CN117199327B - Quick-charging silicon-based negative electrode material for lithium battery and preparation method thereof - Google Patents

Abstract

The present invention discloses a fast-charging silicon-based negative electrode material for lithium batteries and a preparation method thereof. The negative electrode is composed of micro-nano-scale silicon-based particles, buffer nanoparticle conductive channels embedded therein, and carbon shell conductive channels coated on the surface thereof. The preparation process of the negative electrode adopts a ball milling sintering process compatible with the industrial lithium battery material preparation process. During the charge and discharge cycle, the charge can be quickly transferred and transmitted through the buffer nanoparticle conductive channels embedded in the silicon-based particles and the carbon shell coated on the surface of the silicon particles, thereby achieving the fast charge and discharge performance of the silicon negative electrode under large currents. At the same time, the buffer nanoparticle conductive channels embedded in the silicon-based particles and the carbon shell coated on the surface of the silicon-based particles can effectively alleviate the volume change of the silicon-based negative electrode material during the charge/discharge process, stabilize the solid electrolyte interface film (SEI) on the surface of the negative electrode particles, and thus improve the cycle stability of the silicon-based negative electrode material.

Description

A fast-charging silicon-based negative electrode material for lithium batteries and a preparation method thereof

Technical Field

The present invention relates to silicon negative electrode technology for lithium batteries, and in particular to a fast-charging silicon-based negative electrode material for lithium batteries and a preparation method thereof, belonging to the technical field of energy storage batteries.

Background technique

Compared with traditional fuel vehicles, problems such as range anxiety and long charging time have become the main problems hindering the development of electric vehicles. Therefore, the improvement of energy density and fast charging capability has become a common development goal for battery manufacturers and vehicle manufacturers. As the negative electrode material of lithium batteries, silicon has a theoretical specific capacity of ~4200 mAh g-1, which is more than ten times the theoretical specific capacity of commercial graphite negative electrodes. It is considered to be one of the most promising negative electrode materials for the next generation of high-energy lithium secondary batteries. However, when lithium ions are embedded in/extracted from silicon, its huge volume expansion/contraction causes silicon particles to break, pulverize, and lose electrical contact with the substrate, greatly reducing its cycle life. Nanoscale silicon materials prevent the pulverization of silicon negative electrode materials during the cycle due to their high specific capacity, good stress release, promotion of ion/electron transport and maintenance of structural stability, providing a solution for improving battery cycle stability. After decades of development, high-energy lithium batteries using silicon negative electrodes instead of carbon negative electrodes are at the beginning of commercial application. Dozens of companies at home and abroad are mass-producing silicon negative electrode materials and working hard to develop the next generation of silicon-based lithium batteries.

The large specific capacity of silicon makes it a strong candidate for the development of next-generation high-energy-density batteries. However, due to the limitations of its own electrical properties, the fast charging ability of silicon materials under high currents has not met the expectations of researchers and companies. Charge transfer is a major aspect that limits the fast charging of electrode materials. According to the band theory, electrons in the valence band pass through the forbidden band into the conduction band, making the solid negative electrode material conductive. Therefore, in order to achieve fast charging, negative electrode materials with high intrinsic electronic conductivity are promising, such as carbon, metals or alloys with small or zero band gaps. However, as a typical semiconductor material, silicon has much worse conductivity than commercial graphite materials. Even single-crystal silicon materials with good conductivity will be transformed into amorphous silicon during the insertion/extraction of lithium ions, making their conductivity worse. In traditional semiconductor processes, the conductivity of silicon materials can be effectively improved by doping with boron and phosphorus atoms. However, the original bonding state of such boron and phosphorus-doped silicon materials will be interrupted during the insertion/extraction of lithium ions, losing their excellent electronic conductivity properties. Typical silicon-carbon negative electrode materials in current commercial silicon-based negative electrode materials are made by coating carbon materials on the surface of nano-silicon particles. Coating the surface of silicon materials with better conductivity carbon materials can improve the charge transfer and transmission of small-sized nano-silicon materials. However, when the size of silicon materials increases, its poor conductivity will greatly limit the charge transfer in silicon negative electrode materials, making the rapid charging and discharging of silicon negative electrode materials under large currents very limited, and it is difficult to achieve the fast charging performance required by power batteries. Therefore, overcoming a series of problems caused by volume expansion of silicon materials, especially large-sized micro-nano silicon negative electrode materials during the insertion/removal of lithium ions, and improving the conductivity of the silicon material itself are the key to the development of silicon negative electrode lithium batteries.

