CN115881443A - Method for improving electrochemical performance and safety of negative electrode material - Google Patents
Method for improving electrochemical performance and safety of negative electrode material Download PDFInfo
- Publication number
- CN115881443A CN115881443A CN202111118099.1A CN202111118099A CN115881443A CN 115881443 A CN115881443 A CN 115881443A CN 202111118099 A CN202111118099 A CN 202111118099A CN 115881443 A CN115881443 A CN 115881443A
- Authority
- CN
- China
- Prior art keywords
- safety
- electrochemical performance
- precursor
- negative electrode
- improving
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 41
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 25
- 239000000463 material Substances 0.000 claims abstract description 73
- 239000002243 precursor Substances 0.000 claims abstract description 20
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- 239000010703 silicon Substances 0.000 claims description 14
- 239000013084 copper-based metal-organic framework Substances 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 239000010405 anode material Substances 0.000 claims description 9
- OJLGWNFZMTVNCX-UHFFFAOYSA-N dioxido(dioxo)tungsten;zirconium(4+) Chemical compound [Zr+4].[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O OJLGWNFZMTVNCX-UHFFFAOYSA-N 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 239000013086 titanium-based metal-organic framework Substances 0.000 claims description 8
- 239000007772 electrode material Substances 0.000 claims description 7
- JFBZPFYRPYOZCQ-UHFFFAOYSA-N [Li].[Al] Chemical compound [Li].[Al] JFBZPFYRPYOZCQ-UHFFFAOYSA-N 0.000 claims description 5
- 239000013094 zinc-based metal-organic framework Substances 0.000 claims description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 229910052744 lithium Inorganic materials 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- JVPGYYNQTPWXGE-UHFFFAOYSA-N 2-(4-methylphenyl)-1,3-benzothiazole Chemical compound C1=CC(C)=CC=C1C1=NC2=CC=CC=C2S1 JVPGYYNQTPWXGE-UHFFFAOYSA-N 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- -1 lithium aluminum pyrophosphate Chemical compound 0.000 claims description 3
- 229910052582 BN Inorganic materials 0.000 claims description 2
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 229940009868 aluminum magnesium silicate Drugs 0.000 claims description 2
- WMGSQTMJHBYJMQ-UHFFFAOYSA-N aluminum;magnesium;silicate Chemical compound [Mg+2].[Al+3].[O-][Si]([O-])([O-])[O-] WMGSQTMJHBYJMQ-UHFFFAOYSA-N 0.000 claims description 2
- SXQXMCWCWVCFPC-UHFFFAOYSA-N aluminum;potassium;dioxido(oxo)silane Chemical compound [Al+3].[K+].[O-][Si]([O-])=O.[O-][Si]([O-])=O SXQXMCWCWVCFPC-UHFFFAOYSA-N 0.000 claims description 2
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 claims description 2
- 229910052733 gallium Inorganic materials 0.000 claims description 2
- 229910052735 hafnium Inorganic materials 0.000 claims description 2
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 2
- 239000012621 metal-organic framework Substances 0.000 claims description 2
- 229940005657 pyrophosphoric acid Drugs 0.000 claims description 2
- YHKRPJOUGGFYNB-UHFFFAOYSA-K sodium;zirconium(4+);phosphate Chemical compound [Na+].[Zr+4].[O-]P([O-])([O-])=O YHKRPJOUGGFYNB-UHFFFAOYSA-K 0.000 claims description 2
- MVGWWCXDTHXKTR-UHFFFAOYSA-J tetralithium;phosphonato phosphate Chemical compound [Li+].[Li+].[Li+].[Li+].[O-]P([O-])(=O)OP([O-])([O-])=O MVGWWCXDTHXKTR-UHFFFAOYSA-J 0.000 claims description 2
- PBYZMCDFOULPGH-UHFFFAOYSA-N tungstate Chemical compound [O-][W]([O-])(=O)=O PBYZMCDFOULPGH-UHFFFAOYSA-N 0.000 claims description 2
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 2
- 150000003623 transition metal compounds Chemical class 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 17
- 238000011065 in-situ storage Methods 0.000 abstract description 7
- 230000002829 reductive effect Effects 0.000 abstract description 4
- 239000003990 capacitor Substances 0.000 abstract description 3
- 238000004146 energy storage Methods 0.000 abstract description 3
- 238000002360 preparation method Methods 0.000 abstract description 3
- 230000009467 reduction Effects 0.000 abstract description 3
- 230000033228 biological regulation Effects 0.000 abstract description 2
- 238000004880 explosion Methods 0.000 abstract description 2
- 230000006866 deterioration Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 35
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 18
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 14
- 230000004048 modification Effects 0.000 description 10
