CN115207336B - Modified organic silicon coating of lithium ion battery cathode and preparation method thereof - Google Patents
Modified organic silicon coating of lithium ion battery cathode and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the field of new materials and electrochemistry, and particularly relates to a modified organic silicon coating of a lithium ion battery cathode and a preparation method thereof. Using dimethylacetamide as solvent, carboxylating SiO 2 The nano particles and 4' -hydroxybenzo-15-crown-5-ether are mixed and then react under the catalysis of p-toluenesulfonic acid to obtain modified organosilicon spin-coating liquid, and the modified organosilicon spin-coating liquid is coated on the surface of an electrode slice by a spin-coating instrument to finally obtain the electrode slice with a modified organosilicon coating; the prepared spin coating liquid is prepared by SiO 2 The nano particle is taken as a core, and 4' -hydroxybenzo-15-crown-5-ether is grafted to SiO through esterification reaction 2 The reactive sites of the (B) are used for enabling the 4' -hydroxybenzo-15-crown-5-ether to be uniformly coated on SiO 2 Outside, the lithium ion intercalation and deintercalation is effectively ensured, and meanwhile, the existence of the silicon oxide can effectively maintain the higher theoretical capacity of the battery.
Description
Technical Field
The invention belongs to the field of new materials and electrochemistry, and particularly relates to a modified organic silicon coating of a lithium ion battery cathode and a preparation method thereof.
Background
With the development of industries such as electronics, communication, aerospace, automobiles and the like and the improvement of electrification requirements of living goods, the demands of people on miniaturization and high energy of lithium ion batteries are increasingly urgent. The current commercial lithium ion battery cathode material is mainly a graphite cathode material, and is difficult to meet the requirement of portable electronic equipment and electric automobiles on high energy density of the lithium ion battery due to lower theoretical capacity, wherein Si is considered as a candidate material which is most promising to replace graphite, is a second most abundant element in crust because of rich content, has ultrahigh theoretical capacity, and is about 10 times of the theoretical capacity of the current commercial graphite cathode material. However, since silicon is a semiconductor and its electron conductivity is slightly poor, it is thought that adding a small amount of silicon material to the existing pure graphite negative electrode system increases the capacity without affecting the electron transport properties of the electrode. However, due to the nature of the electron state distribution of graphite and silicon materials, lithium ions of the graphite-doped silicon negative electrode system are preferentially intercalated into a silicon lattice to form a lithium-silicon alloy when lithium is intercalated (corresponding to the charging process of a battery), and then the graphite lattice is intercalated into the lithium-carbon alloy. Therefore, silicon has serious volume effect in the process of completely inserting and extracting lithium, the volume change rate is about 400 percent, the electrode material is easy to pulverize and separate from the current collector, so that the silicon material loses electrochemical activity in the early cycle stage of the battery, and therefore, how to inhibit the volume expansion effect of the silicon-based electrode in the cycle process becomes the object of research.
The Chinese patent with application number 201510945346.3 discloses a matched silicon-carbon negative electrode lithium ion battery electrolyte and a silicon-carbon negative electrode lithium ion battery, wherein the lithium ion battery electrolyte consists of a non-aqueous organic solvent, lithium salt and an additive, and the additive comprises fluoroethylene carbonate, ethylene sulfite and a borate compound with an M-type structure. Through the synergistic effect generated by the combined use of the three additives, the SEI film formed on the surface of the electrode is more stable and compact, and the physical and chemical structural stability of the surface of the silicon-carbon negative electrode is improved, so that the battery has better cycle performance and high-temperature storage performance, and simultaneously, the gas production of the battery is inhibited. In the scheme, the SEI film can be normally generated in the circulating process by adding the corresponding film forming substances in the electrolyte, and the expansion of the electrode is not effectively inhibited.
