CN108336345B - Preparation method of nano-microstructure silicon negative electrode material - Google Patents

Preparation method of nano-microstructure silicon negative electrode material Download PDF

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CN108336345B
CN108336345B CN201810124248.7A CN201810124248A CN108336345B CN 108336345 B CN108336345 B CN 108336345B CN 201810124248 A CN201810124248 A CN 201810124248A CN 108336345 B CN108336345 B CN 108336345B
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杨娟
陈松
唐晶晶
周向阳
张佳明
任永鹏
于亚文
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Hunan Chenxing New Material Research Institute Co.,Ltd.
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Central South University
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Abstract

The invention discloses a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps of (1) dispersing metallurgical-grade micron silicon in organic dispersion liquid; (2) preparing an HF-metal salt solution as an etching agent, and slowly adding the etching agent into the pre-dispersion liquid of the silicon to obtain micron silicon with metal particles deposited on the surface; (3) re-dispersing the micron silicon with the metal particles deposited on the surface in the organic dispersion liquid; (4) HF-H2O2Adding the solution into silicon dispersion liquid, and intermittently adding organic dispersion liquid; (5) soaking porous silicon in HNO3Obtaining high-purity porous silicon in the solution; (6) high-purity porous silicon is subjected to ball milling treatment with controllable oxidation degree. The invention adopts a method of combining metal-assisted chemical etching and ball milling with controllable oxidation degree to prepare SiO with a compact oxide layer smoothly coated on the surfacexAnd the nano-micro structure silicon negative electrode material rich in micropores can shorten a lithium ion transmission path and accommodate silicon volume expansion, and has excellent cycle stability.

Description

Preparation method of nano-microstructure silicon negative electrode material
Technical Field
The invention belongs to the technical field of porous nano functional materials, and relates to a preparation method of a nano-microstructure silicon negative electrode material.
Background
The lithium ion battery is used as an energy storage device, has the advantages of high energy density, good cycle performance, environmental protection and the like, and is widely applied to the field of portable electronic equipment such as mobile phones, notebook computers, game machines, unmanned planes and the like. In China, new energy automobiles and energy storage industries are vigorously developed in recent years, and the development of battery cathode materials with higher specific capacity and low cost is urgently needed. Silicon has the advantages of high theoretical specific capacity, low lithium intercalation potential and wide source, and has the potential to replace graphite to become the cathode material of the next generation of high-energy lithium ion battery. However, the volume expansion of the silicon material reaches 300% in the battery charging and discharging process, the electrode structure is damaged due to repeated volume change in the cycle process, and the cycle performance is reduced rapidly, so as to solve the problems of the silicon negative electrode material, the following preparation method is mainly adopted at present:
firstly, preparing a nano silicon negative electrode material, which comprises silicon nano particles, a silicon nano film, silicon nano wires, a silicon nano tube and the like. The reduction of the silicon size can effectively inhibit the volume expansion in the lithium extraction process and shorten the lithium ion transmission path, but the nano silicon material has an electrochemical sintering phenomenon in the charging and discharging process, the production process of the nano silicon material usually involves the technologies of chemical vapor deposition, thermal evaporation and the like, the production cost is high, and the agglomeration phenomenon is easy to generate. In addition, the specific surface area of the nano silicon material is large, so that the coulomb efficiency of the battery is low, and the practical application of the battery is influenced.
Second, the silicon is combined with conductive substrates such as carbon, metals and oxides to produce composite materials. The matrix in the composite material can inhibit the volume expansion to a certain extent, and simultaneously can improve the conductivity of the silicon electrode. Patent CN 106450329A reports a preparation method of a silicon-carbon composite material for a lithium ion battery, amorphous carbon is uniformly grown on the surface of porous silicon by using a liquid phase method, the reversible capacity is 1460-1520 mAh/g after 100 cycles, inactive substances are often used as a matrix in the composite material, and in order to ensure the structural stability of silicon, the addition amount of the matrix is large, which leads to the reduction of the actual specific capacity of an electrode.
