CN112103480B - Treatment method of prelithiation SiOx anode material - Google Patents
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Abstract
The invention relates to a treatment method of a pre-lithiated SiOx anode material. A treatment method of a pre-lithiated SiOx anode material comprises the following steps: mixing the pre-lithiated SiOx anode material with a first solid compound to obtain a first mixture, wherein X is more than 0 and less than 2, and the first solid compound is at least one of ammonium fluoride and ammonium phosphate; and (3) in the atmosphere of protective gas, carrying out heat preservation sintering on the first mixture at 50-300 ℃ to obtain the first pre-lithium silicon anode material. The treatment method of the pre-lithiated SiOx anode material can improve the stability of the pre-lithiated SiOx anode material.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a treatment method of a pre-lithiated SiOx anode material.
Background
Along with the increasing requirements of people on the endurance mileage of the electric automobile, the energy density of a battery system of the passenger car is required to be continuously improved, and the conventional graphite cathode cannot meet the current energy density requirement of the power battery. Because silicon-based negative electrodes have higher gram capacities, silicon-based negative electrodes are important research materials.
Silicon oxide SiO compared with pure Si cathode x Has higher gram capacity, lower expansion and better cycle life, and is regarded as a next-generation anode material. However, conventional silicon oxygen compounds SiO x The problem of low initial efficiency exists, the commercialized application of the silicon-oxygen compound is seriously restricted, the initial efficiency of the silicon-oxygen compound is improved at present, two main modes exist, one is pole piece end design, the initial efficiency is improved through pole piece end lithium supplement, and the other is lithium supplement during material end synthesis, and the initial efficiency is improved. The metal lithium powder adopted for pole piece end lithium supplement has explosion safety risks, and in addition, the metal lithium powder has contact injury risks to the respiratory tract, eyes and skin of operators. In contrast, material-end lithium supplementation can fundamentally avoid the above-mentioned risks faced by cell manufacturers. However, the pre-lithiated SiOx negative electrode material formed by material end lithium supplement has poor stability.
Disclosure of Invention
Accordingly, it is necessary to provide a method for treating a prelithiated SiOx anode material to obtain a prelithiated SiOx anode material with good stability.
A method of treating a prelithiated SiOx negative electrode material, comprising the steps of:
mixing a pre-lithiated SiOx anode material with a first solid compound to obtain a first mixture, wherein X is more than 0 and less than 2, and the first solid compound is at least one of ammonium fluoride and ammonium phosphate;
and (3) in the atmosphere of protective gas, carrying out heat preservation sintering on the first mixture at 50-300 ℃ to obtain the first pre-lithium silicon anode material.
According to the treatment method of the pre-lithiated SiOx negative electrode material, the pre-lithiated SiOx negative electrode material reacts with ammonia fluoride and/or ammonium phosphate at high temperature, so that alkaline substances lithium oxide and lithium hydroxide on the surface of the pre-lithiated SiOx negative electrode material are converted into LiF or lithium phosphate, the problem of alkaline substances on the surface layer of the lithium SiOx negative electrode material is solved from a root, and the stability of the pre-lithiated SiOx negative electrode material is improved; meanwhile, by controlling the dosage of ammonia fluoride or ammonium phosphate, a layer of artificial inorganic SEI film is formed on the surface of the pre-lithiated SiOx negative electrode material, and the artificial SEI film is compact, controllable in thickness and hydrophobic, can inhibit the dissolution rate of core lithium silicate, and improves the stability of the pre-lithiated SiOx negative electrode material.
In one embodiment, the mass ratio of the prelithiated SiOx anode material to the first solid compound is 100:0.1-100:10.
In one embodiment, in the step of performing heat-preserving sintering on the first mixture at 50-300 ℃, the heating rate is 5-50 ℃/min, and the heat-preserving time is 1-24 h.
In one embodiment, the particle size of the prelithiated SiOx negative electrode material is 1 μm to 10 μm.
In one embodiment, the pre-lithiated SiOx anode material has a carbon coating amount of 0.1wt% to 6wt%.
In one embodiment, the step of performing heat preservation sintering on the first mixture at 50-300 ℃ to obtain the first pre-lithium silicon anode material further comprises the following steps:
mixing the first pre-lithium silicon anode material with a second solid compound to obtain a second mixture, wherein the second solid compound is selected from at least one of nitrogen-containing organic matters and boron oxides;
and (3) in the atmosphere of protective gas, carrying out heat preservation sintering on the second mixture at 100-600 ℃ to obtain a second pre-lithium silicon anode material.