The Chinese patent with application number 201910147026.1 discloses a graphene-silicon-based composite negative electrode material for a lithium ion battery and a preparation method thereof, wherein nano silicon, graphene and graphite are mixed, and are dispersed and heated with an organic carbon source in an organic solvent, then dried and granulated, and heated until the organic carbon source is completely melted and carbonized at high temperature, so that the graphene-silicon-based composite negative electrode material coated with organic pyrolysis carbon is obtained, the deformation stress of the silicon is effectively relieved, and meanwhile, the graphene-silicon-based composite negative electrode material has excellent electrical conductivity and thermal conductivity. However, graphene is difficult to completely disperse uniformly in the use process.
Disclosure of Invention
In order to solve the problems, the invention provides a modified organic silicon coating of a lithium ion battery cathode and a preparation method thereof, which uses dimethylacetamide as a solvent and carboxylates SiO 2 Nanoparticles and 4' -hydroxyAnd mixing the base benzo-15-crown-5-ether, reacting under the catalysis of p-toluenesulfonic acid to obtain modified organosilicon spin-coating liquid, and coating the modified organosilicon spin-coating liquid on the surface of the electrode slice by using a spin-coating instrument to finally obtain the electrode slice with the modified organosilicon coating.
The technical scheme adopted by the invention for achieving the purpose is as follows:
the preparation method of the modified organic silicon coating for the lithium ion battery cathode comprises the steps of coating modified organic silicon spin-coating liquid on the surface of an electrode plate through a spin-coating instrument;
the modified organic silicon spin coating liquid comprises the following components: using dimethylacetamide as solvent, carboxylating SiO 2 The nano particles and 4' -hydroxybenzo-15-crown-5-ether are mixed and then reacted under the catalysis of p-toluenesulfonic acid to obtain the nano-particles.
Further, the preparation method of the modified organic silicon spin coating liquid comprises the following steps:
s1, adding silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding vinyl triethoxysilane and triethylamine, heating and stirring for full reaction, cooling to room temperature after the reaction is finished, centrifuging to remove a solvent, flushing with ethanol, centrifuging, and freeze-drying to obtain a SiO2 nano particle carrier with the surface modified by the vinyl triethoxysilane;
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Adding acidic potassium permanganate solution after the nanoparticle carrier is uniformly dispersed, heating and stirring, centrifuging after the reaction is finished, flushing with NaCl solution, centrifuging, and freeze-drying to obtain carboxylated SiO 2 A nanoparticle;
s3, adding 4 '-aminobenzo-15-crown-5-ether and sodium nitrite into dilute sulfuric acid, stirring at a low temperature, fully reacting, adding dilute sulfuric acid again, and heating and refluxing to obtain 4' -hydroxybenzoic-15-crown-5-ether;
s4, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 And (3) after the nano particles are uniformly dispersed, adding the 4' -hydroxybenzo-15-crown-5-ether and p-toluenesulfonic acid obtained in the step (S3), heating for reaction, and then performing reduced pressure distillation to obtain the modified organosilicon spin-coating liquid.
The invention has the following beneficial effects:
the spin coating liquid prepared by the invention adopts SiO 2 The nano particle is taken as a core, and 4' -hydroxybenzo-15-crown-5-ether is grafted to SiO through esterification reaction 2 The reactive sites of the (B) are used for enabling the 4' -hydroxybenzo-15-crown-5-ether to be uniformly coated on SiO 2 Outside, effectively ensures the intercalation and deintercalation of lithium ions, simultaneously the existence of silicon oxide can effectively maintain the battery to have higher theoretical capacity, and the electrode is coated on SiO if expanding in the circulation process 2 The outer polymer has a ring structure which forms a net-like structure to limit the expansion of the electrode, thereby effectively inhibiting the further expansion of the electrode.
Drawings
FIG. 1 is a FESEM image of the surface of an electrode sheet containing a modified silicone coating prepared in example 3 of the present invention;
fig. 2 is a graph showing the first charge and discharge of the battery prepared in example 3 of the present invention;
fig. 3 is a cycle performance chart of the battery prepared in example 3 according to the present invention.
Detailed Description
The following description of the technical solutions in the embodiments of the present application will be made clearly and completely in connection with the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
The silica nanoparticles used in the present invention were purchased from the company An Tepu Narco Corp.
