阅读说明：本技术 具有碳涂覆宏观孔的硅的阳极的电池 (Battery with carbon coated macroscopic pore silicon anode ) 是由 宋敏圭 车永焕 于 2018-09-06 设计创作，主要内容包括：本文公开了适合用作阳极材料的硅材料及其相关的生产方法。在一实施例中,硅材料包括基质中的晶体硅和分布在晶体硅的基质中的宏观孔。宏观孔可以具有大于100纳米的尺寸,并且宏观孔的晶体硅的表面涂覆有碳。(Silicon materials suitable for use as anode materials and associated methods of production are disclosed herein. In one embodiment, the silicon material includes crystalline silicon in a matrix and macroscopic pores distributed in the matrix of crystalline silicon. The macro pores may have a size greater than 100 nanometers, and the surface of the crystalline silicon of the macro pores is coated with carbon.)

1. A method of forming a silicon material for a battery anode, the method comprising:

reacting a metal or a mixture of metals with silicon (Si) in a solid state reaction to form a metal silicide;

CO-TREATING METAL SILICIDE FORMED WITH CARBON DIOXIDE₂-a thermal oxidation process to form a composite comprising one or more metal oxides, silicon and carbon; and

contacting a composite comprising one or more metal oxides, silicon and carbon with an acid to remove the one or more metal oxides from the composite to obtain silicon material particles having the following characteristics, respectively:

in CO₂-silicon formed in a thermal oxidation process; and

macroscopic pores in silicon, corresponding to metal oxides removed by acid, and having a surface coated with carbon derived from CO₂-a thermal oxidation process.

2. The method of claim 1, wherein reacting the metal or mixture of metals with silicon comprises reacting the metal or mixture of metals with silicon (Si) in a solid state reaction in an inert reaction environment.

3. The method of claim 1, wherein:

reacting the metal or mixture of metals with silicon comprises a solid state reaction between the metal or mixture of metals and silicon, the metal or mixture of metals exceeding a stoichiometric ratio, thereby forming a metal silicide using an excess of the metal or mixture of metals; and

carrying out CO₂-the thermal oxidation process comprises reacting with an excess of metal or mixture of metals to form the further metal oxide or oxides and the further carbon.

4. The method of claim 1, wherein the CO is performed₂-the thermal oxidation process comprises performing said CO at a reaction temperature of 600 ℃ to 800 ℃₂Thermal oxidation process, reverse reaction for 50 to 600 minutesTime should be taken.

5. The method of claim 1, wherein the CO is performed₂-the thermal oxidation process comprises: carbon dioxide gas is flowed through the formed metal silicide at a reaction temperature of 600 ℃ to 800 ℃ for a reaction time of 50 minutes to 600 minutes.

6. The method of claim 1, wherein the CO is performed₂-the thermal oxidation process comprises flowing carbon dioxide gas through the formed metal suicide at a reaction temperature of 600 ℃ to 800 ℃ for a reaction time of 50 minutes to 600 minutes to form a composite comprising one or more metal oxides, silicon and carbon, wherein the one or more metal oxides are distributed in the silicon of the formed composite, and wherein the surface of the silicon is substantially uniformly coated by the formed carbon.

7. The method of claim 1, wherein:

reacting the metal or mixture of metals with silicon comprises reacting one of magnesium (Mg), calcium (Ca), or barium (Ba) with silicon (Si); and

carrying out CO₂Thermal oxidation process involving the use of magnesium silicide (Mg)₂Si), calcium silicide (CaSi)₂) And barium silicide (BaSi)₂) One of (1) to carry out CO₂-a thermal oxidation process.

8. The method of claim 1, wherein:

reacting a metal or a mixture of metals with silicon comprises reacting at least two of the group comprising magnesium (Mg), calcium (Ca) and barium (Ba) with silicon (Si); and

carrying out CO₂The thermal oxidation process comprises subjecting two of the groups to CO₂-a thermal oxidation process, said group comprising magnesium silicide (Mg)₂Si), calcium silicide (CaSi)₂) And barium silicide (BaSi)₂)。

9. The method of claim 1, wherein:

reacting a metal or mixture of metals with silicon includes: reacting magnesium (Mg) with silicon (Si) to form magnesium silicide (Mg)₂Si), the reaction is as follows:

2Mg+Si→Mg₂Si；

carrying out CO₂-the thermal oxidation process comprises: magnesium silicide (Mg)₂Si) to CO₂-a thermal oxidation process to form a composite comprising magnesium oxide (MgO), silicon and carbon, the reaction being as follows:

Mg₂Si+CO₂→ Si + C +2 MgO; and

contacting the formed complex with an acid comprises: the formed composite is contacted with an acid to remove magnesium oxide (MgO) from the formed composite.