In one embodiment, the mass ratio of the first pre-lithium silicon anode material to the second solid compound is 100:0.1-100:6.
In one embodiment, in the step of performing heat-preserving sintering on the second mixture at 100-600 ℃, the heating rate is 5-50 ℃/min, and the heat-preserving time is 1-24 h.
In one embodiment, the step of sintering the second mixture at 100-600 ℃ under heat preservation specifically comprises the following steps: and (3) sintering the second mixture at the temperature of 450-550 ℃.
In one embodiment, the nitrogen-containing organic is selected from at least one of fatty amines and anilines.
Detailed Description
This invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The treatment method of the pre-lithiated SiOx anode material in one embodiment comprises the following steps:
step S110: the pre-lithiated SiOx negative electrode material is mixed with a first solid compound to obtain a first mixture.
Wherein, 0 < X < 2 in SiOx. For example, siO.
Specifically, the first solid compound is at least one selected from ammonium fluoride and ammonium phosphate.
Further, the mass ratio of the pre-lithiated SiOx anode material to the first solid compound is 100:0.1-100:10.
Specifically, the particle diameter of the prelithiated SiOx anode material is 1 μm to 10 μm. The particle size is too small, the specific surface area is too large, the side reaction is too large, and the electrical performance is deteriorated; the particle size is too large, so that the dynamics of the silicon negative electrode is influenced, in addition, the stress release of the large particles is slow, local stress concentration is caused, and the interface is deteriorated, so that the electrical performance of the silicon negative electrode is deteriorated.
Specifically, the carbon coating amount of the prelithiated SiOx anode material is 0.1 to 6wt%. The coating effect cannot be achieved due to the too low carbon coating amount; too high, the gram capacity and high temperature performance of the silicon negative electrode are deteriorated.
The method comprises the steps that a silicate phase formed by pre-lithiation of an inner core of a SiOx anode material has a certain solubility in water, and the dissolution of lithium silicate can cause the alkalinity of anode slurry, deteriorate the stability of the anode slurry and influence the coating of the anode slurry; meanwhile, the surface layer of the pre-lithiated SiOx anode material is provided with lithium oxide, lithium hydroxide and lithium carbonate which are formed after pre-lithiation, the pre-lithiated SiOx anode material is sensitive to air, and the pre-lithiated SiOx anode material presents strong alkalinity in aqueous slurry, so that the stability of the anode slurry is deteriorated. In addition, the pre-lithiated SiOx anode material has high core activity, can slowly react with deionized water in the anode slurry to produce gas, and can deteriorate the electrical property of the anode material.
Among them, the prelithiated SiOx anode material may be obtained by being purchased in the market, or may be obtained by being prepared. In this example, a prelithiated SiOx anode material was obtained by preparation.
In an embodiment, the preparation method of the prelithiated SiOx anode material is selected from one of a thermodynamic heating method, a wet doping method and an electrochemical deposition method.
Specifically, the thermodynamic heating method is to heat-react SiOx with metallic lithium or a lithium-containing compound. Among them, the lithium-containing compound includes lithium oxide, lithium carbonate, lithium hydroxide, and the like.
Specifically, the wet doping method is to react SiOx with an organic solution containing metallic lithium at normal temperature.
Specifically, the electrochemical deposition method is to perform lithium deposition on the surface of SiOx.
Step S120: and (3) in the atmosphere of protective gas, carrying out heat preservation sintering on the first mixture at 50-300 ℃ to obtain the first pre-lithium silicon anode material.
Further, the step of sintering the first mixture at 50-300 ℃ under heat preservation is specifically as follows: and (3) carrying out heat preservation sintering on the first mixture at 150-200 ℃. Specifically, the shielding gas is nitrogen.
The acidic substance generated by the first solid compound neutralizes the alkaline substance on the surface layer of the pre-lithiated SiOx anode material by adopting a solid heating decomposition method, and forms a layer of ion-conducting LiF or Li with controllable thickness on the surface layer of the pre-lithiated SiOx anode material 3 PO 4 . By reasonably controlling the dosage of the solid compounds, no extra solid waste slag is generated.