And thirdly, silicon oxide such as silicon monoxide is adopted. LiO generated in the process of first lithium intercalation of silicon monoxide2Can act as a matrix to suppress the volume expansion of silicon, and siliconCan be easily dispersed in the matrix at nanometer level. Patent CN 103474631 a reports a preparation method of a silica composite negative electrode material, which comprises preparing a silica matrix, a nano silicon material uniformly deposited on the silica matrix, and a nano conductive material coating layer on the silica/nano silicon surface by nano silicon chemical vapor deposition, nano conductive material coating modification, sieving and demagnetizing treatment. The prepared material has the characteristics of high specific capacity (1600mAh/g) and high conductivity. But irreversibly generates LiO during the first charge-discharge process2Part of lithium is consumed, so that the first charging and discharging coulombic efficiency of the battery is low.
And fourthly, preparing porous silicon as the negative electrode material of the lithium ion battery. CN 105399100A prepares a precursor Mg by alloying silicon powder and magnesium powder2And then carrying out dealloying treatment on the Si/Mg composite material to prepare the nano porous silicon. In patent CN 106115708A, after reducing part of silicon oxide into simple substance silicon by magnesiothermic reduction, hydrofluoric acid etching treatment is used to obtain silicon with honeycomb three-dimensional continuous porous structure. The difficulty in preparing the porous silicon anode material is that the pore size distribution is difficult to control. The porous silicon material has lower first charge-discharge coulombic efficiency and low tap density due to larger specific surface area, so that the high-volume specific capacity battery is difficult to realize.
Disclosure of Invention
The invention aims to provide a preparation method of a nano-microstructure silicon negative electrode material, which has the advantages of stable structure, high purity, excellent electrochemical performance, low cost and easy industrial production.
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in an organic dispersion liquid to obtain a pre-dispersion liquid of silicon;
(2) preparing an HF-metal salt solution as an etching agent, slowly adding the etching agent into the pre-dispersion liquid of the silicon obtained in the step (1) through a peristaltic pump, and performing suction filtration after reaction to obtain micron silicon with metal particles deposited on the surface;
(3) re-dispersing the micron silicon with the metal particles deposited on the surface in the step (2) in an organic dispersion liquid, and stirring to obtain a silicon dispersion liquid;
(4) HF-H2O2Slowly adding the solution into the silicon dispersion liquid obtained in the step (3) through a peristaltic pump, intermittently adding the organic dispersion liquid through a spraying device, stirring, and performing suction filtration to obtain porous silicon;
(5) soaking the porous silicon obtained in the step (4) in HNO3Obtaining high-purity porous silicon in the solution;
(6) and (5) performing ball milling treatment on the high-purity porous silicon obtained in the step (5) with controllable oxidation degree to finally obtain the silicon cathode material with the nano-microstructure.
Preferably, in the step (1), the granularity of the metallurgical-grade micron silicon is 5-20 microns, and the purity is 85% -99.9%.
Preferably, in the step (1), the step (3) and the step (4), the organic dispersion liquid is the same dispersion liquid, the organic dispersion liquid is one or more of methanol, ethanol and isopropanol in an organic matter aqueous solution, and the content of organic matters is 2-50 wt%.
Preferably, in the step (1), an ultrasonic or homogeneous disperser is used to disperse the metallurgical-grade micron silicon in the organic dispersion liquid, and the dispersion time is 10-120 min.
Preferably, in the step (2), the metal salt in the etchant is AgNO3，Cu(NO3)2，PdCl2，KAuCl4Wherein the concentration of the metal salt is 0.001-1 mol/L.
Preferably, the liquid inlet speed of the peristaltic pump in the step (2) and the step (4) is 5-20 ml/min, and the contact area of the silicon powder and the etching agent HF is increased in a liquid-liquid mixing mode, so that the etching reaction is promoted.
Preferably, in the step (4), a spraying device is adopted to intermittently add the organic dispersion liquid, and 5-10 ml of the organic dispersion liquid is intermittently sprayed within 10min of the initial stage of the etching reaction.
Preferably, in the step (4), the stirring time is 1-12 h.
Preferably, in the step (5), the porous silicon is in HNO3The soaking time in the solution is 0.5 to 12 hoursThe mass concentration of the nitric acid solution is 5-20 percent, and the nitric acid solution is treated by HNO3And (4) collecting Ag in the porous silicon for recycling by solution treatment.
