Composite-coated nano-tin negative electrode material and preparation method and use thereof
11362328 · 2022-06-14
Assignee
Inventors
Cpc classification
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H01M10/0525
ELECTRICITY
H01M4/0471
ELECTRICITY
H01M4/628
ELECTRICITY
International classification
H01M4/36
ELECTRICITY
Abstract
The invention provides a composite-coated nano-tin negative electrode material, which comprises a tin-based nanomaterial, a nano-copper layer coated on the surface of the tin-based nanomaterial and a conductive protective layer coated on the surface of the nano-copper layer. The nano-copper layer can inhibit the volume expansion of nano-tin, keep the nano-tin material from cracking, avoid direct contact between nano-tin and electrolyte to form stable SEI and increase the conductivity of the electrode. Coating a conductive layer on the surface of the nano-copper layer can effectively inhibit the oxidation of nano-copper, thus improving its electrochemical performance. The composite-coated nano-tin negative electrode material according to the invention is used as a negative electrode material of a lithium-ion battery, has excellent electrochemical performance, and has potential application prospects in portable mobile devices and electric vehicles.
Claims
1. A composite-coated nanosized-tin negative electrode material, comprising: a tin-based nanomaterial, a copper layer coated on the surface of the tin-based nanomaterial, and a conductive protective layer coated on the surface of the copper layer, wherein a carbon layer is further provided between the tin-based nanosized material and the copper layer, and wherein the copper layer is a layer of nanosized copper particles or a copper film having a nanometer thickness.
2. The nanosized-tin negative electrode material according to claim 1, wherein the tin-based nanosized material is one or more of tin nanosized material, tin-carbon nanosized material or tin alloy nanosized material.
3. The nanosized-tin negative electrode material according to claim 2, wherein in the tin-carbon nanosized material and the tin alloy nanosized material, the weight percentage content of tin is 2%-70%.
4. The nanosized-tin composite negative electrode material according to claim 1, wherein the particle size of the copper particles is 0.5-100 nm; and the thickness of the copper film is 0.5-100 nm.
5. The nanosized-tin composite negative electrode material according to claim 1, wherein the weight of the copper layer accounts for 2-70 wt % of the nanosized-tin-based negative electrode material; and the weight of the conductive protective layer accounts for 0.1-20 wt % of the nanosized-tin-based negative electrode material.
6. A method for preparing a nanosized-tin negative electrode material according to claim 1, comprising the steps of: (1) adding a tin-based nanosized material into a solvent to obtain a suspension, and then ultrasonically dispersing the suspension; (2) adding a copper plating agent to the ultrasonically dispersed suspension, adding a reducing agent to perform chemical copper plating, and filtrating, washing and drying the same in a vacuum oven to obtain a copper-coated tin-based nanosized composite material; and (3) coating a conductive protective layer on the surface of the copper-coated tin-based nanosized composite material wherein the method further comprises coating a carbon layer on the surface of the nanosized-tin-based material before step (1).
7. The method according to claim 6, wherein the method further comprises: (4) treating the composite material obtained in step (3) with heat to cure it.
8. The method according to claim 6, wherein the solvent in step (1) is one or more of water, methanol, ethanol, propanol, isopropanol, butanol, and ethylene glycol.
9. The method according to claim 6, wherein the composition of the copper plating agent in step (2) comprises one or more of tetrakis(acetonitrile)copper(I) hexafluorophosphate, CuCl.sub.2, CuCl, CuC.sub.2O.sub.4, Cu(CH.sub.3COO).sub.2, CuSO.sub.4 or Cu(NO.sub.3).sub.2: 1-20 g.Math.L.sup.−1; potassium sodium tartrate: 5-100 g.Math.L.sup.−1; ethylenediaminetetraacetic acid or ammonia water: 5-100 g.Math.L.sup.−1; 2,2-bipyridine: 1-50 mg.Math.L.sup.−1; and the reducing agent is sodium borohydride, sodium hypophosphite, borane or formaldehyde, and the concentration of the reducing agent is 1-20 g.Math.L.sup.−1.
10. The method according to claim 6, wherein the conductive protective layer in step (3) is one or more of carbon, polyaniline, polypyrrole, polythiophene, and polyacetylene.