Example 1
The preparation method of the modified organic silicon coating of the lithium ion battery cathode comprises the steps of coating modified organic silicon spin coating liquid on the surface of an electrode plate through a spin coating instrument;
the modified organic silicon spin coating liquid comprises the following components: using dimethylacetamide as solvent, carboxylating SiO 2 Nanoparticles and 4' -hydroxy groupsMixing benzo-15-crown-5-ether and then reacting under the catalysis of p-toluenesulfonic acid.
The specific preparation method of the modified organosilicon spin coating liquid comprises the following steps:
s1, adding 8 parts by weight of silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding 30 parts by weight of vinyltriethoxysilane and 3 parts by weight of triethylamine, wherein the triethylamine is used as an accelerator, heating to 110 ℃ and stirring to fully react for 6 hours, after the reaction is finished, closing heating and cooling to room temperature, centrifuging to remove the solvent, washing with ethanol, centrifuging, and freeze-drying to obtain SiO with the surface modified by vinyltriethoxysilane 2 A nanoparticle carrier; the preparation method of the anhydrous toluene comprises the following steps: adding toluene and diphenyl ketone into the device, wherein the diphenyl ketone is blue under absolute anhydrous condition, cutting sodium blocks with surface kerosene removed into small blocks, adding the small blocks into toluene, replacing air in the device with nitrogen, heating and refluxing for 2-3h, turning blue, and distilling and collecting, wherein the reaction process is shown as follows:
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Dispersing nanoparticle carrier by ultrasonic method for 20min, adding 2 weight parts of acidic potassium permanganate solution after uniform dispersion, heating to 40deg.C, stirring, centrifuging after reaction, washing with 0.1M NaCl solution, centrifuging, and lyophilizing to obtain carboxylated SiO 2 Nanoparticles, the reaction process of this step is schematically shown below:
s3, adding 40 parts by weight of 4 '-aminobenzo-15-crown-5-ether and 5 parts by weight of sodium nitrite into dilute sulfuric acid, stirring at a low temperature of 0 ℃, adding 0.2M dilute sulfuric acid again into the mixture after full reaction, and heating and refluxing to obtain 4' -hydroxybenzo-15-crown-5-ether, wherein the reaction process is schematically as follows:
s4, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 After the nano particles are uniformly dispersed, adding the 4' -hydroxybenzo-15-crown-5-ether and p-toluenesulfonic acid obtained in the step S3, heating to 85 ℃ for reaction, and then performing reduced pressure distillation to obtain modified organosilicon spin-coating liquid, wherein the reaction process of the step is shown as follows:
in the preparation process of the electrode slice, carbon black is adopted as a conductive agent, polyvinylidene fluoride is adopted as a binder, active substances, carbon black and polyvinylidene fluoride are weighed and mixed according to a mass ratio of 8:1:1, fully ground, N-methyl pyrrolidone is added in the grinding process and uniformly mixed to obtain slurry, the obtained slurry is coated on a copper foil, the copper foil is dried in vacuum and then stamped into a round electrode slice, the prepared modified organosilicon spin-coating liquid is coated on the prepared round electrode slice in a glove box through a spin-coating instrument, and the electrode slice containing the modified organosilicon coating is obtained, wherein spin-coating parameters are as follows: 600r/min,60s;1200/min,120s; wherein the active substance is a silicon carbon negative electrode material, and comes from the Hemsl of novel carbon materials of the Emblica.
Lithium sheets are used as counter electrodes; in 1M LiPF 6 DMC+DEC+EC (volume ratio 1:1:1) as electrolyte; celgard 2400 is a septum with a diameter of 19mm; the used batteries are CR2032 type button batteries; battery was assembled in a glove box, operating environment within the glove box: the argon atmosphere and the water and oxygen content are all lower than 0.1ppm.
Example 2
Compared with the example 1, the preparation parameters of the modified organosilicon spin coating liquid are different, and the rest are unchanged, specifically: in the step S1, the heating temperature is 125 ℃, and the heating reaction is carried out for 4 hours; in the step S2, the ultrasonic duration is 30min, and the heating temperature is 50 ℃; in the step S3, the low-temperature reaction temperature is 10 ℃; the heating temperature is 100℃in step S4.
