Disclosure of Invention
The invention provides a method for sintering a silicon oxide anode material, which aims to solve the problem of overlong preparation time of silicon oxide.
According to a first aspect of the present invention, there is provided a method of sintering a silicon oxide negative electrode material for preparing a silicon oxide negative electrode material, comprising:
Ball-milling and mixing silicon powder and silicon dioxide powder to form mixture particles after ball milling; wherein, the mole percent of the silicon powder is as follows: the mole percentages of the silicon dioxide powder are: 40% -50%: 50% -60%;
Sintering the mixture particles subjected to ball milling and mixing at a high temperature to obtain silicon oxide gas; wherein, the high temperature sintering temperature is: 2000-2500 deg.c; the high-temperature sintering time is as follows: 1-3 min;
condensing the silica gas into silica solid particles.
Optionally, before sintering the mixture particles after ball milling and mixing at high temperature, the method further comprises:
Preheating the mixture particles after ball milling and mixing; the preheating temperature is as follows: 1000-1200 ℃; the preheating time is as follows: 1-2 min.
Optionally, after sintering the mixture particles after ball milling and mixing at high temperature, the method further comprises:
Heat preservation is carried out at 1000-1200 ℃; the heat preservation time is as follows: 1-2 min.
Optionally, when high-temperature sintering is carried out on the mixture particles after ball milling and mixing, the high-temperature sintering temperature is 2300-2500 ℃; high-temperature sintering time: 2 min-2.5 min.
Optionally, the particle size of the mixture particles after ball milling and mixing is as follows: 2um to 10um.
Optionally, after condensing the silica gas into silica solid particles, the method further comprises:
ball milling and sieving are carried out on the silica solid particles so as to obtain silica ball milling particles with uniform particle size; wherein, the particle size of the silica ball milling particles is as follows: 1um to 2um.
Optionally, sintering the mixture particles after ball milling and mixing by using a joule heating device, wherein the working voltage and the working current of the joule heating device are respectively set as follows: 30A-40A;
300V-400V to provide a high temperature sintering temperature of 2000-2500 ℃.
Optionally, the method for sintering the silicon oxygen anode material comprises the following steps: sintering the mixture particles after ball milling and mixing by adopting a Joule heating device, wherein the working voltage and the working current of the Joule heating device are respectively as follows: 35A to 40A; 350V-400V to provide a high temperature sintering temperature of 2300 ℃ to 2500 ℃.
According to a second aspect of the present invention there is provided a silicon oxygen anode material prepared by the method of sintering a silicon oxygen anode material according to any one of the first aspects of the present invention.
According to a third aspect of the present invention, there is provided a method for preparing a negative electrode sheet of a lithium battery, including the method for sintering a silicon oxygen negative electrode material according to any one of the first aspect of the present invention, the method for preparing a negative electrode sheet of a lithium battery further including:
Mixing the silica solid particles, a conductive additive and a binder to prepare a slurry of a negative electrode material; wherein, the mass of the silicon oxide solid particles is as follows: the mass of the conductive additive is as follows:
The mass of the binder is as follows: 90% >: 5%:5%;
Wherein the conductive additive comprises: acetylene black and carbon nanotubes; the mass of the acetylene black is as follows:
The mass of the carbon nano tube is as follows: 1:1, a step of;
The binder comprises: sodium carboxymethyl cellulose and styrene butadiene rubber; the mass of the sodium carboxymethyl cellulose is as follows: the styrene-butadiene rubber comprises the following components in percentage by mass: 1:1, a step of;
and coating the slurry of the negative electrode material on a copper foil, and drying to form the lithium battery pole piece.
Optionally, the preparation method of the lithium battery negative electrode piece further comprises the following steps:
Cutting the dried lithium battery pole piece into a round pole piece; wherein, the radius of circular pole piece is: 1 to 1.2cm;
Vacuumizing and drying the round pole piece in a vacuum drying oven for 8-10 hours; wherein, the stoving temperature is: 100-120 ℃.
Optionally, the conductive additive includes: carbon black.
Optionally, when the slurry of the negative electrode material is coated on the copper foil to be dried, the slurry is dried in a blast drying oven, and the drying temperature is as follows: 45-60 ℃; the drying time is 1-2 hours.
