CN113871606A - Silica anode material and preparation method and application thereof - Google Patents
Silica anode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a silicon-oxygen cathode material and a preparation method and application thereof. The silicon-oxygen anode material comprises an inner core and a carbon coating layer coated on the surface of the inner core; the preparation method comprises the following steps: and pre-lithiating the Li-aromatic hydrocarbon compound solution and a silica material, carrying out solid-liquid separation, and then carrying out heat treatment in a protective atmosphere to obtain the silica anode material. The inner core is made of silicon oxygen material with lithium embedded inside. According to the invention, the silica material is subjected to pre-lithiation by adopting the Li-aromatic hydrocarbon compound solution, and then is subjected to heat treatment, so that the pre-lithiation of the silica cathode on the material layer is realized, the carbon coating layer on the surface of the silica cathode further realizes the effect of inhibiting the internal volume expansion of the silica material, and a protective barrier is formed between the pre-lithiated silica particles and the electrolyte to separate the pre-lithiated silica particles from the electrolyte, so that the cleaning link is saved, the structural stability of the material is improved, and the cycle stability and the rate capability of the battery are improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a silica negative electrode material, and a preparation method and application thereof.
Background
The lithium ion battery is generally applied to electric vehicles and 3C products due to the characteristics of higher energy density, higher working voltage, higher charging speed, safety, no pollution and the like. The negative electrode material is used as a key factor for the development of the lithium ion battery, mainly takes a graphite material as a main material, the specific capacity of the graphite material is close to a theoretical value, and the capacity of the graphite material is difficult to improve by modifying the graphite. Therefore, the development of novel anode materials with high specific capacity and high safety performance has become a key point.
The theoretical specific capacity of SiO is 2443mAh/g, which is more than 6 times of that of the traditional graphite material, and the silicon is abundant in natural reserves, clean and pollution-free, and is considered as the next-generation lithium ion negative electrode material with the most development potential. However, the silicon-oxygen material still has the disadvantages of low first efficiency, poor conductivity, large volume expansion and the like. The main reason is that lithium ions preferentially react with silicon oxygen to generate Li in the process of being inserted into silicon oxygen cathode materials2O、Li4SiO4The two substances have the function of hindering the expansion effect of silicon in the process of lithium intercalation and deintercalation, and the cycle stability and the service life are improved compared with those of a pure silicon material, but the two substances are also just caused by irreversible Li generation2O、Li4SiO4The first cycle efficiency of the silicon-oxygen cathode material is low, and the conductivity is poor; further, the silicon-oxygen negative electrode material still has a problem of large volume expansion compared to the graphite material.
Currently, the prelithiation mainly comprises positive prelithiation and negative prelithiation, wherein the negative prelithiation is researched more and the technology is relatively mature. The negative electrode prelithiation is divided into direct addition of exogenous lithium, active additive prelithiation, electrochemical prelithiation and chemical prelithiation according to the prelithiation mode. The chemical prelithiation is simple to operate and has low requirements on a drying environment, so that researchers pay more attention to the prelithiation technical research in recent years.
The selection of a suitable prelithiation regime for silicon oxygen anode materials is key to ensuring that chemical prelithiation techniques are moving towards commercial applications. Thus, the key problems of the application of chemical prelithiation to silicon-oxygen cathodes remain to be studied further.
CN104538591A discloses a prelithiation method for a negative electrode material of a lithium ion battery, which limits the current of prelithiation by coating or wrapping a lithium ion barrier layer on the surface of metal lithium and/or controlling the resistance of a connection conductor, adjusts the reaction speed of a primary battery between the metal lithium and the negative electrode material, and regulates the lithium insertion speed and the surface SEI film formation speed of the negative electrode material, thereby improving the cycle performance of the negative electrode material on the basis of improving the first coulomb efficiency of the negative electrode material. In the method, the pre-lithiation current is limited by adjusting the resistance value, the controllable parameters are less, and the control difficulty is higher; in addition, the outer coating may additionally increase the cell mass.
