Process for preparing multi-level structured silicon-lithium battery negative electrode using diatomite

Abstract

The present invention relates to the technical field of new energy batteries, and specifically, to a process for preparing a multi-level structure of a silicon-lithium battery negative electrode from diatomite. The process uses a capacity expansion method to increase the pore volume and specific surface area of ​​diatomite, uses a deposition method to increase the content of active silicon and the number of pores, obtains an active silicon dioxide multi-level framework material, and then obtains a silicon silicon dioxide multi-level framework material through an aluminum-magnesium reduction method, and silicon and silicon dioxide are fused with each other to form a final Si-SiOx multi-level framework material through high-temperature treatment under vacuum or inert gas protection. The solid battery made of the treated Si-SiOx multi-level framework material as the negative electrode has almost no obvious capacity decay after 1000 cycles, and the cycle performance has been greatly improved, which improves the service life of the solid-state battery. At the same time, the low-temperature aluminum-magnesium reduction method does not require high temperature to achieve, which reduces energy consumption and reduces the cost of industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to a process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomaceous earth. Background Art

[0002] With the popularity of new energy vehicles, the application of lithium batteries is getting higher and higher, but the main disadvantage of existing liquid batteries is that the power storage density is too low and the battery reserve decays too much. Current battery technology uses liquid electrolytes to store electrical energy, and its energy density has reached the ceiling, and it is difficult to increase the density. And because the electrolyte is a chemical liquid, it is easy to cause electrolyte leakage, which causes fire and explosion accidents in an endless stream. It can be seen that liquid batteries themselves have accident hazards. Using new non-flammable solid electrolytes to replace traditional flammable organic electrolytes can significantly reduce the risk of fire and explosion of lithium metal batteries. However, the commercialization of solid-state batteries has always been limited by limited cycle life. After a few charging and discharging, the battery reserve decays rapidly, and frequent battery replacement causes excessively high usage costs. Summary of the invention

[0003] The purpose of the present invention is to provide a process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomite to solve the problems raised in the above background technology.

[0004] To achieve the above object, on the one hand, the present invention provides a process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomite, comprising the following steps:

[0005] S1, take 90-110g of diatomaceous earth and add it to 0.8-1.2L of 1-53% sodium hydroxide solution, heat and stir, wash with water until the pH value is neutral, then soak and wash the diatomaceous earth with 1-50% sulfuric acid and hydrochloric acid, remove the impurities on the surface, wash with water until the pH value is neutral, and then dry it, detect its pores and specific surface area, it can be seen that its pore volume increases, the number of pores increases, and the surface is pure silicon dioxide crystal without impurities;

[0006] S2, adding 1-100g of silicate solution with a content of 1-50% under vacuum, and drying or baking at room temperature after the diatomaceous earth is evenly adsorbed, so that amorphous silicon dioxide forms small compartments in the diatomaceous earth, increasing the specific surface area and the number of pores of the diatomaceous earth silicon dioxide multi-level framework;

[0007] S3, adding a mixture of aluminum, magnesium and aluminum chloride in proportion under vacuum, and then heating the mixture for reaction and then cooling it down. Aluminum chloride can directly participate in the metal thermal reduction process, catalyzing aluminum powder and magnesium powder to directly reduce silicon dioxide at high temperature to form silicon crystals, thereby forming a silicon-silicon dioxide multi-level framework material;

[0008] S4, adding the silicon-silicon dioxide multi-level framework material to 0.8-1.2L of a sodium hydroxide solution having a content of 1-53%, heating and stirring, washing away part of the silicon crystals on the surface to leak out the silicon dioxide, and finally forming a silicon-silicon dioxide multi-level framework material in which silicon and silicon dioxide are exposed at intervals;

[0009] S5, placing the silicon-silicon dioxide multi-level framework material into a high-temperature vacuum furnace, and heating it under the protection of vacuum or inert gas to obtain Si-SiOx crystals;

[0010] S6. The Si-SiOx multi-level framework material is mixed with molten lithium metal and the mixture is stirred to react to obtain a Li-Si-SiOx composite powder. The Li-Si-SiOx composite powder is surface-modified with a poly-solid electrolyte and then pressed to obtain a composite silicon-lithium metal negative electrode with a multi-level structure.

