CN108649206B - Lithium/nano silicon carbide cell and preparation process thereof - Google Patents
Lithium/nano silicon carbide cell and preparation process thereof Download PDFInfo
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/381—Alkaline or alkaline earth metals elements
- H01M4/382—Lithium
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Abstract
The invention discloses a lithium/nanometer silicon carbide battery and a preparation process thereof, wherein the battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, the positive plate is made of nanometer silicon carbide material, the negative plate is made of a composite material of lithium-aluminum alloy and nanometer silicon carbide, the diaphragm is Celguard, the electrolyte is hexafluorophosphorous lithium or solid electrolyte, and the mass ratio of lithium in the negative plate to the nanometer silicon carbide in the positive plate is not more than 0.7: 1. According to the invention, the proportion relation between the lithium content in the lithium aluminum alloy and the nano silicon carbide negative plate and the specific capacity of the nano silicon carbide in the positive electrode is accurately controlled, so that the electrode with high strength and high safety performance is formed, the lithium consumption can be greatly reduced, and the explosion caused by short circuit contact of a circuit caused by lithium can be reduced to the minimum.
Description
Technical Field
The invention relates to the technical field of lithium secondary batteries, in particular to a lithium/nano silicon carbide battery and a preparation process thereof.
Background
The lithium metal sheet can be used for a lithium secondary battery, but the lithium sheet has three disadvantages when being used for a counter electrode of the battery, namely, lithium is easy to be excessive, lithium metal is wasted, the strength of the lithium metal sheet is low, the lithium/nano silicon carbide battery can be broken down after long-term circulation, and lithium can be provided in the battery with high concentration, so that lithium is excessive, lithium ions which are extracted from the lithium sheet and enter a solution are inserted into a crystal of a positive electrode material in the long-term electrochemical circulation process of the battery, lithium atoms which are extracted from the positive electrode and move to the negative electrode in the charging process are easy to grow lithium dendrites on the lithium atoms, and the battery has potential short circuit risk. There is a significant risk especially in the event of a short circuit in the battery. The lithium metal particles are dispersed and prepared into alloy together with other metal particles, and active nano silicon carbide is added to form a composite material electrode, so that the electrode strength is increased, the lithium alloy and nano silicon carbide composite material electrode cannot be cracked, lithium atoms are transferred into the nano silicon carbide of the composite electrode in the charging and discharging process, lithium dendrites are not easy to generate, the short circuit risk is eliminated, and the explosion risk is not easy to occur. In addition, the total amount of lithium metal resources is low and expensive, and in order to reduce the cost of the battery, it is necessary to prepare an electrode having an accurate amount of lithium, high strength and good safety, which is of practical value for a lithium secondary battery.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides a lithium/nano silicon carbide battery and a preparation method thereof, which can accurately control the proportion relation between the lithium content in a lithium aluminum alloy and a nano silicon carbide negative plate and the specific capacity of nano silicon carbide in a positive electrode, thereby forming an electrode with high strength and high safety performance.
In order to achieve the purpose, the lithium/nano silicon carbide battery provided by the invention comprises a positive plate, a negative plate, a diaphragm and electrolyte, and is characterized in that the positive plate is made of nano silicon carbide materials, the negative plate is made of a composite material of lithium aluminum alloy and nano silicon carbide, the diaphragm is Celguard, the electrolyte is lithium hexafluorophosphate or solid electrolyte, and the mass ratio of lithium in the negative plate to nano silicon carbide in the positive plate is not more than 0.7: 1-0.9: 1. The proportion range of lithium in the range of 0.7-0.9 is to consider first cycle discharge, a part of lithium forms a Solid Electrolyte Interface (SEI) film on the surface of the nano silicon carbide of the anode, a certain amount of lithium ions are consumed, and the part of lithium ions do not return to the cathode under the normal charging condition. Considering that the same electrochemical process occurs in the first charging process, the negative electrode nano silicon carbide is correspondingly reduced.
Furthermore, the content of lithium element in the negative plate is 0.7 g-0.9 g, and the content of nano silicon carbide in the positive plate is 1 g.
Furthermore, the content of the nano silicon carbide in the negative plate is 0.8-1 g.
Furthermore, the content of lithium element in the negative plate is 0.7-0.9 g, the content of aluminum element is 0.3-0.5 g, and the content of nano silicon carbide is 0.9-1 g.