Preferably, in the step (6), the ball milling treatment with controllable oxidation degree is to introduce an oxidizing gas into a ball milling tank or to add an additive into the raw materials during ball milling. The volume percentage of oxygen in the oxidizing gas is 20-50%; the additive is H2O，H2O2And one or more of NaOH. The mass ratio of the silicon source to the additive to the ball-milled beads is (5-50): 1 (0-2), the ball-milling time is 3-12 h, the rotating speed of the ball mill is 300-600 r/min, the size of silicon is further reduced and the pore size distribution is adjusted through ball-milling treatment, and finally the silicon cathode material with the nano-microstructure is obtained.
The invention also provides a silicon cathode material prepared by the preparation method of the nano-microstructure silicon cathode material.
The principle of the invention is that firstly, a metal-assisted chemical etching method is adopted, high-purity porous silicon which is easy to ball mill and has rich microporous structures is prepared in metallurgical-grade micron silicon through the catalytic action of metal particles and the etching action of hydrofluoric acid, and then the ball milling method with controllable oxidation degree is adopted to carry out surface modification and aperture adjustment on the porous silicon. The method for combining metal-assisted chemical etching and ball milling with controllable oxidation degree prepares SiO with a compact oxide layer smoothly coated on the surfacexAnd the nano-micro structure silicon cathode material with rich micropores inside not only retains the advantages that the nano-porous silicon material can shorten a lithium ion transmission path and accommodate the volume expansion of silicon, but also can avoid the defects of overhigh activity, low coulombic efficiency and low tap density caused by large specific surface area of the porous silicon.
Compared with the prior art, the invention has the following beneficial technical effects:
(1) according to the invention, by using a metal-assisted chemical etching-ball milling method with controllable oxidation degree, the prepared silicon cathode material is spherical-like, and the particle size distribution is 20-500 nm. The ball milling process adopts a ball milling method with controllable oxidation degree, and comprises introducing oxygen in a certain proportion into a ball milling tank and addingSpecific oxidizing substances are used. The oxidation degree controllable ball milling method ensures that the surface of the silicon is smooth and is wrapped by a layer of compact oxide layer SiOxThe compact oxide layer can avoid direct contact between silicon particles and electrolyte, inhibit volume expansion of silicon in the charging and discharging process, ensure the structural stability of silicon and be beneficial to improving the cycle performance of a silicon electrode.
(2) According to the invention, the nano-microstructure silicon negative electrode material is obtained by a metal-assisted chemical etching-ball milling combined method with controllable oxidation degree, the pore distribution of the nano-microstructure silicon negative electrode material is effectively adjusted, the size of the material is obviously reduced, macropores (larger than 50nm) on the surface disappear, micropores left by dissolving metal impurities in the material are retained, the average pore diameter of the micropores is 5-20 nm, and the silicon negative electrode material with the special structure shows high first coulombic efficiency and excellent cycle performance.
(3) The organic dispersion liquid is sprayed intermittently in the metal-assisted chemical etching process to promote the etching reaction, gas is generated by the violent reaction in the initial stage of the etching process, the solution is boiled due to the violent heat release, a large amount of micron silicon floats on the surface of the etching agent and cannot participate in the reaction, unreacted silicon can be immersed into the etching agent again by intermittently spraying the organic dispersion liquid in the initial stage of the etching, hydrofluoric acid can enter the inside of the micron silicon to dissolve more metal impurities, the purity of the silicon reaches 99.99 percent, uniformly etched porous silicon is obtained, the etching effect of the silicon can be greatly improved by adding the organic dispersion liquid to adjust the dispersion of the silicon, the ball milling time of the silicon can be shortened, and the silicon cathode material with a mesoporous structure can be obtained.
(4) The invention takes cheap and easily obtained metallurgical-grade micron silicon as a raw material, adopts a simple and easy wet etching and ball milling method, can recycle the metal salt used in the process, has higher product yield which is more than 45 percent (the yield is less than 20 percent by using a magnesiothermic reduction method), has short preparation time and controllable conditions, and is suitable for large-scale industrial production.
Drawings
Fig. 1 is an SEM image of the nano-microstructured silicon negative electrode material obtained in example 1. It can be seen that the surface of the high purity porous silicon after ball milling becomes smooth and the particle size is reduced to below 500 nm.