10. The method of claim 1, wherein:

reacting a metal or mixture of metals with silicon includes: reacting calcium (Ca) with silicon (Si) to form calcium silicide (CaSi)₂) The reaction is as follows:

Ca+2Si→CaSi₂；

carrying out CO₂-the thermal oxidation process comprises: calcium silicide (CaSi)₂) Carrying out CO₂-a thermal oxidation process to form a composite comprising calcium oxide (CaO), silicon and carbon, the reaction being as follows:

2CaSi₂+CO₂→ 4Si + C +2 CaO; and

contacting the formed complex with an acid comprises: the formed complex is contacted with an acid to remove calcium oxide (CaO) in the formed complex, resulting in particles having a layered two-dimensional silicon morphology.

11. A battery, comprising:

a first electrode;

an electrolyte in electrical communication with the first electrode, the electrolyte comprising a plurality of metal ions; and

a second electrode spaced from the first electrode and in electrical communication with the first electrode via an electrolyte, the second electrode comprising particles of silicon material having:

a crystalline silicon substrate; and

the silicon substrate comprises macro pores, wherein the macro pores are distributed in the silicon substrate, the size of each macro pore is larger than 100nm, and the surface of the crystalline silicon of each macro pore is coated with carbon.

12. The battery of claim 11, wherein the crystalline silicon surface of the macroscopic pores is substantially uniformly coated with carbon.

13. The battery of claim 11, wherein:

the macro pores are randomly distributed in the crystal silicon substrate; and

the crystalline silicon surface of the macroscopic pores is substantially uniformly coated with carbon.

14. The battery of claim 11, wherein:

the macro pores are randomly distributed in the crystal silicon substrate; and

the crystalline silicon surface of the macroscopic pores is substantially uniformly coated with carbon, and the carbon is in an amorphous state, a semi-crystalline state or a crystalline state, or a mixed state thereof.

15. The battery of claim 11, wherein:

the first electrode is made of lithium cobaltate (LiCoO)₂) Lithium iron phosphate (LiFePO)₄) Lithium manganese oxide (LiMn)₂O₄) Lithium nickel oxide (LiNiO)₂) Lithium iron fluorophosphate (Li)₂FePO₄F) LiNiCoAlO containing 80% nickel, 15% cobalt and 5% aluminum₂100% cobalt in LiCoO₂LiMn containing 100% manganese₂O₄LiNiMnCoO containing 33.3% nickel, 33.3% manganese and 33.3% cobalt₂Containing 100% iron or lithium cobalt nickel manganese oxide (LiCo)_1/3Ni_1/3Mn_1/3O₂) LiFePO of₄Any one of the above constitutions; and

the electrolyte comprises LiPF₆、LiAsF₆、LiClO₄、LiBF₄Or lithium trifluoromethanesulfonate.

16. A silicon material, comprising:

a crystalline silicon substrate; and

macroscopic pores distributed in a crystalline silicon matrix, the macroscopic pores having a size greater than 100 nanometers, wherein a surface of the crystalline silicon in the macroscopic pores is coated with carbon.

17. The silicon material of claim 16, wherein surfaces of the crystalline silicon in the macro-holes are substantially uniformly coated with carbon.

18. The silicon material of claim 16, wherein:

the macro pores are randomly distributed in the crystal silicon substrate; and

the crystalline silicon surface of the macroscopic pores is substantially uniformly coated with carbon.

19. The silicon material of claim 16, wherein:

the macro pores are randomly distributed in the crystal silicon substrate; and

the crystalline silicon surface of the macroscopic pores is substantially uniformly coated with carbon, and the carbon is in an amorphous state, a semi-crystalline state or a mixed state thereof.

20. The silicon material of claim 16, wherein:

the macro pores are randomly distributed in the crystalline silicon substrate; and

the crystalline silicon surface of the macroscopic hole is substantially uniformly coated with carbon, and the carbon is in an amorphous state, a semi-crystalline state or a mixed state thereof; and

the crystalline silicon matrix has a layered two-dimensional silicon morphology.

Background

A lithium ion battery is a battery in which lithium ions move from a negative electrode to a positive electrode when discharged and from a negative electrode to a positive electrode when charged. Lithium ion batteries may include an electrolyte in contact with an intercalated lithium compound as a cathode and a carbon-based anode to form a battery cell. Lithium ion batteries have a high energy to weight ratio, low or no memory effect, and long charge retention when not in use. In addition to applications in consumer electronics, lithium ion batteries are also widely used in defense, automotive and aerospace applications. Such new applications place a continuing need to improve the energy density of lithium ion batteries.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Some lithium ion batteries use carbon-based materials such as graphite as the anode. However, such carbon-based materials may limit the charge capacity of lithium ion batteries. For example, lithiation of carbon-based anodes can yield a charge capacity of about 372mA · h/g, while lithiation of silicon (Si) -based anodes can yield a charge capacity of about 4,200mA · h/g. However, lithiation of silicon-based anodes may involve a volume change of about 300%. Thus, after a few charge-discharge cycles, the bulk silicon-based anode will be crushed. Silicon-based anodes can also form unstable solid electrolyte interphase layers with the electrolyte in lithium batteries. Thus, the poor mechanical stability and chemical passivation properties of silicon can render the silicon electrode unsuitable for practical battery systems.