The invention also provides a preparation process of the lithium/nano silicon carbide battery, which is characterized by comprising the following steps of:
1) preparing a lithium aluminum alloy plated nano silicon carbide pressing sheet, wherein the lithium element content in the lithium aluminum alloy plated nano silicon carbide pressing sheet is 0.7-0.9 g;
2) preparing a nano silicon carbide pressed sheet, wherein the content of the nano silicon carbide electrode pressed sheet is 1 g;
3) assembling the battery: placing the nano silicon carbide pressing sheet as a positive plate and the lithium aluminum alloy plated nano silicon carbide pressing sheet as a negative plate in sequence, injecting an electrolyte of lithium hexafluorophosphate into the nano silicon carbide positive plate, the diaphragm Celguard and the lithium aluminum alloy plated nano silicon carbide negative plate, and packaging to form a lithium hexafluorophosphate electrolyte for 72 hours;
4) and (3) testing the cycle characteristics of the battery: and putting the battery after formation into a charging and discharging voltage window, and completing the preparation when the battery is circularly charged and discharged for 10 times under the conditions of voltage 4.2-0V and current density 1C, wherein the charging and discharging specific capacity reaches 2450 mAh/g.
Preferably, the specific steps of step 1) include:
1a1) placing active substance nano silicon carbide powder in a flat-bottom graphite boat, paving the flat-bottom graphite boat into a uniform thin layer, and placing the flat-bottom graphite boat on an anode base of a vacuum chamber of a magnetron sputtering machine;
1a2) respectively placing a high-purity lithium block and a high-purity aluminum block on two target holders of a magnetron sputtering machine;
1a3) closing the vacuum chamber, sequentially opening a mechanical pump and a molecular pump power supply, vacuumizing until the vacuum degree is 5x10-4Pa, and heating to 500 ℃; injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering lithium block, starting a sputtering aluminum block after the completion, and forming a metal film on the surface of active substance nano silicon carbide powder in the flat-bottom graphite boat;
1a4) turning off a sputtering power supply, raising the temperature of the vacuum chamber to 650 ℃, and naturally cooling to room temperature after 5-30 minutes of duration;
1a5) pressing the nano silicon carbide composite material with the surface formed with the metal film into a wafer, wherein the lithium element content in the single-piece lithium aluminum alloy plated nano silicon carbide pressing sheet is 0.7g, and the nano silicon carbide content is 0.1 g.
Preferably, the specific steps of step 2) include:
21) uniformly mixing active substance nano silicon carbide powder, a conductive agent and an adhesive in a mass ratio of 85:8:7, adding nmp, and uniformly mixing to obtain slurry;
22) coating the slurry on the foamed nickel, putting the foamed nickel coated with the slurry into a vacuum drying box, drying for 24 hours at 110-180 ℃ after vacuumizing, and naturally cooling to room temperature;
23) pressing the nano silicon carbide substance on the foamed nickel into a wafer, so that the content of the single nano silicon carbide electrode wafer is 1 g.
Preferably, the specific steps of step 1) include:
1b1) placing active substance nano silicon carbide powder in a flat-bottom graphite boat, paving the flat-bottom graphite boat into a uniform thin layer, and placing the flat-bottom graphite boat on an anode base of a vacuum chamber of a magnetron sputtering machine;
1b2) respectively placing a high-purity lithium block and a high-purity aluminum block on two target holders of a magnetron sputtering machine;
1b3) closing the vacuum chamber, sequentially turning on the power supply of the mechanical pump and the molecular pump, and vacuumizing until the vacuum degree is 5x10-4Pa, and heating to 500 ℃; injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering lithium block, starting a sputtering aluminum block after the completion, and forming a metal film on the surface of active substance nano silicon carbide powder in the flat-bottom graphite boat;
1b4) uniformly mixing the lithium-aluminum alloy plated nano silicon carbide powder and the adhesive in a mass ratio of 90:10, adding nmp, and uniformly mixing to obtain slurry;
1b5) coating the slurry on the foamed nickel, putting the foamed nickel coated with the slurry into a vacuum drying box, drying for 24 hours at 80-150 ℃ after vacuumizing, and naturally cooling to room temperature;
1b6) pressing the lithium aluminum alloy plated nano silicon carbide mixed substance on the foamed nickel into a wafer, wherein the lithium element content, the aluminum element content and the nano silicon carbide content in the single lithium aluminum alloy plated nano silicon carbide pressed wafer are respectively 0.7-0.9 g, 0.3-0.5 g and 0.8-1 g.