Fig. 2 is a TEM image of the nano-microstructured silicon anode material obtained in example 1. It can be seen that the porous silicon surface disappears and becomes smooth after ball milling, and the particle size is about 200 nm.
Fig. 3 is an HRTEM image of the nano-microstructured silicon negative electrode material obtained in example 1. It can be seen that a compact oxide layer SiO is formed on the surface of the porous silicon after the ball milling with controllable oxidation degreex。
Fig. 4 is a pore size distribution diagram of the nano-microstructured silicon anode material obtained in example 1. It can be seen that after the porous silicon is subjected to ball milling treatment, the pore diameter is mainly distributed to be 5-55 nm, and macropores larger than 60nm basically disappear.
Fig. 5 shows the cycle performance and coulombic efficiency of the nano-microstructured silicon negative electrode material obtained in example 1 under the condition of 0.2C. It can be seen that it has a high first effect and excellent cycle performance.
Fig. 6 shows the cycle performance and coulombic efficiency of the nano-microstructured silicon negative electrode material obtained in example 1 under the condition of 1C. The capacity after 500 cycles is up to 900mA h/g.
Fig. 7 is an SEM image of the high purity porous silicon prepared in comparative example 3. It can be seen that the etched silicon without ball milling has a porous morphology.
Fig. 8 is a pore size distribution diagram of the high purity porous silicon prepared in comparative example 3. It can be seen that the etched porous silicon has both mesopores with the pore diameter of 2-50 nm and a large number of macropores with the pore diameter of more than 50 nm.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by those skilled in the art without any creative work based on the embodiments of the present invention belong to the protection scope of the present invention.
The experimental procedures described in the following examples are conventional unless otherwise specified, and the reagents and materials described therein are commercially available without further specification.
Example 1
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3And (4) solution system. HF concentration of 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface obtained in the step (2) in 5% ethanol dispersion liquid, and stirring to obtain silicon dispersion liquid;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
ICP detection is carried out on metallurgical-grade micron silicon and high-purity porous silicon, and the results are shown in Table 1, that metal impurities Cr, Fe, Mn, Ni and Zr in the etched porous silicon are greatly reduced, and the conductivity of the silicon can be improved by a very small amount of silver which is not completely removed. Preparing slurry from the silicon negative electrode material with the nano-micro structure obtained after ball milling, acetylene black and sodium alginate in a deionized water medium according to the mass ratio of 6:2:2, coating the slurry on a copper foil, performing vacuum drying at 120 ℃, taking a lithium sheet as a counter electrode, taking a polypropylene film as a diaphragm and taking 1ML LiPF as electrolyte6/(EC: DEC ═ 1:1) + 10% FEC, battery case model 2025. Charging and discharging at current density of 0.1C (1C is 4200mA/g) in the first three cycles, and then charging and discharging at 0.2C, and charging and discharging in voltage range of 0.01-1.2V; the first three cycles were charged and discharged at a current density of 0.1C, followed by 1C.
Table 1 shows the analysis results of the ICP measurement of metallurgical grade micro silicon and high purity porous silicon for each impurity content, unit: ug/g
Figure BDA0001573034440000061
Example 2
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.005mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface obtained in the step (2) in 5% ethanol dispersion liquid, and stirring to obtain silicon dispersion liquid;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 3
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at the concentration of 0.02mol/L through a peristaltic pump at the concentration of 10ml/min, carrying out reaction for 5min, and then carrying out suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 4
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 10min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration was 2% and 10ml of ethanol dispersion was added intermittently over 10min using a spray device. Stirring for 2h, and performing suction filtration to obtain porous silicon;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 5
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 30min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4)HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 6
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 1.5%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, the solution is subjected to water bath reaction for 1h at the temperature of 50 ℃, the Ag in the silicon particles is collected for recycling, and high purity is obtained by suction filtrationPorous silicon;
(6) ball milling is carried out on the high-purity porous silicon, the volume ratio of oxygen in a ball milling tank is 30%, the ball milling time is 5h, the ball material ratio is 20:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 7
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration was 2% and 10ml of ethanol dispersion was added intermittently over 10min using a spray device. Stirring for 2h, and performing suction filtration to obtain porous silicon;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling is carried out on the high-purity porous silicon, water is added as an additive for controlling the oxidation degree, the ball milling time is 5 hours, the mass ratio of ball milling beads to silicon source to water is 20:1:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Example 8
The invention relates to a preparation method of a nano-microstructure silicon negative electrode material, which comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in 10% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3And (4) solution system. HF concentration of 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball-milling high-purity porous silicon, adding NaOH as an additive for controlling the oxidation degree, wherein the ball-milling time is 5 hours, the mass ratio of ball-milling beads to silicon source to NaOH is 20:1:1, and the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Comparative example 1
And (3) carrying out ball milling on the micron silicon for 12h at a ball-to-material ratio of 20:1, wherein the rotating speed of a ball mill is 500r/min, then preparing an electrode, assembling a battery and testing the performance according to the same method as in example 1.