- 238000012986 modification Methods 0.000 description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- 239000000843 powder Substances 0.000 description 7
- 239000010936 titanium Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 239000010406 cathode material Substances 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 239000010439 graphite Substances 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 6
- MKGYHFFYERNDHK-UHFFFAOYSA-K P(=O)([O-])([O-])[O-].[Ti+4].[Li+] Chemical compound P(=O)([O-])([O-])[O-].[Ti+4].[Li+] MKGYHFFYERNDHK-UHFFFAOYSA-K 0.000 description 5
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 229910008452 SnFe Inorganic materials 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000011889 copper foil Substances 0.000 description 4
- 230000001351 cycling effect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000005543 nano-size silicon particle Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000001994 activation Methods 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- QMKYBPDZANOJGF-UHFFFAOYSA-N benzene-1,3,5-tricarboxylic acid Chemical compound OC(=O)C1=CC(C(O)=O)=CC(C(O)=O)=C1 QMKYBPDZANOJGF-UHFFFAOYSA-N 0.000 description 2
- 239000012921 cobalt-based metal-organic framework Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000010277 constant-current charging Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000000113 differential scanning calorimetry Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000000284 resting effect Effects 0.000 description 2
- 239000011856 silicon-based particle Substances 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- XIOUDVJTOYVRTB-UHFFFAOYSA-N 1-(1-adamantyl)-3-aminothiourea Chemical compound C1C(C2)CC3CC2CC1(NC(=S)NN)C3 XIOUDVJTOYVRTB-UHFFFAOYSA-N 0.000 description 1
- GPNNOCMCNFXRAO-UHFFFAOYSA-N 2-aminoterephthalic acid Chemical compound NC1=CC(C(O)=O)=CC=C1C(O)=O GPNNOCMCNFXRAO-UHFFFAOYSA-N 0.000 description 1
- 239000006245 Carbon black Super-P Substances 0.000 description 1
- 229910000502 Li-aluminosilicate Inorganic materials 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- APQHKWPGGHMYKJ-UHFFFAOYSA-N Tributyltin oxide Chemical compound CCCC[Sn](CCCC)(CCCC)O[Sn](CCCC)(CCCC)CCCC APQHKWPGGHMYKJ-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910002064 alloy oxide Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- FPCJKVGGYOAWIZ-UHFFFAOYSA-N butan-1-ol;titanium Chemical compound [Ti].CCCCO.CCCCO.CCCCO.CCCCO FPCJKVGGYOAWIZ-UHFFFAOYSA-N 0.000 description 1
- YHWCPXVTRSHPNY-UHFFFAOYSA-N butan-1-olate;titanium(4+) Chemical compound [Ti+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] YHWCPXVTRSHPNY-UHFFFAOYSA-N 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000001938 differential scanning calorimetry curve Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000011799 hole material Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 description 1
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000004729 solvothermal method Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229910001134 stannide Inorganic materials 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Images
Classifications
-
- Y—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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention relates to the technical field of energy storage, provides a method for removing heat of a battery and a capacitor in situ to reduce deformation and improve electrochemical performance and safety, relates to the utilization of a negative thermal expansion material or a precursor thereof to improve the electrochemical performance and safety of an energy device, and aims to solve the safety problems of capacity attenuation, bulging, leakage, explosion and the like caused by heat and volume expansion in the circulation process of the conventional energy device. The preparation method comprises the following steps: the negative thermal expansion material or the precursor thereof is mixed with the negative electrode material or the precursor thereof, and the negative thermal expansion material or the precursor thereof absorbs heat in the negative electrode circulation process to shrink in volume, so that the overall volume expansion in the circulation process is counteracted or reduced, and performance deterioration and safety accidents caused by deformation and heat are eliminated or reduced. The method has the advantages of simple process, strong operability, easy implementation, simultaneous volume and heat influence regulation and control, small overall deformation of the device, reduction of heat hazard, improvement of electrochemical performance, heat and cycle stability, extreme condition performance, safety and the like.
