CN117766741A - Universal method for improving stability of layered oxide anode material by tunnel functional structure and application of universal method in sodium ion battery - Google Patents
Universal method for improving stability of layered oxide anode material by tunnel functional structure and application of universal method in sodium ion battery Download PDFInfo
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- 229910001415 sodium ion Inorganic materials 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 36
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 239000010405 anode material Substances 0.000 title abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 49
- 239000011159 matrix material Substances 0.000 claims abstract description 43
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000001301 oxygen Substances 0.000 claims abstract description 10
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 10
- 239000011734 sodium Substances 0.000 claims description 44
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 36
- 238000001354 calcination Methods 0.000 claims description 32
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 20
- 159000000000 sodium salts Chemical class 0.000 claims description 16
- 239000010406 cathode material Substances 0.000 claims description 15
- 229910052723 transition metal Inorganic materials 0.000 claims description 14
- 229940071125 manganese acetate Drugs 0.000 claims description 13
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 claims description 13
- 235000006408 oxalic acid Nutrition 0.000 claims description 12
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 10
- 235000002639 sodium chloride Nutrition 0.000 claims description 10
- 150000002696 manganese Chemical class 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 8
- 238000012986 modification Methods 0.000 claims description 7
- 230000004048 modification Effects 0.000 claims description 7
- -1 transition metal salt Chemical class 0.000 claims description 7
- 150000003624 transition metals Chemical class 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 6
- 239000002243 precursor Substances 0.000 claims description 6
- 239000001632 sodium acetate Substances 0.000 claims description 6
- 235000017281 sodium acetate Nutrition 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 4
- 235000017550 sodium carbonate Nutrition 0.000 claims description 4
- 239000011780 sodium chloride Substances 0.000 claims description 4
- 239000004317 sodium nitrate Substances 0.000 claims description 4
- 235000010344 sodium nitrate Nutrition 0.000 claims description 4
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 claims description 4
- 229940039790 sodium oxalate Drugs 0.000 claims description 4
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 4
- 235000011152 sodium sulphate Nutrition 0.000 claims description 4
- 239000011656 manganese carbonate Substances 0.000 claims description 2
- 235000006748 manganese carbonate Nutrition 0.000 claims description 2
- 229940093474 manganese carbonate Drugs 0.000 claims description 2
- 229940099596 manganese sulfate Drugs 0.000 claims description 2
- 239000011702 manganese sulphate Substances 0.000 claims description 2
- 235000007079 manganese sulphate Nutrition 0.000 claims description 2
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 2
- RGVLTEMOWXGQOS-UHFFFAOYSA-L manganese(2+);oxalate Chemical compound [Mn+2].[O-]C(=O)C([O-])=O RGVLTEMOWXGQOS-UHFFFAOYSA-L 0.000 claims description 2
- 229910000016 manganese(II) carbonate Inorganic materials 0.000 claims description 2
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 claims description 2
- XMWCXZJXESXBBY-UHFFFAOYSA-L manganese(ii) carbonate Chemical compound [Mn+2].[O-]C([O-])=O XMWCXZJXESXBBY-UHFFFAOYSA-L 0.000 claims description 2
- 238000000643 oven drying Methods 0.000 claims description 2
- 238000001556 precipitation Methods 0.000 claims description 2
- 239000013590 bulk material Substances 0.000 claims 1
- 239000003513 alkali Substances 0.000 abstract description 11
- 230000005540 biological transmission Effects 0.000 abstract description 9
- 238000006243 chemical reaction Methods 0.000 abstract description 9
- 230000000694 effects Effects 0.000 abstract description 6
- 238000003860 storage Methods 0.000 abstract description 4
- 238000011065 in-situ storage Methods 0.000 abstract 1
- 239000011572 manganese Substances 0.000 description 43
- 239000010936 titanium Substances 0.000 description 37
- 229910021260 NaFe Inorganic materials 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 22
- 239000007774 positive electrode material Substances 0.000 description 16
- 239000010410 layer Substances 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- 238000002360 preparation method Methods 0.000 description 11
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 10
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 10
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 10
- 229910052708 sodium Inorganic materials 0.000 description 10
- 238000012360 testing method Methods 0.000 description 8
- 238000012512 characterization method Methods 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 6
- 239000002033 PVDF binder Substances 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 239000011259 mixed solution Substances 0.000 description 5
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 239000004408 titanium dioxide Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 239000005486 organic electrolyte Substances 0.000 description 4
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 239000003365 glass fiber Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 230000002427 irreversible effect Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000002848 electrochemical method Methods 0.000 description 2
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 2
- BAZAXWOYCMUHIX-UHFFFAOYSA-M sodium perchlorate Chemical compound [Na+].[O-]Cl(=O)(=O)=O BAZAXWOYCMUHIX-UHFFFAOYSA-M 0.000 description 2
- 229910001488 sodium perchlorate Inorganic materials 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910000314 transition metal oxide Inorganic materials 0.000 description 2
