Siloxyl negative electrode material and preparation method and application thereof

Abstract

This invention relates to the field of lithium-ion battery technology, and more specifically, to a silicon-oxygenated anode material, its preparation method, and its application. The silicon-oxygenated anode material comprises SiO₂. x / C composite material core and coated on SiO x An amorphous carbon shell on the outer surface of the SiOx / C composite core, and a void layer between the SiOx / C composite core and the amorphous carbon shell; the SiOx / C composite core has an amorphous carbon shell on the outer surface of the core; x C-coated SiO in the core of the / C composite material x This silicon-oxygenated anode material exhibits excellent long-cycle performance and rate capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a siloxy negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the demand for battery energy density in mobile storage, power grid and other industries has risen rapidly, and the development of lithium ion batteries with high energy density and high safety has become the focus. Replacing the traditional graphite negative electrode with a new type of negative electrode material with high theoretical specific capacity is currently the most promising way to improve the energy density of lithium ion batteries and meet the new generation of energy needs. Silicon material has the advantages of extremely high theoretical capacity (about 4200mAh g -1 ), low working voltage (about 0.3V vs Li + / Li), and abundant crustal reserves, and is an extremely attractive negative electrode material for the next generation of high-energy-density lithium ion batteries. However, when elemental silicon material stores lithium through alloying reaction mechanism, it often accompanies a high intrinsic volume change of up to 300%, which will cause the collapse of the electrode structure, leading to rapid capacity decay of the battery, and seriously restricting the practical application of silicon-based materials in commercial lithium batteries.

[0003] Silicon oxide (SiO x ) is a main material in silicon-based materials. Compared with elemental silicon material with high volume expansion rate in the process of lithium extraction and insertion, the presence of structural oxygen in silicon oxide material makes it form inert products (Li2O, Li4SiO4 and Li2Si2O5, etc.) in situ during the initial alloying process, which becomes a buffer matrix of active material in the subsequent electrochemical process, and the overall volume effect of the material is significantly reduced. At the same time, its natural amorphous structure can reduce the material cracking and pulverization problem caused by uneven stress during alloying process, which helps to maintain the integrity of the structure. In addition, SiO x also has the advantages of low cost and simple synthesis. Therefore, silicon oxide is the most potential choice for the short-term commercialization of silicon-based materials.

[0004] However, on the one hand, SiO x negative electrode material still has an indelible volume expansion problem in the process of lithium extraction and insertion, which cannot meet the requirements of long battery life; on the other hand, the inherent low conductivity of SiO x negative electrode material cannot meet the high rate requirement of the battery. In practical application, SiO x material still has a lot of room for improvement in cycle stability and rate performance.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The first object of the present application is to provide a siloxyl negative electrode material with good long cycle performance and rate performance.

[0007] The second object of the present application is to provide a preparation method of the siloxyl negative electrode material.

[0008] The third object of the present application is to provide a negative electrode sheet.

[0009] The fourth object of the present application is to provide a lithium ion battery.

[0010] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0011] In a first aspect, the present application provides a siloxyl negative electrode material, which comprises a SiO x / C composite material core and an amorphous carbon shell coated on the outer surface of the SiO x / C composite material core. x / C composite material core and the amorphous carbon shell have a gap layer therebetween.

[0012] The SiO x / C composite material core in the siloxyl negative electrode material provided by the present application comprises SiO x .

[0013] Referring to Figure 1 , a cross-sectional structure schematic diagram of the siloxyl negative electrode material provided by the present application.

[0014] The Si element in the siloxyl negative electrode material provided by the present application includes Si 4+ , Si 3+ and Si 2+ , and the average valence of the Si element is about 3.01-3.27.

[0015] The siloxyl negative electrode material provided by the present application has a dual synergistic effect of the amorphous carbon shell and the gap layer (cavity structure), which can effectively relieve the internal stress of the silox material in the reversible deintercalation / intercalation process, is conducive to the formation of a stable solid electrolyte interface film (SEI), and at the same time improves the overall conductivity, allowing high-speed transmission of lithium ions, thereby improving the rate performance of the lithium ion battery prepared from the siloxyl negative electrode material.

[0016] Specifically, the SiO x / C core plays a role in maintaining the spherical structure; the gap layer can relieve the volume expansion of the SiO x ; and the carbon in the amorphous carbon shell and the amorphous carbon in the SiO x / C composite material core not only reduce the volume change of the SiO x , but also improve the conductivity of the composite material.

[0017] Therefore, the lithium ion battery made of the siloxyl-based negative electrode material has good long cycle performance and rate performance.

[0018] Preferably, the total mass fraction of carbon elements in the siloxyl-based negative electrode material is 20% to 35%, including but not limited to any one of the point values of 23%, 25%, 28%, 30%, 32% or a range value between any two of them.

[0019] Preferably, the thickness of the void layer is 80 to 120 nm, including but not limited to any one of the point values of 90 nm, 100 nm, 110 nm or a range value between any two of them; the thickness of the amorphous carbon shell is 15 to 40 nm, including but not limited to any one of the point values of 20 nm, 25 nm, 30 nm, 35 nm or a range value between any two of them.