Description
Technical Field
The invention relates to the field of energy materials and technologies, in particular to a method for reducing harm and volume expansion caused by heat of a negative electrode material and improving electrochemical performance and safety by using a negative thermal expansion material or a precursor thereof.
Background
Batteries and supercapacitors are energy devices which are widely used at present, and important components of the batteries and the supercapacitors are electrodes, diaphragms and electrolytes. In the using process of the energy devices, heat is generated due to charge transfer or electrochemical reaction, the internal temperature of the energy storage device is rapidly increased due to heat accumulation, the battery is overheated, thermal runaway is caused in severe cases, the volume expansion and the internal stress are increased, and safety accidents such as swelling, leakage, combustion or explosion are generated. Batteries, especially high-energy density batteries with long endurance mileage, have outstanding thermal safety problems during use, induce battery safety accidents in different degrees, hinder the healthy development of electric vehicles and high-performance energy storage devices, and arouse high attention of users and researchers.
In the prior art, modification measures such as modification, doping and combination are often performed on an electrode material to improve thermal stability and reduce the risk of thermal runaway, the problem that deformation is neglected only by considering heat exists, and the electrochemical performance and safety of a device are greatly influenced by volume change caused by heat. In fact, deformation is a significant feature before the battery or capacitor is put in danger, which occurs when the internal stresses of the device are greater than the strength of the case. Therefore, it is urgently needed to consider and improve the electrochemical performance and safety of the device from the viewpoint of heat and deformation, and no report is made to control both heat and deformation at present.
The negative electrode material greatly affects the performance and safety of batteries and supercapacitors. In various negative electrode materials, the theoretical specific capacity of silicon can reach 4200mAh g -1 10 times that of commercial graphite, and a discharge potential of about 0.2V (vs. Li) + /Li), lower than most other alloy and metal oxide anodes, and abundant in nature (second in abundance in the earth crust), are of high interest. However, the following problems with silicon severely limit its development: as a semiconductor material, the conductivity of the material itself is poor (10 to 10) –3 S cm –1 ) (ii) a The heat generation problem of silicon in the circulating process is prominent, and thermal runaway is easy to occur; volume of silicon during lithium deintercalation in charge-discharge cyclesThe variation is particularly great (>300%), the particles can crack or even crush, lose electrical contact and even fall off from the current collector, which leads to the structural damage or pulverization of the silicon electrode and the loss of active substances; forming unstable solid electrolyte interface film on the surface of silicon material, consuming large amount of Li + And electrolytes, increasing resistance, decreasing coulombic efficiency, resulting in fast capacity fade and poor cycle stability. Aiming at the problems of the silicon negative electrode material, the following measures are mainly adopted to modify the silicon negative electrode material at present: thinning particles (mostly reaching the nanometer level), structural specialization (such as core shell, fiber, hole and the like), metal ion doping, and compounding with carbon materials, conductive polymers, MXene and other materials. At present, no report that the deformation of the negative electrode material is regulated by using heat generated by the negative electrode material is found, and no report that the electrochemical performance and safety are improved by regulating and controlling the heat and the deformation is found.
Compared with the common Materials with thermal expansion and cold contraction, the negative thermal expansion material has the characteristics of thermal contraction and cold expansion, the volume of the negative thermal expansion material shrinks when being heated, the average linear expansion coefficient is a negative value in a certain temperature range [ Advanced Materials,2016,28 (37): 8079-96 ], and the negative thermal expansion material is expected to be compounded with other Materials to prepare low-expansion or zero-expansion Materials, and has wide application prospect. Based on our original work, the negative thermal expansion material is expected to absorb heat in the electrode circulation process in situ to reduce the volume, so that effective regulation and control of heat and deformation are realized.
Disclosure of Invention
The invention aims to: the method solves the problems of deformation, side reaction, thermal runaway, stress and the like caused by heat in the current electrode material circulating process, how to utilize the heat in the circulating process to reduce the deformation in situ, overcomes the defects that the thermal runaway is only considered in the current electrode material modification method and the electrochemical performance is only considered in the modification measures, simultaneously regulates and controls the heat and the deformation, improves the interface of the electrode material and electrolyte, and improves the rate characteristic, the high-temperature performance, the circulating stability and the safety of the electrode material.