Preferably, the specific method for sputtering the lithium block and the aluminum block in the step 1a3) is as follows: starting a lithium block sputtering program for 30 seconds to 5 minutes until the thickness of a metal film formed on the surface of the active substance nano silicon carbide powder reaches 70nm, then starting an aluminum block sputtering program, controlling the strength of the aluminum block sputtering to be gradually increased from 10% to 100%, and continuing for 10 to 50 minutes until the thickness of the metal film formed on the surface of the active substance nano silicon carbide powder reaches 500nm to 5 um.
Preferably, the specific method for sputtering the lithium block and the aluminum block in the step 1b3) is as follows: starting a lithium block sputtering program for 30 seconds to 5 minutes until the thickness of a metal film formed on the surface of the active substance nano silicon carbide powder reaches 70nm, then starting an aluminum block sputtering program, controlling the strength of the aluminum block sputtering to be gradually increased from 10% to 100%, and continuing for 10 to 50 minutes until the thickness of the metal film formed on the surface of the active substance nano silicon carbide powder reaches 500nm to 5 um.
Compared with the prior art, the lithium/nano silicon carbide battery and the preparation process thereof solve the problem of micro-nano silicon carbide
The fusion problem of the nano silicon carbide and the lithium-aluminum alloy is realized, a part of crystals are crystallized on the surface of the lithium-aluminum alloy after the reduction of lithium ions, and in addition, the lithium-aluminum alloy is subjected to the reaction
And a part of the silicon carbide is embedded into the negative electrode nano silicon carbide. And lithium in the lithium aluminum alloy is mainly transferred to the lithium aluminum alloy during long-term circulation
And in the negative electrode nano silicon carbide, the minimum lithium content of the lithium-aluminum alloy is reserved.
Because the strength of the pure lithium sheet is low, the composite material electrode formed by the pure lithium sheet and the nano silicon carbide is difficult to stably exist in the battery, and the pure lithium sheet and the nano silicon carbide are required to be prepared into the lithium-aluminum alloy firstly and then form the electrode with the nano silicon carbide. In the research process of the invention, the preparation of the lithium-aluminum alloy is realized by considering the lithium ion intercalation amount of the counter electrode, so that the component proportion of the lithium-aluminum alloy is designed, the lithium-aluminum alloy and the nano silicon carbide form a composite material, and the lithium-aluminum alloy is formed to be transited from lithium to aluminum, namely, the lithium concentration in the lithium-aluminum is absolute dominant, and then the lithium-aluminum alloy is transited to the low-lithium-aluminum alloy step by step, and then the lithium-aluminum alloy nano silicon carbide composite material is formed by mixing and sintering the lithium-aluminum alloy and the nano silicon carbide. Meanwhile, aluminum as an ion can form electrochemical behavior similar to that of lithium, and can be used as an ion to migrate to the nano silicon carbide of the anode in the discharging process of the battery, and aluminum migrates back to the lithium aluminum alloy and the nano silicon carbide in the charging process to form the nano silicon carbide containing lithium atoms and aluminum atoms. However, in the lithium/nano silicon carbide battery, lithium ion migration is mainly generated between the positive electrode and the negative electrode, and aluminum ions are used for supplementing the lithium/nano silicon carbide battery, so that the quantity of the aluminum ions is not large.
The invention provides a limit on the content of nano silicon carbide in positive and negative plates, which is 0.8-1 g. Meanwhile, the content of lithium and aluminum in the negative electrode is limited. In the charge and discharge process of the negative electrode lithium aluminum alloy and nano silicon carbide composite electrode, during the charge process, lithium ions in the positive electrode are reduced and then are removed from the electrolyte, and the negative electrode is moved, because metal crystallization energy is not consumed, one part of lithium can be directly inserted into the nano silicon carbide of the negative electrode, the other part of lithium is crystallized into the metal lithium aluminum alloy, and the electrochemical cycle repeatedly occurs in this way, so that the lithium of a negative electrode lithium aluminum sheet is gradually reduced, the lithium in the nano silicon carbide in the negative electrode is gradually increased, and finally the lithium reaching the negative electrode is mainly moved into the nano silicon carbide, and the lithium aluminum metal keeps the minimum lithium amount. Thus, the lithium/nano silicon carbide cell will remain safe for charging and discharging.
The lithium/nanometer silicon carbide battery provided by the invention has the characteristics of high specific energy, high specific capacity, long service life and high safety.
Drawings
FIG. 1 scanning electron micrograph of nano silicon carbide composite of lithium aluminum alloy plated film in example 1.
Fig. 2 is a voltage-specific capacity cycling characteristic diagram of a lithium/nano silicon carbide battery composed of a lithium aluminum alloy, a nano silicon carbide composite electrode and a nano silicon carbide positive electrode with accurate lithium dosage in example 1.