Further, in the step of carrying out heat preservation and sintering on the first mixture at 50-300 ℃, the heating rate is 5-50 ℃/min, and the heat preservation time is 1-24 h. The heating rate is 5-50 ℃/min, the composition and the duty ratio of silicate crystal phases in the silicon negative electrode are affected, and the electrochemical performance of the silicon negative electrode is improved; the heat preservation time is 1-24 h, the grain size of the core silicon and the grain size of the silicate are influenced, and the electrochemical performance of the silicon cathode is improved.
The step of sintering the first mixture at 50-300 ℃ to obtain the first pre-lithium silicon anode material further comprises the following steps:
step S130: and mixing the first pre-lithium silicon anode material with a second solid compound to obtain a second mixture.
Wherein the second solid compound is selected from at least one of nitrogen-containing organic matter and boron oxide. Further, the nitrogen-containing organic matter is selected from at least one of aliphatic amine and aniline to form a nitrogen-doped carbon coating. In one embodiment, the aniline is melamine.
In one embodiment, the oxide of boron is boron trioxide. So as to form a boron doped carbon coating layer, promote the conductivity of the silicon cathode and improve the circulation.
Further, the mass ratio of the first pre-lithium silicon anode material to the second solid compound is 100:0.1-100:6. The second solid compound content is too low, the conductivity of the silicon negative electrode is limited, and the carbon coating effect cannot be achieved; the second solid compound content is too high, which affects the capacity exertion of the silicon anode, and further deteriorates the high temperature performance.
Step S140: and (3) in the atmosphere of protective gas, carrying out heat preservation sintering on the second mixture at 100-600 ℃ to obtain a second pre-lithium silicon anode material.
Further, the step of sintering the second mixture at 100-600 ℃ in a heat preservation way specifically comprises the following steps: and (3) sintering the second mixture at 450-550 ℃ in a heat-preserving way. Specifically, the shielding gas is nitrogen.
Further, in the step of carrying out heat preservation and sintering on the second mixture at 100-600 ℃, the heating rate is 5-50 ℃/min, and the heat preservation time is 1-24 h. The heating rate is 5-50 ℃/min, the composition and the duty ratio of silicate crystal phases in the silicon negative electrode are affected, and the electrochemical performance of the silicon negative electrode is improved; the heat preservation time is 1-24 h, the grain size of the core silicon and the grain size of the silicate are influenced, and the electrochemical performance of the silicon cathode is improved.
The silicate crystal phase type of the core of the pre-lithiated SiOx anode material is regulated and controlled by controlling the heating temperature, the heating rate and the heat preservation time, namely, the phase of the lithium metasilicate and the phase of the lithium disilicate are converted from the phase of the lithium metasilicate; meanwhile, the element doping is carried out on the inner core of the pre-lithiated SiOx anode material, and the intrinsic conductivity of the silicon anode after pre-lithiation is improved, so that the processing performance and the electrochemical performance of the silicon anode are improved. Wherein the element doping mainly refers to nitrogen element and boron element doping.
The treatment method of the pre-lithiated SiOx anode material has at least the following advantages:
1) According to the treatment method of the pre-lithiated SiOx anode material, the pre-lithiated SiOx anode material reacts with ammonia fluoride or ammonium phosphate at high temperature, so that alkaline substances lithium oxide and lithium hydroxide on the surface of the pre-lithiated SiOx anode material are converted into LiF or lithium phosphate, the problem of alkaline substances on the surface layer of the lithium SiOx anode material is solved from the root, and the stability of the pre-lithiated SiOx anode material is improved; meanwhile, by controlling the dosage of ammonia fluoride or ammonium phosphate, a layer of artificial inorganic SEI is formed on the surface of the pre-lithiated SiOx negative electrode material, the artificial SEI is compact, the thickness is controllable and hydrophobic, the dissolution rate of the core lithium silicate can be inhibited, and the stability of the pre-lithiated SiOx negative electrode material is improved.
2) According to the treatment method of the pre-lithiated SiOx negative electrode material, a layer of artificial inorganic SEI is formed on the surface of the pre-lithiated SiOx negative electrode material, so that the trouble of material processing caused by strong alkalinity on the surface of the pre-lithiated SiOx negative electrode material is solved radically. In addition, the artificial SEI can reduce the consumption of first irreversible lithium, and the artificial SEI is resistant to electrolyte corrosion, so that the first effect and electrochemical properties such as cycle life and storage life of the pre-lithiated SiOx anode material can be further improved.