According to a fourth aspect of the invention, a lithium battery negative electrode plate is provided, and the lithium battery negative electrode plate is prepared by the preparation method of the lithium battery negative electrode plate according to the third aspect of the invention.
According to a fifth aspect of the present invention, there is provided a method for preparing a lithium battery, including any one of the method for preparing a lithium battery negative electrode sheet of the fourth aspect of the present invention, the method for preparing a lithium battery further comprising:
Providing an anode plate, the lithium battery cathode plate, a diaphragm and electrolyte;
And assembling the positive electrode plate, the lithium battery negative electrode plate, the diaphragm and the electrolyte into a lithium battery.
According to a sixth aspect of the present invention, there is provided a lithium battery prepared by the method for preparing a lithium battery according to the fifth aspect of the present invention.
The invention provides a method for sintering a silicon-oxygen negative electrode material, which comprises the steps of carrying out high-temperature sintering on silicon and silicon dioxide ball-milling mixture particles with a certain mole percentage, and condensing silicon oxide gas into silicon oxide solid particles; wherein, the high temperature sintering temperature is: 2000-2500 deg.c; the high-temperature sintering time is as follows: 1-3 min; therefore, according to the technical scheme provided by the invention, the silicon and silicon dioxide ball-milling mixture particles can be rapidly gasified to generate the silicon oxide gas, so that the preparation time of the silicon oxide can be greatly shortened, the energy consumption cost is reduced, and the production efficiency is improved.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims and in the above drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The traditional preparation method of the silicon-oxygen anode material in the industry adopts lower sintering temperature, so that the reaction speed is slower, the preparation time is long (generally, the temperature is raised for 4-5 hours, the temperature is kept for 3-5 hours, and the cooling is carried out for 8-10 hours); and also the following limitations: b. the requirement on the vacuum degree of the equipment is high (less than or equal to 15 Pa); c. the synthesis cost is high: 50% of the current material synthesis costs are energy consumption costs.
In view of this, the inventors of the present application made a series of studies and experiments on a method of sintering a silicon oxide negative electrode material by preparing the silicon oxide negative electrode material using an ultrafast sintering apparatus, and found that: the mixed powder of SiO2 and Si is gasified rapidly, so that the preparation time of the silicon oxide can be greatly shortened, the energy consumption cost is reduced, and the production efficiency is improved.
The technical scheme of the invention is described in detail below by specific examples. The following embodiments may be combined with each other, and some embodiments may not be repeated for the same or similar concepts or processes.
Referring to fig. 1 to 5, according to an embodiment of the present invention, there is provided a method for sintering a silicon oxide anode material, a process flow chart of the method for preparing a silicon oxide anode material, the method for sintering a silicon oxide anode material is shown in fig. 1, the method includes:
s11: ball-milling and mixing silicon powder and silicon dioxide powder to form mixture particles after ball milling; wherein, the mole percent of the silicon powder is as follows: the mole percentages of the silicon dioxide powder are: 40% -50%: 50% -60%;
S12: sintering the mixture particles subjected to ball milling and mixing at a high temperature to obtain silicon oxide gas; wherein, the high temperature sintering temperature is: 2000-2500 deg.c; the high-temperature sintering time is as follows: 1-3 min;
s13: condensing the silica gas into silica solid particles.
In step S11, silicon powder: 40-50% (mole percent) of silicon dioxide powder: ball-milling and mixing 50-60% (mole percent) to form ball-milled mixture particles; the specific reference is as follows: in the mixture particles after ball milling, the silicon powder accounts for the following proportion: 40-50% (mole percent), the silicon dioxide powder accounts for: 50-60% (mole percent).
The invention provides a method for sintering a silicon-oxygen negative electrode material, which comprises the steps of carrying out high-temperature sintering on silicon and silicon dioxide ball-milling mixture particles with a certain mole percentage, and condensing silicon oxide gas into silicon oxide solid particles; wherein, the high temperature sintering temperature is: 2000-2500 deg.c; the high-temperature sintering time is as follows: 1-3 min; therefore, according to the technical scheme provided by the invention, the silicon and silicon dioxide ball-milling mixture particles can be rapidly gasified to generate the silicon oxide gas, so that the preparation time of the silicon oxide can be greatly shortened, the energy consumption cost is greatly reduced, and the production efficiency is improved.