- ZPFAVCIQZKRBGF-UHFFFAOYSA-N 1,3,2-dioxathiolane 2,2-dioxide Chemical compound O=S1(=O)OCCO1 ZPFAVCIQZKRBGF-UHFFFAOYSA-N 0.000 description 1
- WDXYVJKNSMILOQ-UHFFFAOYSA-N 1,3,2-dioxathiolane 2-oxide Chemical compound O=S1OCCO1 WDXYVJKNSMILOQ-UHFFFAOYSA-N 0.000 description 1
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- BJWMSGRKJIOCNR-UHFFFAOYSA-N 4-ethenyl-1,3-dioxolan-2-one Chemical compound C=CC1COC(=O)O1 BJWMSGRKJIOCNR-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000006115 defluorination reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- TYTHZVVGVFAQHF-UHFFFAOYSA-N manganese(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Mn+3].[Mn+3] TYTHZVVGVFAQHF-UHFFFAOYSA-N 0.000 description 1
- GEYXPJBPASPPLI-UHFFFAOYSA-N manganese(III) oxide Inorganic materials O=[Mn]O[Mn]=O GEYXPJBPASPPLI-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
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- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
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- 230000009467 reduction Effects 0.000 description 1
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- 230000006641 stabilisation Effects 0.000 description 1
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- 239000007858 starting material Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- IIVDETMOCZWPPU-UHFFFAOYSA-N trimethylsilyloxyboronic acid Chemical compound C[Si](C)(C)OB(O)O IIVDETMOCZWPPU-UHFFFAOYSA-N 0.000 description 1
Abstract
The invention discloses a universal method for improving stability of a layered oxide anode material of a sodium ion battery by a tunnel functional structure and application of the universal method in the sodium ion battery. According to the invention, partial residual alkali on the surface of the layered oxide matrix material is converted into the tunnel structure interface layer by the tunnel structure in-situ interface conversion technology, so that the tunnel structure interface layer which is intrinsically stable is formed while the residual alkali on the surface of the material is eliminated, the contact between the matrix and humid air is effectively isolated, and the air storage performance of the material is improved. Meanwhile, by means of the layered tunnel interlocking effect, lattice oxygen escape behavior of the matrix under high voltage is inhibited, and energy conversion efficiency is greatly improved. In addition, due to the S-shaped sodium ion transmission channel of the tunnel structure, the sodium ion transmission dynamics and the electrochemical performance of the matrix are improved. The method overcomes the difficulty of storing and transporting the layered oxide anode material and greatly improves the comprehensive performance of the material. Therefore, the method has strong practicability and wide application prospect.
Description
Technical Field
The invention belongs to the field of energy material preparation and electrochemistry, and particularly relates to a universal method for eliminating residual alkali on the surface of layered oxide by converting a tunnel functional structure and enhancing air stability, structural stability and energy conversion efficiency and application of the universal method in a sodium ion battery.
Background
Currently, sodium ion batteries benefit from a rich reserve of sodium resources and similar properties to lithium ion batteries, which are widely recognized as viable alternatives to lithium ion batteries.
Layered transition metal oxide Na compared to other cathode materials x TMO 2 The positive electrode material (x is more than 0 and less than or equal to 1, TM represents one or more transition metals) has the advantages of simple preparation process, high specific capacity, high ionic conductivity, environmental friendliness and industrial production amplification, and is considered to have very good application prospect. However, in practical applications, some critical technical problems still need to be solved. First, na x TMO 2 The cathode material has poor chemical stability to air, is extremely liable to have performance loss during processing and storage, and is considered to be made of electrochemically inert NaOH or Na 2 CO 3 Is caused by the formation of (a). In addition, these alkaline substances also initiate defluorination of the polyvinylidene fluoride (PVDF) binder, resulting in particle agglomeration and slurry gelation during electrode preparation, greatly impeding its practical feasibility. Secondly, because the radius of sodium ions is larger, the layered oxide positive electrode material is easy to generate a complex phase transition process in the process of sodium ion deintercalation, and the contraction and expansion of the unit cell volume can be caused, so that the transmission dynamics of sodium ions between transition metal layers is greatly influenced. In addition, in order to increase the energy density of the sodium ion battery, the voltage window of charge and discharge is further increased, but in the high voltage state, part of Na x TMO 2 The positive electrode material can have the phenomenon of lattice oxygen escape, so that the capacity attenuation of the positive electrode material is serious. Modification strategies currently available for such materials: such as stabilization of the layered structure by elemental doping, and reduction of interfacial side reactions between the material and the electrolyte by the coating. For example, for the patent application with publication number CN116435508A, a P2 structural substance is disclosedThe coated O3 structure layered metal oxide sodium ion battery anode material and the preparation method thereof are enhanced in air stability, but the problems of residual alkali on the surface, irreversible lattice oxygen behavior under high voltage and the like are not solved. Therefore, the modification method is difficult to realize the improvement of transportation, storage and reaction characteristics of sodium ions at the interface, and difficult to realize the three-in-one stability of air, interface and bulk phase, and is quite unfavorable for industrial production. There is a need for an easy and efficient method for achieving Na x TMO 2 The performance of the positive electrode material is improved in all aspects.