CN111900368A discloses a silicon monoxide negative electrode material, which is prepared by mixing silicon monoxide with a lithium source, and preserving the temperature at 300-700 ℃ to obtain pre-lithiated silicon monoxide; putting the pre-lithiated silicon monoxide into a rotary kiln, and performing carbon coating by adopting vapor deposition to obtain a pre-lithiated silicon monoxide/carbon composite material; finally, the mixture is uniformly mixed with the metal oxide, and the metal oxide is uniformly coated on the surface of the silicon oxide/carbon composite material. In the patent, during the process of pre-lithium, the variety and the dosage of the lithium source are regulated and controlled, so that the variety of the generated lithium silicate can be regulated and controlled, and the Li is improved2Si2O5In a ratio of (1), reduction of Li2SiO3And Li4SiO4On the other hand, the surface of the material is coated with a layer of metal oxide, so that the precipitation of silicate and the sedimentation of the material can be inhibited, and great help is brought to the improvement of the stability of the battery slurry. In this document, Li is regulated only by the kind and amount of the lithium source2Si2O5But water-insoluble Li2Si2O5And water-soluble Li2SiO3And there is a completely mixed relationship between, in the silica material, Li2SiO3And still exposed to the surface of the silica material, can result in a higher pH of the slurry during homogenization. Although the outermost layer of the carbon layer is coated with a metal oxide layer, the conductivity of the carbon layer is significantly reduced, and the original meaning of carbon coating is lost.
Therefore, how to realize the effective and rapid pre-lithiation of the silicon-oxygen material and simultaneously inhibit the volume expansion of the silicon-oxygen material and improve the electrochemical performance of the silicon-oxygen material is a technical problem to be solved urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a silicon-oxygen anode material and a preparation method and application thereof. According to the invention, the silica material is subjected to pre-lithiation by adopting the Li-aromatic hydrocarbon compound solution, and then is subjected to heat treatment, so that the pre-lithiation of the silica cathode on the material layer is realized, the carbon coating layer on the surface of the silica cathode further realizes the effect of inhibiting the internal volume expansion of the silica material, and a protective barrier is formed between the pre-lithiated silica particles and the electrolyte to separate the pre-lithiated silica particles from the electrolyte, so that the cleaning link is saved, the structural stability of the material is improved, and the cycle stability and the rate capability of the battery are improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a silicon-oxygen anode material, which comprises an inner core and a carbon coating layer coated on the surface of the inner core; the inner core is made of silicon oxygen material with lithium embedded inside.
According to the invention, the silica material is internally embedded with lithium, so that the pre-lithiation of the material layer is realized, and the volume of particles after pre-embedding with lithium can undergo a pre-expansion process, so that the volume effect of the battery after the battery is manufactured can be greatly buffered, and the long-cycle battery core shape can be maintained; the carbon coating layer on the surface not only increases the conductivity of the negative electrode, but also can isolate the direct contact between the pre-lithiated silica particles inside and the electrolyte, and can also reduce the consumption of effective lithium inside the battery on the particle surface during the formation of the battery, thereby reducing the irreversible capacity loss; after the obtained negative electrode material product is prepared into the lithium ion battery, the consumption of the electrolyte and the effective Li in the battery can be effectively reduced, the electrolyte injection amount required by the production of the lithium ion battery and the generation of gas during the working of the lithium battery product can be reduced, the production process flow and the formation flow of the lithium ion battery are further simplified, and the problem of unstable SEI formation in the conventional lithium battery is solved.
In a second aspect, the present invention provides a method for preparing the silicon-oxygen anode material according to the first aspect, wherein the method for preparing the silicon-oxygen anode material comprises:
and pre-lithiating the Li-aromatic hydrocarbon compound solution and a silica material, carrying out solid-liquid separation, and then carrying out heat treatment in a protective atmosphere to obtain the silica anode material.