Further, since the physical properties of Si and SiO2 are changed by the rapid heating mode, the gasification temperature of Si and SiO2 is reduced, thereby being more beneficial to the preparation of SiO.
In theory, the smaller the particle size of the mixture particles after ball milling and mixing is, the better the effect is, but the energy consumption is high, which is not beneficial to mass production; the too large particle size of the mixture particles after ball milling mixing may cause insufficient mixing and may also be affected during gasification at high temperature sintering. Thus, in a preferred embodiment, the mixture particles after ball milling are of the particle size: 2um to 10um.
In one embodiment, in step S12, before sintering the mixture particles after ball milling and mixing at high temperature, the method further includes:
Preheating the mixture particles after ball milling and mixing;
The preheating function of the mixture particles after ball milling and mixing is as follows: so that the sintering is more sufficient. Too short a preheating time may result in uneven gasification; thereby affecting the quality of the finally produced silica;
thus, in a preferred embodiment, the preheating temperature is: 1000-1200 ℃; the preheating time is as follows: 1-2 min.
In other embodiments, the implementation manners of the preheating temperature and the preheating time may be other implementations, which are not limited to the present invention.
In one embodiment, in step S12, after performing high-temperature sintering on the mixture particles after ball milling and mixing, the method further includes:
heat preservation is carried out at 1000-1200 ℃;
Wherein, the effect of carrying out heat preservation to the mixture particles after high-temperature sintering is: the uniform condensation of steam is facilitated, and the insufficient condensation of the steam can be caused due to the short condensation time, so that the yield of solid mixture particles is reduced;
in a preferred embodiment, the incubation time is: 1-2 min.
In other embodiments, the implementation manner of the heat preservation time may be other implementations, which is not limited to the present invention.
In one embodiment, in step S12, sintering the mixture particles after ball milling and mixing by using a joule heating device, where the working voltage and the working current of the joule heating device are set as follows: 30A-40A; 300V-400V to provide a high temperature sintering temperature of 2000-2500 ℃.
As shown in fig. 5, which is a schematic view of the joule heating apparatus, the joule heating apparatus includes: graphite tube 1, ammeter 5, voltmeter 4, resistor 6 and power supply 3; wherein, the power supply 3, the resistor 6, the ammeter 5 and the graphite tube 1 are sequentially connected in series; the voltmeter 4 is connected in parallel with two ends of the graphite tube 1; the graphite tube 1 is connected with the two ends of the voltmeter 4 through the conductive die clamp 2.
When the mixture particles after ball milling are sintered by using a Joule heating device, the specific operation steps are described as follows:
1. loading the mixture particles after ball milling and mixing into a graphite tube 1; wherein a vacuum environment is set in the graphite tube 1 (the vacuum degree is set to be less than 500 Pa);
Compared with the prior art that the vacuum degree of equipment is required to be less than or equal to 15Pa, the technical scheme provided by the patent has lower requirement on the vacuum degree;
2. connecting a power supply 3, setting output voltage and current to control temperature, and starting an external circuit; the voltage and the current can be regulated in the middle to control the temperature;
and 3, closing the device when the time is reached, namely, the temperature is reduced (consistent with the temperature rising rate), and taking out the powder.
Similar joule devices can be seen in: the third page of the high temperature ultrafast material preparation device HTS and FJH introduction V2.1 and the product atlas-2023.02 of the in situ technology Co., ltd.
The voltage output controllable by the Joule heating device adopted by the invention is as follows: the current output is 0-40V: 0-500A; the Joule heating device adopted by the invention has high safety, and is suitable for high-temperature sintering at the temperature of more than 2000 ℃.
In a preferred embodiment, in step S12, when the mixture particles after ball milling and mixing are sintered at a high temperature, the high temperature sintering temperature is 2300 ℃ to 2500 ℃; high-temperature sintering time: 2 min-2.5 min.
Correspondingly, in one embodiment, the mixture particles after ball milling and mixing are sintered by a joule heating device, and the working voltage and the working current of the joule heating device are set as follows: 35A to 40A; 350V-400V to provide a high temperature sintering temperature of 2300 ℃ to 2500 ℃.