In this regard, we consider tunnel oxides: na (Na) y MnO 2 (0.22.ltoreq.y.ltoreq.0.5) positive electrode material. For Na y MnO 2 Positive electrode material, because of its intrinsic structural stability and air stability, excellent Na due to S-channel for rapid diffusion of sodium ions + Transmission kinetics such that they can exactly complement Na x TMO 2 Defects in the positive electrode material. Therefore, the invention provides a universal method for improving the stability of the layered oxide of the sodium ion battery by using the tunnel functional structure. The method can realize that the residual alkali on the surface is converted into the interface protection layer of the tunnel oxide coated on the surface of the layered oxide material, and can prevent the contact between the external environment and the bulk phase material while eliminating the influence of the residual alkali on the material performance, thereby improving the air stability and interface stability of the material. Second, S-type ion macrochannels and excellent Na using tunnel oxide + And the transmission kinetics improves the sodium ion transmission efficiency of the material. In addition, by means of the layered tunnel interlocking effect, the lattice oxygen behavior of the matrix material under high voltage is optimized, and the energy conversion efficiency is greatly improved. Meanwhile, the universal value of the method is also proved, and the practical value of the method in the industrial development of sodium ion batteries is realized.
Disclosure of Invention
In view of Na x TMO 2 The invention aims to provide a tunnel function structure for improving the stability of layered oxide of a sodium ion battery, which has a series of scientific problems existing in layered oxide cathode materialsThe universal method is used for eliminating residual alkali on the surface of the material, strengthening the air stability and improving the energy conversion efficiency and the comprehensive electrical property.
In order to achieve the aim of the invention, the invention provides a universal method for improving the stability of a layered oxide anode material of a sodium ion battery by using a tunnel functional structure and application of the universal method in the sodium ion battery, and the universal method is realized by adopting the following technical scheme.
(1) According to the composition characteristics of the layered oxide matrix, sodium salt and transition metal salt are fully mixed, pressed into a wafer, and then fully calcined under proper atmosphere and temperature to obtain the layered oxide matrix Na x TMO 2 Wherein 0 < x.ltoreq.1, and TM represents one or more transition metals.
(2) According to the mole ratio of the tunnel oxide interface layer to the layered oxide matrix material and the composition characteristics of the tunnel oxide interface layer material, the layered oxide anode material Na of the step (1) is prepared x TMO 2 Mixing with sodium salt and manganese salt in absolute ethanol, adding appropriate amount of oxalic acid solution for precipitation, and oven drying to obtain Na x TMO 2 @Na y MnO 2 Is a precursor material of (a).
(3) Fully calcining the precursor material under proper atmosphere and temperature to obtain the tunnel structure interface modified layered oxide material: na (Na) x TMO 2 @Na y MnO 2 Wherein x is more than 0 and less than or equal to 1,0.22 and y is more than or equal to 0.5, TM represents one or more transition metals, and the mol ratio of the tunnel oxide interface layer material to the layered oxide matrix material is 0.02-0.5:1.
Further, the sodium salt in the step (1) is at least one of sodium oxalate, sodium acetate, sodium nitrate, sodium sulfate, sodium chloride and sodium carbonate, and the transition metal salt is one or more selected from V, ti, fe, mn, cu, zn, zr, ni, co, cr.
Further, the molar ratio of the sodium salt to the transition metal salt added in the step (1) should be calculated according to the molar number of the sodium element and the total transition metal element, and the sodium salt is excessive by 10% to compensate for the loss in the sintering process. Specifically, the molar ratio of the sodium salt to the total transition metal salt is preferably 0.737:1 and 1.1:1.
Further, the calcining atmosphere in the step (1) is air or oxygen, the calcining temperature is 700-1200 ℃, the heating rate is 2-6 ℃/min, and the calcining time is 13-19 h. Further preferably, the calcination temperature in step (1) may be selected from 1000 ℃. The calcination time may be selected from 15 h. The heating rate is preferably 5 ℃/min. The calcination atmosphere is air.
Further, the sodium salt in the step (2) is at least one of sodium oxalate, sodium acetate, sodium nitrate, sodium sulfate, sodium chloride and sodium carbonate. Preferably sodium acetate, and the manganese salt is at least one of manganese oxalate, manganese acetate, manganese nitrate, manganese sulfate and manganese carbonate, preferably manganese acetate.
Further, the molar ratio of the sodium salt to the manganese salt added in the step (2) is calculated according to the molar ratio of the sodium element to the manganese element, and the molar ratio of the sodium salt to the manganese salt is as follows: 0.242-0.55:1 (sodium salt excess 10% to compensate for losses during sintering). Specifically, the molar ratio of the sodium salt to the manganese salt is preferably 0.484:1.