Summary of the invention

In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a fast-charging silicon-based negative electrode material for a lithium battery and a preparation method thereof, which effectively solves the problems in the background technology.

To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a fast-charging silicon-based negative electrode material for a lithium battery, the negative electrode being composed of micro-nano-scale silicon particles, buffer nanoparticle conductive channels embedded in the interior/surface of the silicon particles, and carbon shell conductive channels coated on the surface of the silicon particles.

Preferably, the size of the silicon-based negative electrode material includes commercial silicon nanoparticles with a diameter between 20-30 nm for lithium battery negative electrodes, micron particles with a diameter between 1 um and 100 um, and micro-nano silicon particles with a diameter between 50 nm and 100 um obtained by ball milling silicon waste discarded from semiconductor processes.

Preferably, the type of silicon-based negative electrode material is silicon-based material, including silicon monoxide, silicon dioxide, silicon oxide, and its size is commercial silicon oxide nanoparticles with a diameter between 20 nm and 1000 nm for lithium battery negative electrodes, micron particles with a diameter between 1 um and 100 um, and micro-nano silicon oxide particles with a diameter between 50 nm and 100 um obtained by industrial ball milling of silicon waste discarded from semiconductor processes.

Preferably, the nanoparticles include gold, silver, copper, iron, aluminum, nickel metal nanoparticles, alloy nanoparticles and non-metallic nanoscale particles, and the alloy nanoparticles include copper-silicon alloy, silver-silicon alloy, aluminum-silicon alloy, nickel-silicon alloy and iron-silicon alloy.

Preferably, the carbon shell layer includes but is not limited to graphite, graphene, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black materials,

The fast-charging silicon-based material is composed of 5% to 90% by mass of silicon-based micro-nano particles, 5% to 75% of metal-based nanoparticle conductive channels, and 1% to 20% of carbon shell conductive channels.

The fast-charging silicon-based negative electrode is composited by 5% to 85% by mass of a fast-charging silicon-based material, 3% to 50% by mass of a conductive agent, and 3% to 15% by mass of a binder.

Preferably, the method comprises ball milling, high temperature pyrolysis to prepare silicon monoxide, magnesium thermal reduction to prepare silicon dioxide, and hydrofluoric acid etching to directly prepare silicon-based materials.

Preferably, the fast-charging silicon-based negative electrode material also includes other negative electrode materials with high specific capacity, including alloy materials such as germanium, tin, phosphorus and their oxides, or a composite of two or more thereof.

Preferably, the shell conductive channel also includes a type of material, including one or a composite of two or more of molybdenum sulfide two-dimensional material and titanium dioxide intercalation material.

Preferably, it is characterized in that: the preparation method of the fast-charging silicon-based negative electrode material comprises the following steps:

In the first step, a mixed powder of micro-nano silicon particles, buffer nanoparticles and carbon is weighed in a mass ratio of 50%-98%: 3%-20%: 5%-50%, and the mixed powder is put into a ball mill and mixed uniformly at 1600 rmin ^-1 -1800 rmin ^-1 ;

The second step is to transfer the mixed material into a sintering furnace and anneal and sinter at 1200°C to 1800°C for 12 hours to 24 hours;

The third step is to use a typical industrial carbon coating method to coat the surface of micro-nano silicon particles after high-temperature sintering with a carbon shell material to obtain a silicon-based negative electrode material. The experimental parameters of the carbon coating and the thickness of the coating layer can refer to the parameters of carbon coating on the surface of silicon particles in industry.