The present invention will be analyzed experimentally in providing a high temperature sintering temperature of: the sintering time at the high temperature is 2300-2500 ℃, and the sintering time at the high temperature is as follows: 2 min-2.5 min, the product performance of the silicon-oxygen anode material in some specific embodiments; a constant-current charge and discharge mode test is carried out by using a charge and discharge instrument; wherein, the discharge cut-off voltage is 0.05V, the charge cut-off voltage is 1V, the first round of charge and discharge test is performed under C/20 current density, and the fourth round and subsequent discharge tests are performed under C/2 current density.
Specific example 1:
High-temperature sintering temperature is 2500 ℃, and sintering time is 2 minutes;
referring to fig. 2, fig. 2 shows a graph of the cycle specific capacity of a lithium battery including the silicon oxygen anode material prepared in example 1.
As can be seen from FIG. 2, the activation of C/20 was performed three times before 0.05V-1V, and 0.5C long cycles were performed at 0.05V-1V; wherein after 300 circles of circulation, the specific capacity is 958mAh/g, and the corresponding specific capacity retention rate is as follows: 79.4%. From this, it is seen that in example 1, a silicon oxide anode material having relatively good performance was produced by sintering at a high temperature for a relatively long time.
Specific example 2:
high-temperature sintering temperature is 2000 ℃, sintering time is 2 minutes;
referring to fig. 3, fig. 3 shows a graph of the cycle specific capacity of a lithium battery including the silicon oxygen anode material prepared in example 2.
As can be seen from fig. 3, the specific capacity after 300 circles is 556mAh/g, the corresponding specific capacity retention rate is 45.9%, and the cycle performance is obviously reduced when the sintering temperature is reduced; this is due to insufficient sintering, where there is some residual of insufficiently sintered SiO2, and where this part itself is an electrically inert substance, which affects the conductive network in the whole electrode and thus the electrochemical performance.
Specific example 3:
high-temperature sintering temperature is 2500 ℃, and sintering time is 1 minute;
Referring to fig. 4, fig. 4 shows a graph of the cycle specific capacity of a lithium battery including the silicon oxygen anode material prepared in example 3.
As can be seen from fig. 4, at 0.5C, the initial capacity is 1055mAh/g, the subsequent cycle has obvious climbing process, the residual capacity after 300 cycles has 938mAh/g, and the corresponding capacity retention rate is 74.3%; it can be seen that as the sintering time decreases, a significant decrease in rate capability can be seen.
After the mixture particles after ball milling and mixing are sintered at high temperature to obtain silicon oxide gas, in step S13, the condensation mode adopted when condensing the silicon oxide gas into silicon oxide solid particles is as follows: natural condensation; the condensing time is as follows: 1 min-2 min. The condensing time described herein is a proper natural condensing time, and the condensing time is not limited herein, and a specific condensing time may be selected as the case may be.
In one embodiment, step S13, after condensing the silica gas into silica solid particles, further includes:
ball milling and sieving are carried out on the silica solid particles so as to obtain silica ball milling particles with uniform particle size; wherein, the particle size of the silica ball milling particles is as follows: 1um to 2um.
Wherein, the too large particle size of the silica ball milling particles can lead to the reduction of the overall conductivity, thereby reducing the cycle performance of the battery. The particle size of the silicon oxide ball-milling particles is too small, and the energy consumption is large, and when the silicon oxide ball-milling particles are ball-milled into nano-scale particles, a high-energy ball-milling mode is needed, and the energy consumption is large.
According to an embodiment of the present invention, there is also provided a silicon-oxygen anode material prepared by the method for sintering a silicon-oxygen anode material according to any one of the preceding embodiments of the present invention.
Secondly, according to an embodiment of the present invention, there is further provided a method for preparing a negative electrode sheet of a lithium battery, including the method for sintering a silicon oxygen negative electrode material according to any one of the foregoing embodiments of the present invention, the method for preparing a negative electrode sheet of a lithium battery further includes:
Mixing the silica solid particles, a conductive additive and a binder to prepare a slurry of a negative electrode material; wherein, the mass of the silicon oxide solid particles is as follows: the mass of the conductive additive is as follows: the mass of the binder is as follows: 90% >: 5%:5%;
Wherein the conductive additive comprises: acetylene black and carbon nanotubes; the mass of the acetylene black is as follows: the mass of the carbon nano tube is as follows: 1:1, a step of;
The binder comprises: sodium carboxymethyl cellulose and styrene butadiene rubber; the mass of the sodium carboxymethyl cellulose is as follows: the styrene-butadiene rubber comprises the following components in percentage by mass: 1:1.