11. A negative electrode which comprises a current collector and a negative electrode material, a conductive additive and a binder loaded on the current collector, wherein the negative electrode material is a negative electrode material of claim 1 or a negative electrode material prepared by a method according to claim 6.
12. A lithium-ion battery which comprises a battery shell, an electrode assembly, and an electrolyte, the electrode assembly and electrolyte being sealed in the battery shell, and the electrode assembly comprising a positive electrode, a separator, and a negative electrode, wherein the negative electrode is a negative electrode of claim 11.
13. The nanosized-tin negative electrode material according to claim 2, wherein the tin nanosized-material, the tin-carbon nanosized-material or the tin alloy nanosized-material comprise nanoparticles, nanowires, or nanosheets.
14. The nanosized-tin negative electrode material according to claim 13, wherein the nanoparticles have a particle size of 5-1000 nm; the nanowire has a length of 10-5000 nm, and a diameter of 5-1000 nm; and the nanosheet has a length and a width of 10-5000 nm and a thickness of 1-500 nm.
15. The nanosized-tin negative electrode material according to claim 2, wherein the thickness of the copper layer is 0.5-100 nm, and the thickness of the conductive layer is 1-100 nm.
16. The nanosized-tin negative electrode material according to claim 3, wherein the tin alloy is selected from one or more of tin-aluminum alloy, tin-tin alloy, tin-silver alloy, and tin-magnesium alloy.
17. The nanosized-tin negative electrode material according to claim 4, wherein the particle size of the copper particles is 1-50 nm; and the thickness of the copper coating layer is 1-50 nm.
18. The nanosized-tin negative electrode material according to claim 5, wherein the weight of the copper layer accounts for 10-30 wt % of the nanosized-tin-based negative electrode material; and the weight of the conductive protective layer accounts for 1-10 wt % of the nanosized-tin-based negative electrode material.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:
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BEST MODE FOR CARRYING OUT THE INVENTION
(15) The present invention will be described in further detail below with reference to specific embodiments. The examples given are only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention.
Example 1
(16) (1) 2 g of tin powder with a particle size of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(17) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(18) (3) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min, to obtain the composite-coated nano-tin negative electrode material.
Example 2
(19) (1) 2.5 g of tin dioxide powder with a particle size of 80 nm was a weighted and placed in a tube furnace and coated with carbon by C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 50 sccm, the heating rate was 50° C./min, and the temperature was maintained at 600° C. for 30 min;
(20) (2) The carbon-coated tin-based material is immersed into 5% hydrogen peroxide for 10 minutes, then it was filtered and oven dried, then it was placed in 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(21) (3) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g of sodium borohydride was added to 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin solution at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(22) (4) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min.
Example 3
(23) (1) 2 g of tin powder with a particle size of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(24) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material;
(25) (3) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min, to obtain the composite-coated nano-tin negative electrode material; and
(26) (4) The carbon-coated nano-copper-coated nano-tin composite material was placed in an ultra-high-speed microwave heating furnace protected by nitrogen and microwave-heated to 300° C., and then cooled to obtain a double layer composite-coated nano-silicon negative electrode material.
Example 4
(27) (1) 2 g of tin powder with a particle size of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(28) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(29) (3) The nano-copper-coated nano-tin composite material was placed in a 200 ml reaction kettle, then 1 g toluene and 0.2 g Ti(OBu).sub.4-AlEt.sub.3 catalyst were added, then the reaction kettle was filled with acetylene, and the reaction kettle was placed in a −78° C. oven to react for 10 hours. After completion of the reaction, 100 ml of 10% hydrochloric acid was added to the mixture to destroy the catalyst, and finally it was filtrated, washed, and oven dried to obtain the composite material with polyacetylene coated on the surface of the copper layer.
Example 5
(30) (1) 2 g of tin powder with a particle size of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(31) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(32) (3) The nano-copper-coated nano-tin composite material and 2 ml aniline were added into 50 ml deionized water and ultrasonically mixed, then 0.5 g of ammonium persulfate was added to the mixed solution, and after reacting for 2 hours, the mixture was filtrated, washed, and oven dried to obtain a composite material with polyaniline coated on the surface of the copper layer.