In view of this, the invention provides a method for reducing deformation and improving performance by using heat generated in a cycle process of a negative electrode material in situ, and aims to solve the performance reduction and safety problems caused by heat and deformation generated in the charge and discharge processes of the existing battery and capacitor.
In order to achieve the purpose, the invention mainly adopts the following technical scheme:
a method for improving the electrochemical performance and safety of a negative electrode material is characterized by comprising the following steps: mixing the negative thermal expansion material or the precursor thereof with the negative electrode material or the precursor thereof according to a certain proportion, and optionally carrying out heat treatment.
Preferably, the negative thermal expansion material refers to a material having a linear expansion coefficient of less than 0 when heated in the working temperature range of the negative electrode material.
Preferably, the specific ratio is a mass ratio (0.01 to 50) of the negative thermal expansion material or the precursor thereof to the electrode material or the precursor thereof to 50.
Preferably, the heat treatment is a heat treatment at 500 to 1500 ℃.
Preferably, the working temperature range is-20 to 800 ℃.
Preferably, the negative expansion material refers to lithium aluminum silicate, potassium aluminum silicate, aluminum magnesium silicate, pyrophosphoric acid, lithium pyrophosphate, lithium aluminum pyrophosphate, sodium zirconium phosphate, lithium zirconium metaphosphate, aluminum tungstate, zirconium tungstate, hafnium tungstate, gallium vanadate, boron nitride, titanium-based metal organic framework material, tin-based metal organic framework material, copper-based metal organic framework material, zinc-based metal organic framework material and covalent metal framework material.
Compared with the prior art, the invention has the following beneficial effects:
the method provided by the invention utilizes the heat of the cathode material in the circulating process to regulate and control the performance and the deformation of the cathode material, utilizes the heat generated in the circulating process in situ to reduce the deformation and the side reaction, improves the interface, improves the performance, eliminates or reduces the deformation, the side reaction, the performance reduction and the related safety problems caused by the heat, improves the performance and the safety from the perspective of the heat and the deformation, overcomes the defect that the porous material is used for inhibiting the deformation and neglects the heat at present, and has simple process and strong operability.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments of the present application will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram showing the working principle of an energy source material added with a negative thermal expansion material;
FIG. 2 shows Differential Scanning Calorimetry (DSC) curves before and after modification of Si with a negative thermal expansion material zirconium tungstate;
FIG. 3 shows high temperature cycling stability curves before and after modification of Si with a negative thermal expansion material zirconium tungstate;
FIG. 4 shows the deformation diagrams before and after modification of Si with zirconium tungstate, a negative thermal expansion material;
FIG. 5 shows the room temperature cycling performance curves before and after modification of Si with a titanium-based metal organic framework material.
Fig. 6 shows the cycle performance curves at high temperature before and after Si modification with copper-based metal organic framework materials.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making creative efforts shall fall within the protection scope of the present application.
The embodiment provides a method for improving the performance and safety of an anode material, which comprises the following steps:
example 1
Zirconium tungstate ZrW prepared from negative thermal expansion material 2 O 8 The electrochemical performance of the Si negative electrode material is improvedSafety, will ZrW 2 O 8 ZrW with different proportions is prepared by mixing with nano silicon (30-50 nm) in mass ratios of 0%, 1%, 2%, 3%, 5% and 10% 2 O 8 @ Si active material samples, named Si, SZ1, SZ2, SZ3, SZ5, and SZ10, respectively. ZrW 2 O 8 The method comprises the following steps of mixing a @ Si active substance, a lithiated polyacrylic acid PAA-Li adhesive and a Super P conductive agent according to a mass ratio of 8 6 The test voltage window is 0.01-1.0V, the negative thermal expansion material absorbs heat emitted by the silicon electrode in situ in the circulation process to reduce the volume, space is provided for the volume expansion of the energy material, side reactions, volume changes, stress and the like caused by heat are eliminated or reduced, the working principle is shown in figure 1, the tested differential scanning calorimetry DSC curve is shown in figure 2, the high-temperature circulation stability is shown in figure 3, the deformation in the circulation process is shown in figure 4, 2% of zirconium tungstate can greatly improve the thermodynamic stability and the circulation stability of silicon, reduce the deformation in the pure silicon circulation process, improve the interface of the electrode and electrolyte, and the performance is improved more obviously along with the increase of current density or temperature. Therefore, the negative thermal expansion material zirconium tungstate ZrW 2 O 8 The thermal stability, the electrochemical performance and the safety of the Si electrode are improved.