In the invention, silicon-based negative electrode particles with micron-sized particle sizes are soaked in an organic solution taking a Li-aromatic hydrocarbon compound as a chemical pre-lithiation reagent to form a pre-lithiation silicon-oxygen negative electrode with an artificial SEI film coated on the surface and lithium embedded inside; because the operation object of the pre-lithiation process is micron-sized silicon-oxygen negative electrode particles, the formation of a surface artificial SEI film and lithium insertion of a silicon-oxygen particle phase can be quickly completed after contacting a liquid-phase pre-lithiation reagent in the chemical pre-lithiation process, so that the pre-lithiation purpose is achieved; the organic matter remaining on the surface of the silica particles after the chemical pre-lithiation is removed in a carbonization mode in a protective atmosphere, and a coating layer is formed on the surface of the silica negative electrode particles of the pre-lithiation, so that the pre-lithiation of the material is realized, the internal volume expansion effect of the silica material is further inhibited, a protective barrier is formed between the pre-lithiation silica particles and an electrolyte and is separated from the pre-lithiation silica particles, the structural stability of the obtained material is improved, and the cycle stability and the rate capability of the battery are further improved.
The method for pre-lithiation provided by the invention further accelerates the time for pre-lithiation of the battery, saves the cleaning link and forms a carbon coating layer, and is more favorable for the structural stability of the silicon monoxide particles in the charging and discharging processes, thereby improving the service life of the battery.
Preferably, the heat treatment includes sequentially performing a primary temperature rise and a secondary temperature rise.
In the invention, the heat treatment adopts a method of sequentially carrying out primary heating and secondary heating, which is more favorable for forming the carbon coating layer, and can better realize the conversion of organic impurities compared with direct carbonization.
Preferably, the temperature rise rate of the primary temperature rise is 1-10 ℃/min, such as 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min, and the like.
Preferably, the temperature after the primary temperature rise is 400 to 550 ℃, for example, 400 ℃, 410 ℃, 420 ℃, 430 ℃, 440 ℃, 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃, 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃ or the like.
Preferably, the heat preservation time after the primary temperature rise is 1-5 h, such as 1h, 2h, 3h, 4h or 5 h.
Preferably, the temperature rise rate of the secondary temperature rise is 1-10 ℃/min, such as 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min, and the like.
Preferably, the temperature after the secondary temperature rise is 700 to 1000 ℃, for example 700 ℃, 720 ℃, 750 ℃, 780 ℃, 800 ℃, 820 ℃, 850 ℃, 880 ℃, 900 ℃, 920 ℃, 950 ℃, 980 ℃ or 1000 ℃.
Preferably, the holding time after the secondary temperature rise is 1 to 10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.
Preferably, the aromatic hydrocarbon in the Li-aromatic hydrocarbon complex solution comprises any one of benzene, biphenyl, biphenylene, polyphenyl, poly-substituted aliphatic hydrocarbon or polycyclic aromatic hydrocarbon or a combination of at least two of the same, preferably methyl-modified aromatic hydrocarbon.
The methyl-modified aromatic hydrocarbon includes, but is not limited to, any one or a combination of at least two of 4,4 '-dimethylbiphenyl, 2-methylbiphenyl, 3', 4,4 '-tetramethylbiphenyl, 3' -dimethylbiphenyl, methylnaphthalene, 2-methylnaphthalene or 9, 9-dimethyl-9H-fluorene.
In the invention, the electron cloud distribution of the polycyclic aromatic hydrocarbon molecules is improved by adopting the molecular engineering science, so that the pre-lithiation reagent with lower oxidation-reduction potential is obtained, namely the aromatic hydrocarbon molecules are modified by methyl, and the oxidation-reduction potential of the material can be further reduced.
In the invention, the redox potential of the fluorine-containing Li-arene compound solution is lower than that of the micron-sized silicon-oxygen material, after chemical prelithiation, an SEI film is formed on the particle surface, and exogenous lithium can be spontaneously embedded into the silicon-oxygen negative electrode particle bulk phase, and when the silicon-oxygen negative electrode particle contacts a chemical prelithiation reagent Li-arene compound, the Li-arene compound with lower redox potential can be converted into a silicon-based material (SiO) with higher redox potentialx) Bulk spontaneous transport of Li+And electrons, thereby forming a silicon-based negative electrode pre-embedded with lithium, and meanwhile, after removing Li from the Li-aromatic hydrocarbon compound, oxidizing the Li-aromatic hydrocarbon compound again into a neutral aromatic hydrocarbon compound; if the redox potential of the Li-arene complex solution containing fluorine is higher than that of the micron-sized silicon oxygen material, the SEI film may be formed only on the surface of the silicon oxygen material after chemical pre-lithiation, and the effect of lithium intercalation of the internal material is difficult to achieve, so that the pre-lithiation effect is poor.