FIG. 3 scanning electron micrograph of nano silicon carbide composite of lithium aluminum alloy plated film in example 2.
Fig. 4 is a graph of voltage-specific capacity cycling characteristics of a lithium/nano silicon carbide battery composed of an electrode of lithium-containing aluminum alloy and nano silicon carbide composite material with accurate lithium dosage and a nano silicon carbide positive electrode in example 2.
Detailed Description
The invention is described in further detail below with reference to the following figures and examples, which should not be construed as limiting the invention.
Example 1
In the lithium/nano silicon carbide battery provided in the embodiment, the positive plate is made of a nano silicon carbide material, the negative plate is made of a composite material of a lithium-aluminum alloy and nano silicon carbide, the diaphragm is Celguard, and the electrolyte is mainly lithium hexafluorophosphate or solid electrolyte. The content of the nano silicon carbide in the positive plate is 1g, and the content of the lithium in the lithium-aluminum alloy and nano silicon carbide nano composite material is 0.7-0.9 g. The specific capacity of lithium is 4300mAh/g, and the lithium-inserting specific capacity of the nano silicon carbide is 2450mAh/g, so that the amount of the nano silicon carbide in the negative plate is 0.8-1 g. Considering an SEI film formed by the first discharge anode material, a part of lithium is consumed on the anode active material, and the lithium is adjusted to be between 0.7 and 0.9 g.
The preparation process comprises the following steps: and (4) measuring the lithium intercalation amount of the nano silicon carbide in the positive electrode material, and taking the lithium intercalation amount as the amount of lithium in the lithium aluminum alloy of the counter electrode. The synthetic lithium-aluminum alloy material can be obtained by the following preparation process: (1) preparing a raw material sample, weighing nano silicon carbide powder, paving 100g of nano silicon carbide linear, flaky or spherical particle powder into a flat-bottom graphite boat with the diameter of 250mm, paving the flat-bottom graphite boat into a uniform thin layer, and placing the sample-carrying graphite boat on an anode base of a vacuum chamber of a multi-target magnetron sputtering machine; preparing a double-target material, weighing 150g of high-purity lithium block and 500g of aluminum block, and respectively placing the high-purity lithium block and the aluminum block on two target seats; closing the sample chamber, and sequentially opening the power supplies of the mechanical pump and the molecular pump; (2) the vacuum chamber was evacuated to a vacuum of 5X10-4Pa, and heating to 500 ℃; (3) injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering power supply, starting a single sputtering program, firstly sputtering a lithium block for 30 seconds to 5 minutes without stopping, measuring the thickness of a metal film formed on the surface of the nano silicon carbide powder to reach 70nm through model calculation, starting an aluminum block sputtering program, controlling the strength of sputtered aluminum to enable the sputtering strength to be one tenth of the sputtering strength of lithium, gradually increasing the strength of sputtered aluminum to reach the same strength as lithium for a time equal to the lithiumLasting for 10-50 minutes; the thickness of the sputtered mixed metal film is 500 nm-5 um; (4) turning off the sputtering power supply, raising the temperature to 650 ℃, and keeping the temperature for 5-30 minutes; (5) transferring the mixture to a tabletting chamber, and tabletting the lithium-aluminum alloy and nano silicon carbide composite material to a thickness of 50 um; naturally cooling to room temperature; (6) cut into 50 disks with a diameter of 15 mm. The cut single-piece lithium aluminum alloy and nano silicon carbide electrode plate contains 0.8-1 g of nano silicon carbide and 0.7-0.9 g of lithium.
The composite is characterized by being a composite of lithium aluminum alloy and nano silicon carbide through x-ray phase identification. The composite material has high strength and excellent electrochemical performance. Only the lithium aluminum alloy and nano silicon carbide phases were detected from the raman spectra, indicating that no lithium or aluminum silicon carbide alloy phases were formed, no lithium or aluminum was contained in the nano silicon carbide, and only the diffraction peaks of the metallic lithium, aluminum and nano silicon carbide were present in the x-ray diffraction pattern.