Example 2
Using negative thermal expansion material lithium aluminium silicate LiAlSiO 4 Improving the electrochemical performance and safety of SnFe, and adding different amounts of LiAlSiO 4 Mixing with SnFe powder to prepare active material, adding SnFe @ LiAlSiO 4 The active material, the Super-P conductive agent and the polyvinylidene fluoride (PVDF) binder are mixed according to the mass ratio of 8:1:1 and a proper amount of N-methylpyrrolidone NMP solvent, and then ball-milling the mixture for 3 hours in a zirconia ball-milling tank by using a planetary ball mill to obtain viscous uniform slurry. The slurry was coated on a clean copper foil using a doctor blade, dried at 60 ℃ for 1h, then the active-loaded copper foil was cut into a circular sheet with a diameter of 14mm, and vacuum-dried at 80 ℃ for 12h. To prepareThe electrode is a working electrode, the metal lithium is a counter electrode and a reference electrode, half-cell assembly and electrochemical performance test are carried out, and the battery is placed for 8-12 hours after being assembled so as to be fully soaked by the electrolyte. The battery device is first activated after resting. The activation process is at 200 mA.g -1 The current density of the lithium aluminum silicate is measured, constant current charging and discharging are carried out for 3 circles, and then the lithium aluminum silicate LiAlSiO serving as a negative thermal expansion material is tested under different conditions 4 The thermal stability, the electrochemical performance and the safety of the SnFe alloy electrode are improved to different degrees.
Example 3
The electrochemical performance and safety of the cathode material SnO are improved by using the lithium titanium phosphate, the lithium titanium phosphate is synthesized by adopting a sol-gel method, lithium hydroxide monohydrate and ammonium dihydrogen phosphate are dissolved in pure water (marked as solution A), a proper amount of tetrabutyl titanate is dissolved in an ethanol solution (marked as solution B), the solution B is added into the solution A, finally, the solution A is stirred for 2 hours at a certain temperature, the solution A is placed in a 60-90 ℃ oven for drying for 12 hours to obtain a precursor, the precursor is calcined for 5-8 hours at 400-700 ℃ in a tubular furnace, and the lithium titanium phosphate powder is obtained after cooling. Subsequently, uniformly mixing the lithium titanium phosphate powder and nano SnO according to different mass ratios of 1. The slurry was coated on a clean copper foil using a doctor blade, and after drying at 60 ℃ for 1h, the active-material-loaded copper foil was cut into a circular sheet with a diameter of 14mm, which was vacuum-dried at 80 ℃ for 12h. And (3) carrying out half-cell assembly and electrochemical performance test by using the prepared electrode as a working electrode and using metal lithium as a counter electrode and a reference electrode, and standing for 8-12 h after the cell is assembled so as to be convenient for the electrolyte to be fully soaked. The battery device is first activated after resting. The activation process is at 200 mA.g -1 The current density of the SnO electrode is controlled, constant current charging and discharging are carried out for 3 circles, and then tests are carried out under different conditions, so that the thermal stability, the electrochemical performance and the safety of the SnO electrode are improved to different degrees by the negative thermal expansion material lithium titanium phosphate.