Comparative example 2
(1) Dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.005mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface obtained in the step (2) in 5% ethanol dispersion liquid, and stirring to obtain silicon dispersion liquid;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling high-purity porous silicon, introducing nitrogen into a ball milling tank, ball milling for 5 hours at a ball-to-material ratio of 20:1,
the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Comparative example 3
(1) Dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.005mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface obtained in the step (2) in 5% ethanol dispersion liquid, and stirring to obtain silicon dispersion liquid;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) at the speed of 10ml/min by a peristaltic pump, and concentrating HFDegree of 5mol/L, H2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3In the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain high-purity porous silicon;
(6) ball milling high-purity porous silicon, introducing pure oxygen into a ball milling tank, ball milling for 5 hours at a ball-to-material ratio of 20:1,
the rotating speed of the ball mill is 500 r/min.
The silicon negative electrode material with the nano-microstructure obtained after ball milling was used for preparing an electrode, assembling a battery and testing the performance in the same manner as in example 1.
Comparative example 4
(1) Dispersing metallurgical-grade micron silicon in 50ml of water solution, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 50ml of aqueous solution, and stirring to obtain silicon dispersion liquid;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, and porous silicon is obtained by suction filtration after stirring for 2 hours;
(5) soaking porous silicon in 20% HNO3And in the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain the high-purity porous silicon.
The resulting high-purity porous silicon was dried in an oven at 60 ℃ for 12 hours, and an electrode, a battery and properties were fabricated by the same method as in example 1.
Comparative example 5
(1) Dispersing metallurgical-grade micron silicon in 5% ethanol dispersion, and performing ultrasonic dispersion for 10min to obtain a pre-dispersion liquid of silicon;
(2) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(3) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(4) HF-H2O2Adding the solution into the silicon dispersion liquid obtained in the step (3) by a peristaltic pump at the speed of 10ml/min, wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(5) soaking porous silicon in 20% HNO3And in the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain the high-purity porous silicon.
The resulting high-purity porous silicon was dried in an oven at 60 ℃ for 12 hours, and an electrode, a battery and properties were fabricated by the same method as in example 1.
Comparative example 6
(1) Carrying out ball milling on the micron silicon for 12 hours at a ball-material ratio of 20:1 and a ball mill rotation speed of 500r/min to obtain silicon powder;
(2) dispersing the silicon powder obtained in the step (1) in 5% ethanol dispersion liquid, and performing ultrasonic dispersion for 30min to obtain a pre-dispersion liquid of silicon;
(3) by HF-AgNO3Solution system, HF concentration is 5mol/L, AgNO3Slowly adding the etching agent into the pre-dispersion liquid of silicon at a concentration of 0.01mol/L through a peristaltic pump at a rate of 10ml/min, reacting for 5min, and performing suction filtration to obtain micron silicon with Ag particles deposited on the surface;
(4) re-dispersing the micron silicon with Ag particles deposited on the surface in 5% ethanol dispersion, and stirring to obtain silicon dispersion;
(5) HF-H2O2The solution was pumped through a peristaltic pump at a rate of 10ml/minAdding the silicon into the silicon dispersion liquid obtained in the step (4), wherein the concentration of HF is 5mol/L, and H is2O2The concentration is 2%, 10ml of ethanol dispersion liquid is added intermittently within 10min by using a spraying device, and after stirring for 2h, porous silicon is obtained by suction filtration;
(6) soaking porous silicon in 20% HNO3And in the solution, carrying out water bath reaction for 1h at 50 ℃ to collect Ag in the silicon particles for recycling, and carrying out suction filtration to obtain the high-purity porous silicon.