[0020] Preferably, the average particle size of the siloxyl-based negative electrode material is 600 to 1000 nm, including but not limited to any one of the point values of 700 nm, 800 nm, 900 nm or a range value between any two of them.

[0021] Preferably, the initial discharge specific capacity of the siloxyl-based negative electrode material at 0.1 A / g is ≥1100 mAh / g; including but not limited to any one of the point values of 1200 mAh / g, 1300 mAh / g, 1400 mAh / g, 1500 mAh / g or a range value between any two of them.

[0022] The initial coulombic efficiency of the siloxyl-based negative electrode material at 0.1 A / g is ≥61%; including but not limited to any one of the point values of 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70% or a range value between any two of them.

[0023] The capacity retention rate of the siloxyl-based negative electrode material at 0.5 A / g after 200 cycles is ≥84%; including but not limited to any one of the point values of 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92% or a range value between any two of them.

[0024] Preferably, the total resistance of the siloxyl-based negative electrode material is ≤98 Ω, including but not limited to any one of the point values of 95 Ω, 92 Ω, 90 Ω, 88 Ω, 85 Ω, 83 Ω, 80 Ω or a range value between any two of them.

[0025] In a second aspect, the present application provides a preparation method of the siloxyl-based negative electrode material as described above, comprising the following steps:

[0026] The organic silane solution and ammonia water are mixed uniformly, and then subjected to hydrothermal treatment, hydrolysis and self-condensation reaction, and then subjected to solid-liquid separation to obtain organic silicon nanospheres; the organic silicon nanospheres are calcined (carbonized) to form a core to obtain C-coated SiO x / C composite material. x / C composite material.

[0027] The reaction equation in the hydrolysis and self-condensation reaction process includes:

[0028]

[0029] The organic silane is used as a silicon source and a carbon source, and ammonia water is used as an alkali catalyst, and the organic silicon nanospheres are prepared through hydrolysis and self-condensation reaction of the organic silane.

[0030] In some specific embodiments of the present application, after the solid-liquid separation, a washing and / or drying step is further included.

[0031] The SiO x / C composite material is mixed uniformly with a polydiallyldimethylammonium chloride (PDDA) solution, and then subjected to solid-liquid separation, so that the polydiallyldimethylammonium chloride is coated on the surface of the SiO x / C composite material to obtain a SiO x / C@PDDA composite material.

[0032] In some specific embodiments of the present application, the SiO x / C composite material is mixed with the polydiallyldimethylammonium chloride solution by ultrasonic mixing.

[0033] The SiO x / C@PDDA composite material is mixed uniformly with an aniline solution, an oxidizing agent solution is added thereto to perform a polymerization reaction, polyaniline (PANI) is formed and coated on the surface of the SiO x / C@PDDA composite material, and then subjected to solid-liquid separation to obtain a SiO x / C@PDDA@PANI composite material.

[0034] In some specific embodiments of the present application, the SiO x / C@PDDA composite material is mixed with the aniline solution in the mixing process, and an acid solution is further added.

[0035] Preferably, the acid solution includes at least one of a hydrochloric acid solution, a phosphoric acid solution, a phytic acid solution, a perchloric acid solution and a sulfuric acid solution.

[0036] Preferably, the molar concentration of the acid solution is 0.5-4 mol / L, including but not limited to any one of 1 mol / L, 2 mol / L, 3 mol / L or a range value between any two of them.

[0037] Preferably, the pH of the acid solution added to the mixture is 1-3, including but not limited to any one of 1.5, 2, 2.5 or a range value between any two of them.

[0038] Preferably, the preparation method of the oxidizing agent solution comprises: uniformly mixing the oxidizing agent and the acid solution.

[0039] In some specific embodiments of the present application, after the solid-liquid separation, the steps of washing to neutral and then drying are further included.

[0040] The SiO x / C@PDDA@PANI composite is calcined, and in the process of calcination, the poly diallyl dimethyl ammonium chloride forms a void layer (poly diallyl dimethyl ammonium chloride pyrolysis and gas escape to form a cavity) after high-temperature pyrolysis, and the polyaniline forms an amorphous carbon shell (amorphous carbon coating layer) after high-temperature carbonization, to obtain the siloxy negative electrode material.

[0041] The preparation method of the siloxy negative electrode material provided by the present application can enhance the stability of the siloxy negative electrode material in the reversible deintercalation / intercalation process of lithium, improve the electrochemical performance of the siloxy negative electrode material, and prolong the service life of the battery.

[0042] Preferably, the organosilane includes at least one of mercaptopropyl trimethoxysilane (MPTMS), vinyl trimethoxysilane (VTMS), vinyl triethoxysilane (CTMS), and cyanoethyl triethoxysilane (CTES).

[0043] In some specific embodiments of the present application, the solvent in the organosilane solution includes water and / or ethanol.

[0044] Preferably, the mass fraction of the organosilane solution is 2%-8%, including but not limited to any one of 3%, 4%, 5%, 6%, 7% or a range value between any two of them.

[0045] The mass fraction of the ammonia water is 25%-28%, including but not limited to any one of 26%, 27%, 28% or a range value between any two of them.