Several embodiments of the disclosed technology relate to battery systems having an anode comprising a carbon-coated macroscopic porous silicon material. The carbon coated macro-porous silicon material may include grains of crystalline silicon having macro-pores each greater than about 100nm in size. Both the inner and outer surfaces of the crystalline silicon may be, at least partially, coated with carbon in an amorphous, semi-crystalline or crystalline state or a mixture thereof. Experiments have shown that batteries with anodes exemplarily constructed of carbon-coated macroscopic porous silicon materials exhibit high electrical capacity and cyclability. Accordingly, the silicon materials disclosed herein are suitable for battery applications.

According to embodiments of the disclosed technology, CO may be used₂-thermal oxidation process (CO-OP) to prepare carbon coated macroscopic porous silicon material. In certain embodiments, CO₂The thermal oxidation process may comprise an initial solid state reaction between silicon and a metal or metal mixture to form a metal silicide. Examples of suitable metals may include magnesium (Mg), calcium (Ca), and barium (Ba). The solid state reaction, exemplified by magnesium, can be represented as follows:

2Mg+Si→Mg₂Si

in other examples, mixtures of at least two of the foregoing metals (e.g., magnesium and calcium) can also be used in the solid state reaction. Thus, the metal silicide formed may be a binary, ternary, quaternary, or other metal system of suitable order.

After the solid state reaction is completed, CO₂The thermal oxidation process may comprise a thermal reaction, wherein carbon dioxide (CO) is used₂) The prepared metal silicide is oxidized to form crystalline silicon particles coated with carbon and having a plurality (e.g., several hundreds) of nano-sized metal oxide structures in a single reaction. One example technique for performing thermal reactions may include: at a suitable temperature (e.g. 700 ℃) in CO₂The metal silicide is annealed or otherwise processed in ambient. Under such conditions, the metal silicide (e.g. Mg)₂Si) may be reacted with CO₂Reacting to form a metal oxide,Silicon and carbon, for example, as follows:

Mg₂Si+CO₂→Si+C+2MgO

then, CO₂The thermal oxidation process may comprise an acid leaching operation to remove the metal oxide from the composite resulting from the thermal reaction to form a silicon substrate. Thus, the removed metal oxide may leave macroscopic pores (e.g., several hundred nanometers in size) randomly distributed or otherwise suitably distributed in the silicon matrix. In this way, the metal oxide (e.g., MgO) can act as a sacrificial template for creating macroscopic pore structures in crystalline silicon. The resulting particles comprise carbon-coated macroscopic pore silicon and can be suitable for use as battery anodes. We believe that the carbon coating can help form a protective Solid Electrolyte Interphase (SEI), thus leading to good cycling performance. Thus, CO₂Several embodiments of the thermal oxidation process can simultaneously produce the surface carbon coating and the macroscopic pore structure of the silicon particles. In this way, separate carbon coating operations, such as time consuming chemical vapor deposition and carbonization of toxic organic precursors, can be avoided.

Without being bound by theory, it is believed that by selecting or adjusting the appropriate combination and/or relative composition of the metal or metal mixture to form the metal silicide, different macro and/or microstructures can be formed in the carbon-coated macroscopic porous silicon particles. For example, carbon formed using calcium coats macroscopic porous silicon particles and the morphology of the carbon may be quite different from that formed using magnesium. In particular, experiments have shown that the use of calcium can produce a unique layered two-dimensional silicon morphology in the resulting silicon particles. Thus, combining magnesium with calcium (or other suitable metals) in appropriate relative compositions (e.g., molar ratios, percentages, etc.) can produce unique morphologies in the formed silicon particles.

In addition, in the case of solid-state reactions, the metals or metal mixtures can also exceed silicon, depending on the stoichiometric ratio. It is also believed that by selecting or adjusting the excess level or percentage of metal or mixture of metals, different macro and/or micro structures may be formed in the carbon coated macro-porous silicon material. For example, in the above-described examples of solid state reactions, magnesium may be present in an excess of 10%, 20%, 30%, 40%, or more, relative to siliconMuch more. In the thermal reaction, excess magnesium will react with CO₂The reaction, as shown below:

2Mg+CO₂→C+2MgO

the magnesium oxide (MgO) formed can then be acid leached away to form macroscopic pores in the final granules. Thus, by adjusting the excess level of magnesium, different amounts and/or formation of macroscopic pores can be obtained in the resulting silicon particles. Moreover, carbon formation on the silicon surface can enhance the overall conductivity of the resulting silicon particles when used in a battery anode, which can be beneficial for cycling performance. In further embodiments, the foregoing selections or adjustments of the components of the metal or metal mixture, as well as the relative levels or percentages of excess metal or metal mixture, may be applied in combination to produce a desired morphology in the resulting carbon-coated macroscopic porous silicon material.