The resulting high-purity porous silicon was dried in an oven at 60 ℃ for 12 hours, and an electrode, a battery and properties were fabricated by the same method as in example 1.
The test results of the lithium half-cell are shown in Table 2, and the electrochemical test results of the examples 1 to 8 and the comparative example 1 show that only the micron silicon in the comparative example 1 is subjected to ball milling, and the metal-assisted chemical etching-oxidation degree controllable ball milling combined method can improve the specific charge capacity of the silicon cathode from 1981.6mAh/g to 2401.4mAh/g (average value), improve the lithium intercalation capacity of the silicon cathode material, and improve the capacity retention rate from 36.7% to 86.7% (average value) after 100 cycles under the condition of 0.2C, which shows that the structural stability of the silicon cathode material prepared by the method is remarkably improved, and the method is favorable for industrialization of the silicon cathode material.
According to the electrochemical test results of the embodiments 1 to 8 and the comparative example 2, the etching porous silicon in the comparative example 2 is subjected to ball milling in a nitrogen atmosphere, and the ball milling method with controllable oxidation degree is adopted, so that a compact oxide layer is formed on the surface of the silicon in the ball milling process, the capacity retention rate of the silicon cathode after being cycled for 100 cycles at 0.2C can be improved from 64.9% to 87.6% (average value), and the structural cycle life of the silicon cathode material prepared by the method is remarkably prolonged.
According to the electrochemical test results of the embodiments 1 to 8 and the comparative example 3, the etched porous silicon in the comparative example 3 is ball-milled in an oxygen atmosphere, and the content of oxygen introduced into the ball-milling with controllable oxidation degree adopted by the invention is 20 to 50 percent. The ball milling is carried out in the pure oxygen atmosphere, so that a large amount of silicon is oxidized, the first charging specific capacity of the silicon cathode is reduced to 1565.7mAh/g from 2401.4mAh/g (average value), and the capacity retention rate is reduced to 64.9% from 86.7% after the silicon cathode is cycled for 100 circles at 0.2C. The invention shows that the structural cycle life of the silicon cathode material prepared by the ball milling process controlled by a certain content of oxygen is obviously prolonged.
According to the electrochemical test results of the embodiments 1 to 8 and the comparative example 4, the micron silicon in the comparative example 4 is only subjected to metal-assisted chemical etching, and the aqueous solution is used as the dispersion liquid in the comparative example 4, and the method for the combination of metal-assisted chemical etching and ball milling with controllable oxidation degree, disclosed by the invention, has the advantages that the ethanol is added to adjust the dispersion of the silicon, so that the etching effect of the silicon is greatly improved, the time is shortened in the subsequent ball milling process, and the silicon cathode material with better aperture adjusting effect is obtained. The charging specific capacity of the silicon cathode is improved from 2201.7 to 2401.4mAh/g, the lithium insertion capacity of the silicon cathode material is improved, and the capacity retention rate is improved from 61.3% to 86.7% (average value) after 100 cycles under the condition of 0.2C, which shows that the structural cycle life of the silicon cathode material prepared by the invention is obviously prolonged.
According to the electrochemical test results of the embodiments 1 to 8 and the comparative example 5, only the metal-assisted chemical etching is performed on the micron silicon in the comparative example 5, the structural stability of the silicon cathode can be remarkably improved by the metal-assisted chemical etching-oxidation degree controllable ball milling combined method, the capacity retention rate is improved from 71.1% to 86.7% (average value) after 100 cycles under the condition of 0.2C, and the long cycle performance under high rate is also improved, so that the porous silicon prepared by the method can inhibit the volume expansion of the silicon cathode in the cycle process.
According to the electrochemical test results of the embodiments 1 to 8 and the comparative example 6, the specific charge capacity, the first charge-discharge efficiency and the cycle retention rate in the comparative example 6 are obviously inferior to those of the invention, and the comparative example 6 is that high-energy ball milling is performed first and then metal auxiliary chemical etching is performed. The ball milling generates a large amount of silicon oxide, which is not beneficial to the adhesion of metal particles and influences the etching effect. At the same time, the silicon oxide is liable to react with hydrofluoric acid, resulting in extremely low yield. The invention adopts a method of combining metal auxiliary chemical etching and ball milling with controllable oxidation degree, firstly adopts an improved metal auxiliary chemical etching method in the preparation process to prepare high-purity porous silicon which is easy to ball mill and has rich microporous structures, and then uses the ball milling method with controllable oxidation degree to adjust the particle size and the pore diameter of the porous silicon by ball milling and introduce an oxide layer, thereby greatly improving the electrochemical performance of the porous silicon.