3) The treatment method of the pre-lithiated SiOx anode material can not generate a large amount of industrial waste acid or waste water, and can not form toxic organic waste liquid, thereby being environment-friendly.
4) According to the treatment method of the pre-lithiated SiOx negative electrode material, the silicate crystal phase of the inner core of the pre-lithiated SiOx negative electrode material is regulated and controlled by controlling the heat treatment temperature and the heating rate, so that the high-water-solubility lithium orthosilicate is converted into the low-water-solubility lithium metasilicate or lithium disilicate phase, the dissolution of the lithium silicate phase is inhibited from the root, the dissolution rate of the lithium silicate is reduced from the root, and the structural stability and the electric conductivity of the pre-lithiated SiOx negative electrode material are improved; in addition, the lithium metasilicate phase is electrochemically inert, so that the side reaction of the material in the circulation process or during high-temperature storage can be reduced, the structural stability of the material is maintained, and the material is beneficial to prolonging the circulation life and improving the high-temperature storage performance.
In addition, when the silicate crystal phase is regulated and controlled by controlling the heat treatment temperature, nitrogen-containing organic matters or boron-containing compounds with low decomposition temperature are added to form a nitrogen-doped pre-lithiated SiOx negative electrode material core or a boron-doped pre-lithiated SiOx negative electrode material core, so that the intrinsic electron conductivity of the SiOx negative electrode material core is improved; in addition, the low decomposition temperature reduces the risk of silicon grain growth, improves the intrinsic electronic conductivity of the silicon negative electrode, improves the electrical property of the material, and improves the quick charging property of the material; meanwhile, a carbon coating protective layer is formed on the LiF outer core or the lithium phosphate outer core on the surface layer, so that double-layer coating is formed, and the electrical property of the silicon-based negative electrode is improved.
5) The surface of the pre-lithiated SiOx anode material presents alkalinity, can react irreversibly with water and carbon dioxide in the air when stored at conventional humidity, and deteriorates the material performance. The pre-lithiated SiOx anode material is reacted with ammonia fluoride or ammonium phosphate at high temperature, alkaline substances lithium oxide and lithium hydroxide on the surface of the pre-lithiated SiOx anode material are converted into LiF or lithium phosphate, the problem of alkaline substances on the surface layer of the lithium SiOx anode material is solved radically, a compact artificial inorganic protective layer is formed on the surface layer, the protective layer is hydrophobic, electrochemically stable and air stable, the electrical property of the material is not deteriorated even if the material is stored under normal conditions, and the storage requirement of the pre-lithiated SiOx anode material is reduced.
6) The method for processing the pre-lithiated SiOx negative electrode material removes the strong alkaline substances on the surface layer of the pre-lithiated SiOx negative electrode material, reduces the pH of the material, thereby reducing the alkalinity of the negative electrode slurry, improving the stability of the negative electrode slurry, improving the processability of the negative electrode slurry, improving the quality of the negative electrode plate and reducing the manufacturing cost of the battery cell. In addition, compared with alkaline slurry, neutral slurry has lower corrosion to equipment pipelines.
The following are the specific examples section:
example 1
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
1) 100g of 6 μm of SiO and 10g of Li 2 O is mechanically ball-milled and mixed for 3 hours, and then roasting is carried out for 2 hours at 500 ℃ under the protection of inert atmosphere nitrogen, so as to obtain the pre-lithiated SiOx anode material, which is marked as a sample S1;
taking S1 g with the particle diameter of 6 mu m and the carbon coating amount of 3wt percent, and taking NH 4 F5 g, stirring for 1h at room temperature, uniformly mixing, placing the mixed sample in a tube furnace, introducing nitrogen, wherein the nitrogen introducing rate is 50mL/min, starting heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to 30 ℃/min, preserving heat for 0.5h after the temperature rises to 190 ℃, grinding and screening the obtained powder, and finally obtaining the pre-lithiated SiOx anode material with the surface coated with a layer of LiF, which is marked as a sample D1.