[0011] As a further improvement of the technical solution, in S1, the heating temperature is 90-110° C., and the stirring time is 1-10 h.

[0012] As a further improvement of the technical solution, in S2, the silicate solution is selected from one or more of sodium silicate, potassium silicate, silica sol and lithium silicate solution.

[0013] As a further improvement of the technical solution, in S3, the heating temperature is 190-210°C, and the reaction time is 10-600h.

[0014] As a further improvement of the technical solution, in S4, the ratio of silicon to silicon dioxide is adjusted according to the concentration and time of silicon and silicon dioxide soaking in sodium hydroxide, and the ratio is 0.1-100:100-0.1.

[0015] As a further improvement of the present technical solution, in S4, the silicon-silicon dioxide multi-level framework material is pickled with hydrochloric acid and sulfuric acid to remove the remaining impurities after the reaction and then dried to obtain a multi-level framework material with a surface of pure silicon-silicon dioxide crystals.

[0016] As a further improvement of the technical solution, in S4, the heating temperature is 90-110° C., and the stirring time is 1-10 h.

[0017] As a further improvement of the technical solution, in S5, in the Si-SiOx crystal, the range of x is 0-2.

[0018] As a further improvement of the technical solution, in S5, the heating temperature is 100-1500° C., the processing time is 1-24 hours, and the ratio of Si-SiOx is controlled according to different reaction times and temperatures to control the reversible capacity of the battery.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. In the process of preparing the negative electrode of the silicon-lithium battery with a multi-level structure from the diatomite, the volume expansion of up to 300% during the lithium embedding process of silicon will cause cracks to form on the surface of the silicon during the lithium embedding process, leaking out new electrodes to react with lithium, thereby reducing the capacity of the battery; the pore volume and specific surface area of ​​the diatomite are increased by a capacity expansion method, and the content of active silicon and the number of pores are increased by a deposition method to obtain an active silicon dioxide multi-level framework material, and then the silicon-silicon dioxide multi-level framework material is obtained by an aluminum-magnesium reduction method, and the silicon and silicon dioxide are fused with each other to form the final Si-SiOx multi-level framework material by high-temperature treatment under vacuum or inert gas protection; the solid battery made of the treated Si-SiOx multi-level framework material as the negative electrode has almost no obvious capacity decay after 1000 cycles, and the cycle performance has been greatly improved, thereby increasing the service life of the solid-state battery, and at the same time, the low-temperature aluminum-magnesium reduction method can be implemented without high temperature, thereby reducing energy consumption and the cost of industrial production.

[0021] 2. In the process of preparing multi-level structured silicon-lithium battery negative electrode with diatomite, the Si-SiOx multi-level framework material has a specific surface area of ​​127m / g and a pore volume of 0.576cm 3 / g has an internal surface area of ​​13.12m / g, which greatly improves the contact area with lithium ions. It can also be made under the condition of Si-SiOx cross-doping. Silicon can be embedded with relatively high lithium materials, making the solid-state battery have a relatively large capacity. The space of diatom micropores stores metallic lithium and undertakes the volume change of the electrode during the charging and discharging process, making the battery less prone to bulging. The existence of SiOx separates the bonding surface of silicon embedded in lithium, making the embedded lithium distribution more uniform and absorbing the expansion generated by silicon embedding. At the same time, the original appearance of the diatomite pores is maintained. Even if silicon falls off, it is adsorbed in the pores and its capacity will not be reduced. Therefore, the prepared battery can still reach a capacity of 1070mAh / g after 1000 cycles, and the capacity retention rate is 92%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an overall flow chart of Example 1. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1 A process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomite, comprising:

[0025] Step 1, take 90-110g of diatomaceous earth and add it to 0.8-1.2L of 1-53% sodium hydroxide solution, heat it at 90-110°C and stir it for 1-10h, then wash it with clean water until the pH value is neutral, then soak and wash the diatomaceous earth with 1-50% sulfuric acid and hydrochloric acid, remove the impurities on its surface, wash it with clean water until the pH value is neutral, and then dry it, detect its pores and specific surface area, it can be seen that its pore volume increases, the number of pores increases, and the surface is pure silicon dioxide crystal without impurities;

[0026] Step 2: Add 1-50% silicate solution 1-100g under vacuum, wherein the silicate solution is selected from one or more of sodium silicate, potassium silicate, silica sol and lithium silicate solution, and the diatomaceous earth is evenly adsorbed and then dried at room temperature or baked. Amorphous silicon dioxide forms small compartments in the diatomaceous earth, thereby increasing the specific surface area and the number of pores of the diatomaceous earth silicon dioxide multi-level framework;

[0027] Step 3: Add a mixture of aluminum, magnesium and aluminum chloride in proportion under vacuum, and then heat to 190-210°C for 10-600 hours and then cool down. Aluminum chloride can directly participate in the metal thermal reduction process, catalyzing aluminum powder and magnesium powder to directly reduce silicon dioxide at high temperature to form silicon crystals, thereby forming a silicon-silicon dioxide multi-level framework material.

[0028] Step 4: Add the silicon-silicon dioxide multi-level framework material to 0.8-1.2L of a sodium hydroxide solution with a content of 1-53%, heat to 90-110°C and stir for 1-100min, wash away part of the silicon crystals on the surface to leak out the silicon dioxide, and finally form a silicon-silicon dioxide multi-level framework material in which silicon and silicon dioxide are exposed at intervals, and adjust the silicon-silicon dioxide ratio according to the concentration and time of immersion of silicon and silicon dioxide in sodium hydroxide. The ratio is 0.1-100:100-0.1, and the silicon-silicon dioxide multi-level framework material is pickled with hydrochloric acid and sulfuric acid to remove the remaining impurities after the reaction, and then dried to obtain a multi-level framework material with a surface of pure silicon-silicon dioxide crystals;

[0029] Step 5: Place the silicon-silicon dioxide multi-level framework material into a high-temperature vacuum furnace, heat it to 100-1500°C under vacuum or inert gas protection, and treat it for 1-24 hours to obtain Si-SiOx crystals, where 2≥x≥0. The ratio of Si-SiOx can be controlled according to different reaction times and temperatures to control the reversible capacity of the battery.

[0030] Step 6: Mix the Si-SiOx multi-level framework material with molten lithium metal and fully stir the reaction to obtain Li-Si-SiOx composite powder. Use a poly-solid electrolyte to modify the surface of the Li-Si-SiOx composite powder and then press it to obtain a composite silicon-lithium metal negative electrode with a multi-level structure.

[0031] In the process of preparing a multi-level structured silicon-lithium battery negative electrode from diatomite of the present invention, the composition state and specific surface area data of each step of the multi-level framework material are specifically shown in Table 1:

[0032] Table 1

[0033] Serial number Element Specific surface area Pore ​​volume Internal surface area diatomite Silicon dioxide 20m / g <![CDATA[0.06cm 3 / g]]> 3.2m / g Step 1 Silicon dioxide 127m / g <![CDATA[0.576cm 3 / g]]> 13.12m / g Step 2 Silicon dioxide 121m / g <![CDATA[0.528cm 3 / g]]> 15.68m / g Step 3 Silicon-Silicon Dioxide 136m / g <![CDATA[0.497cm 3 / g]]> 14.82m / g Step 4 Silicon-Silicon Dioxide 129m / g <![CDATA[0.518cm 3 / g]]> 13.97m / g Step 5 Si-SiOx 126m / g <![CDATA[0.539cm 3 / g]]> 13.63m / g

[0034] As shown in Table 1, it can be seen that after pore expansion, the specific surface area of ​​diatomite increases by more than 6 times, and the contact area with the electrolyte is larger, making the lithium insertion speed faster and more uniform. At the same time, the pore volume also increases by more than 10 times, making the space for lithium insertion and expansion more abundant.