Example 6
(33) (1) 1 g of tin-carbon powder (Sn:C=1:1) with a particle size of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(34) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution; 2 g CuSO.sub.4, 20 g potassium sodium tartrate, 20 g ethylenediaminetetraacetic acid, and 10 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 1 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(35) (3) The nano-copper-coated nano-tin-carbon composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 380° C. for 90 min, to obtain the composite-coated nano-tin-carbon negative electrode material.
Example 7
(36) (1) 1.5 g of tin-aluminum alloy (Sn:Al=95:5) with a particle size of 100 nm was weighted and added into 1000 ml water, then 10 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(37) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(38) (3) The nano-copper-coated nano-tin-aluminum composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 380° C. for 90 min, to obtain the composite-coated nano-tin-aluminum negative electrode material.
Example 8
(39) (1) 2 g of tin nanowires with a length of 1000 nm and a diameter of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(40) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(41) (3) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min, to obtain the composite-coated nano-tin negative electrode material.
Example 9
(42) (1) 2 g of tin nanowires with a length of 1000 nm and a diameter of 100 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(43) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(44) (3) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min, to obtain the composite-coated nano-tin negative electrode material.
Example 10
(45) (1) 2 g of tin nanosheets with a length of 200 nm, a width of 100 nm and a thickness of 20 nm was weighted and added into 1000 ml water, then 20 ml of ethanol was added to obtain a nano-tin suspension, and then the nano-tin suspension was placed in an ultrasonic machine and subjected to ultrasonic treatment for 2 h;
(46) (2) The ultrasonic dispersed nano-tin suspension was continuously stirred with a magnetic stirrer while nitrogen gas was continuously introduced into the solution. Then a copper plating agent having the following composition was added to the solution: 1 g CuSO.sub.4, 10 g potassium sodium tartrate, 10 g ethylenediaminetetraacetic acid, and 5 mg 2,2-bipyridine, and then sodium hydroxide was added to adjust pH to 10. Then 0.6 g sodium borohydride was added into 200 ml water, sodium hydroxide was also added to adjust pH to 10, and then it was added dropwise into the nano-tin suspension at a rate of about 30 drops/min, and finally it was filtered, washed with a copper protective agent being added, and dried in vacuum oven to obtain the nano-copper-coated nano-tin composite material; and
(47) (3) The nano-copper-coated nano-tin composite material was placed in a tube furnace and coated with carbon using C.sub.2H.sub.2 in nitrogen, the N.sub.2 flow rate was 300 sccm, the C.sub.2H.sub.2 flow rate was 100 sccm, the heating rate was 50° C./min, and the temperature was maintained at 300° C. for 90 min, to obtain the composite-coated nano-tin negative electrode material.
(48) The electrical properties of the negative electrode materials prepared in Examples 1-7 were tested. The testing steps were as follows:
(49) The prepared composite-coated nano-tin negative electrode material was uniformly mixed with super-p (conductive carbon black) and sodium alginate at a mass ratio of 6:3:1 by a mixer, then it was uniformly coated on a copper foil, placed in a vacuum drying oven, vacuum-dried at 120° C. for 12 hours, and taken out and prepared into an electrode plate.
(50) The lithium plate was used as a counter electrode, the electrolyte was 1 mol/l LiPF.sub.6 in EC+DMC (1:1 by volume), and a PP/PE/PP three-layer film was used as a separator (purchased from Celgard Corporation, USA), a CR2032 button battery was assembled in an argon-filled glove box.
(51) The electrochemical properties test of the assembled battery was carried out using a Land tester (purchased from Wuhan LAND Electronics Co. Ltd.), with cycling for one cycle at a rate of 0.05 C and then cycling for another 49 cycles at a rate of 0.2 C, the charge-discharge cutoff voltage ranges from 0.01V to 1.0V.
Comparative Example 1
(52) According to the above method for preparing the button battery, tin particles with a particle size of 100 nm were directly prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
Comparative Example 2
(53) According to the above method for preparing a button battery, the only copper-coated tin nanoparticles prepared in the step (2) of Example 1 were prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
Comparative Example 3
(54) According to the above method for preparing a button battery, a tin nanowire having a length of 1000 nm and a diameter of 100 nm was prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
Comparative Example 4
(55) According to the above method for preparing a button battery, a tin nanosheet having a length of 200 nm, a width of 100 nm and a thickness of 20 nm was prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
Comparative Example 5
(56) According to the above method for preparing a button battery, tin-carbon composite particles with a particle size of 100 nm were directly prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
Comparative Example 6
(57) According to the above method for preparing a button battery, tin-aluminum alloy with a particle size of 100 nm was prepared into a button battery and the battery was subjected to charge-discharge cycling performance test in accordance with the electrochemical performance test conditions.
