio of 80:10:10 preparing a positive pole piece, and matching the positive pole piece with a silicon/graphite composite negative pole to assemble a button cell for electrochemical test.
In the examples included in the present invention, the lithium supplementing effect of different composite lithium supplementing agents in the battery is shown in table 1.
TABLE 1 electrochemical Properties of lithium ion batteries of different examples
According to the embodiment, different composite lithium supplementing agents have good lithium supplementing effects, and compared with the original lithium borate material, the lithium supplementing effect is remarkably improved by element doping and carbon coating. Optimizing the doping element and doping amount can improve the conductivity of the material and release more active lithium at lower voltage. From the comparison between example 1 and examples 8 and 9, it can be seen that the conductivity of the material is closely related to the quality of the carbon coating layer, and compared with the amorphous carbon formed after the carbonization of the organic carbon source, the addition of a small amount of graphite oxide can significantly improve the conductivity of the composite lithium supplement agent, and the electrochemical performance is also more excellent. On the other hand, example 10 shows that it is difficult to achieve a good effect by adding graphite oxide alone, because graphite oxide and lithium supplement agent lack interaction and are difficult to coat uniformly on the surface of lithium supplement material. The composite carbon source of the organic carbon source and the graphite oxide is added, so that the electronic conductivity of the composite lithium supplement agent can be improved, the decomposition voltage of the lithium supplement agent can be further reduced, the lithium supplement agent can be completely decomposed in a conventional positive working voltage range, and the first-turn coulomb efficiency and the long-cycle stability are improved.
In conclusion, the preparation method of the composite lithium supplement agent is simple, the decomposition voltage of the lithium supplement agent is reduced through doping and carbon coating, the composite lithium supplement agent is compatible with the conventional battery system, and the composite lithium supplement agent has a good lithium supplement effect. The composite lithium supplement agent prepared by the invention has better air stability, is compatible with a battery preparation process, and has potential large-scale application.
Claims (10)
1. A composite lithium supplement is a carbon-coated transition metal doped lithium borate and/or a carbon-coated transition metal doped lithium thioborate.
2. The composite lithium supplement agent as claimed in claim 1, wherein the molar ratio of Li to B in the composite lithium supplement agent is 1-5:1; preferably, the lithium borate comprises Li 2 B 4 O 7 ，LiBO 2 ，Li 4 B 2 O 5 ，Li 3 BO 3 ，Li 5 BO 4 Of (a), the lithium thioborate includes Li 2 B 2 S 5 ，Li 3 BS 3 At least one of (1).
3. The composite lithium supplementing agent according to claim 1, wherein the carbon coating has a thickness of 1 to 10nm, preferably 2 to 5nm.
4. The composite lithium supplement agent according to claim 1, wherein the transition metal doped lithium borate is represented by the chemical formula Li x M a B y O z Transition metal doped lithium thioborate formula expressed as Li x M a B y S z Wherein x is between 2 and 5, y is between 1 and 4, z is between 2 and 7, a is between 0.01 and 1, preferably 01 to 0.5, and the values of x, y, z and a satisfy the conservation of charge of the compound; the transition metal is selected from at least one of Al, ti, mn, fe, co, ni and Cu;
further, the transition metal-doped lithium borate is Li 3-2x M x BO 3 The transition metal doped lithium thioborate is Li 3- 2x M x BO 3 (ii) a x is 0.01 to 1, preferably 0.05 to 0.1.
5. The preparation method of the composite lithium supplementing agent of any one of claims 1 to 4, which is characterized by comprising the following steps:
(S1) adding a lithium source, a boron source and a transition metal source, optionally adding a sulfur source, uniformly mixing in a solvent, evaporating the solvent to dryness, mechanically grinding, and calcining in an inert atmosphere to obtain transition metal doped lithium borate and/or transition metal doped lithium thioborate;
and (S2) crushing the material obtained in the step (S1), uniformly mixing the crushed material with a carbon source, and calcining the mixture in an inert atmosphere to obtain carbon-coated transition metal-doped lithium borate and/or transition metal-doped lithium thioborate.
6. The production method according to claim 5, wherein, in step (S1), the lithium source includes lithium carbonate (Li) 2 CO 3 ) Lithium hydroxide monohydrate (LiOH. H) 2 O), lithium nitrate (LiNO) 3 ) Lithium acetate (CH) 3 COOLi), lithium sulfide (Li) 2 S) at least one of; the transition metal source is a salt of a transition metal, such as an oxalate, a nitrate, a halide salt of a transition metal M; the boron source is boric acid or a boron simple substance, and the sulfur source is a sulfur simple substance.
7. The method according to claim 5, wherein in steps (S1) and (S2), the inert atmosphere is one or a mixture of nitrogen and argon in any proportion; the calcining temperature of the step (S1) is 600-800 ℃, and the calcining time is 6-10h; the calcining temperature of the step (S2) is 500-700 ℃, and the calcining time is 2-4h.
8. The production method according to claim 5, wherein in the step (S2), the carbon source is an organic carbon source and/or an inorganic carbon source; the organic carbon source comprises at least one of organic acid and polysaccharide, the organic acid comprises at least one of citric acid, oxalic acid and malic acid, and the polysaccharide comprises at least one of glucose, sucrose and fructose; the inorganic carbon source comprises at least one of graphite oxide, single-layer graphene oxide and carbon nanotubes (hydroxyl multi-walled carbon nanotubes, fluorinated carbon nanotubes, single-walled carbon nanotubes and the like); the adding amount of the carbon source is 5-10% of the mass of the material obtained in the step (S1).
9. The preparation method according to claim 8, wherein the carbon source is an organic carbon source and a graphite-based carbon source in a mass ratio of 90-95:5-10 of compound carbon source.
10. A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte; the positive electrode contains the composite lithium supplement agent according to any one of claims 1 to 4; preferably, the composite lithium supplement agent accounts for 5-15wt% of the positive electrode active material, and preferably 10-15wt%.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116053440A (en) * | 2023-02-09 | 2023-05-02 | 浙江锂宸新材料科技有限公司 | Multi-ion doped pre-lithiated silica material and preparation method thereof |
| CN117638081A (en) * | 2024-01-23 | 2024-03-01 | 上海瑞浦青创新能源有限公司 | Composite lithium supplementing agent, preparation method thereof, positive electrode plate and lithium ion battery |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116053440A (en) * | 2023-02-09 | 2023-05-02 | 浙江锂宸新材料科技有限公司 | Multi-ion doped pre-lithiated silica material and preparation method thereof |
| CN117638081A (en) * | 2024-01-23 | 2024-03-01 | 上海瑞浦青创新能源有限公司 | Composite lithium supplementing agent, preparation method thereof, positive electrode plate and lithium ion battery |
| CN117638081B (en) * | 2024-01-23 | 2024-04-26 | 上海瑞浦青创新能源有限公司 | Composite lithium supplementing agent, preparation method thereof, positive electrode plate and lithium ion battery |
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