[0046] Preferably, the volume ratio of the organosilane solution and the aqueous ammonia is 2-4:0.5-2.5, such as 2:0.5, 2:1, 2:1.5, 2:2, 2:2.5, 3:0.5, 3:1, 3:1.5, 3:2, 3:2.5, 4:0.5, 4:1, 4:1.5, 4:2, 4:2.5, etc.

[0047] Preferably, the temperature of the mixture during the hydrothermal treatment is 65-180℃; including but not limited to any one of the point values of 70℃, 80℃, 90℃, 100℃, 120℃, 140℃, 150℃, 160℃ or a range value between any two of them.

[0048] The time of the hydrothermal treatment is 4-24h, including but not limited to any one of the point values of 5h, 8h, 10h, 13h, 15h, 18h, 20h, 22h or a range value between any two of them.

[0049] Preferably, the calcination temperature of the organosilicon nanospheres is 600-1200℃, including but not limited to any one of the point values of 700℃, 800℃, 900℃, 1000℃, 1100℃ or a range value between any two of them.

[0050] The heating rate is 2-10℃ / min, including but not limited to any one of the point values of 3℃ / min, 5℃ / min, 7℃ / min, 9℃ / min or a range value between any two of them.

[0051] In some specific embodiments of the present application, the calcination of the organosilicon nanospheres is carried out in a non-oxidizing atmosphere, such as a nitrogen atmosphere, an argon atmosphere, etc., but is not limited thereto.

[0052] The calcination time of the organosilicon nanospheres is 0.5-4h, including but not limited to any one of the point values of 1h, 2h, 3h or a range value between any two of them.

[0053] Preferably, the mass ratio of the SiOx / C composite material to the polydimethyldiallylammonium chloride in the polydimethyldiallylammonium chloride solution is 0.4-0.5:3-7.

[0054] Preferably, the mass fraction of the polydimethyldiallylammonium chloride solution is 3%-7%, including but not limited to any one of the point values of 4%, 5%, 6% or a range value between any two of them.

[0055] By controlling the concentration of the polydimethyldiallylammonium chloride solution and the amount thereof, the thickness of the void layer can be controlled.

[0056] Preferably, the oxidizing agent comprises at least one of ammonium persulfate, manganese dioxide, ferric chloride and benzoyl peroxide.

[0057] Preferably, the molar ratio of aniline in the aniline solution to the ammonium persulfate is 0.5-2:1; including but not limited to any one of 0.8:1, 1:1, 1.2:1, 1.5:1 or a range value between any two of them.

[0058] Preferably, the temperature of the mixture during the polymerization reaction is 0-5℃; including but not limited to any one of 1℃, 2℃, 3℃, 4℃ or a range value between any two of them.

[0059] The time of the polymerization reaction is 6-48h, including but not limited to any one of 8h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h or a range value between any two of them.

[0060] In some specific embodiments of the present application, the SiO x The temperature of the mixture during the mixing of the SiO

[0061] Preferably, the SiO x The calcination temperature of the SiO

[0062] The calcination temperature of the SiO x The holding time of the calcination of the SiO

[0063] In some specific embodiments of the present application, the SiO x The calcination of the SiO

[0064] In some specific embodiments of the present application, the method for mixing the materials uniformly can adopt any conventional method, such as stirring, ultrasonic, etc., but is not limited thereto.

[0065] In a third aspect, the present application provides a negative electrode sheet, which is mainly prepared from the silicon-oxygen-based negative electrode material as described above.

[0066] In a fourth aspect, the present application provides a lithium ion battery comprising the negative electrode sheet as described above.

[0067] The lithium ion battery has excellent electrochemical performance, especially good long cycle performance and rate performance.

[0068] Compared with the prior art, the present application has the following beneficial effects:

[0069] The silicon-oxygen-based negative electrode material provided by the present application can effectively relieve the internal stress of the silicon-oxygen material during the reversible deintercalation / intercalation of lithium, is conducive to the formation of a stable solid electrolyte interface film, and improves the overall electrical conductivity, allowing high-speed transmission of lithium ions, thereby improving the rate performance and long cycle performance of the lithium ion battery prepared from the silicon-oxygen-based negative electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0070] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0071] Figure 1 A cross-sectional structure schematic diagram of the silicon-oxygen-based negative electrode material provided by the present application;

[0072] Figure 2 The XRD pattern of the silicon-oxygen-based negative electrode material prepared in Example 1 provided by the present application. DETAILED DESCRIPTION

[0073] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are all conventional products that can be purchased on the market.

[0074] The silicon-oxygen-based negative electrode material provided in each of the following embodiments of the present application comprises a SiO x / C composite material core and a SiO xAn amorphous carbon shell on the outer surface of the SiOx / C composite core, and a void layer between the SiOx / C composite core and the amorphous carbon shell; wherein, the SiOx / C composite core has an amorphous carbon shell on the outer surface of the core; x C-coated SiO in the core of the / C composite material x .

[0075] like Figure 1 The figure shown is a schematic cross-sectional view of the silicon-oxygen anode material provided by the present invention.