Example 2
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
mixing 10g of biphenyl with 100g of tetrahydrofuran, adding 0.5g of metal lithium powder to obtain an organic solution containing metal lithium, adding 10g of 6 mu m SiO, stirring for 12 hours, filtering, washing with tetrahydrofuran to obtain a pre-lithiated SiOx anode material, and marking the pre-lithiated SiOx anode material as a sample S2;
taking S2 g with the particle diameter of 6 mu m and the carbon coating amount of 3wt percent, and taking NH 4 F5 g, stirring for 1h at room temperature, uniformly mixing, placing the mixed sample in a tube furnace, introducing nitrogen, wherein the nitrogen introducing rate is 50mL/min, starting heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to 30 ℃/min, preserving heat for 0.5h after the temperature rises to 190 ℃, grinding and screening the obtained powder, and finally obtaining the pre-lithiated SiOx anode material with the surface coated with a layer of LiF, which is marked as a sample D2.
Example 3
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
mixing 100g of 6 mu m SiO negative electrode with 5g of metal lithium powder, adding 100g of electrolyte, standing for 12 hours at normal temperature to obtain a pre-lithiated SiOx negative electrode material, and marking as a sample S3, wherein the solute of the electrolyte is 1.2mol/L lithium hexafluorophosphate, and the solvent is ethylene carbonate EC;
taking S3 g with the particle diameter of 6 mu m and the carbon coating amount of 3wt percent, and taking NH 4 F5 g, stirring for 1h at room temperature, uniformly mixing, placing the mixed sample in a tube furnace, introducing nitrogen, wherein the nitrogen introducing rate is 50mL/min, starting heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to 30 ℃/min, preserving heat for 0.5h after the temperature rises to 190 ℃, grinding and screening the obtained powder, and finally obtaining the pre-lithiated SiOx anode material with the surface coated with a layer of LiF, which is marked as a sample D3.
Example 4
The method of treating the prelithiated SiOx anode material of this example was substantially the same as that of example 1, except that NH 4 F is replaced by ammonium phosphate (NH) 4 ) 3 PO 4 The resulting sample was designated as D4.
Example 5
The method of treating the prelithiated SiOx anode material of this example was substantially the same as that of example 2, except that NH 4 F is replaced by ammonium phosphate (NH) 4 ) 3 PO 4 The resulting sample was designated D5.
Example 6
The method of treating the prelithiated SiOx anode material of this example was substantially the same as that of example 3, except that NH 4 F is replaced by ammonium phosphate (NH) 4 ) 3 PO 4 The resulting sample was designated D6.
Example 7
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 10g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at the rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to5 ℃/min, and after the temperature is raised to 600 ℃, preserving heat for 8h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D7.
Example 8
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 20g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at a nitrogen introducing rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to5 ℃/min, and after the temperature is raised to 600 ℃, preserving heat for 8h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D8.
Example 9
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 20g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at a nitrogen introducing rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to5 ℃/min, and after the temperature is raised to 500 ℃, preserving heat for 8h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D9.
Example 10
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 20g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at a rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to5 ℃/min, and after the temperature is raised to 560 ℃, preserving heat for 8h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D10.
Example 11
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 20g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at the rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to 30 ℃/min, and after the temperature is raised to 560 ℃, preserving heat for 8h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D11.
Example 12
The treatment method of the prelithiated SiOx anode material of this embodiment is as follows:
taking 100g of a D1 sample in the embodiment 1, taking 20g of a melamine sample, stirring for 1h to mix uniformly, then placing the mixed sample in a tube furnace, introducing nitrogen at the rate of 50mL/min, heating to 190 ℃ after introducing nitrogen for half an hour, controlling the heating rate to 30 ℃/min, and after the temperature is raised to 560 ℃, preserving heat for 5h, grinding and screening the obtained powder, and finally obtaining the nitrogen-doped and surface-layer second-layer carbon-coated prelithiated SiOx anode material, which is marked as D12.
And (3) testing:
the pre-lithiated SiOx negative electrode materials prepared in examples 1-12 and S1, S2 and S3 were subjected to material pH, surface lithium carbonate and lithium hydroxide detection, water reaction time recording, and buckling CR2032 and 3Ah soft package full-electric performance detection, and the test results are shown in Table 1;
the negative electrode ratio of the button cell is that an active substance is conductive agent SP, and the active substance is 100% pre-lithiated SiOx negative electrode material, wherein the button cell mainly tests the gram capacity and first effect of the negative electrode, and the first effect is charging capacity/discharging capacity;
the anode proportion of the soft-packed battery is that an active substance is conductive agent SP, modified polyacrylic acid=93:3:4, the soft-packed battery mainly represents the cycle life and the anode thickness expansion, wherein the active substance consists of 15% of pre-lithiated SiOx anode material and 85% of artificial graphite.