Example 4
Improving the electrochemistry of silicon by using Ti-based metal organic framework material Ti-MOFThe preparation method is safe, silicon powder is added during the synthesis of Ti-MOF, and the three-dimensional silicon-based negative electrode material is prepared in situ by a solvothermal method, and the preparation method comprises the following specific steps: an amount of Si nanoparticles (about 30 nm) was uniformly dispersed in a polyvinylpyrrolidone (PVP) solution (0.5 g PVP in 30ml ethanol). Then the solution is stirred for 10 to 15 hours and centrifuged to obtain an intermediate product Si @ PVP. Then, si @ pvp was ultrasonically dispersed in a mixture of MeOH and DMF (volume ratio 3. Weighing a certain mass of 2-amino terephthalic acid (H2 ATA), slowly dripping the solution into the solution, stirring the solution until the solution is completely dissolved, then slowly adding butyl titanate (TBOT) into the solution, continuously stirring the solution, then transferring the mixed solution into a 50ml stainless steel reaction kettle with a polytetrafluoroethylene lining, reacting the solution at 110-160 ℃ for 24H, cooling the solution to room temperature after the reaction is finished, washing the product obtained after centrifugation by using DMF and MeOH, and drying the product at 60 ℃ in vacuum for 6H to obtain yellow powder. And in an argon atmosphere, heating to 400-700 ℃ at a rate of 3 ℃/min, and roasting for 1-5 h to prepare the titanium and nitrogen codoped porous carbon coated Si nanoparticle composite material derived from Si @ C-NH 2-MIL-125. The first discharge specific capacity of a sample roasted for 3h at the temperature of 600 ℃ at the multiplying power of 1C at the temperature of 25 ℃ is 693.2mAh g -1 And the specific discharge capacity after circulating for 100 circles is improved to 784.5mAh g -1 The specific discharge capacity after 50 times of circulation at 60 ℃ and 1C multiplying power is still 844.9mAh g -1 The capacity retention rate reaches 88.6%, the strain is reduced by 80.8% compared with the whole Si, the cycling performance of samples prepared under different conditions is shown in figure 5, the high-temperature cycling performance is shown in figure 6, and the thermal stability, the electrochemical performance and the safety of the Si electrode are improved by the titanium-based metal organic framework material Ti-MOF.
Example 5
FeP enhancement with copper-based metal organic framework material Cu-MOF y The electrochemical performance and safety of the method are that 1,3, 5-benzene tricarboxylic acid is dissolved in ethanol, and Cu (NO) is added 3 ) 2 ·3H 2 Dissolving O in deionized water, mixing the two solutions uniformly, transferring the mixture into a hydrothermal kettle, adjusting the temperature to enable the mixture to react for 10 to 18 hours at the temperature of between 100 and 150 ℃, removing a reaction product after the reaction kettle is cooled to room temperature, washing the reaction product with an ethanol solution, and performing suction filtration on the reaction product to obtain blue crystalsDrying the sample to obtain a copper-based metal organic framework material, and mixing the Cu-MOF and FeP which are not subjected to heat treatment y Mixing the powder according to a certain proportion to obtain the copper-based metal organic framework material modified FeP y The material is tested under different conditions, and the copper-based metal organic framework material Cu-MOF improves FeP to different degrees y Thermal stability, electrochemical performance and safety of the electrode.
Example 6
Improving Li of cathode material by using Co-based metal organic framework material ZIF67 4 Ti 5 O 12 The electrochemical performance and safety of the method are that 0.025g of nano Li is added into a beaker 4 Ti 5 O 12 Powder, 0.015g of cetyltrimethylammonium bromide (surfactant CTAB prevents agglomeration of Si particles) and 50mL of methanol, sonicated for 30 minutes (solution a). Then, 1.644g of 2-methylimidazole was added to solution A and magnetically stirred for 30min (solution B). Meanwhile, 1.455g of cobalt nitrate hexahydrate is added into 50ml of methanol solution, stirred for 30 minutes (solution C), the solution C is quickly dripped into the solution B, slowly stirred for 24 hours, then centrifuged, and dried at 60 ℃ for 12 hours to obtain a precursor Li 4 Ti 5 O 12 @ ZIF-67 sample. Finally, the composite material obtained is heated to 550-630 ℃ in a tube furnace at a rate of 3 ℃/min and kept for 2h under Ar atmosphere. Cooling the material to room temperature, grinding to obtain Li 4 Ti 5 O 12 Cobalt and nitrogen co-doped porous carbon coated Li derived from @ C-ZIF67 4 Ti 5 O 12 The particle composite material is tested under different conditions, and the Co-based metal organic framework material ZIF67 improves Li to different degrees 4 Ti 5 O 12 Thermal stability, electrochemical performance and safety of the electrode.