[0076] Example 1

[0077] This embodiment provides a method for preparing a silicon-oxygenated anode material, including the following steps:

[0078] (1) 3 mL of mercaptopropyltrimethoxysilane (MPTMS) was dispersed in a mixed solution containing 50 mL of deionized water and 10 mL of ethanol. After magnetic stirring for 1 h, 2 mL of ammonia (25 wt%) was added dropwise, and the mixture was sonicated for 4 h to obtain a milky white solution. The milky white solution was transferred to the lining of a 100 mL high-temperature reactor and subjected to continuous hydrothermal treatment at 150 °C for 6 h to carry out hydrolysis and self-condensation reactions. After the product was cooled to room temperature, it was centrifuged, washed, and then dried in a 60 °C drying oven for 12 h to obtain white organosilicon nanospheres.

[0079] (2) The white organosilicon nanospheres obtained in step (1) were placed in a quartz ceramic boat and calcined in a tube furnace. The temperature was increased to 800°C at a heating rate of 5°C / min under an argon atmosphere and held for 2 hours to form a core, thus obtaining C-coated SiO2. x SiO x / C composite material.

[0080] (3) Take 0.45g of the SiO2 obtained in step (2). x The / C composite material was added to 100 mL of a 5 wt% aqueous solution of polydiallyl dimethyl ammonium chloride (PDDA), ultrasonically stirred for 30 mins, then centrifuged to collect the product, and dried in a 60 °C oven for 12 h to obtain SiO2. x / C@PDDA composite material.

[0081] (4) Dissolve 200 mg of aniline monomer in 50 mL of 1 M HCl solution, and add 0.5 g of SiO2 obtained in step (3) to the solution. x The / C@PDDA composite material was stirred for 30 mins, then sonicated for 120 s, and then transferred to a constant temperature oven at 2℃ for pre-cooling. 0.49 g of ammonium persulfate (APS) was weighed and dissolved in 40 mL of pre-cooled 1 mol / L HCl solution. Then, the above-mentioned solution containing aniline and SiO2 was added to the solution. xThe mixture of / C@PDDA was stirred at low temperature (2℃) for 24 hours to carry out the polymerization reaction. Then, it was centrifuged and washed until neutral, and then dried in a 60℃ drying oven for 12 hours to obtain SiO2. x / C@PDDA@PANI composite material.

[0082] (5) The SiO2 obtained in step (4) x The / C@PDDA@PANI composite material was heated to 400℃ at a heating rate of 2℃ / min under argon atmosphere protection, and then heated to 800℃ at a heating rate of 5℃ / min for calcination, held at that temperature for 2 hours, and then naturally cooled to obtain the final product M-SiO. x / C@void@C-200.

[0083] Testing revealed that the total carbon content in the silicon-oxygenated anode material prepared in this embodiment was 28% by mass. The thickness of the void layer was 100 nm, and the thickness of the amorphous carbon shell was 30 nm. The average particle size of the silicon-oxygenated anode material was 800 nm.

[0084] Example 2

[0085] This embodiment provides a method for preparing a silicon-oxygenated anode material, including the following steps:

[0086] (1) 3 mL of mercaptopropyltrimethoxysilane (MPTMS) was dispersed in a mixed solution containing 50 mL of deionized water and 10 mL of ethanol. After magnetic stirring for 1 h, 2 mL of ammonia (25 wt%) was added dropwise, and the mixture was sonicated for 4 h to obtain a milky white solution. The milky white solution was transferred to the lining of a 100 mL high-temperature reactor and subjected to continuous hydrothermal treatment at 150 °C for 6 h to carry out hydrolysis and self-condensation reactions. After the product was cooled to room temperature, it was centrifuged, washed, and then dried in a 60 °C drying oven for 12 h to obtain white organosilicon nanospheres.

[0087] (2) The white organosilicon nanospheres obtained in step (1) were placed in a quartz ceramic boat and calcined in a tube furnace. The temperature was increased to 800°C at a heating rate of 5°C / min under an argon atmosphere and held for 2 hours to form a core, thus obtaining C-coated SiO2. x SiO x / C composite material.

[0088] (3) Take 0.45g of the SiO2 obtained in step (2). x The / C composite material was added to 100 mL of a 5 wt% aqueous solution of polydiallyl dimethyl ammonium chloride, ultrasonically stirred for 30 mins, then centrifuged to collect the product, and dried in a 60 °C oven for 12 h to obtain SiO2. x / C@PDDA composite material.

[0089] (4) 100 mg aniline monomer was dissolved in 50 mL 1M HCl solution, 0.5 g SiO x / C@PDDA composite material, after stirring for 30 mins, ultrasonic treatment for 120 s, and then transferred to a constant temperature box at 2℃ for precooling. 0.245 g ammonium persulfate (APS) was weighed and dissolved in 40 mL HCl solution with a molar concentration of 1 mol / L which was pre-cooled, and then the above-mentioned mixture solution containing aniline and SiO x / C@PDDA was added thereto, and the polymerization reaction was carried out under low temperature (2℃) stirring for 24 h, followed by centrifugation, washing to neutral, and drying in a 60℃ drying box for 12 h to obtain SiO x / C@PDDA@PANI composite material.

[0090] (5) The SiO x / C@PDDA@PANI composite material obtained in step (4) was calcined under an argon atmosphere at a temperature increasing rate of 2℃ / min to 400℃, and then at a temperature increasing rate of 5℃ / min to 800℃, and kept for 2 h, and the final product M-SiO x / C@void@C-100 was obtained after natural cooling.