Further, the manganese salt in the step (2) and the layered oxide matrix Na in the step (1) x TMO 2 The molar ratio of (2) is: 0.02-0.5:1. Preferably the manganese salt and the layered oxide matrix Na of step (2) x TMO 2 The molar ratio of (2) may be independently selected from 0.02:1, 0.05:1, 0.1:1, 0.2:1, 0.5:1, or any ratio between the two.
Further, the oxalic acid solution in the step (2) is a precipitant, and the concentration is controlled to be 0.01-0.2 mol/L. The concentration of the oxalic acid solution in the step (2) is preferably independently selected from 0.01 mol/L, 0.02 mol/L and 0.05 mol/L.
Further, the calcining atmosphere in the step (3) is air or oxygen, the calcining temperature is 600-1000 ℃, the heating rate is 2-6 ℃/min, and the calcining time is 13-17 h. The calcination temperature in the step (3) is preferably 700-900 ℃, the calcination time is preferably 14-16 h, and the heating rate is preferably 5 ℃/min. The calcination atmosphere is air.
The invention also provides a preparation method of the positive pole piece of the sodium ion battery. The positive electrode plate of the sodium ion battery comprises a layered oxide positive electrode material with a tunnel structure interface modified by the preparation method.
Specifically, the preparation raw materials of the positive electrode plate further comprise a conductive agent, a binder and a slurry solvent; the conductive agent is preferably conductive carbon black (Super P); the binder is preferably PVDF; the slurry solvent was N-methylpyrrolidone (NMP). The mass ratio of the positive electrode material to the conductive agent to the binder is 6-9:0.5-2:0.5-2, preferably 7:2:1.
The invention also provides a sodium ion battery which comprises a positive electrode plate, a diaphragm, organic electrolyte and negative metal sodium. The positive electrode plate of the sodium ion battery comprises a tunnel oxide coated O3 type layered transition metal oxide positive electrode material obtained by the preparation method. The diaphragm is a glass fiber diaphragm. The solvent in the organic electrolyte is at least one of diethyl carbonate, ethylene carbonate, dimethyl carbonate, propylene carbonate, methyl ethyl carbonate, methyl acetate, ethyl acetate and ethyl propionate, and is preferably a mixed solvent of ethylene carbonate and diethyl carbonate; the additive in the organic electrolyte is at least one of vinylene carbonate, vinyl ethylene carbonate, ethylene sulfate, ethylene sulfite, trimethylsilyl borate and fluoroethylene carbonate, preferably fluoroethylene carbonate; the sodium salt in the organic electrolyte is at least one of sodium perchlorate, sodium hexafluorophosphate and sodium bistrifluoromethylsulfonylimide, and is preferably sodium perchlorate.
Compared with the prior art, the invention has the following beneficial technical effects:
1. according to the invention, the tunnel oxide interface layer is constructed on the surface of the layered oxide matrix material, and the contact and reaction of the matrix material and humid air can be effectively prevented by utilizing the intrinsic stability of the tunnel oxide material, so that the air stability of the matrix material is improved, the material is easy to store, transport, coat and the like, and the material is more suitable for large-scale production. In addition, the stable coating layer prevents the electrolyte from contacting with the matrix material, so that the side reaction of the material interface is reduced, the surface structure collapse of the matrix material is inhibited, the surface defects of the material are reduced, the structural stability of the material is further improved, and the electrochemical performance of the material is improved.
2. According to the invention, a tunnel oxide interface layer is constructed on the surface of the layered oxide matrix material, and the S-shaped ion transmission channel of the tunnel oxide material is utilized, so that the sodium ion transmission kinetics and the comprehensive electrochemical performance of the material are greatly improved.
3. According to the invention, the tunnel oxide interface layer is constructed on the surface of the layered oxide matrix material, and the local lattice oxygen environment of the matrix material is reasonably regulated and controlled by the tunnel interface layer by virtue of the layered tunnel interlocking effect, so that the lattice oxygen escape behavior of the matrix material under high voltage is inhibited, and meanwhile, the problem of voltage hysteresis of the matrix material under a wide voltage window is also overcome to a great extent, so that the energy conversion efficiency of the sodium ion battery is greatly improved.
4. The tunnel oxide interfacial layer coating has little impact on the specific capacity of the matrix material relative to inert material coating or inactive element doping. Meanwhile, the residual alkali existing on the surface of the matrix material can be effectively reduced, so that the residual alkali is reasonably utilized and converted into tunnel oxide modified on the surface of the matrix material.
5. The tunnel structure interface modification strategy is a universal application strategy, can not only modify the O3 type matrix material, but also has a universal effect on the P2 type and other oxide anode materials.
Drawings
Fig. 1 is an X-ray diffraction refinement chart (XRD) of example 1 and comparative example 1.
Fig. 2 is a Scanning Electron Microscope (SEM) image of example 1 and comparative example 1.
Fig. 3 is fourier infrared spectra (FTIR) of example 1 and comparative example 1.