And coating the slurry of the negative electrode material on a copper foil, and drying to form the lithium battery pole piece.
In one embodiment, the preparation method of the lithium battery negative electrode piece further comprises the following steps:
Cutting the dried lithium battery pole piece into a round pole piece; wherein, the radius of circular pole piece is: 1 to 1.2cm;
Vacuumizing and drying the round pole piece in a vacuum drying oven for 8-10 hours; wherein, the stoving temperature is: 100-120 ℃.
In one embodiment, the conductive additive includes: carbon black.
In one embodiment, when the slurry of the negative electrode material is coated on the copper foil and dried, the slurry is dried in a blast drying oven at the following drying temperature: 45-60 ℃; the drying time is 1-2 hours.
In addition, according to an embodiment of the present invention, there is also provided a lithium battery negative electrode sheet, which is prepared by using the preparation method of the lithium battery negative electrode sheet according to the foregoing embodiment of the present invention.
Again, according to an embodiment of the present invention, there is further provided a method for preparing a lithium battery, including the method for preparing a lithium battery negative electrode sheet according to any one of the foregoing embodiments of the present invention, the method for preparing a lithium battery further includes:
Providing an anode plate, the lithium battery cathode plate, a diaphragm and electrolyte;
And assembling the positive electrode plate, the lithium battery negative electrode plate, the diaphragm and the electrolyte into a lithium battery.
Finally, according to an embodiment of the present invention, there is also provided a lithium battery manufactured by using the method for manufacturing a lithium battery according to the foregoing embodiment of the present invention.
The following conditions for sintering provided by the invention are: the method for sintering the silicon-oxygen anode material is specifically described by taking a high-temperature sintering temperature of 2500 ℃ and a high-temperature sintering time of 2 minutes as an example:
1. The silicon powder and the silicon dioxide powder after ball milling and mixing are filled into a graphite tube 1 (specifically, the graphite tube 1 can be a graphite boat), the device is pumped to a low vacuum state (500 pa), the output voltage is set to 40V, the current is set to 400A, the temperature is cut off to 2500 ℃, and the heat is preserved for 2 minutes.
When the switch is turned on, electric joule heating is started, the temperature of the graphite tube 1 is rapidly increased to 2500 ℃, raw materials start to react and sublimate, and collision heat exchange is carried out in the process, so that a uniform SiO product is formed.
2. Turning off the power supply 3, and at the moment, no voltage or current exists, rapidly cooling the graphite tube 1 to room temperature, waiting for 5 minutes, and condensing the high-purity silicon oxide SiO finished product into solid;
3. Taking out the materials, ball milling again, and sieving to obtain SiO particles (-2 um) with uniform particle size.
4. The silicon dioxide with uniform particle size obtained above is used as a cathode active material, and is mixed with carbon black as a conductive additive, sodium carboxymethyl cellulose as a binder and styrene-butadiene rubber (the mass ratio is 1:1) according to the mass ratio of 95%:2%:3% is weighed, and the mixture is put into a refiner at room temperature for slurry preparation. And uniformly coating the prepared slurry on the copper foil. Drying in a blast drying oven at 60deg.C for 2 hr, cutting into 8×8mm pole pieces, and vacuum drying in a vacuum drying oven at 100deg.C for 10 hr. Transferring the dried pole piece into a glove box for standby use to assemble a battery; wherein, the assembly of the battery is carried out in a glove box containing high-purity Ar atmosphere.
5. A battery was assembled using a dispersion of LiPF 6 of 1M in Ethylene Carbonate (EC), diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) (volume ratio v: v=45:45:10) as an electrolyte, as a counter electrode.
6. The constant current charge and discharge mode test was performed using a charge and discharge meter, with a discharge cut-off voltage of 0.05V and a charge cut-off voltage of 1V, with a first week of charge and discharge test at C/20 current density, and a fourth week and subsequent discharge tests at C/2 current density.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.