[0091] It was detected that the total mass fraction of carbon element in the siloxyl negative electrode material prepared in this embodiment was 20%. The thickness of the void layer was 100 nm, and the thickness of the amorphous carbon shell was 15 nm. The average particle size of the siloxyl negative electrode material was 750 nm.

[0092] Example 3

[0093] The present embodiment provides a preparation method of a siloxyl negative electrode material, comprising the following steps:

[0094] (1) 3 mL mercaptopropyltrimethoxysilane (MPTMS) was dispersed in a mixed solution containing 50 mL deionized water and 10 mL ethanol, and after magnetic stirring for 1 h, 2 mL ammonia water (25 wt%) was added dropwise, and after ultrasonic treatment for 4 h, a milky white solution was obtained. The milky white solution was transferred to the inner liner of a 100 mL high-temperature reaction kettle, and hydrolysis and self-condensation reactions were carried out under the condition of 150℃ for 6 h, and after the product was cooled to room temperature, centrifugation, washing, and then drying in a 60℃ drying box for 12 h, white silicone nanospheres were obtained.

[0095] (2) The white silicone nanospheres obtained in step (1) were placed in a quartz boat and calcined in a tube furnace under an argon atmosphere at a temperature increasing rate of 5℃ / min to 800℃, and kept for 2 h to form a core, and C-coated SiO x was obtained.x / C composite material.

[0096] (3) 0.45 g of SiO x / C composite material was added into 100 mL of a 5 wt% polydiallyldimethylammonium chloride aqueous solution, and ultrasonic stirring was performed for 30 mins, followed by centrifugal collection of the product and drying in a 60℃ oven for 12 h to obtain a SiO x / C@PDDA composite material.

[0097] (4) 400 mg of aniline monomers were dissolved in 50 mL of a 1M HCl solution, and 0.5 g of SiO x / C@PDDA composite material was added, and after stirring for 30 mins, ultrasonic stirring was performed for 120 s, and then the mixture was transferred to a constant-temperature oven pre-cooled at 2℃. 0.98 g of ammonium persulfate (APS) was weighed and dissolved in 40 mL of a HCl solution with a molar concentration of 1 mol / L pre-cooled in advance, and then the above mixture containing aniline and SiO x / C@PDDA was added, and low-temperature (2℃) stirring was performed for 24 h to perform a polymerization reaction, followed by centrifugal washing until neutral, and then drying in a 60℃ drying oven for 12 h to obtain a SiO x / C@PDDA@PANI composite material.

[0098] (5) The SiO x / C@PDDA@PANI composite material obtained in step (4) was calcined at a temperature rising rate of 2℃ / min to 400℃, and then at a temperature rising rate of 5℃ / min to 800℃ under an argon atmosphere, and was kept at 800℃ for 2 h, and the final product M-SiO x / C@void@C-400.

[0099] It was detected that the total mass fraction of carbon elements in the siloxyl negative electrode material prepared in this embodiment was 40%. The thickness of the void layer was 100 nm, and the thickness of the amorphous carbon shell was 40 nm. The average particle size of the siloxyl negative electrode material was 1000 nm.

[0100] Example 4

[0101] The embodiment provides a preparation method of a siloxyl negative electrode material, including the following steps:

[0102] (1) Take 3 mL of vinyltrimethoxysilane (VTMS) dispersed in a mixed solution containing 50 mL of deionized water and 10 mL of ethanol, and stir magnetically for 1 h. Then, add 2 mL of ammonia water (25 wt%) dropwise, and ultrasonic for 4 h to obtain a milky white solution. Transfer the milky white solution into a 100 mL high temperature reaction kettle liner, and perform continuous hydrothermal treatment at 150℃ for 6 h to perform hydrolysis and self-polycondensation reaction. After the product is cooled to room temperature, centrifugal, washing, and then placed in a 60℃ drying oven for 12 h to obtain white silicone nanospheres.

[0103] (2) Put the white silicone nanospheres obtained in step (1) into a quartz boat, and place it into a tube furnace for calcination. Heat to 800℃ at a heating rate of 5℃ / min under argon atmosphere, and keep for 2 h to form a core to obtain C-coated SiO x / SiO x / C composite material.

[0104] (3) Take 0.45 g of the SiO x / C composite material prepared in step (2) and add it into 100 mL of a 5 wt% polydiallyldimethylammonium chloride aqueous solution, and ultrasonic stir for 30 mins. Then, centrifugal collect the product, and place it in a 60℃ oven for drying for 12 h to obtain SiO x / C@PDDA composite material.

[0105] (4) Dissolve 200 mg of aniline monomer in 50 mL of 1M HCl solution, and add 0.5 g of the SiO x / C@PDDA composite material prepared in step (3) to it. Stir for 30 mins, and then ultrasonic for 120 s. Then, transfer it to a constant temperature box pre-cooled at 2℃. Weigh 0.245 g of ammonium persulfate (APS), and dissolve it in 40 mL of 1 mol / L HCl solution pre-cooled. Then, add the above mixture containing aniline and SiO x / C@PDDA to it. Stir at low temperature (2℃) for 24 h to perform polymerization reaction. Then, centrifugal, washing to neutral, and then place it in a 60℃ drying oven for drying for 12 h to obtain SiO x / C@PDDA@PANI composite material.