Fig. 4 is a plot of first turn voltage versus specific capacity for example 1 and comparative example 1 at 0.1C x over a voltage range of 2 to 4.3V.
Fig. 5 is a plot of first turn voltage versus specific energy for example 1 and comparative example 1 at 0.1C x over a voltage range of 2 to 4.3V.
Fig. 6 is a charge-discharge graph of example 1 and comparative example 1 in the voltage range of 2 to 4.3V.
Fig. 7 is a graph of the rate performance of example 1 and comparative example 1 over a voltage range of 2 to 4.3V.
Fig. 8 is a graph of the cycle performance of example 1 and comparative example 1 at 2C x over a voltage range of 2 to 4.3V.
Fig. 9 is a voltage hysteresis diagram of example 1 and comparative example 1 in the voltage range of 2 to 4.3V.
Fig. 10 is an XRD pattern of example 1 and comparative example 1 exposed to air for different days.
Fig. 11 is a graph of charge and discharge in the voltage range of 2 to 4.3V for example 1 and comparative example 1 exposed to air for various days.
FIG. 12 is a graph showing the rate performance of example 1 and comparative example 1 over a voltage range of 2 to 4.3V when exposed to air for various days
Fig. 13 is the contact angle test results of the electrode sheets of example 1 and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to test examples and specific embodiments. It should not be construed that the scope of the above subject matter of the present invention is limited to the following embodiments, and all techniques realized based on the present invention are within the scope of the present invention.
Unless defined otherwise, all technical and scientific terms used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the present invention.
Unless otherwise indicated, all starting materials in the examples of the present invention were purchased commercially.
Example 1
Material preparation
(1) Uniformly mixing sodium carbonate, ferric oxide, titanium dioxide and manganese sesquioxide according to the molar ratio of Na to Fe to Ti to Mn=1.1 to 0.2 to 0.6, pressing into a wafer, placing in an air atmosphere, calcining 15 h at 1000 ℃ at a heating rate of 5 ℃/min to obtain a layered oxide matrix material NaFe 0.2 Ti 0.2 Mn 0.6 O 2 。
(2) Firstly, sodium acetate and manganese acetate are mixed with sodium element and manganese element according to the molar ratio: adding the mixture into a proper amount of ethanol solution at a ratio of 0.484:1, uniformly mixing, and mixing according to manganese acetate and a layered oxide matrix material NaFe 0.2 Ti 0.2 Mn 0.6 O 2 The layered oxide matrix NaFe is added in a molar ratio of 0.05:1 0.2 Ti 0.2 Mn 0.6 O 2 Adding the above ethanol solution, mixing, and continuously stirring the mixed solution at 500 r/min; adding 0.02 mol/L oxalic acid solution into the mixed solution in a dropwise manner, wherein the oxalic acid dosage is 1.1 times of the total molar quantity of the transition metal; continuously stirring the solution 1 h after the dripping is finished, and drying the obtained mixed solution in a baking oven at 120 ℃ to obtain NaFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 Precursor materials.
(3) NaFe is added to 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The precursor material is placed in an air atmosphere, and calcined at the temperature rising rate of 5 ℃/min and the temperature of 800 ℃ for 15 h, so that the layered oxide material with the tunnel structure interface modification is obtained: naFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 （NaFTM@NMO）。
Material structure and electrochemical characterization
Research on NaFe by powder X-ray diffractometer 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The crystal structure of the cathode material is shown in fig. 1: naFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The characteristic of the crystal structure of the typical O3 type sodium-based layered oxide proves that the modification of the tunnel structure interface can not damage the original layered structure of the sampleConstructing a structure. Characterization of NaFe Using scanning electron microscope 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 Is smooth, and some impurities covered by the surface are removed (fig. 2). And fourier transform infrared spectroscopy was used to demonstrate the removal of surface residual alkali (fig. 3).
NaFe is added to 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 Mixing the positive electrode material, super P and PVDF in a mass ratio of 7:2:1 in NMP to form a slurry, and uniformly coating the slurry on an aluminum foil current collector to obtain NaFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 And a positive pole piece. By NaFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The pole piece is a positive pole piece, the metal sodium piece is used as a negative pole material, a glass fiber membrane (Whatman GF/D) is used as a diaphragm, and 1 mol/L NaClO is used as a diaphragm 4 Solvent (solvent is EC and DEC mixed solution with volume ratio of 1:1, and FEC with mass fraction of 5%) is added as electrolyte, and the button cell is assembled in a glove box protected by argon.
The assembled battery is subjected to constant-current charge and discharge test on a Xinwei charge and discharge tester, and the charge and discharge voltage interval is 2-4.3V #vs.Na/Na + ). As can be seen in FIG. 4, in NaFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 In the electrode, the first-turn discharge specific capacity reaches 184.93 mAh g -1 The initial coulomb efficiency reaches 91.43 percent, and the irreversible capacity loss is 17.33 mAh g -1 The method comprises the steps of carrying out a first treatment on the surface of the As can be seen in FIG. 5, naFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The electrode reaches 604.95 Wh Kg under 0.1C -1 Is a high energy density of (a). As can be seen from the combination of fig. 6 and 7, at 3C, naFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The positive electrode provided 98.17 mAh g -1 Is a high rate capability of (2). As can be seen from fig. 8, the cycle capacity retention rate reached 70% at 2C. As can be seen from FIG. 9, naFe 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The positive electrode showed a low voltage hysteresis of 0.4V in the first cycle of 0.1C. The electrochemical properties obtained are shown in Table 1.