The remainder of the preparation and testing process is described in example 1.
Example 3
Compared with the example 1, the preparation parameters of the modified organosilicon spin coating liquid are different, and the rest are unchanged, specifically: in the step S1, the heating temperature is 115 ℃, and the heating reaction is carried out for 5 hours; in the step S2, the ultrasonic duration is 30min, and the heating temperature is 45 ℃; in the step S3, the low-temperature reaction temperature is 5 ℃; the heating temperature is 90℃in step S4.
The remainder of the preparation and testing process is described in example 1.
Comparative example 1
Compared with the embodiment 3, in the preparation process of the electrode slice, the modified organic silicon spin coating liquid is not coated on the electrode slice, namely, the prepared electrode slice is free of the modified organic silicon coating.
The preparation method of the electrode slice comprises the following steps: in the preparation process of the electrode slice, carbon black is adopted as a conductive agent, polyvinylidene fluoride is adopted as a binder, active substances, carbon black and polyvinylidene fluoride are weighed and mixed according to a mass ratio of 8:1:1, the mixture is sufficiently ground, N-methyl pyrrolidone is added in the grinding process and uniformly mixed to obtain slurry, the obtained slurry is coated on a copper foil, the copper foil is dried in vacuum and then punched into a round electrode slice, and the round electrode slice is dried in vacuum for standby.
The remainder of the preparation and testing process is described in example 3.
Comparative example 2
In comparison with example 3, the modified silicone spin coating liquid was prepared by using SiO whose surface was modified with vinyltriethoxysilane 2 The nano particles are used as modified organosilicon spin coating liquid.
The specific preparation method of the modified organosilicon spin coating liquid comprises the following steps: adding 8 parts by weight of silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, adding 30 parts by weight of vinyltriethoxysilane and 3 parts by weight of triethylamine as an accelerator, heating to 115 ℃ and stirring for fully reacting for 5 hours, closing heating and cooling to room temperature after the reaction is finished, centrifuging to remove the solvent, flushing with ethanol, centrifuging, and freeze-drying to obtain the tableSiO modified by vinyl triethoxy silane 2 Nanoparticle carriers.
The remainder of the preparation and testing process is described in example 3.
Comparative example 3
In contrast to example 3, the modified silicone spin coating was prepared by replacing 4 '-aminobenzo-15-crown-5-ether with 4' -aminobenzo-18-crown-6.
The specific preparation method of the modified organosilicon spin coating liquid comprises the following steps:
s1, adding 8 parts by weight of silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding 30 parts by weight of vinyltriethoxysilane and 3 parts by weight of triethylamine, wherein the triethylamine is used as an accelerator, heating to 115 ℃ and stirring to fully react for 5 hours, after the reaction is finished, closing heating and cooling to room temperature, centrifuging to remove the solvent, washing with ethanol, centrifuging, and freeze-drying to obtain SiO with the surface modified by vinyltriethoxysilane 2 A nanoparticle carrier; the preparation method of the anhydrous toluene comprises the following steps: adding toluene and diphenyl ketone into the device, wherein the diphenyl ketone is blue under absolute anhydrous condition as an indicator, cutting sodium blocks with surface kerosene removed into small blocks, adding the small blocks into toluene, replacing air in the device with nitrogen, heating and refluxing for 2-3h, turning blue, and distilling and collecting;
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Dispersing nanoparticle carrier by ultrasonic method for 30min, adding 2 weight parts of acidic potassium permanganate solution after uniform dispersion, heating to 45deg.C, stirring, centrifuging after reaction, washing with 0.1M NaCl solution, centrifuging, and lyophilizing to obtain carboxylated SiO 2 A nanoparticle;
s3, adding 45 parts by weight of 4 '-aminobenzo-18-crown-6 and 6 parts by weight of sodium nitrite into dilute sulfuric acid, stirring at a low temperature of 5 ℃, adding 0.2M dilute sulfuric acid again after full reaction, and heating and refluxing to obtain 4' -hydroxybenzo-18-crown-6;
s4, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 After the nano particles are uniformly dispersed, adding the step S3 to obtainAnd (2) heating the 4' -hydroxybenzo-18-crown-6 and p-toluenesulfonic acid to 90 ℃ for reaction, and then carrying out reduced pressure distillation to obtain the modified organosilicon spin-coating liquid.