[0106] (5) Take the SiO x / C@PDDA@PANI composite material prepared in step (4), and heat to 400℃ at a heating rate of 2℃ / min under argon atmosphere protection. Then, heat to 800℃ at a heating rate of 5℃ / min, and keep for 2 h. After natural cooling, the final product V-SiO x / C@void@C-200 is obtained.

[0107] The total mass fraction of carbon element in the siloxyl negative electrode material prepared in this embodiment is 30% after detection. The thickness of the void layer is 100 nm, and the thickness of the amorphous carbon shell is 30 nm. The average particle size of the siloxyl negative electrode material is 850 nm.

[0108] Example 5

[0109] This embodiment provides a preparation method of a siloxyl negative electrode material, comprising the following steps:

[0110] (1) 3 mL of cyanoethyl triethoxysilane (CTES) was dispersed in a mixed solution containing 50 mL of deionized water and 10 mL of ethanol, and after magnetic stirring for 1 h, 2 mL of ammonia water (25 wt%) was added dropwise. After ultrasonic treatment for 4 h, a milky white solution was obtained. The milky white solution was transferred to the inner liner of a 100 mL high-temperature reaction kettle, and hydrolysis and self-condensation reactions were carried out under the condition of continuous hydrothermal treatment at 150 °C for 6 h. After the product was cooled to room temperature, centrifugation, washing and drying in a 60 °C drying box for 12 h were performed, and white silicone nanospheres were obtained.

[0111] (2) The white silicone nanospheres obtained in step (1) were placed in a quartz boat and placed in a tube furnace for calcination. The temperature was raised to 800 °C at a rate of 5 °C / min under an argon atmosphere, and the temperature was kept for 2 h to form a core, and a C-coated SiO x / SiO x / C composite material was obtained.

[0112] (3) 0.45 g of the SiO x / C composite material prepared in step (2) was added to 100 mL of a 5 wt% polydiallyldimethylammonium chloride aqueous solution, and ultrasonic stirring was performed for 30 mins. The product was then collected by centrifugation and dried in a 60 °C oven for 12 h to obtain a SiO x / C@PDDA composite material.

[0113] (4) 200 mg of aniline monomer was dissolved in 50 mL of 1M HCl solution, and 0.5 g of the SiO x / C@PDDA composite material prepared in step (3) was added, stirred for 30 mins, and then ultrasonically treated for 120 s. Then it was transferred to a constant temperature box pre-cooled at 2 °C. 0.49 g of ammonium persulfate (APS) was weighed and dissolved in 40 mL of 1 mol / L HCl solution pre-cooled, and then the above mixture containing aniline and SiO x / C@PDDA was added. The mixture was stirred at low temperature (2 °C) for 24 h for polymerization reaction, and then centrifuged, washed to neutral, and dried in a 60 °C drying box for 12 h to obtain a SiO x / C@PDDA@PANI composite material.

[0114] (5) The SiO x The C-SiO x / C@void@C-200.

[0115] It is detected that the total mass fraction of carbon element in the siloxyl negative electrode material prepared in this embodiment is 35%. The thickness of the void layer is 100 nm, and the thickness of the amorphous carbon shell is 15 nm. The average particle size of the siloxyl negative electrode material is 900 nm.

[0116] Example 6

[0117] The present embodiment provides a preparation method of a siloxyl negative electrode material, comprising the following steps:

[0118] (1) 3 mL of mercaptopropyltrimethoxysilane (MPTMS) is dispersed in a mixed solution containing 50 mL of deionized water and 10 mL of ethanol, and after magnetic stirring for 1 h, 2 mL of ammonia water (25 wt%) is added dropwise. After ultrasonic treatment for 4 h, a milky white solution is obtained. The milky white solution is transferred to the inner liner of a 100 mL high-temperature reaction kettle, and hydrolysis and self-condensation reactions are carried out under continuous hydrothermal treatment at 80℃ for 20 h. After the product is cooled to room temperature, centrifugation, washing, and then drying in a 60℃ drying box for 12 h, white silicone nanospheres are obtained.

[0119] (2) The white silicone nanospheres obtained in step (1) are placed in a quartz boat and placed in a tube furnace for calcination. Under an argon atmosphere, the temperature is raised to 1200℃ at a rate of 5℃ / min, and the temperature is maintained for 1 h to form a core, obtaining C-coated SiO x SiO x / C composite material.

[0120] (3) 0.45 g of SiO x / C composite material prepared in step (2) is added to 100 mL of a 7 wt% polydiallyldimethylammonium chloride aqueous solution, and ultrasonic stirring is performed for 30 mins. Then, the product is collected by centrifugation and dried in a 60℃ oven for 12 h to obtain SiO x / C@PDDA composite material.

