CN117913272A - Dekalium-sodium-embedded modified Prussian blue analogue, and preparation method and application thereof - Google Patents
Dekalium-sodium-embedded modified Prussian blue analogue, and preparation method and application thereof Download PDFInfo
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- CN117913272A CN117913272A CN202211236727.0A CN202211236727A CN117913272A CN 117913272 A CN117913272 A CN 117913272A CN 202211236727 A CN202211236727 A CN 202211236727A CN 117913272 A CN117913272 A CN 117913272A
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- sodium
- prussian blue
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- potassium
- positive electrode
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- DCYOBGZUOMKFPA-UHFFFAOYSA-N iron(2+);iron(3+);octadecacyanide Chemical class [Fe+2].[Fe+2].[Fe+2].[Fe+3].[Fe+3].[Fe+3].[Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] DCYOBGZUOMKFPA-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 229910001415 sodium ion Inorganic materials 0.000 claims abstract description 39
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 claims abstract description 36
- 229910052700 potassium Inorganic materials 0.000 claims abstract description 18
- 239000007774 positive electrode material Substances 0.000 claims abstract description 11
- 239000010405 anode material Substances 0.000 claims abstract description 7
- 239000011734 sodium Substances 0.000 claims description 57
- 239000000243 solution Substances 0.000 claims description 57
- 229910052708 sodium Inorganic materials 0.000 claims description 40
- 239000000463 material Substances 0.000 claims description 38
- -1 sodium ferrocyanide monohydrate Chemical class 0.000 claims description 38
- 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 claims description 36
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 24
- 239000002904 solvent Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- OBKARMSLSGWHQK-UHFFFAOYSA-K tripotassium;2-hydroxypropane-1,2,3-tricarboxylate;dihydrate Chemical compound O.O.[K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O OBKARMSLSGWHQK-UHFFFAOYSA-K 0.000 claims description 19
- 239000001509 sodium citrate Substances 0.000 claims description 18
- 239000003792 electrolyte Substances 0.000 claims description 16
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 15
- 239000012266 salt solution Substances 0.000 claims description 15
- 229910052757 nitrogen Inorganic materials 0.000 claims description 14
- 239000000264 sodium ferrocyanide Substances 0.000 claims description 14
- 235000012247 sodium ferrocyanide Nutrition 0.000 claims description 14
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 13
- 238000006243 chemical reaction Methods 0.000 claims description 12
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims description 12
- 238000001291 vacuum drying Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 239000013078 crystal Substances 0.000 claims description 10
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 10
- 239000000276 potassium ferrocyanide Substances 0.000 claims description 10
- 239000002244 precipitate Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 claims description 9
- BAZAXWOYCMUHIX-UHFFFAOYSA-M sodium perchlorate Chemical compound [Na+].[O-]Cl(=O)(=O)=O BAZAXWOYCMUHIX-UHFFFAOYSA-M 0.000 claims description 9
- 229910001488 sodium perchlorate Inorganic materials 0.000 claims description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000002033 PVDF binder Substances 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 238000000975 co-precipitation Methods 0.000 claims description 8
- 239000011888 foil Substances 0.000 claims description 8
- 239000011259 mixed solution Substances 0.000 claims description 8
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 8
- 239000002482 conductive additive Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 238000002441 X-ray diffraction Methods 0.000 claims description 6
- 239000006229 carbon black Substances 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 239000011261 inert gas Substances 0.000 claims description 6
- HRXKRNGNAMMEHJ-UHFFFAOYSA-K trisodium citrate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O HRXKRNGNAMMEHJ-UHFFFAOYSA-K 0.000 claims description 6
- GTSHREYGKSITGK-UHFFFAOYSA-N sodium ferrocyanide Chemical compound [Na+].[Na+].[Na+].[Na+].[Fe+2].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] GTSHREYGKSITGK-UHFFFAOYSA-N 0.000 claims description 5
- 159000000000 sodium salts Chemical class 0.000 claims description 5
- 239000011230 binding agent Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 3
- 229910002651 NO3 Inorganic materials 0.000 claims description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 3
- 239000006230 acetylene black Substances 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- QEWYKACRFQMRMB-UHFFFAOYSA-N fluoroacetic acid Chemical compound OC(=O)CF QEWYKACRFQMRMB-UHFFFAOYSA-N 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- KBBYYFOMJKSRSM-UHFFFAOYSA-N potassium;cyanide;hydrate Chemical compound O.[K+].N#[C-] KBBYYFOMJKSRSM-UHFFFAOYSA-N 0.000 claims description 3
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 claims description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 2
- 239000004584 polyacrylic acid Substances 0.000 claims description 2
- 238000001556 precipitation Methods 0.000 claims description 2
- 239000011164 primary particle Substances 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 2
- 238000005119 centrifugation Methods 0.000 claims 1
- 238000012986 modification Methods 0.000 abstract description 3
- 230000004048 modification Effects 0.000 abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 28
- 229960003351 prussian blue Drugs 0.000 description 23
- 239000013225 prussian blue Substances 0.000 description 23
- 229910002548 FeFe Inorganic materials 0.000 description 19
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 12
- 229960003975 potassium Drugs 0.000 description 12
- 239000011591 potassium Substances 0.000 description 12
- 239000000203 mixture Substances 0.000 description 10
- 239000000047 product Substances 0.000 description 9
- 239000003365 glass fiber Substances 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 238000004080 punching Methods 0.000 description 4
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 238000009616 inductively coupled plasma Methods 0.000 description 3
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 3
- 238000009830 intercalation Methods 0.000 description 3
- 230000002687 intercalation Effects 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- 238000004626 scanning electron microscopy Methods 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 2
- 150000003385 sodium Chemical class 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 102000004310 Ion Channels Human genes 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920000447 polyanionic polymer Chemical class 0.000 description 1
- 229910001414 potassium ion Inorganic materials 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention belongs to the technical field of modification of sodium ion battery anode materials, and particularly relates to a potassium-removed sodium-embedded modified Prussian blue analogue, a preparation method thereof and application thereof as a sodium ion battery anode material. Prussian blue analogues having a structure represented by formula I; a 2‑xFe[Fe(CN)6 ], formula I; a is at least one of K, na; x is more than 1.82 and less than 2; the invention obtains the Prussian blue analogues with the nanometer scale below 50nm, the A-site ratio is improved from 1.53 to 1.84, and as the positive electrode material of the sodium ion battery, the first discharge capacity is improved from 115mAh g ‑1 to 140mAh g ‑1, the coulomb efficiency is improved from 98.2 to 99 percent to 98.7 to 100 percent, and the coulomb efficiency is obviously improved. From the two plateau duty cycles of the charge-discharge curve, it can be seen that by extending the second plateau, the potassium-substituted sample has a higher specific capacity.