The remainder of the preparation and testing process is described in example 3.
Example 4
In contrast to example 3, the modified silicone spin coating was prepared by replacing 4' -aminobenzo-15-crown-5-ether with benzo-12-crown-4-ether.
The specific preparation method of the modified organosilicon spin coating liquid comprises the following steps:
s1, adding 8 parts by weight of silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding 30 parts by weight of vinyltriethoxysilane and 3 parts by weight of triethylamine, wherein the triethylamine is used as an accelerator, heating to 115 ℃ and stirring to fully react for 5 hours, after the reaction is finished, closing heating and cooling to room temperature, centrifuging to remove the solvent, washing with ethanol, centrifuging, and freeze-drying to obtain SiO with the surface modified by vinyltriethoxysilane 2 A nanoparticle carrier; the preparation method of the anhydrous toluene comprises the following steps: adding toluene and diphenyl ketone into the device, wherein the diphenyl ketone is blue under absolute anhydrous condition as an indicator, cutting sodium blocks with surface kerosene removed into small blocks, adding the small blocks into toluene, replacing air in the device with nitrogen, heating and refluxing for 2-3h, turning blue, and distilling and collecting;
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Dispersing nanoparticle carrier by ultrasonic method for 30min, adding 2 weight parts of acidic potassium permanganate solution after uniform dispersion, heating to 45deg.C, stirring, centrifuging after reaction, washing with 0.1M NaCl solution, centrifuging, and lyophilizing to obtain carboxylated SiO 2 A nanoparticle;
s3, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 After the nano particles are uniformly dispersed, adding benzo-12-crown-4-ether, heating to 90 ℃ and stirring for 40min to obtain the modified organosilicon spin-coating liquid.
Example 5
Compared with example 3, the preparation method of the modified organosilicon spin coating liquid is differentDirectly carboxylating SiO during the preparation process 2 Mixed with 4' -hydroxybenzo-15-crown-5-ether.
The specific preparation method of the modified organosilicon spin coating liquid comprises the following steps:
s1, adding 8 parts by weight of silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding 30 parts by weight of vinyltriethoxysilane and 3 parts by weight of triethylamine, wherein the triethylamine is used as an accelerator, heating to 115 ℃ and stirring to fully react for 5 hours, after the reaction is finished, closing heating and cooling to room temperature, centrifuging to remove the solvent, washing with ethanol, centrifuging, and freeze-drying to obtain SiO with the surface modified by vinyltriethoxysilane 2 A nanoparticle carrier; the preparation method of the anhydrous toluene comprises the following steps: adding toluene and diphenyl ketone into the device, wherein the diphenyl ketone is blue under absolute anhydrous condition as an indicator, cutting sodium blocks with surface kerosene removed into small blocks, adding the small blocks into toluene, replacing air in the device with nitrogen, heating and refluxing for 2-3h, turning blue, and distilling and collecting;
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Dispersing nanoparticle carrier by ultrasonic method for 30min, adding 2 weight parts of acidic potassium permanganate solution after uniform dispersion, heating to 45deg.C, stirring, centrifuging after reaction, washing with 0.1M NaCl solution, centrifuging, and lyophilizing to obtain carboxylated SiO 2 A nanoparticle;
s3, adding 40 parts by weight of 4 '-aminobenzo-15-crown-5-ether and 5 parts by weight of sodium nitrite into dilute sulfuric acid, stirring at a low temperature of 5 ℃, adding 0.2M dilute sulfuric acid again after full reaction, and heating and refluxing to obtain 4' -hydroxybenzo-15-crown-5-ether;
s4, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 And (3) uniformly mixing the nano particles with the 4' -hydroxybenzo-15-crown-5-ether obtained in the step (S3).
Correlation test:
1. the electrode sheet containing the modified organic silicon coating prepared in example 3 is subjected to field emission scanning electron microscope characterization, the working voltage is 5kV, and the test results are shown in figure 1. The figure shows that the surface of the electrode is flat and smooth after the modified organic silicon is coated, which is favorable for the uniform deposition of lithium ions.