1) Material pH testing refers to general rules for pH measurement of GB/T9724-2007 chemical reagents;
2) The method is a universal method for measuring the acidity and alkalinity of the chemical reagent of the reference GB/T9736-2008 for testing the content of lithium on the surface of the material and the content of lithium hydroxide and lithium carbonate;
3) Powder resistance test refers to GB/T30835-2014 carbon composite lithium iron phosphate anode material for lithium ion batteries;
3) Material reaction time with water t record: from t=0, 5g of powder was added to 100mL of water, and the time t for generating bubbles was observed.
4) First charge gram capacity and first effect test:
after the button cell is assembled, (1) discharging: 0.2C DC to5mV,0.1C DC to5mV,0.05C DC to5mV,0.02C DC to5mV,0.01C DC to5mV the specific discharge capacity is denoted as Q1; (2) charging: 0.1 CC to 2v, charge capacity noted Q2; q2 is the first charge gram capacity; the first effect of the electricity is abbreviated as ICE, ice=q2/Q1.
5) Capacity retention test:
(1) charging: 1C CC to 4.2V,Rest 10min; (2) discharging: 1C DC to 2.5V,Rest 0min the number of the individual pieces of the plastic, the discharge capacity was recorded as Qn (n) =1, 2,3 · 200); (3) repeating the steps (1) and (2) for 200 circles. The capacity retention rate of the full power 200 circles is as follows: Q200/Q1.
6) Volume expansion test:
and (3) circulating 200 circles of battery cells, fully-charged disassembling, wherein the thickness of a micrometer card is d2, the rolling thickness d1 of a fresh pole piece, and calculating the fully-charged expansion of 200 circles of battery cells: (d 2-d 1)/(d 1-8).
7) Capacity fade loss ratio
Capacity fade loss ratio = (pre-exposure capacity-post-exposure capacity)/pre-exposure capacity.
TABLE 1
From table 1, the pre-lithiated SiOx negative electrode material has no post-treatment process, has strong surface alkalinity and high pH, and can cause gram capacity reduction and initial efficiency reduction when stored in air. Wherein the capacity loss of the comparative examples 1-3 is 9% -10%, the capacity attenuation rate of the post-treated examples 1-12 is 0.1% -0.9%, the attenuation rate of the comparative examples is 10-1000 times of that of the example group, and obviously, the post-treatment improves the stability of the pre-lithiated SiOx anode material.
By means of surface treatment of ammonia fluoride or ammonium phosphate, the pH is obviously reduced by 3 points, the surface alkaline substance lithium hydroxide is reduced to more than 80%, the content of lithium carbonate is reduced by more than 90%, the stability in water is improved by more than 10 times, the gas production starting time is prolonged by more than 10 times, and the stability of the pre-lithiated SiOx anode materials prepared in examples 1-12 is better. In addition, the ammonia fluoride or ammonium phosphate treatment can form a layer of artificial SEI on the surface layer, so that the air stability is improved, and the first effect and the cycle life are improved.
From the data in Table 1, the electric conductivity of the D7-D12 powder is improved, the pH value is reduced, the alkali content of the surface layer is kept at a lower level, and no obvious change exists through heat treatment and nitrogen doping; the silicate phase of the silicon cathode core is regulated and controlled by heat treatment, the water resistance is improved, and the time for generating bubbles in water is prolonged by more than 2 times; the pH value is reduced, the electric conductivity is improved, the silicate is regulated and controlled, and the cycle life and the volume expansion of the pre-lithium silicon negative electrode are improved.
From D7 to D8, the nitrogen doping amount is properly increased, and the conductance of the silicon cathode can be increased, so that the capacity exertion and the cycle life are increased.
From D8 to D10, the heat treatment temperature is too high, which is unfavorable for the cycle life and expansion, and the cycle life can be improved by properly controlling the temperature.
From D10 to D11, the heating rate influences the crystal phase of the silicon core, so that the water resistance of the silicon core is influenced, the rate is properly increased, the crystal phase of the silicon core is more favorably converted into silicate with strong water resistance, the water resistance of the silicon core is increased, and meanwhile, the silicate with strong water resistance is electrochemically inert, so that the structural stability of silicon in the circulation process can be maintained, and the circulation life is prolonged.