[0035] At the same time, the material has also changed from pure silicon dioxide crystals to a situation where Si-SiOx is doped with each other at intervals, so that SiOx can fully absorb the expansion caused by the embedding of silicon into lithium ions without causing the silicon dioxide to react with lithium ions to form irreversible lithium sulfate, thereby improving the first effect and the attenuation rate of the storage capacity.

[0036] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomite, characterized in that: The following steps are involved: S1, take 90-110g of diatomaceous earth and add it to 0.8-1.2L of 1-53% sodium hydroxide solution, heat and stir, wash with water until the pH value is neutral, then soak and wash the diatomaceous earth with 1-50% sulfuric acid or hydrochloric acid, remove the impurities on the surface, wash with water until the pH value is neutral, and then dry; S2, adding 1-100g of silicate solution with a content of 1-50% under vacuum, and drying after diatomaceous earth adsorbs evenly; S3, adding a mixture of aluminum, magnesium and aluminum chloride in proportion under vacuum, heating for reaction and then cooling to form a silicon-silicon dioxide multi-level framework material; S4, adding the silicon-silicon dioxide multi-level framework material to 0.8-1.2L of a sodium hydroxide solution having a content of 1-53%, heating and stirring, washing away part of the silicon crystals on the surface to leak out the silicon dioxide, and finally forming a silicon-silicon dioxide multi-level framework material in which silicon and silicon dioxide are exposed at intervals; S5, placing the silicon-silicon dioxide multi-level framework material into a high-temperature vacuum furnace, and heating it under the protection of vacuum or inert gas to obtain Si-SiOx crystals; S6, mixing the Si-SiOx multi-level framework material with molten lithium metal and fully stirring the reaction to obtain a Li-Si-SiOx composite powder, and using a poly-solid electrolyte to modify the surface of the Li-Si-SiOx composite powder and then pressing it to obtain a composite silicon-lithium metal negative electrode with a multi-level structure; In S1, the heating temperature is 90-110° C. and the stirring time is 1-10 h; In S2, the silicate solution is selected from one or more of sodium silicate, potassium silicate and lithium silicate solutions; In S3, the heating temperature is 190-210° C., and the reaction time is 10-600 h; In S4, the silicon-silicon dioxide multi-level framework material is pickled with hydrochloric acid and sulfuric acid to remove the impurities remaining after the reaction, and then dried to obtain a multi-level framework material with a surface of pure silicon-silicon dioxide crystals.

2. The process for preparing a multi-level structured silicon-lithium battery negative electrode from diatomite according to claim 1, characterized in that: In S4, the ratio of silicon to silicon dioxide is adjusted according to the concentration and time of silicon and silicon dioxide soaking in sodium hydroxide, and the ratio is 0.1-100:100-0.

1.

3. The process for preparing a multi-level structured silicon-lithium battery negative electrode from diatomite according to claim 1, characterized in that: In the step S4, the heating temperature is 90-110° C. and the stirring time is 1-10 h.

4. The process for preparing a multi-level structured silicon-lithium battery negative electrode from diatomite according to claim 1, characterized in that: In the S5, in the Si-SiOx crystal, the range of x is 0-2.

5. The process for preparing a multi-level structured silicon-lithium battery negative electrode using diatomite and the preparation method thereof according to claim 1, characterized in that: In the S5, the heating temperature is 100-1500° C. and the treatment time is 1-24 hours.

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