Example 2
Compared with the embodiment 1, the molar ratio of Na to Fe to Ti to Mn=1.1 to 0.2 to 0.6 in the sodium carbonate, the ferric oxide, the titanium dioxide and the manganese oxide in the step (1) is replaced by sodium carbonate, ferric oxide, titanium dioxide and manganese oxide Na to Fe to Mn=0.73 to 1/3 to 2/3, the charge-discharge voltage interval is replaced by 2.5 to 4.3 to V, and the rest steps are unchanged.
Example 3
In comparison with example 1, manganese acetate and a layered oxide matrix NaFe of step (2) 0.2 Ti 0.2 Mn 0.6 O 2 The molar ratio is replaced by 0.02:1 from 0.05:1, and the rest steps are unchanged.
Example 4
In comparison with example 1, manganese acetate and a layered oxide matrix NaFe of step (2) 0.2 Ti 0.2 Mn 0.6 O 2 The molar ratio is replaced by 0.05:1 to 0.1:1, and the rest steps are unchanged.
Example 5
In comparison with example 1, manganese acetate and a layered oxide matrix NaFe of step (2) 0.2 Ti 0.2 Mn 0.6 O 2 The molar ratio is replaced by 0.05:1 to 0.2:1, and the rest steps are unchanged.
Example 6
In comparison with example 1, manganese acetate and a layered oxide matrix NaFe of step (2) 0.2 Ti 0.2 Mn 0.6 O 2 The molar ratio is replaced by 0.05:1 to 0.5:1, and the rest steps are unchanged.
Example 7
Compared with example 1, the concentration of the oxalic acid solution in the step (2) was replaced by 0.02 mol/L to 0.01 mol/L.
Example 8
Compared with example 1, the concentration of the oxalic acid solution in the step (2) was replaced by 0.02 mol/L to 0.05 mol/L.
Example 9
In comparison with example 1, the calcination temperature in step (3) was changed from 800℃to 700℃with the remaining steps unchanged.
Example 10
In comparison with example 1, the calcination temperature in step (3) was changed from 800℃to 900℃with the remaining steps unchanged.
Example 11
In comparison with example 1, the calcination time in step (3) was replaced by 13 h from 15 h, the remaining steps being unchanged.
Example 12
In comparison with example 1, the calcination time in step (3) was replaced by 14h from 15 h, the remaining steps being unchanged.
Example 13
In comparison with example 1, the calcination time in step (3) was replaced by 16 h from 15 h, the remaining steps being unchanged.
Example 14
In comparison with example 2, manganese acetate and layered oxide matrix Na of step (2) 2/3 Fe 1/3 Mn 2/3 O 2 The molar ratio is replaced by 0.02:1 from 0.05:1, and the rest steps are unchanged.
Example 15
In comparison with example 2, manganese acetate and layered oxide matrix Na of step (2) 2/3 Fe 1/3 Mn 2/3 O 2 The molar ratio is replaced by 0.05:1 to 0.1:1, and the rest steps are unchanged.
Example 16
In comparison with example 2, manganese acetate and layered oxide matrix Na of step (2) 2/3 Fe 1/3 Mn 2/3 O 2 The molar ratio is replaced by 0.05:1 to 0.2:1, and the rest steps are unchanged.
Example 17
In comparison with example 2, manganese acetate and layered oxide matrix Na of step (2) 2/3 Fe 1/3 Mn 2/3 O 2 The molar ratio is replaced by 0.05:1 to 0.5:1, and the rest steps are unchanged.
Example 18
Compared with example 2, the concentration of the oxalic acid solution in the step (2) was replaced by 0.02 mol/L to 0.01 mol/L.
Example 19
Compared with example 2, the concentration of the oxalic acid solution in the step (2) was replaced by 0.02 mol/L to 0.05 mol/L.
Example 20
In comparison with example 2, the calcination temperature in step (3) was changed from 800℃to 700℃with the remaining steps unchanged.
Example 21
In comparison with example 2, the calcination temperature in step (3) was changed from 800℃to 900℃with the remaining steps unchanged.
Example 22
In comparison with example 2, the calcination time in step (3) was replaced by 13 h from 15 h, the remaining steps being unchanged.
Example 23
In comparison with example 2, the calcination time in step (3) was replaced by 14h from 15 h, the remaining steps being unchanged.
Example 24
In comparison with example 2, the calcination time in step (3) was replaced by 16 h from 15 h, the remaining steps being unchanged.