Preparing a positive plate containing pure nano silicon carbide: weighing 500g of nano silicon carbide powder, uniformly mixing active substance nano silicon carbide powder, a conductive agent and an adhesive in a mass ratio of 85:8:7, adding nmp, uniformly mixing to obtain slurry, uniformly coating the slurry on foamed nickel, putting the foamed nickel coated with the slurry into a vacuum drying box, vacuumizing to 0.1MPa, heating to 110-180 ℃, continuing for 24hrs, naturally cooling to room temperature, taking out the foamed nickel, tabletting, and cutting into wafers with the diameter of 15mm, wherein the content of each nano silicon carbide wafer is 1 g. The lithium aluminum alloy and nano silicon carbide composite electrode plate contains 0.7g of metallic lithium. The lithium-aluminum alloy and the nanometer silicon carbide negative plate prepared in the way are accurately matched with the lithium insertion amount of the positive nanometer silicon carbide.
Assembling the battery: the nano silicon carbide pressing sheet is used as a positive plate, the nano silicon carbide pressing sheet plated with the lithium-aluminum alloy is used as a negative plate, the nano silicon carbide positive plate, the diaphragm Celguard and the nano silicon carbide negative plate plated with the lithium-aluminum alloy are sequentially placed, electrolyte mainly containing lithium hexafluorophosphate is injected, the battery is packaged, and the battery is formed for 480 hours at 50 ℃.
And (3) carrying out a battery charge-discharge cycle test: and carrying out a cyclic dynamics test at a window voltage of 4.2V-0.0V and a current density of 1C. Discharging for the first time, wherein the discharge capacity is 2000mAh/g, and the charge capacity is 2100 mAh/g; at the 10 th cycle, the discharge capacity reaches 2450mAh/g and the charge capacity is 2450mAh/g, until 500 cycles, the charge-discharge capacity is kept unchanged, and the coulombic efficiency is kept 100% in the process.
This shows that this technique accurately constructs the amount of lithium used in the positive electrode sheet, can greatly reduce the amount of lithium used, and can minimize explosion caused by short-circuit contact of the circuit due to lithium. During the first discharging process of the battery in the circulating process, lithium is oxidized into lithium ions, the lithium ions are transferred from the negative electrode of the lithium-aluminum alloy and the nano silicon carbide to the positive electrode and are inserted into the nano silicon carbide of the positive electrode, all lithium of the negative electrode is transferred to the positive electrode, and after the lithium is completely inserted into the nano silicon carbide, the battery is discharged. During the charging process, lithium ions in the positive plate are reduced into atoms and transferred from the positive electrode to the negative electrode, and because the energy formed by lithium inserted into the lithium-aluminum alloy is greater than the energy formed by lithium atoms inserted into the nano silicon carbide, one part of the transferred lithium atoms forms lithium metal, and the other part of the transferred lithium atoms is inserted into the nano silicon carbide in the negative plate; during the subsequent charge and discharge processes, a part of lithium is released from the lithium metal in the lithium aluminum alloy to the positive electrode and a part is released from the nano silicon carbide in the negative electrode during charge. During the charging process, more lithium atoms are inserted into the nano silicon carbide. Considering the charging link of the cycle process, a part of lithium atoms removed from the positive electrode are inserted into the nano silicon carbide, and a part of lithium atoms form lithium metal in the lithium-aluminum alloy. During the discharging process, lithium is released from the lithium-aluminum alloy and the coated nano silicon carbide and is embedded into the nano silicon carbide of the positive electrode. In the circulation process, lithium atoms in the charging process do not need to consume energy to be crystallized into lithium metal, a part of the lithium atoms are directly inserted into the nano silicon carbide of the negative electrode, the process is repeated, lithium is gradually increased and migrated into the nano silicon carbide, and lithium migrated back into the lithium-aluminum alloy is gradually reduced, so that when the circulation is performed for 20-50 times, an equilibrium state is reached, namely the lithium/nano silicon carbide battery is charged after 10 circulation cycles to enable lithium to be inserted into the nano silicon carbide, and meanwhile, the lithium/nano silicon carbide battery is continuously crystallized into the lithium-aluminum alloy. After 100 cycles, the lithium in the lithium-aluminum alloy in the negative plate is gradually reduced to the minimum value, meanwhile, the nanometer silicon carbide lithium in the negative plate reaches the maximum value, and during discharging, the lithium is mainly migrated from the nanometer silicon carbide and reaches the positive electrode; during charging, lithium ions in the positive electrode are oxidized into atoms which mainly migrate into the nano silicon carbide in the negative electrode.
Test results of 7 100 samples of the button cell were selected and numbered sequentially, see table 1.