The fourth step is to weigh a certain mass of silicon-based negative electrode material, mix it with a binder and a conductive agent in a mass ratio of 7:1.5-2.0:1.5 to 1.0, put it into a ball mill and stir it evenly, and then add a certain mass of solvent and stir it until it is uniform;

The fifth step is to apply the mixed slurry on the copper foil by using a scraper coating or industrial coating process;

Step 6: Assemble the battery and test it;

Or adopt the following process preparation process:

In the first step, a mixed powder of micro-nano silicon particles, buffer nanoparticles and carbon is weighed in a mass ratio of 50%-98%: 3%-20%: 5%-50%, and the mixed powder is put into a ball mill and mixed uniformly at 1600 rmin ^-1 -1800 rmin ^-1 ;

The second step is to transfer the mixed material into a sintering furnace and sinter at 1200° C. to 1800° C. for 12 to 24 hours to obtain a silicon negative electrode material;

The third step is to weigh a certain mass of silicon-based negative electrode material, mix it with a binder and a conductive agent in a mass ratio of 7:1.5-2.0:1.5 to 1.0, put it into a ball mill and stir it evenly, and then add a certain mass of solvent and stir it until it is uniform;

The fourth step is to apply the mixed slurry on the copper foil by using a scraper coating or industrial coating process;

Step 5: Assemble the battery and test it.

Compared with the prior art, the present invention has the following beneficial effects:

1) During the charge and discharge cycle, the charge of the micro-nano silicon negative electrode material prepared by combining the process of embedded buffer nanoparticle conductive channels in the body and the carbon shell conductive channels coated on the surface can be quickly transferred and transmitted through the buffer nanoparticle conductive channels embedded in the silicon-based particles and the carbon shell coated on the surface of the silicon particles, thereby improving the rapid charge and discharge capability of the silicon-based negative electrode material under large current.

2) The buffer nanoparticle conductive channels embedded in the silicon-based particles and the carbon shell conductive channels coated on the surface of the silicon-based particles can also alleviate the volume change of the silicon-based particles, which is beneficial to improving the cycle stability of the silicon-based negative electrode;

3) The carbon shell layer on the surface can not only promote the charge transfer of silicon-based particles but also stabilize the SEI film on the surface of the particles, thereby further improving the cycle stability of the silicon-based negative electrode.

4) The preparation process is compatible with the preparation process of industrial lithium battery materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

FIG1 is a schematic diagram of the structure of a fast-charging silicon negative electrode material according to an embodiment of the present invention;

FIG. 2 is a cycle rate diagram of a silicon negative electrode material prepared in an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

As shown in Figures 1-2, the present invention discloses a fast-charging silicon-based negative electrode material and a preparation method thereof, which is characterized in that: the fast-charging silicon-based negative electrode material is composed of micro-nano-scale silicon-based particles, buffer nanoparticle conductive channels embedded in the silicon-based particles, and carbon shell conductive channels coated on the surface of the silicon-based particles. The preparation process adopts a ball milling sintering process that is compatible with the industrial lithium battery preparation process.

Based on the ball milling and sintering process compatible with the industrial lithium battery material preparation process, a buffer nanoparticle conductive channel is embedded in the micro-nano silicon-based particle body phase, and a carbon shell conductive layer is coated on the surface of the silicon-based particles to obtain a silicon-based negative electrode material that can be quickly charged and discharged. During the charge and discharge cycle, the charge can be quickly transmitted through the buffer nanoparticle conductive channel embedded in the silicon-based particles and the carbon shell coated on the surface of the silicon particles, thereby improving the rapid charge and discharge capability of the silicon-based negative electrode under large currents. At the same time, the buffer nanoparticle conductive channel embedded in the silicon-based particles and the carbon shell conductive channel coated on the surface of the silicon-based particles can also alleviate the volume change of the silicon-based particles and stabilize the SEI film on the surface of the particles, thereby further improving the cycle stability of the silicon-based negative electrode material.