TABLE 2 electrochemical Performance test results of silicon negative electrode materials obtained in examples 1 to 8 and comparative examples 1 to 6
Figure BDA0001573034440000151

Claims (8)

1. A preparation method of a nano-microstructure silicon negative electrode material comprises the following steps:
(1) dispersing metallurgical-grade micron silicon in an organic dispersion liquid to obtain a pre-dispersion liquid of silicon;
(2) preparing an HF-metal salt solution as an etching agent, slowly adding the etching agent into the pre-dispersion liquid of the silicon obtained in the step (1) through a peristaltic pump, and performing suction filtration after reaction to obtain micron silicon with metal particles deposited on the surface;
(3) re-dispersing the micron silicon with the metal particles deposited on the surface in the step (2) in an organic dispersion liquid, and stirring to obtain a silicon dispersion liquid;
(4) HF-H2O2Slowly adding the solution into the silicon dispersion liquid obtained in the step (3) through a peristaltic pump, intermittently adding the organic dispersion liquid through a spraying device, stirring, and performing suction filtration to obtain porous silicon;
(5) soaking the porous silicon obtained in the step (4) in HNO3Obtaining high-purity porous silicon in the solution;
(6) performing ball milling treatment on the high-purity porous silicon obtained in the step (5) with controllable oxidation degree to finally obtain a silicon cathode material with a nano-microstructure;
step (1), step (3), wherein the organic dispersion liquid in step (4) is the same dispersion liquid, the organic dispersion liquid is an aqueous solution of organic matters, and the content of the organic matters is 2-50 wt%; the organic matter is one or more of methanol, ethanol and isopropanol;
in the step (6), ball milling with controllable oxidation degreeThe treatment is to introduce oxidizing gas into the ball milling tank or add additives into the raw materials during ball milling; the volume percentage of oxygen in the oxidizing gas is 20-50%, and the additive is H2O，H2O2One or more of NaOH; the mass ratio of the silicon source to the additive to the ball-milling beads subjected to ball-milling treatment is (5-50): 1, (0-2), the ball-milling time is 3-12 hours, and the rotating speed of the ball mill is 300-600 r/min.
2. The preparation method of the nano-micro structure silicon negative electrode material as claimed in claim 1, wherein the grain size of the metallurgical grade micron silicon in the step (1) is 5-20 μm, and the purity is 85% -99.9%.
3. The preparation method of the nano-micro structure silicon negative electrode material as claimed in claim 1, wherein in the step (1), an ultrasonic or homogeneous disperser is adopted to disperse the metallurgical-grade micron silicon in the organic dispersion liquid, and the dispersion time is 10-120 min.
4. The method for preparing nano-micro structure silicon cathode material according to claim 1, wherein in the step (2), the metal salt in the etching agent is AgNO3，Cu(NO3)2，PdCl2，KAuCl4Wherein the concentration of the metal salt is 0.001-1 mol/L.
5. The preparation method of the nano-micro structure silicon negative electrode material as claimed in claim 1, wherein a liquid-liquid mixing method is adopted in the step (2) and the step (4), and the liquid inlet speed of a peristaltic pump is 5-20 ml/min.
6. The preparation method of the nano-micro structure silicon negative electrode material as claimed in claim 1, wherein in the step (4), the organic dispersion liquid is intermittently added by a spraying device, and 5-10 ml of the organic dispersion liquid is intermittently sprayed within 10min of the initial stage of the etching reaction.
7. The nano-micro structured silicon negative electrode as claimed in claim 1The preparation method of the pole material is characterized in that in the step (5), the porous silicon is in HNO3The soaking time in the solution is 0.5-12 h, and the mass concentration of the nitric acid solution is 5% -20%.
8. The silicon negative electrode material prepared by the preparation method of the silicon negative electrode material with the nano-micro structure according to any one of claims 1 to 7.
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