2. The batteries assembled in examples 1 to 3 and comparative examples 1 to 5 were subjected to constant current charge and discharge tests using a blue electric test device (LanD CT2001A, wuhan City blue electric electronics Co., ltd.) at a current density of 0.1A/g and a charge and discharge voltage range of 0.01 to 2.5V, and the test results of the first discharge specific capacity and the charge specific capacity and the discharge specific capacity after 100 cycles are shown in Table 1.
TABLE 1
From the test results of the table, it can be found that, in examples 1-3 and comparative examples 1-5, the first discharge specific capacity and the first charge specific capacity of example 3 are the highest, and after 100 cycles, the discharge specific capacity of the battery assembled in example 3 can also reach 716.5mAh/g, i.e., the battery prepared in example 3 still has a higher discharge specific capacity after long-time cycles, and has good cycle stability. From the test data of example 3 and comparative example 1, it can be found that the test performance is greatly improved after the modified organosilicon coating is modified, and it is possible that the existence of the modified organosilicon coating can effectively prevent the volume expansion of the silicon-based anode material and reduce the damage to the formed SEI film in the charge and discharge process; comparative example 3 and comparative examples 3-4, it was found that carboxylated SiO was prepared using 4' -aminobenzo-15-crown-5-ether 2 The battery material obtained by modification has good cycle performance, probably because the cavity structure contained in the 4' -aminobenzo-15-crown-5-ether is beneficial to Li in the charge and discharge process + And simultaneously can effectively prevent the silicon-based material from expanding in the circulation process.
3. The assembled battery of example 3 was subjected to constant current charge and discharge test with a current density of 0.1A/g and a charge and discharge voltage in the range of 0.01 to 2.5V, wherein the initial charge and discharge curve is shown in fig. 2, and the battery cycle performance is shown in fig. 3. As can be seen from fig. 3, the first-turn discharge specific capacity reaches 1415.8mAh/g, and after 5-turn circulation, the discharge specific capacity is flattened, which is probably due to the fact that the battery is in an activation stage during an initial circulation, the discharge specific capacity is flattened after the SEI film is formed, and the discharge capacity is still maintained at a higher level after long-time circulation, and the situation that the capacity is suddenly reduced due to the expansion of the electrode does not occur, so that it can be shown that the modified organosilicon coating prepared after long-time circulation effectively protects the electrode.
In the lithium ion battery cathode material, the carbon material is most widely applied, but the theoretical specific capacity is lower, and the requirement of a lithium ion battery with high energy density is difficult to meet, wherein the silicon has ultrahigh theoretical capacity and attracts attention, however, the silicon is severely expanded in volume in the charge and discharge process and is extremely easy to cause the damage of an electrode structure. In the invention, the vinyl triethoxysilane is utilized to carry out preliminary modification on the silicon dioxide nano particles to obtain SiO with the surface modified by the vinyl triethoxysilane 2 A nanoparticle carrier; oxidizing the carbon-carbon double bond into carboxyl by using acidic potassium permanganate to obtain carboxylated SiO 2 A nanoparticle; meanwhile, diazotizing 4 '-aminobenzo-15-crown-5-ether by utilizing sodium nitrite, and heating and hydrolyzing under an acidic condition to obtain 4' -hydroxybenzo-15-crown-5-ether; and then the obtained carboxylated SiO 2 The nano particles and 4' -hydroxybenzo-15-crown-5-ether are mixed and subjected to esterification reaction under the catalysis of p-toluenesulfonic acid, and finally the modified organosilicon spin-coating liquid required by the invention is obtained. In the modified organosilicon spin coating liquid constructed by the invention, siO is used as the raw material 2 The nanometer particle is used as a core, a layer of polymer is wrapped outside, so that the polymer can be evenly wrapped on the SiO 2 Around the nanoparticle, to SiO 2 Carboxylation is carried out to form corresponding reactive sites, and 4 '-aminobenzo-15-crown-5-ether is hydroxylated, and 4' -hydroxybenzo-15-crown-5-ether is