The technical solution further defined in the present invention is: the negative electrode material includes but is not limited to one of the alloy materials silicon (Si), germanium (Ge), phosphorus (P), tin (Sn), antimony (Sb), bismuth (Bi), aluminum (Al) and their oxides, or a composite material of two or more thereof.

Furthermore, the buffer nanoparticle conductive channel embedded in the silicon-based material includes but is not limited to the buffer nanoparticles embedded in the silicon-based material, characterized in that: the nanoparticles include but are not limited to metals and their oxide nanoparticles such as gold (Au), silver (Ag), copper (Cu), iron (Fe), aluminum (Al), cobalt (Co), nickel (Ni), manganese (Mn), molybdenum (Mu), vanadium (V), etc., gold-silicon (Au-Si), silver-silicon (Ag-Si), copper-silicon (Cu-Si), iron-silicon (Fe-Si), aluminum-silicon (Al-Si), nickel-silicon (Ni-Si), cobalt-silicon (Co-Si), nickel silicon (Ni-Si), manganese silicon (Mn-Si), molybdenum silicon (Mu-Si), vanadium silicon (V-Si), etc. alloy nanoparticles, and at least one of disulfide nanoparticles of transition metals such as molybdenum (Mu), iron (Fe), tungsten (W), and vanadium (V).

Furthermore, the carbon shell conductive channel includes but is not limited to the carbon shell conductive conduction, characterized in that: the shell conductive channel includes but is not limited to at least one of intercalated graphite, graphene, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black and other carbon-based materials, layered titanium-based oxides, niobium-based oxides and other oxides, layered molybdenum-based sulfides, tungsten-based sulfides and other sulfur compounds.

The fast-charging silicon negative electrode is composed of 10% to 90% by mass of a micro-nano silicon-based particle matrix, 3% to 50% of a nanoparticle conductive channel, and 1% to 50% of a carbon shell conductive channel in accordance with the structure described in FIG1 ;

The present invention also discloses a method for preparing a fast-charging silicon negative electrode material, characterized in that: the preparation process of the fast-charging silicon-based negative electrode material includes but is not limited to at least one of a ball milling sintering process, a chemical vapor deposition method, a high-temperature solid phase reaction method, a mechanical alloying method, and an electrostatic spinning method that are compatible with the preparation of existing lithium battery negative electrode materials. The preparation process of a typical process includes the following steps:

The first step is to weigh a mixed powder of micro-nano silicon particles, buffer nanoparticles and carbon according to the mass ratio of (50%~98%): (3%~20%): (5%~50%), put it into a ball mill and mix it evenly at 1600 rmin ^-1 -1800 rmin ^-1 ;

The second step is to transfer the mixed material into a sintering furnace and anneal and sinter at 1200°C to 1800°C for 12 hours to 24 hours;

The third step is to use typical industrial carbon coating methods (such as pyrolysis, ball milling, chemical vapor deposition, etc.) to coat the surface of micro-nano silicon particles after high-temperature sintering to obtain silicon-based negative electrode materials. Among them, the experimental parameters of carbon coating and the thickness of the coating layer can refer to the parameters of carbon coating on the surface of silicon particles in industry.

The fourth step is to weigh a certain mass of silicon-based negative electrode material, mix it with a binder and a conductive agent in a mass ratio of 7: (1.5-2.0): (1.5 to 1.0), put it into a ball mill and stir it evenly, and then add a certain mass of solvent and stir it until it is uniform;

The fourth step is to apply the mixed slurry on the copper foil by using a knife coating or industrial coating process.

Step 5: Assemble the battery and test it.

Or adopt the following process preparation process:

The first step is to weigh a mixed powder of micro-nano silicon particles, buffer nanoparticles and carbon according to the mass ratio of (50%~98%): (3%~20%): (5%~50%), put it into a ball mill and mix it evenly at 1600 rmin ^-1 -1800 rmin ^-1 ;

The second step is to transfer the mixed material into a sintering furnace and sinter at 1200° C. to 1800° C. for 12 to 24 hours to obtain a silicon negative electrode material;

The third step is to weigh a certain mass of silicon-based negative electrode material, mix it with a binder and a conductive agent in a mass ratio of 7: (1.5-2.0): (1.5 to 1.0), put it into a ball mill and stir it evenly, and then add a certain mass of solvent and stir it until it is uniform;

In the fourth step, the mixed slurry is applied to the copper foil by a knife coating or industrial coating process.