Example 25
NaFe obtained in example 1 0.2 Ti 0.2 Mn 0.6 O 2 @Na 0.44 MnO 2 The positive electrode material was divided into four equal parts, 300 mg was weighed into sample tubes, and then exposed to air for 1, 3, 5, 7 days, after which the exposed material was subjected to structural characterization XRD (fig. 10), electrochemical performance testing (fig. 11, 12), and contact angle testing of the pole pieces (fig. 13). The electrochemical performance characterization of the cells was the same as in example 1 and the cell performance is shown in Table 2.
Comparative example 1
Material preparation
(1) Uniformly mixing sodium carbonate, ferric oxide, titanium dioxide and manganese oxide according to the molar ratio of Na to Fe to Ti to Mn=1.1 to 0.2 to 0.6Pressing into a wafer, placing in air atmosphere, calcining at 1000deg.C at a heating rate of 5deg.C/min for 15 h to obtain layered oxide matrix material NaFe 0.2 Ti 0.2 Mn 0.6 O 2 （NaFTM）。
Material structure and electrochemical characterization
Research on NaFe by powder X-ray diffractometer 0.2 Ti 0.2 Mn 0.6 O 2 The crystal structure of the cathode material is shown in fig. 1: naFe 0.2 Ti 0.2 Mn 0.6 O 2 Is a typical crystal structure characteristic of sodium-based layered oxide of the O3 type. Characterization of NaFe Using scanning electron microscope 0.2 Ti 0.2 Mn 0.6 O 2 Is rough, and impurities are present (figure 2). Fourier transform infrared spectroscopy was used to confirm that surface impurities were residual bases (fig. 3).
NaFe is added to 0.2 Ti 0.2 Mn 0.6 O 2 Mixing the positive electrode material, super P and PVDF in a mass ratio of 7:2:1 in NMP to form a slurry, and uniformly coating the slurry on an aluminum foil current collector to obtain NaFe 0.2 Ti 0.2 Mn 0.6 O 2 And a positive pole piece. By NaFe 0.2 Ti 0.2 Mn 0.6 O 2 The pole piece is a positive pole piece, the metal sodium piece is used as a negative pole material, a glass fiber membrane (Whatman GF/D) is used as a diaphragm, and 1 mol/L NaClO is used as a diaphragm 4 Solvent (solvent is EC and DEC mixed solution with volume ratio of 1:1, and FEC with mass fraction of 5%) is added as electrolyte, and the button cell is assembled in a glove box protected by argon.
The assembled battery is subjected to constant-current charge and discharge test on a Xinwei charge and discharge tester, and the charge and discharge voltage interval is 2-4.3V #vs.Na/Na + ). As can be seen in FIG. 4, in NaFe 0.2 Ti 0.2 Mn 0.6 O 2 In the electrode, the first-turn discharge specific capacity is 144.3 mAh g -1 The initial coulomb efficiency is only 73.1%, and the irreversible capacity loss is up to 49.36 mAh g -1 . As can be seen in FIG. 5, naFe 0.2 Ti 0.2 Mn 0.6 O 2 The electrode was 462.39 mWh g at 0.1. 0.1C -1 Is a high energy density of (a). As can be seen in connection with fig. 6 and 7NaFe at 3C 0.2 Ti 0.2 Mn 0.6 O 2 The positive electrode only provides 52.81 mAh g -1 Is poor in rate performance. As can be seen from fig. 8, the cycle capacity retention rate was only 56% at 2C, and the cycle performance was poor. As can be seen from FIG. 9, naFe 0.2 Ti 0.2 Mn 0.6 O 2 The positive electrode showed a high voltage hysteresis of 1.1V in the first cycle of 0.1C. The electrochemical properties obtained are shown in Table 1.
Comparative example 2
Compared with comparative example 1, the molar ratio of Na to Fe to Ti to Mn=1.1:0.2:0.2:0.6 in sodium carbonate, ferric oxide, titanium dioxide and manganese oxide in step (1) is replaced by sodium carbonate, ferric oxide and manganese oxide Na to Fe to Mn=0.73:1/3:2/3, the charge-discharge voltage interval is replaced by 2-4.3V to 2.5-4.3V, and the rest steps are unchanged.
Comparative example 3
NaFe obtained in comparative example 1 0.2 Ti 0.2 Mn 0.6 O 2 The positive electrode material was divided into four equal parts, 300 mg was weighed into sample tubes, and then exposed to air for 1, 3, 5, 7 days, after which the exposed material was subjected to structural characterization XRD (fig. 10), electrochemical performance testing (fig. 11, 12), and contact angle testing of the pole pieces (fig. 13). The electrochemical performance characterization of the cells was the same as that of comparative example 1, and the cell performance is shown in Table 2.