From D11 to D12, the heat treatment time can also influence the electrical property of the pre-lithiated silicon negative electrode, and proper time reduction is beneficial to prolonging the cycle life of the silicon negative electrode.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (9)
1. A method for treating a prelithiated SiOx anode material, comprising the steps of:
mixing a pre-lithiated SiOx anode material with a first solid compound to obtain a first mixture, wherein X is more than 0 and less than 2, and the first solid compound is at least one of ammonium fluoride and ammonium phosphate;
under the atmosphere of protective gas, carrying out heat preservation sintering on the first mixture at 50-300 ℃ to obtain a first pre-lithium silicon anode material; after the heat preservation and sintering, the alkaline substances lithium oxide and lithium hydroxide on the surface of the pre-lithiated SiOx anode material are converted into LiF or lithium phosphate;
mixing the first pre-lithium silicon anode material with a second solid compound to obtain a second mixture, wherein the second solid compound is selected from at least one of nitrogen-containing organic matters and boron oxides;
in the atmosphere of protective gas, carrying out heat preservation sintering on the second mixture at 100-600 ℃ to obtain a second pre-lithium silicon anode material;
the second pre-lithium silicon anode material comprises a core doped with nitrogen or boron, and the core comprises SiOx and lithium silicate; the surface of the inner core is provided with a LiF or lithium phosphate outer core; the outermost side of the second pre-lithium silicon anode material comprises a carbon coating layer.
2. The method for treating a prelithiated SiOx negative electrode material according to claim 1, wherein the mass ratio of the prelithiated SiOx negative electrode material to the first solid compound is 100:0.1-100:10.
3. The method for treating a prelithiated SiOx negative electrode material according to claim 1, wherein in the step of heat-insulating and sintering the first mixture at 50-300 ℃, the heating rate is 5-50 ℃/min, and the heat-insulating time is 1-24 h.
4. The method for treating a prelithiated SiOx negative electrode material according to claim 1, wherein the particle size of the prelithiated SiOx negative electrode material is 1 μm to 10 μm.
5. The method of treating a prelithiated SiOx anode material according to claim 1, wherein the carbon coating layer has a carbon coating amount of 0.1-6 wt%.
6. The method of claim 1, wherein the mass ratio of the first pre-lithiated silicon anode material to the second solid compound is 100:0.1-100:6.
7. The method of claim 1, wherein the second mixture is subjected to heat-insulating sintering at a temperature of 100 ℃ to 600 ℃ at a heating rate of 5 ℃/min to 50 ℃/min and a heat-insulating time of 1h to 24h.
8. The method for treating a prelithiated SiOx negative electrode material according to claim 1, wherein the step of sintering the second mixture at 100-600 ℃ is specifically: and (3) sintering the second mixture at the temperature of 450-550 ℃.
9. The method for treating a prelithiated SiOx negative electrode material according to claim 1, wherein the nitrogen-containing organic matter is at least one selected from aliphatic amines and anilines.
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| CN106654194A (en) * | 2016-11-07 | 2017-05-10 | 中国科学院化学研究所 | Element-doped SiOx negative electrode composite material as well as preparation method and application thereof |
| CN109599551A (en) * | 2018-12-28 | 2019-04-09 | 安普瑞斯（南京）有限公司 | A kind of doping type multi-layer core-shell silicon based composite material and preparation method thereof for lithium ion battery |
| CN109713286A (en) * | 2018-12-29 | 2019-05-03 | 安普瑞斯（南京）有限公司 | A kind of silicon based composite material and preparation method thereof for lithium ion secondary battery |
| CN110800142A (en) * | 2017-12-08 | 2020-02-14 | 株式会社Lg化学 | Negative active material for lithium secondary battery and method for preparing same |
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| CN106654194A (en) * | 2016-11-07 | 2017-05-10 | 中国科学院化学研究所 | Element-doped SiOx negative electrode composite material as well as preparation method and application thereof |
| CN110800142A (en) * | 2017-12-08 | 2020-02-14 | 株式会社Lg化学 | Negative active material for lithium secondary battery and method for preparing same |
| CN109599551A (en) * | 2018-12-28 | 2019-04-09 | 安普瑞斯（南京）有限公司 | A kind of doping type multi-layer core-shell silicon based composite material and preparation method thereof for lithium ion battery |
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