Step 5: Assemble the battery and test it.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. A quick-charging silicon-based negative electrode material for a lithium battery is characterized in that: the silicon-based anode material consists of micro-nano silicon-based particles, buffer nano particle conductive channels embedded in the silicon-based particles and carbon shell conductive channels coated on the surfaces of the silicon-based particles;

the silicon-based anode material comprises commercial silicon nano particles with the diameter of 20-30nm for lithium battery anode, silicon micro particles with the diameter of 1-100 mu m and micro nano silicon particles with the diameter of 50-100 mu m obtained by ball milling of waste silicon waste materials of semiconductor process, or comprises silicon oxide nano particles with the diameter of 20-1000 nm for lithium battery anode, silicon oxide micro particles with the diameter of 1-100 mu m and micro nano silicon oxide particles with the diameter of 50-100 mu m obtained by ball milling of waste silicon waste materials of semiconductor process;

the buffer nanoparticle comprises at least one of a metal nanoparticle and an alloy nanoparticle, the metal nanoparticle comprises at least one of gold, silver, copper, iron, aluminum and nickel, and the alloy nanoparticle comprises at least one of copper-silicon alloy, silver-silicon alloy, aluminum-silicon alloy, nickel-silicon alloy and iron-silicon alloy;

The preparation method of the quick-charging silicon-based anode material comprises the following steps:

Firstly, 50% -98% of the raw materials are mixed according to the mass ratio: 3% -20%: 5% -50% of mixed powder of micro-nano silicon-based particles, buffer nano particles and carbon is weighed, and is put into a ball mill to be ball-milled and mixed uniformly at a speed of 1600rmin ^-1 -1800 rmin ^-1;

and secondly, transferring the mixed materials into a sintering furnace, and annealing and sintering for 12 to 24 hours at the temperature of 1200 to 1800 ℃.

2. The rapid charging silicon-based anode material for lithium batteries according to claim 1, wherein: the carbon shell layer comprises at least one of graphite, graphene, hard carbon, soft carbon, acetylene black and ketjen black.

3. The rapid charging silicon-based anode material for lithium batteries according to claim 1, wherein: the rapid charging silicon-based anode material also comprises one or more than two of germanium, tin, phosphorus and oxides thereof.

4. The rapid charging silicon-based anode material for lithium batteries according to claim 1, wherein: the carbon shell conductive channel also comprises one or two of molybdenum sulfide two-dimensional material and titanium dioxide intercalation material.

5. The method for preparing the quick-charging silicon-based anode material for the lithium battery, which is characterized in that:

the method comprises the following steps:

Firstly, 50% -98% of the raw materials are mixed according to the mass ratio: 3% -20%: 5% -50% of mixed powder of micro-nano silicon-based particles, buffer nano particles and carbon is weighed, and is put into a ball mill to be ball-milled and mixed uniformly at a speed of 1600rmin ^-1 -1800 rmin ^-1;

Secondly, transferring the mixed materials into a sintering furnace, and annealing and sintering for 12 to 24 hours at the temperature of 1200 to 1800 ℃;

thirdly, coating a carbon shell layer material on the surface of the micro-nano silicon-based particles subjected to high-temperature sintering by adopting a carbon coating method of a pyrolysis method, a ball milling method or a chemical vapor deposition method to obtain a quick-charging silicon-based anode material;

Weighing the quick-charging silicon-based anode material, and mixing the quick-charging silicon-based anode material, an adhesive and a conductive agent according to the mass ratio of 7:1.5-2.0:1.5 to 1.0, fully mixing, putting into a ball mill, uniformly stirring, and then adding a solvent and uniformly stirring;

Fifthly, coating the mixed slurry on the copper foil by adopting a coating process;

and sixthly, assembling a battery test.