(58) Test Results and Analysis
(59) It can be observed from the XRD spectrum of
(60) It can be Observed from the SEM image of
(61) It can be observed from the TEM image of
(62) It can be observed from the SEM image of
(63) It can be observed from the TEM image of
(64) It can be observed from the SEM image of
(65) It can be observed from the SEM image of
(66) It can be observed from the TEM image of
(67) It can be observed from the charge-discharge cycle curves of the samples of Examples 1, 2, 3 and Comparative Examples 1 and 2 in
(68) Table 1 lists the electrochemical performance comparisons of the negative electrode materials prepared in the Examples (Ex.) of the present invention and Comparative Examples (CE.). Table 2 lists the comparison of electrochemical performance of nano-tin negative electrode materials under different coating conditions.
(69) TABLE-US-00001 TABLE 1 Ex. 1. Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 CE. 1 CE. 2 Second cycle 871.5 742.2 754.3 761.2 784.6 721.5 738 645.7 reversible capacity (mAh/g) Reversible capacity 423.8 506.5 463.2 446.3 472.3 423.1 36.8 361.6 after 100 cycles (mAh/g) Average Coulomb 96.57 98.10 97.32 97.55 97.12 97.32 96.16 97.25 efficiency from the second cycle to the 100th cycle Capacity retention 48.63 68.21 61.40 58.63 60.19 58.64 5.00 56 rate after the second cycle to 100 cycles
(70) It can be observed from the data in Table 1 that the electrochemical cycling performance of nano-copper-coated nano-tin negative electrode is far superior to that of uncoated nano-tin negative electrode, and the electrochemical cycling performance of the conductive protective layer and copper composite-coated nano-tin negative electrode is significantly superior to that of the only nano-copper-coated nano-tin negative electrode.
(71) TABLE-US-00002 TABLE 2 Average Coulombic Capacity efficiency retention rate Second cycle Reversible from the after the Tin Tin CuSO.sub.4 C.sub.2H.sub.2 C.sub.2H.sub.2 reversible capacity after second cycle second cycle Battery particle content content flow rate introducing capacity 100 cycles to the 100th to 100 cycles number size (nm) (g/L) (g/L) (sccm) time (min) (mAh/g) (mA/g) cycle (%) (%) 1 100 2 1 100 90 754.3 463.2 97.32 61.40 2 100 2 0 0 0 738 36.8 96.16 5.00 3 100 2 1 0 0 645.7 361.6 97.25 56 4 100 2 1 100 30 748.3 458.6 97.28 61.28 5 100 2 1 100 300 747.2 454.6 97.16 60.84 6 100 2 1 50 90 743.5 447.88 97.20 60.24 7 100 2 0.5 0 0 677.8 347. 96.68 51.2 8 100 2 0.5 100 90 762.5 416.3 97.13 54.6 9 100 2 2 100 90 758.6 413.4 96.68 54.5 10 100 2 4 100 90 762.6 393.5 96.55 51.6 11 100 1 1 100 90 742.2 406.7 96.67 54.8 14 500 2 1 100 90 778.5 331.6 97.21 42.6 15 200 2 1 100 90 765.1 394.8 97.26 51.6 16 50 2 1 100 90 734.9 438 97.36 59.6 17 30 2 1 100 90 742.6 432.9 97.34 58.3
(72) It can be observed from the data in Table 2 that it is most suitable that the concentration of tin is at about 2 g/L and the particle size is from 50 to 100 nm; both too little copper coating and too more copper coating have an adverse effect on battery performance; and the tin-copper mass ratio is preferably controlled at 5:1. The electrochemical performance of the battery is obviously improved after the copper layer is coated with the conductive protective layer, but the weight percentage of the conductive protective layer material is preferably controlled to be 5%-10%.