Example 7
Improving the electrochemical performance and safety of the cathode material graphite by using a Zn-based metal organic framework material ZIF8, adding 0.025G of commercial cathode material graphite G powder, 0.015G of hexadecyl trimethyl ammonium bromide (surfactant CTAB prevents the agglomeration of Si particles) and 50mL of methanol into a beaker, and carrying out ultrasonic treatment for 30 minutes (solution A); adding 1.644g of 2-methylimidazole into the solution A and continuously stirring for 30min (solution B); 1.487g of zinc nitrate hexahydrate was added to 50ml of a methanol solution, and stirred for 30 minutes (solution C). Then, the solution C was quickly dropped into the solution B, slowly stirred for 24 hours, centrifuged, and dried at 60 ℃ for 12 hours to obtain a precursor Si @ ZIF-8. And under the argon atmosphere, heating the obtained G @ ZIF-8 precursor to 600 ℃ at the heating rate of 3 ℃/min for carbonizing for 2h, cooling the material to room temperature to obtain a zinc and nitrogen codoped porous carbon coated graphite particle composite material derived from G @ C-ZIF8, and testing under different conditions, wherein the Zn-based metal organic framework material ZIF8 improves the thermal stability, electrochemical performance and safety of the graphite electrode to different degrees.
By way of example, the negative thermal expansion material is zirconium tungstate, lithium aluminum silicate, aluminum tungstate, a titanium-based metal organic framework material, a copper-based metal organic framework material, a zinc-based metal organic framework material. Specifically, the negative electrode material can be silicon, siO, graphite, iron stannide, snO 2 SnO, phosphide, carbide, and the like. It should be understood that the present invention is not limited to the types of negative thermal expansion materials and negative electrode materials, and the above examples should not be construed as limiting the scope of the present invention.
While preferred embodiments of the present application have been described, additional variations and modifications of these embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the true scope of the embodiments of the application.
The method for improving the electrochemical performance and safety of the negative electrode material by using the negative expansion material provided by the application is described in detail above, and the principle and the implementation mode of the application are explained by applying specific examples, and the description of the examples is only used for helping to understand the method and the core idea of the application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (9)
1. A method for improving the electrochemical performance and safety of a negative electrode material is characterized by comprising the following steps: mixing the negative thermal expansion material or the precursor thereof with the negative electrode material or the precursor thereof according to a certain proportion, and optionally carrying out heat treatment.
2. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the negative thermal expansion material refers to a material with an expansion coefficient less than 0 when heated in a working temperature range.
3. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the precursor of the negative thermal expansion material refers to the existence state of the key components of the negative thermal expansion material before the negative thermal expansion material is obtained.
4. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the negative electrode material refers to a material for forming a negative electrode, in particular to carbon, silicon, alloy and lithium-containing transition metal compound.
5. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the precursor of the negative electrode material refers to the existence state of key components of the negative electrode material before the negative electrode material is obtained.
6. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the certain proportion refers to the mass ratio (0.01-50) of the negative thermal expansion material or the precursor thereof to the electrode material or the precursor thereof to 50.
7. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the heat treatment refers to heat treatment at 500-1500 ℃.
8. The method for improving the electrochemical performance and safety of the anode material according to claim 2, comprising: the expansion coefficient refers to linear expansion coefficient or volume expansion coefficient.