Preferably, the molar ratio of lithium to aromatic hydrocarbon in the Li-aromatic hydrocarbon complex solution is (1.5-10): 1, for example, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10: 1.
Preferably, the silicone material has a median particle diameter of 1 to 50 μm, such as 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm, and the like.
The grain size of the silicon-oxygen material is small, the lithium embedding path in the grains is short within the range of 1-50 mu m, and the time for completing the pre-lithium embedding is greatly shortened.
Preferably, the molar ratio of the Li-arene compound to the silicon oxygen material is (1-5): 1, such as 1:1, 2:1, 3:1, 4:1 or 5: 1.
Preferably, the temperature of the prelithiation is 10 to 60 ℃, for example 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃ or 60 ℃.
Preferably, the time of the pre-lithiation is 10-120 min, such as 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min or 120 min.
In the invention, the oxidation-reduction potentials of the same pre-lithiation reagent are different at different temperatures, specifically, the oxidation-reduction potential of the pre-lithiation reagent is reduced when the temperature is increased, so that the lithium intercalation kinetics is improved, meanwhile, the pre-lithiation is more sufficient when the pre-lithiation time is prolonged, but the marginal effect of the increase of the lithium intercalation degree is reduced along with the prolonging of the time, in addition, the pre-lithiation degree of silica particles is too high for a longer time, so that the excessive lithium intercalation easily causes the lithium precipitation in the battery charging and discharging process, and therefore, the temperature and the time of the better pre-lithiation process need to be determined.
As a preferred technical solution, the preparation method comprises:
pre-lithiating the Li-aromatic hydrocarbon compound solution and a silica material at the temperature of 10-60 ℃ for 10-120 min according to the molar ratio of (1-5) to 1, performing solid-liquid separation, heating to 400-550 ℃ at the heating rate of 1-10 ℃/min in a protective atmosphere, then preserving heat for 1-5 h, continuously heating to 700-1000 ℃ at the heating rate of 1-10 ℃/min for the second time, and preserving heat for 1-10 h to obtain the silica negative electrode material;
the aromatic hydrocarbon in the Li-aromatic hydrocarbon compound solution is methyl-modified aromatic hydrocarbon, and the molar ratio of lithium to the aromatic hydrocarbon in the Li-aromatic hydrocarbon compound solution is (1.5-10): 1.
In a third aspect, the present invention also provides a lithium ion battery, which includes the silicon-oxygen negative electrode material according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the silica material is internally embedded with lithium, so that the pre-lithiation of the material layer is realized, and the volume of particles after pre-embedding with lithium can undergo a pre-expansion process, so that the volume effect of the battery after the battery is manufactured can be greatly buffered, and the long-cycle battery core shape can be maintained; the carbon coating layer on the surface not only increases the conductivity of the negative electrode, but also can isolate the direct contact between the pre-lithiated silica particles inside and the electrolyte, and can also reduce the consumption of effective lithium inside the battery on the particle surface during the formation of the battery, thereby reducing the irreversible capacity loss; after the obtained negative electrode material product is prepared into the lithium ion battery, the consumption of the electrolyte and the effective Li in the battery can be effectively reduced, the electrolyte injection amount required by the production of the lithium ion battery and the generation of gas during the working of the lithium battery product can be reduced, the production process flow and the formation flow of the lithium ion battery are further simplified, and the problem of unstable SEI formation in the conventional lithium battery is solved. The first effect of the negative half cell provided by the invention can reach more than 101.23%, the energy density of the full cell can reach more than 298Wh/kg, and the capacity retention rate of 200 circles can reach more than 90.5%.