TABLE 1 electrochemical Properties of Positive electrode Material under different preparation conditions
TABLE 2 electrochemical Properties of cathode materials after air exposure
As is evident from comparison of examples 1 and examples 3 to 6 and examples 2 and examples 14 to 17, when the molar ratio of the tunnel oxide interface layer material to the layered oxide matrix material is too high, the electrical properties of the materials are poor, and the optimum ratio is 0.05:1. As can be seen from a comparison of examples 1 and examples 7-8 and examples 2 and examples 18-19, the optimum concentration of the precipitant for the oxalic acid solution was 0.02 mol/L. As is evident from comparison of examples 1 and 9-13 and examples 2 and 20-24, the optimum sintering temperature at the time of secondary sintering was 800℃and the optimum sintering time was 15 h.
The electrochemical performance data of comparative example 1, example 25 and comparative example 3, and the characterization data in combination with fig. 1-13, show that the tunnel structure interface modification strategy can not only reasonably utilize the residual alkali on the surface of the layered oxide matrix material to convert into the tunnel structure interface layer, but also effectively block the contact of moist air and the matrix material, and improve the air stability of the material, so that the layered oxide is more suitable for storage, transportation, production and the like. Meanwhile, due to the layered tunnel interlocking effect, the beneficial effects of improving the sodium ion transmission dynamics, the energy conversion efficiency and the comprehensive electrochemical performance of the material can be generated. In addition, as can be seen from the combination of the embodiment 2 and the comparative example 2, the tunnel structure interface modification strategy is expanded from the application in the O3 type layered oxide of the embodiment 1 to the application in the P2 type layered oxide of the embodiment 2, so that a general method for improving the stability of the layered oxide of the sodium ion battery by using the tunnel functional structure is successfully formed, and the prospect of the method in industrial application is further demonstrated.
Claims (8)
1. The universal method for improving the stability of the layered oxide cathode material by the tunnel functional structure and the application of the universal method in the sodium ion battery are characterized in that the universal method for improving the stability of the layered oxide cathode material by the tunnel functional structure comprises the following steps:
(1) According to the composition characteristics of the layered oxide matrix material, sodium salt and transition metal salt are uniformly mixed, pressed into tablets and fully calcined under proper atmosphere and temperature to obtain the layered oxide matrix material Na x TMO 2 Wherein 0 < x.ltoreq.1, TM represents one or more transition metals;
(2) According to the tunnel oxide interface layer and the layered oxide baseMolar ratio of bulk material and composition characteristics of tunnel oxide interface layer material, the layered oxide cathode material Na of step (1) x TMO 2 Mixing with sodium salt and manganese salt in absolute ethanol, adding appropriate amount of oxalic acid solution for precipitation, and oven drying to obtain Na x TMO 2 @Na y MnO 2 Is a precursor material of (a);
(3) Fully calcining the precursor material under proper atmosphere and temperature to obtain the layered oxide material Na with tunnel structure interface modification x TMO 2 @Na y MnO 2 Wherein x is more than 0 and less than or equal to 1,0.22 and y is more than or equal to 0.5, and the molar ratio of the tunnel oxide interface layer material to the layered oxide matrix material is 0.02-0.5:1.
2. The method for improving stability of layered oxide cathode material with tunnel function structure and application thereof in sodium ion battery as claimed in claim 1, wherein the sodium salt in step (1) is at least one of sodium oxalate, sodium acetate, sodium nitrate, sodium sulfate, sodium chloride and sodium carbonate, and the transition metal in the transition metal salt is one or more selected from V, ti, fe, mn, cu, zn, zr, ni, co, cr.
3. The universal method for improving stability of layered oxide cathode material by tunnel functional structure and application of the universal method in sodium ion battery according to claim 1, wherein the calcining atmosphere in the step (1) is air or oxygen, the calcining temperature is 700-1200 ℃, the heating rate is 2-6 ℃/min, and the calcining time is 13-19 h.
4. The method for improving stability of layered oxide cathode material with tunnel function structure and application thereof in sodium ion battery as claimed in claim 1, wherein the sodium salt in step (2) is at least one of sodium oxalate, sodium acetate, sodium nitrate, sodium sulfate, sodium chloride and sodium carbonate, and the manganese salt is at least one of manganese oxalate, manganese acetate, manganese nitrate, manganese sulfate and manganese carbonate.
5. The method for improving stability of layered oxide cathode material with tunnel function structure and application thereof in sodium ion battery as claimed in claim 1, wherein oxalic acid solution in step (2) is precipitant, and concentration is controlled to be 0.01-0.2 mol/L.
6. The method for improving the stability of the layered oxide cathode material by using the tunnel functional structure and the application of the method in the sodium ion battery according to claim 1, wherein the calcining atmosphere in the step (3) is air or oxygen, the calcining temperature is 600-1000 ℃, the heating rate is 2-6 ℃/min, and the calcining time is 12-17 h.
7. A universal method for improving stability of layered oxide cathode material by tunnel functional structure and application of the material in sodium ion battery, characterized in that the material comprises the layered oxide cathode material modified by tunnel structural interface as set forth in any one of claims 1-6.
8. A sodium ion battery comprising the tunnel structured interface modified layered oxide positive electrode sheet of claim 7.
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