TABLE 1 electrochemical cycle characteristics test results for lithium/nano silicon carbide cells
Example 2
In the lithium/nano silicon carbide battery provided in the embodiment, the positive plate is made of a nano silicon carbide material, the negative plate is made of a composite material of a lithium-aluminum alloy and nano silicon carbide, the diaphragm is Celguard, and the electrolyte is mainly lithium hexafluorophosphate or solid electrolyte. The content of the nano silicon carbide in the positive plate is 1-2 g, and the content of the lithium in the lithium aluminum alloy and nano silicon carbide nano composite material is 0.7-1.5 g. The specific capacity of lithium is 4300mAh/g, the lithium-inserting specific capacity of the nano silicon carbide is 2450mAh/g, and the amount of the nano silicon carbide in the negative plate is 1-2 g.
The difference between the manufacturing process of the embodiment 2 and the embodiment 1 is that in the process of manufacturing the negative plate, after the process of magnetron sputtering lithium aluminum deposition, the lithium aluminum alloy is directly and naturally cooled to room temperature without heating and pressing into a plate. The Raman spectrum of the product shows that the product is lithium aluminum alloy and nano silicon carbide, and no other phase appears.
The preparation process comprises the following steps: (1) weighing nano silicon carbide powder, including 100g of nano silicon carbide linear, flaky or spherical particle powder, laying the nano silicon carbide powder in a flat-bottom graphite boat with the diameter of 250mm, laying the nano silicon carbide powder into a uniform thin layer, and placing the sample-carrying graphite boat on an anode base of a vacuum chamber of a multi-target magnetron sputtering machine; preparing a double-target material, weighing 150g of high-purity lithium block and 500g of aluminum block, and respectively placing the high-purity lithium block and the aluminum block on two target seats; closing the sample chamber, and sequentially opening the power supplies of the mechanical pump and the molecular pump; (2) the vacuum chamber was evacuated to a vacuum of 5X10-4Pa, and heating to 500 DEG C(ii) a (3) Injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering power supply, starting a single sputtering program, firstly sputtering a lithium block for 30 seconds to 5 minutes without stopping, measuring the thickness of a metal film formed on the surface of the nano silicon carbide powder to reach 70nm through model calculation, starting an aluminum block sputtering program, controlling the strength of sputtered aluminum to enable the sputtering strength of the aluminum to be one tenth of the sputtering strength of lithium, gradually increasing the strength of the sputtered aluminum to reach the same strength as lithium, and lasting for 10 to 50 minutes; the thickness of the sputtered mixed metal film is 500 nm-5 um; (5) the preparation method comprises the following steps of (1) preparing lithium aluminum alloy plated nano silicon carbide powder: weighing the lithium-aluminum alloy plated nano silicon carbide powder and the adhesive in a ratio of 90:10, uniformly mixing, adding nmp, uniformly mixing, coating the mixture into foamed nickel, pressing into a circular sheet, and drying in an oven at 80-150 ℃ for 24 hours. (6) The lithium aluminum alloy coated nano silicon carbide electrode plate 100 is prepared, the lithium content of the plate is controlled to be 0.7 g-0.5 g, the aluminum content is controlled to be 0.3 g-0.5 g, and the nano silicon carbide is controlled to be 0.5 g-1 g.
The preparation of the positive plate can be obtained by the following process: weighing 500g of nano silicon carbide powder, uniformly mixing the nano silicon carbide powder, the conductive agent and the adhesive in a mass ratio of 85:8:7, adding nmp, uniformly mixing to obtain slurry, coating the slurry on foamed nickel, putting the foamed nickel in a vacuum baking oven, vacuumizing, and drying at 80-150 ℃ for 24-48 hours. Naturally cooling to room temperature, and pressing into 100 wafers, wherein the content of the single nano silicon carbide is 1 g.
Assembling a lithium/nano silicon carbide battery: and (3) sequentially placing the nano silicon carbide positive plate, the diaphragm Celguard and the lithium aluminum alloy plated nano silicon carbide negative plate, injecting an electrolyte mainly containing lithium hexafluorophosphate, and packaging. And the formation lasts for 72 hours.
And (3) testing the cycle characteristics of the lithium/nano silicon carbide battery: and (3) charging and discharging voltage window: 4.2-0V and 1C, under the condition, the first discharge capacity is 2000mAh/g, and the first charging specific capacity is 2100mAh/g, so that the charging and discharging specific capacity reaches 2450mAh/g when the cycle is carried out for 20 times, the coulomb efficiency reaches 100%, and the numerical value is maintained to be 100 times of cycle. The cycling kinetics test was performed on 100 button lithium/nano silicon carbide cells, and 8 samples were randomly selected as shown in table 2.
TABLE 2 electrochemical cycle characteristics test results for lithium/nano silicon carbide cells
Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various changes and modifications within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.