(2) In the invention, silicon-based negative electrode particles with micron-sized particle sizes are soaked in an organic solution taking a Li-aromatic hydrocarbon compound as a chemical pre-lithiation reagent to form a pre-lithiation silicon-oxygen negative electrode with an artificial SEI film coated on the surface and lithium embedded inside; the organic matter remaining on the surface of the silica particles after the chemical pre-lithiation is removed in a carbonization mode in a protective atmosphere, and a coating layer is formed on the surface of the silica negative electrode particles of the pre-lithiation, so that the pre-lithiation of the material is realized, the internal volume expansion effect of the silica material is further inhibited, a protective barrier is formed between the pre-lithiation silica particles and an electrolyte and is separated from the pre-lithiation silica particles, the structural stability of the obtained material is improved, and the cycle stability and the rate capability of the battery are further improved.
Detailed Description
The technical solution of the present invention is further illustrated by the following specific examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a silicon oxide negative electrode material, which comprises a core and a carbon coating layer coated on the surface of the core; the inner core is a lithium-embedded silicon oxide material.
The preparation method of the silicon oxide negative electrode material comprises the following steps:
adding lithium sheets into a methyl butyl ether solution of 4,4 '-dimethylbiphenyl (4, 4' -DMBP) with the concentration of 1.0mol/L in a glove box, wherein the molar ratio of Li to 4,4 '-DMBP is set to be 3:1, and fully stirring to obtain a Li-4, 4' -DMBP compound as a chemical prelithiation solution;
putting the silicon oxide particles with the median diameter of 30 mu m into the chemical prelithiation reagent, and adding silicon-oxygen negative electrode particles into the prelithiation solution according to the molar ratio of the Li-4, 4' -DMBP compound to the silicon oxide of 3: 1;
pre-lithiation is carried out for 30min at the temperature of 35 ℃, and pre-lithiation silicon oxide negative electrode particles are separated from a pre-lithiation solution through filtration;
in N2In the atmosphere, heating the pre-lithiated silicon monoxide negative electrode particles to 450 ℃ at the heating rate of 2 ℃/min, and preserving the heat for 2 hours; and then continuously heating to 900 ℃ at the heating rate of 3 ℃/min, and preserving the heat for 4 hours to obtain the silicon monoxide negative electrode material.
Example 2
The difference between this example and example 1 is that in this example, the temperature was raised to 550 ℃ at a rate of 2 ℃/min at one time of temperature rise, and the temperature was maintained for 2 hours.
The remaining preparation methods and parameters were in accordance with example 1.
Example 3
The difference between this example and example 1 is that in this example, the temperature was raised to 450 ℃ at a temperature raising rate of 10 ℃/min and the temperature was maintained for 2 hours.
The remaining preparation methods and parameters were in accordance with example 1.
Example 4
The difference between this example and example 1 is that in this example, the temperature was raised to 450 ℃ at a rate of 2 ℃/min and maintained for 5 hours during one-time temperature raising.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The difference between this example and example 1 is that in this example, the temperature was raised to 900 ℃ at a rate of 1 ℃/min during the second temperature rise, and the temperature was maintained for 5 hours.
The remaining preparation methods and parameters were in accordance with example 1.
Example 6
The difference between this example and example 1 is that in this example, the temperature was raised to 900 ℃ at a rate of 3 ℃/min during the second temperature rise, and the temperature was maintained for 2 hours.
The remaining preparation methods and parameters were in accordance with example 1.
Example 7
The difference between this example and example 1 is that in this example, the temperature was raised to 1000 ℃ at a rate of 3 ℃/min during the second temperature rise, and the temperature was maintained for 4 hours.
The remaining preparation methods and parameters were in accordance with example 1.
Example 8
This example differs from example 1 in that 4, 4' -dimethylbiphenyl in this example is replaced with 9.9-dimethyl-9H-fluorene.
The remaining preparation methods and parameters were in accordance with example 1.