9. The method for improving the electrochemical performance and safety of the anode material according to claim 1, comprising the following steps: the negative expansion material particularly refers to lithium aluminum silicate, potassium aluminum silicate, aluminum magnesium silicate, pyrophosphoric acid, lithium pyrophosphate, lithium aluminum pyrophosphate, sodium zirconium phosphate, lithium zirconium metaphosphate, aluminum tungstate, zirconium tungstate, hafnium tungstate, gallium vanadate, boron nitride, titanium-based metal organic framework material, tin-based metal organic framework material, copper-based metal organic framework material, zinc-based metal organic framework material and covalent metal framework material.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN202111118099.1A CN115881443A (en) | 2021-09-23 | 2021-09-23 | Method for improving electrochemical performance and safety of negative electrode material |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN202111118099.1A CN115881443A (en) | 2021-09-23 | 2021-09-23 | Method for improving electrochemical performance and safety of negative electrode material |
Publications (1)
Publication Number | Publication Date |
---|---|
CN115881443A true CN115881443A (en) | 2023-03-31 |
Family
ID=85762381
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN202111118099.1A Pending CN115881443A (en) | 2021-09-23 | 2021-09-23 | Method for improving electrochemical performance and safety of negative electrode material |
Country Status (1)
Country | Link |
---|---|
CN (1) | CN115881443A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN116646471A (en) * | 2023-07-27 | 2023-08-25 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, preparation method thereof, secondary battery and power utilization device |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2015191768A (en) * | 2014-03-28 | 2015-11-02 | トヨタ自動車株式会社 | secondary battery |
CN110380004A (en) * | 2018-04-13 | 2019-10-25 | 宁德新能源科技有限公司 | Positive electrode and electrochemical appliance |
-
2021
- 2021-09-23 CN CN202111118099.1A patent/CN115881443A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2015191768A (en) * | 2014-03-28 | 2015-11-02 | トヨタ自動車株式会社 | secondary battery |
CN110380004A (en) * | 2018-04-13 | 2019-10-25 | 宁德新能源科技有限公司 | Positive electrode and electrochemical appliance |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN116646471A (en) * | 2023-07-27 | 2023-08-25 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, preparation method thereof, secondary battery and power utilization device |
CN116646471B (en) * | 2023-07-27 | 2023-12-19 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, preparation method thereof, secondary battery and power utilization device |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CN103904321B (en) | The high-temperature solid phase preparation method of lithium ion battery negative material LiMn2O4 | |
CN106848259A (en) | A kind of continuous conduction original position C/Ag, Zr/ZrF4Compound zirconium fluoride anode material for lithium-ion batteries and preparation method thereof | |
CN101997118A (en) | Lithium ferric manganese phosphate as cathode material of lithium ion battery and preparation method thereof | |
CN105336939B (en) | Coating modification method of lithium titanate and lithium ion battery thereof | |
CN103066265A (en) | Sodium ion battery negative pole active substance and preparation method and application thereof | |
CN111029560A (en) | Spinel structure positive active material doped with sodium ions in gradient manner and preparation method thereof | |
CN103700842B (en) | A kind of NiFe 2o 4/ C lithium ion battery cathode material and its preparation method | |
CN103390748B (en) | A kind of preparation method of alumina-coated lithium cobaltate cathode material | |
CN108899541B (en) | Magnesium lithium silicate coated modified lithium zinc titanate negative electrode material and preparation method thereof | |
WO2023087209A1 (en) | Electrochemical device and electronic device | |
CN109942001B (en) | Silicon negative electrode material with spherical thorn-shaped structure and preparation method thereof | |
CN108281620B (en) | Preparation method of negative electrode material titanium dioxide of sodium-ion battery | |
CN112103499B (en) | Graphene-based negative electrode material and preparation method thereof | |
CN115881443A (en) | Method for improving electrochemical performance and safety of negative electrode material | |
CN114335534A (en) | Lithium cobaltate positive electrode material coated and modified by zirconium lithium phosphate fast ion conductor and preparation method and application thereof | |
CN112103482A (en) | Rare earth metal or transition metal doped lithium titanium phosphate/carbon composite material and preparation method and application thereof | |
CN114229807B (en) | Si@SiOx-TiN/C composite anode material, preparation method and lithium ion battery | |
CN116722131A (en) | Low-entropy antimony-based binary superfine nanocrystalline oxide negative electrode material and preparation method thereof | |
CN116565302A (en) | Modified solid electrolyte, preparation method thereof and lithium secondary battery | |
CN105591091B (en) | A kind of sodium ion secondary battery negative electrode active material and its preparation method and application | |
CN115626637A (en) | Preparation method of carbon/graphene/lithium titanate composite negative electrode material | |
CN113991103A (en) | Aqueous lithium ion battery NaTi2(PO4)3Preparation method of/C negative electrode material | |
CN114566647A (en) | Calcium phosphate coated high-nickel ternary cathode material and preparation method and application thereof | |
CN109065879B (en) | Sodium-ion battery negative electrode material and preparation method thereof | |
CN116314611B (en) | Lithium ion battery |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PB01 | Publication | ||
PB01 | Publication | ||
SE01 | Entry into force of request for substantive examination | ||
SE01 | Entry into force of request for substantive examination |