[0121] (4) 200 mg of aniline monomer is dissolved in 50 mL of 1M HCl solution, and 0.5 g of SiO xThe / C@PDDA composite material is stirred for 30 mins and then ultrasonically treated for 120 s, and then transferred to a constant temperature box pre-cooled at 5 DEG C. 0.49 g of ammonium persulfate (APS) is weighed and dissolved in 40 mL of HCl solution with a molar concentration of 1 mol / L pre-cooled in advance, and then the above-mentioned mixture containing aniline and SiO x The mixture of / C@PDDA is stirred at low temperature (5 DEG C) for 36 h to perform a polymerization reaction, and then centrifuged and washed to neutral, and then placed in a drying box at 60 DEG C to dry for 12 h to obtain SiO x The / C@PDDA@PANI composite material.

[0122] (5) The SiO x The / C@PDDA@PANI composite material is calcined at an argon atmosphere protection, with a temperature rising rate of 2 DEG C / min to 400 DEG C, and then with a temperature rising rate of 5 DEG C / min to 600 DEG C, and kept for 6 h, and then naturally cooled to obtain the final product M-SiO x The / C@void@C-200.

[0123] It is detected that the total mass fraction of carbon element in the silicon-oxygen-based negative electrode material prepared in the embodiment is 30%. The thickness of the void layer is 120 nm, and the thickness of the amorphous carbon shell is 35 nm. The average particle size of the silicon-oxygen-based negative electrode material is 850 nm.

[0124] Comparative Example 1

[0125] The preparation method of the silicon-oxygen-based negative electrode material provided in the comparative example is basically the same as that in Embodiment 1, and the difference is only that step (4) is not set, that is, no polyaniline coating is performed.

[0126] Comparative Example 2

[0127] The preparation method of the silicon-oxygen-based negative electrode material provided in the comparative example is basically the same as that in Embodiment 1, and the difference is only that step (3) is not set, that is, no PDDA coating is performed.

[0128] Experimental Example

[0129] The silicon-oxygen-based negative electrode materials prepared by using each of the above embodiments and comparative examples are respectively made into negative electrode sheets, and assembled into button cells to perform electrochemical performance test analysis, and the details are as follows:

[0130] Preparation of negative electrode sheet: according to the mass ratio of active material: conductive agent (super-p): sodium alginate (CMC) = 8:1:1, the three substances were weighed and placed in a agate mortar for dry grinding for 15 mins, so that the three materials were mixed uniformly, then transferred to a glass bottle, added with a proper amount of deionized water, the viscosity of the slurry was adjusted, sealed and continuously stirred at 600 rpm for 6 h to form a uniform slurry, then coated on the rough side of the copper foil in advance by the doctor blade method, the coating thickness was about 200 μm, then transferred into a 60 ℃ oven for pre-drying for 2 h, and then placed in a 100 ℃ vacuum drying oven for drying for 12 h. After natural cooling, the slice machine was used to punch into a circle with a diameter of 14 mm, weighed, sealed and placed in a drying dish for standby.

[0131] Assembly of battery: CR2032 button cell was assembled in a glove box filled with high-purity argon atmosphere, wherein the contents of H2O and O2 were both less than 0.1 ppm. The electrolyte was 1M LiPF6(EC:EMC:DMC=1:1:1vol%) + 5% FEC, and the separator was PP separator.

[0132] Electrochemical performance test analysis: constant current charge / discharge test was carried out at 25 ℃ using LAND CT2001A battery test system, and the charge / discharge voltage window was 0.01-3 V. The electrochemical performance test results are shown in Table 1.

[0133] Table 1 Capacity, initial efficiency and cycle performance test results

[0134]

[0135]

[0136] As can be seen from Table 1, the lithium ion batteries prepared from the silicon-oxygen-based negative electrode material prepared in each embodiment of the application have good long cycle performance and rate performance. In Comparative Example 1, no amorphous carbon shell is formed due to no polyaniline coating, so the cycle performance and rate performance are significantly reduced. In Comparative Example 2, no interstitial layer is formed due to no PDDA coating, so the cycle performance and rate performance are also significantly reduced.

[0137] Further, electrochemical impedance spectroscopy (EIS) test was carried out using PARSTAT PMC-1000 electrochemical workstation to test the interface transfer resistance, charge transfer resistance and total resistance of the silicon-oxygen-based negative electrode material prepared in each embodiment and each comparative example. The electrochemical impedance measurement frequency was 0.01-100 kHz, and the test amplitude was 5 mV. The test results are shown in Table 2.

[0138] Table 2 Resistance test results

[0139]

[0140] As can be seen from Table 2, the resistance of the siloxyl negative electrode material prepared by each embodiment of the present application is significantly lower than that of Comparative Example 1 and Comparative Example 2. It can be seen that the conductivity of the siloxyl negative electrode material provided by the present application is high.

[0141] In addition, the siloxyl negative electrode material prepared by Example 1 was subjected to XRD and XPS detection, and it was found that the XRD test spectrum of the siloxyl negative electrode material has a characteristic diffraction peak of amorphous carbon at at least one of 20-24° and 43°.

[0142] Furthermore, the high-resolution Si 2p spectrum in the XPS test spectrum of the siloxyl negative electrode material provided by the present application can be divided into three characteristic peaks at 104eV, 103eV and 102eV, which correspond to Si 4+ , Si 3+ and Si 2+ , respectively, and the average valence of Si is about 3.01-3.27.

[0143] The XRD spectrum of the siloxyl negative electrode material prepared by Example 1 is shown in Figure 2 .