Claims (8)
1. A lithium/nanometer silicon carbide battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, and is characterized in that: the anode plate is made of a nano silicon carbide material, the cathode plate is made of a composite material of lithium-aluminum alloy and nano silicon carbide, the diaphragm is Celguard, the electrolyte is lithium hexafluorophosphate or a solid electrolyte, and the mass ratio of lithium in the cathode plate to the nano silicon carbide in the anode plate is 0.7: 1-0.9: 1; the content of lithium in the negative plate is 0.7-0.9 g, and the content of nano silicon carbide is 0.8-1 g; the content of the nano silicon carbide in the positive plate is 1g, lithium is oxidized into lithium ions in the first discharging process of the battery in the circulating process, the lithium ions are transferred from the negative electrode of the lithium-aluminum alloy and the nano silicon carbide to the positive electrode and are inserted into the nano silicon carbide of the positive electrode, all lithium of the negative electrode is transferred to the positive electrode, and the battery is discharged after the lithium is completely inserted into the nano silicon carbide; in the circulation process, a part of lithium atoms detached from the positive electrode are embedded into the nano silicon carbide, and a part of lithium atoms form lithium metal in the lithium-aluminum alloy, the process is repeated, lithium gradually increases and migrates into the nano silicon carbide, lithium migrating back to the lithium-aluminum alloy is gradually reduced, the lithium is balanced when circulating for 20-50 times, and lithium is embedded into the nano silicon carbide by charging and continuously crystallized to form the lithium-aluminum alloy; after 100 cycles, the lithium in the lithium aluminum alloy in the negative plate is gradually reduced to the minimum value, and simultaneously, the nano silicon carbide lithium in the negative plate reaches the maximum value.
2. The lithium/nano silicon carbide cell of claim 1, wherein: the content of lithium element in the negative plate is 0.7-0.9 g, the content of aluminum element is 0.3-0.5 g, and the content of nano silicon carbide is 0.9-1 g.
3. A preparation process of a lithium/nanometer silicon carbide battery is characterized by comprising the following steps: the method comprises the following steps:
1) preparing a lithium aluminum alloy plated nano silicon carbide pressing sheet, wherein the content of lithium element in the lithium aluminum alloy plated nano silicon carbide pressing sheet is 0.7-0.9 g;
2) preparing a nano silicon carbide pressing sheet, wherein the content of the nano silicon carbide pressing sheet is 1 g;
3) assembling the battery: placing the nano silicon carbide pressing sheet as a positive plate and the lithium aluminum alloy plated nano silicon carbide pressing sheet as a negative plate in sequence, injecting an electrolyte of lithium hexafluorophosphate into the nano silicon carbide positive plate, the diaphragm Celguard and the lithium aluminum alloy plated nano silicon carbide negative plate, and packaging to form a lithium hexafluorophosphate electrolyte for 72 hours;
4) and (3) testing the cycle characteristics of the battery: placing the battery after formation into a charging and discharging voltage window, and completing the preparation when the battery is circularly charged and discharged for 10 times under the conditions of voltage 4.2-0V and current density 1C, wherein the charging and discharging specific capacity reaches 2450 mAh/g; in the first discharging process of the battery in the circulating process, lithium is oxidized into lithium ions, the lithium ions are transferred from the negative electrode of the lithium-aluminum alloy and the nano silicon carbide to the positive electrode and are inserted into the nano silicon carbide of the positive electrode, all lithium of the negative electrode is transferred to the positive electrode, and the battery is completely discharged after the lithium is completely inserted into the nano silicon carbide;
in the circulation process, a part of lithium atoms detached from the positive electrode are embedded into the nano silicon carbide, and a part of lithium atoms form lithium metal in the lithium-aluminum alloy, the process is repeated, lithium gradually increases and migrates into the nano silicon carbide, lithium migrating back to the lithium-aluminum alloy is gradually reduced, the lithium is balanced when circulating for 20-50 times, and lithium is embedded into the nano silicon carbide by charging and continuously crystallized to form the lithium-aluminum alloy; after 100 cycles, the lithium in the lithium aluminum alloy in the negative plate is gradually reduced to the minimum value, and simultaneously, the nano silicon carbide lithium in the negative plate reaches the maximum value.