grafted to SiO through esterification 2 Such that the 4' -hydroxybenzo-15-crownThe 5-ether can be uniformly coated on SiO 2 Outside, due to the existence of the hollow structure in the 4' -hydroxybenzo-15-crown-5-ether, the intercalation and deintercalation of lithium ions can be ensured, and meanwhile, the existence of silicon oxide can effectively maintain the higher theoretical capacity of the battery; in the battery cycle process, due to the special volume expansion effect of the silicon-based anode material, an SEI film formed in the process of intercalation and deintercalation of lithium ions is continuously destroyed and stripped due to the expansion of the volume of an electrode plate, and when a new electrode material is exposed in electrolyte, a new SEI film is formed again, so that the cycle is performed, on one hand, the electrolyte is seriously consumed, and on the other hand, the SEI film gradually accumulates and thickens, so that the battery performance is rapidly deteriorated. In the present invention, since 4' -hydroxybenzo-15-crown-5-ether exists in SiO 2 If the electrode expands in the circulation process, the ring structure of the electrode can form a similar net structure to limit the further expansion of the electrode, so that the further expansion of the electrode can be effectively restrained, and the data in table 1 show that the discharge specific capacity of the electrode can still reach a higher level after 100 circles of circulation after the modified organosilicon coating is coated, which indicates that the expansion of the electrode is effectively restrained in the circulation process, thereby ensuring the circulation performance of the battery.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. The preparation method of the modified organic silicon coating of the lithium ion battery cathode is characterized in that the modified organic silicon coating is prepared by coating modified organic silicon spin-coating liquid on the surface of an electrode slice through a spin-coating instrument;
the modified organic silicon spin coating liquid comprises the following components: using dimethylacetamide as solvent, carboxylating SiO 2 The nano particles and 4' -hydroxybenzo-15-crown-5-ether are mixed and then react under the catalysis of p-toluenesulfonic acid to obtain the nano-particles;
the preparation method of the modified organosilicon spin coating liquid comprises the following steps:
s1, adding silicon dioxide nano particles into anhydrous toluene, uniformly dispersing, then adding vinyltriethoxysilane and triethylamine, heating and stirring for full reaction, cooling to room temperature after the reaction is finished, centrifuging to remove a solvent, washing with ethanol, centrifuging, and freeze-drying to obtain SiO with the surface modified by vinyltriethoxysilane 2 A nanoparticle carrier; wherein the heating temperature is 110-125 ℃;
s2, adding the modified SiO obtained in the step S1 into ethanol solution 2 Adding acidic potassium permanganate solution after the nanoparticle carrier is uniformly dispersed, heating and stirring, centrifuging after the reaction is finished, flushing with NaCl solution, centrifuging, and freeze-drying to obtain carboxylated SiO 2 A nanoparticle;
s3, adding 4 '-aminobenzo-15-crown-5-ether and sodium nitrite into dilute sulfuric acid, stirring at a low temperature, fully reacting, adding dilute sulfuric acid again, and heating and refluxing to obtain 4' -hydroxybenzoic-15-crown-5-ether; wherein the low temperature is 0-10deg.C;
s4, adding the carboxylated SiO obtained in the step S2 into dimethylacetamide 2 After the nano particles are uniformly dispersed, adding the 4' -hydroxybenzo-15-crown-5-ether and p-toluenesulfonic acid obtained in the step S3, heating for reaction, and then performing reduced pressure distillation to obtain modified organosilicon spin-coating liquid; wherein the heating temperature is 85-100deg.C;
in step S1, the preparation method of the anhydrous toluene includes: adding toluene and diphenyl ketone into the device, adding sodium blocks with surface kerosene removed into toluene, replacing air in the device with nitrogen, heating and refluxing, turning blue, and collecting by distillation;
in step S2 and step S4, dispersion is performed by using an ultrasonic method, and the ultrasonic time is: 20-30min; the NaCl solution concentration was 0.1M.
2. The use of a modified silicone coating for a lithium ion battery anode according to claim 1 in the preparation of a lithium ion battery anode.
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