Example 9
This example differs from example 1 in that 4, 4' -dimethylbiphenyl in this example is replaced with 2-methylnaphthalene.
The remaining preparation methods and parameters were in accordance with example 1.
Example 10
The present example is different from example 1 in that the molar ratio of Li to 4, 4' -DMBP in the present example is set to 2: 1.
The remaining preparation methods and parameters were in accordance with example 1.
Example 11
The present example differs from example 1 in that the molar ratio of Li to 4, 4' -DMBP in the present example is set to 10: 1.
The remaining preparation methods and parameters were in accordance with example 1.
Example 12
This example differs from example 1 in that the silica particles were added to the prelithiation reagent in a molar ratio of Li-4, 4' -DMBP complex to silica of 1: 1.
The remaining preparation methods and parameters were in accordance with example 1.
Example 13
This example differs from example 1 in that the silica particles were added to the prelithiation reagent in a molar ratio of Li-4, 4' -DMBP complex to silica of 5: 1.
The remaining preparation methods and parameters were in accordance with example 1.
Example 14
This example differs from example 1 in that the temperature of prelithiation in this example is 15 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Example 15
This example differs from example 1 in that the temperature of prelithiation in this example is 60 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Example 16
The difference between this example and example 1 is that the prelithiation time in this example is 10 min.
The remaining preparation methods and parameters were in accordance with example 1.
Example 17
The difference between this example and example 1 is that the prelithiation time in this example is 120 min.
The remaining preparation methods and parameters were in accordance with example 1.
Example 18
This example differs from example 1 in that 4, 4' -dimethylbiphenyl in this example is replaced with biphenyl.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The difference between this example and example 1 is that in this example, after the prelithiated silica negative electrode particles were separated from the prelithiation solution, the prelithiated silica negative electrode particles were washed with propylene carbonate and then dried to obtain the silica negative electrode.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 2
The present example is different from example 1 in that the carbon-coated silica particles were prepared by the preparation method of example 1 without adding a lithium sheet, i.e., no lithium was embedded in the silica particles.
The negative electrode materials (named Li-SiO-500) with the specific capacity of 500mAh/g are prepared by mixing the silicon oxide negative electrodes provided by the examples 1 to 18 and the comparative examples 1 to 2 with graphite, after the SiO-500, the conductive agent SP and the binding agent are mixed according to the mass ratio of 90:3:7, a proper amount of NMP is added, and the mixed slurry is coated on the upper surface of the Cu foil and dried. The surface density of the negative electrode is 16.0mg/cm2At a compacted density of 1.6g/cm3Rolling the pole piece to obtain a negative pole piece; and rubbing the pole piece into a circular pole piece to assemble the button cell.
Li(Ni0.8Co0.1Mn0.1)O2The positive electrode, SP and PVDF as a binder are mixed in a ratio of 92:4:4, NMP is added, and the mixed slurry is coated on a carbon-coated Al foil to prepare a positive electrode plate. The ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area was 1.08. And assembling the positive plate, the negative plate and the diaphragm into a battery, and injecting electrolyte to prepare the full battery.
Electrochemical performance tests were performed on the cells provided in examples 1-18 and comparative examples 1-2:
1) specific discharge capacity: discharging the button cell to 0.005V at the current of 0.1C, and calculating the specific discharge capacity according to the discharge capacity and the active material loading capacity;
2) charging specific capacity: charging the button cell which is discharged for the first time to 2.0V by 0.1C current, and calculating the discharge specific capacity according to the discharge capacity and the active material loading capacity;
3) the first efficiency of electricity deduction: the ratio of the first discharge specific capacity to the first discharge specific capacity;
4) capacity retention ratio of the full cell at 200 weeks: and (3) carrying out cyclic charge and discharge according to a charge and discharge system of 0.5C/1C, wherein the discharge capacity at the 200 th week/first discharge capacity ratio is the capacity retention rate.
The data results of the above tests are shown in table 1.
TABLE 1
From the data of examples 1 and 18, it can be seen that the first effect, energy density and cycle stability of the methyl-modified aromatic hydrocarbon are improved.