4. The process of claim 3, wherein the lithium/nano silicon carbide cell is prepared by: the specific steps of the step 1) comprise:
1a1) placing active substance nano silicon carbide powder in a flat-bottom graphite boat, paving the flat-bottom graphite boat into a uniform thin layer, and placing the flat-bottom graphite boat on an anode base of a vacuum chamber of a magnetron sputtering machine;
1a2) respectively placing a high-purity lithium block and a high-purity aluminum block on two target holders of a magnetron sputtering machine;
1a3) closing the vacuum chamber, sequentially turning on the power supply of the mechanical pump and the molecular pump, and vacuumizing until the vacuum degree is 5x10-4Pa, and heating to 500 ℃; injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering lithium block, starting a sputtering aluminum block after the completion, and forming a metal film on the surface of active substance nano silicon carbide powder in the flat-bottom graphite boat;
1a4) turning off a sputtering power supply, raising the temperature of the vacuum chamber to 650 ℃, and naturally cooling to room temperature after 5-30 minutes of duration;
1a5) pressing the nano silicon carbide composite material with the surface formed with the metal film into a wafer, wherein the lithium element content in the single-piece lithium aluminum alloy plated nano silicon carbide pressing sheet is 0.7g, and the nano silicon carbide content is 0.1 g.
5. The process of claim 3, wherein the lithium/nano silicon carbide cell is prepared by: the specific steps of the step 2) comprise:
21) uniformly mixing active substance nano silicon carbide powder, a conductive agent and an adhesive in a mass ratio of 85:8:7, adding nmp, and uniformly mixing to obtain slurry;
22) coating the slurry on the foamed nickel, putting the foamed nickel coated with the slurry into a vacuum drying box, drying for 24 hours at 110-180 ℃ after vacuumizing, and naturally cooling to room temperature;
23) pressing the nano silicon carbide substance on the foamed nickel into a wafer, wherein the content of the single nano silicon carbide pressing sheet is 1 g.
6. The process of claim 3, wherein the lithium/nano silicon carbide cell is prepared by: the specific steps of the step 1) comprise:
1b1) placing active substance nano silicon carbide powder in a flat-bottom graphite boat, paving the flat-bottom graphite boat into a uniform thin layer, and placing the flat-bottom graphite boat on an anode base of a vacuum chamber of a magnetron sputtering machine;
1b2) respectively placing a high-purity lithium block and a high-purity aluminum block on two target holders of a magnetron sputtering machine;
1b3) closing the vacuum chamber, sequentially turning on the power supply of the mechanical pump and the molecular pump, and vacuumizing until the vacuum degree is 5x10-4Pa, and heating to 500 ℃; injecting argon to make the vacuum degree reach 20 Pa; starting a sputtering lithium block, starting a sputtering aluminum block after the completion, and forming a metal film on the surface of active substance nano silicon carbide powder in the flat-bottom graphite boat;
1b4) uniformly mixing the lithium-aluminum alloy plated nano silicon carbide powder and the adhesive in a mass ratio of 90:10, adding nmp, and uniformly mixing to obtain slurry;
1b5) coating the slurry on the foamed nickel, putting the foamed nickel coated with the slurry into a vacuum drying box, drying for 24 hours at 80-150 ℃ after vacuumizing, and naturally cooling to room temperature;
1b6) pressing the lithium aluminum alloy plated nano silicon carbide mixed substance on the foamed nickel into a wafer, wherein the lithium element content, the aluminum element content and the nano silicon carbide content in the single lithium aluminum alloy plated nano silicon carbide pressed wafer are respectively 0.7-0.9 g, 0.3-0.5 g and 0.8-1 g.
7. The process of claim 4, wherein the lithium/nano silicon carbide cell is prepared by: the specific method for sputtering the lithium block and the aluminum block in the step 1a3) comprises the following steps: starting a lithium block sputtering program for 30 seconds to 5 minutes until the thickness of a metal film formed on the surface of the active substance nano silicon carbide powder reaches 70nm, then starting an aluminum block sputtering program, controlling the strength of the aluminum block sputtering to be gradually increased from 10% to 100%, and continuing for 10 to 50 minutes until the thickness of the metal film formed on the surface of the active substance nano silicon carbide powder reaches 500nm to 5 um.
8. The process of claim 6, wherein the lithium/nano silicon carbide cell is prepared by: the specific method for sputtering the lithium block and the aluminum block in the step 1b3) comprises the following steps: starting a lithium block sputtering program for 30 seconds to 5 minutes until the thickness of a metal film formed on the surface of the active substance nano silicon carbide powder reaches 70nm, then starting an aluminum block sputtering program, controlling the strength of the aluminum block sputtering to be gradually increased from 10% to 100%, and continuing for 10 to 50 minutes until the thickness of the metal film formed on the surface of the active substance nano silicon carbide powder reaches 500nm to 5 um.
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