[0144] Although the present application has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limiting thereof; it should be understood by those skilled in the art that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, this means that all these replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A siloxyl negative electrode material, characterized by, The silicon-oxygen-based negative electrode material includes SiO x / C composite core and an amorphous carbon shell covering the outer surface of the SiO x / C composite core and an amorphous carbon shell covering the outer surface of the SiO x / C composite core and the amorphous carbon shell; Wherein, the SiO x C in the SiO x ; The preparation method of the siloxyl-based negative electrode material comprises the following steps. The organic silane solution and ammonia water are uniformly mixed, then hydrolysis and self-polycondensation reactions are carried out through hydrothermal treatment, then solid-liquid separation is carried out, and organic silicon nanospheres are obtained; after the organic silicon nanospheres are calcined, an inner core is formed, and a C-coated SiO x / C composite material is obtained x . The SiO x After the SiO x / C composite material is uniformly mixed with the polydiallyldimethylammonium chloride solution, solid-liquid separation is performed, and the polydiallyldimethylammonium chloride is coated on the surface of the SiO x / C@PDDA composite material; The SiO x After the SiO x / C@PDDA composite material is uniformly mixed with aniline solution, an oxidizing agent solution is added to the mixture to perform a polymerization reaction, so that polyaniline is formed and coated on the surface of the SiO x / C@PDDA@PANI composite material is obtained through solid-liquid separation. The SiO x The SiO / C@PDDA@PANI composite is calcined, in the process of calcination, the poly diallyl dimethyl ammonium chloride is pyrolyzed to form a void layer, and the polyaniline is carbonized to form an amorphous carbon shell, thereby obtaining the siloxy negative electrode material.

2. The siloxyl negative electrode material of claim 1, wherein The total mass fraction of carbon elements in the siloxyl-based negative electrode material is 20%-35%.

3. The siloxyl-based anode material of claim 1, wherein, The thickness of the void layer is 80-120 nm.

4. The siloxyl-based anode material of claim 1, wherein, The thickness of the amorphous carbon shell is 15-40 nm.

5. The siloxyl-based anode material of claim 1, wherein, The average particle size of the siloxyl-based negative electrode material is 600-1000 nm.

6. The siloxyl negative electrode material according to any one of claims 1 to 5, characterized in that, The initial discharge specific capacity of the siloxyl-based negative electrode material at 0.1 A / g is ≥1100 mAh / g.

7. The siloxyl negative electrode material according to any one of claims 1 to 5, characterized in that, The initial coulombic efficiency of the siloxyl-based negative electrode material at 0.1 A / g is ≥61%.

8. The siloxyl negative electrode material according to any one of claims 1 to 5, characterized in that, The capacity retention rate of the siloxyl-based negative electrode material after 200 cycles at 0.5 A / g is ≥84%.

9. The siloxyl negative electrode material according to any one of claims 1 to 5, characterized in that, The total resistance of the siloxyl-based negative electrode material is ≤98 Ω.

10. The siloxyl-based anode material of claim 1, wherein, The organic silane comprises at least one of mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane and cyanoethyltriethoxysilane.

11. The siloxyl-based anode material of claim 1, wherein, The mass fraction of the organic silane solution is 2%-8%.

12. The siloxyl-based anode material of claim 1, wherein, The mass fraction of the ammonia water is 25%-28%.

13. The siloxyl-based anode material of claim 1, wherein, The volume ratio of the organic silane solution to the ammonia water is 2-4:0.5-2.

5.

14. The siloxyl-based anode material of claim 1, wherein, The temperature of the mixture during the hydrothermal treatment is 65-180 ℃; and the hydrothermal treatment time is 4-24 h.

15. The siloxyl-based anode material of claim 1, wherein, The calcination temperature of the organic silicon nanospheres is 600-1200 ℃, and the calcination time of the organic silicon nanospheres is 0.5-4 h.

16. The siloxyl-based anode material of claim 1, wherein, The SiO x The mass ratio of the SiO / C composite to the polydimethyldiallylammonium chloride in the polydimethyldiallylammonium chloride solution is 0.4-0.5:3-7.

17. The siloxyl-based anode material of claim 1, wherein, The mass fraction of the polydiallyldimethylammonium chloride solution is 3%-7%.

18. The siloxyl-based anode material of claim 1, wherein, The oxidizing agent comprises at least one of ammonium persulfate, manganese dioxide, ferric chloride and benzoyl peroxide.

19. The siloxyl-based anode material of claim 18, wherein, The molar ratio of aniline in the aniline solution to the ammonium persulfate is 0.5-2:

1.

20. The siloxyl-based anode material of claim 1, wherein, During the polymerization, the temperature of the mixture is 0-5 ℃; and the polymerization time is 6-48 h.

21. The siloxyl-based anode material of claim 1, wherein, The SiO x The calcination temperature of the / C@PDDA@PANI composite material is 600-1000℃, and the SiO x The holding time of the calcination of the / C@PDDA@PANI composite material is 0.5-6h.

22. A negative electrode sheet characterized by comprising: The siloxyl-based negative electrode material is prepared by the method.

23. A lithium-ion battery, characterized by, The negative electrode sheet comprises the negative electrode material.

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