From the data results of example 1 and comparative example 1, it can be seen that compared with the method of directly washing away organic impurities with an electrolyte, the thermal treatment method provided by the present invention can effectively inhibit the volume expansion of the silicon-oxygen material, and improve the first effect, energy density and cycle performance of the silicon-oxygen material.
From the data results of example 1 and comparative example 2, it is understood that the first effect is significantly reduced and the energy density and cycle performance are also poor by coating only the surface of the silicon oxide material with the carbon coating layer without performing the prelithiation of the internal material.
In conclusion, the silica material is internally embedded with lithium, so that the pre-lithiation of the material layer is realized, and the volume of particles after pre-embedding with lithium is subjected to a pre-expansion process, so that the volume effect of the battery after the battery is manufactured is greatly buffered, and the long-cycle battery core shape is kept; the carbon coating layer on the surface not only increases the conductivity of the negative electrode, but also can isolate the direct contact between the pre-lithiated silica particles inside and the electrolyte, and can also reduce the consumption of effective lithium inside the battery on the particle surface during the formation of the battery, thereby reducing the irreversible capacity loss; after the obtained negative electrode material product is prepared into the lithium ion battery, the consumption of the electrolyte and the effective Li in the battery can be effectively reduced, the electrolyte injection amount required by the production of the lithium ion battery and the generation of gas during the working of the lithium battery product can be reduced, the production process flow and the formation flow of the lithium ion battery are further simplified, and the problem of unstable SEI formation in the conventional lithium battery is solved. The first effect of the negative half cell provided by the invention can reach more than 101.23%, the energy density of the full cell can reach more than 298Wh/kg, and the capacity retention rate of 200 circles can reach more than 90.5%.
It is stated that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The silicon-oxygen anode material is characterized by comprising an inner core and a carbon coating layer coated on the surface of the inner core; the inner core is made of silicon oxygen material with lithium embedded inside.
2. The preparation method of the silicon-oxygen anode material as claimed in claim 1, wherein the preparation method comprises the following steps:
and pre-lithiating the Li-aromatic hydrocarbon compound solution and a silica material, carrying out solid-liquid separation, and then carrying out heat treatment in a protective atmosphere to obtain the silica anode material.
3. The method for producing a silicon-oxygen anode material according to claim 2, wherein the heat treatment comprises sequentially performing a primary temperature rise and a secondary temperature rise.
4. The preparation method of the silicon-oxygen anode material according to claim 3, wherein the temperature rise rate of the first temperature rise is 1-10 ℃/min, the temperature after the first temperature rise is 400-550 ℃, and the heat preservation time after the first temperature rise is 1-5 h.
5. The preparation method of the silicon-oxygen anode material according to claim 3, wherein the temperature rise rate of the secondary temperature rise is 1-10 ℃/min, the temperature after the secondary temperature rise is 700-1000 ℃, and the heat preservation time after the secondary temperature rise is 1-10 h.
6. The preparation method of the silicon-oxygen anode material as claimed in claim 2, wherein the aromatic hydrocarbon in the Li-aromatic hydrocarbon compound solution comprises any one or a combination of at least two of benzene, biphenyl, biphenylene, poly (phenylene) aliphatic hydrocarbon or polycyclic aromatic hydrocarbon.
7. The preparation method of the silicon-oxygen anode material as claimed in claim 6, wherein the aromatic hydrocarbon in the Li-aromatic hydrocarbon compound solution is methyl-modified aromatic hydrocarbon.
8. The preparation method of the silicon-oxygen anode material as claimed in claim 2, wherein the median particle diameter of the silicon-oxygen material is 1-50 μm.
9. The preparation method of the silicon-oxygen anode material according to claim 2, wherein the temperature of the pre-lithiation is 10-60 ℃, and the time of the pre-lithiation is 10-120 min.
10. A lithium ion battery comprising the silicone negative electrode material of claim 1.
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| CN116435494A (en) * | 2023-06-08 | 2023-07-14 | 北京壹金新能源科技有限公司 | High-first-efficiency silicon-based anode material and preparation method and application thereof |
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