Description
Technical Field
The invention belongs to the technical field of modification of sodium ion battery anode materials, and particularly relates to a potassium-removed sodium-embedded modified Prussian blue analogue, a preparation method thereof and application thereof as a sodium ion battery anode material.
Background
Because of higher capacity and stable charge and discharge performance, lithium ion batteries have been rapidly developed in the past decades, and the lithium ion batteries are widely applied to the fields of portable mobile phones, computers, electric automobiles, smart grids and the like. At the same time, however, lithium ion batteries have fatal defects, and lithium resources are scarce and expensive. Therefore, a low cost alternative to the earth with abundant reserves, sodium element, has entered the line of sight of researchers. Sodium belongs to the same main group as lithium and therefore has a similar electrochemical behaviour as lithium, with a potential of-2.71V relative to a standard hydrogen electrode. Since the beginning of sodium ion battery research in the eighties, the most interesting positive electrode materials mainly include layered metal oxides, prussian blue analogues, polyanion salts, and the like, wherein the Prussian blue analogues have received wide attention due to their stable crystal structure, abundant reaction sites and low raw material cost.
Prussian blue analog A 2MFe(CN)6 (A=Na, K; M=Fe, co, mn, etc.) is a compound with an open framework structure, has larger ion channels, and can accommodate larger alkali metal ions (sodium and potassium ions) for intercalation and deintercalation electrochemical reaction therebetween, and is widely paid attention to because of its stable structure and higher theoretical specific capacity (-170 mAhg -1). However, na 2Fe[Fe(CN)6 as a class of sodium ion battery cathode materials of great interest, there are mainly the following problems: na 2Fe[Fe(CN)6 is easy to be lost in the synthesis process, and because sodium is often insufficient in space occupation, the sodium is far less than 2 (generally less than 1.6), and water enters the crystal lattice and Fe (CN) 6 vacancies are generated, so that Na 2-xFe[Fe(CN)6 is actually obtained, wherein x is usually more than 0.4, the final capacity is greatly reduced, and the capacity is far lower than the theoretical capacity. The prior art mainly provides a solution to the sodium deficiency problem, and mainly can be summarized into two schemes, namely, removing bound water by means of drying, freeze drying and the like, and controlling the reaction process to improve the sodium content. The former has been widely used in the synthesis process of Prussian blue, but in order to obtain an electrode material with lower water content and more stable electrochemical performance, the drying temperature needs to be continuously increased, however, when the temperature is increased to 180 ℃, the crystal structure of the Prussian blue material is damaged, and the sodium containing performance of the material is affected. In the latter case, however, sodium-based Prussian blue itself is prone to defects, and thus the improvement achieved by controlling the reaction process is limited.
Disclosure of Invention
Even a small amount of sodium in the material can greatly improve the A-site ratio and the electrochemical performance, while the material K 2-xFe[Fe(CN)6 is easy to synthesize a product with high potassium-site ratio, and x can be less than 0.2. The invention provides an improved method of Prussian blue-based sodium ion battery anode material, which adopts potassium to replace sodium, improves the sodium site ratio, increases the first discharge capacity, has theoretical support, is simple to operate, has low energy consumption and no pollution, and can effectively improve the intrinsic characteristics and electrochemical properties of the material.
The invention provides a Prussian blue analogue, which has a structure shown in a formula I;
A 2-xFe[Fe(CN)6 ], formula I;
A is at least one of K, na; x is more than 1.82 and less than 2.
Optionally, the primary particles of the Prussian blue analogues have a particle size of 50nm or less.
Alternatively, the peak intensity ratio of the 23 to 25 ° peak intensity of the X-ray diffraction peak to the 16 to 18 ° peak of the crystal structure of the prussian blue analog is between 1.0 and 1.2.
The invention also provides a preparation method of the Prussian blue analogue, and the mixed materials undergo a coprecipitation reaction in nitrogen atmosphere to obtain a precipitate containing the Prussian blue analogue; the mixed material contains the following components in percentage by mass:
sodium citrate or tripotassium citrate dihydrate: 0.04 to 0.16 part;
ferrous salt: 0.008-0.033 part;
sodium ferrocyanide monohydrate or potassium ferrocyanide monohydrate: 0.01 to 0.048 portion;
1 part of solvent.
Optionally, the ferrous salt is selected from at least one of ferrous chloride tetrahydrate, ferrous sulfate heptahydrate and ferrous nitrate.
Optionally, the sodium citrate or tripotassium citrate dihydrate is 0.04-0.14 parts.
Alternatively, the sodium ferrocyanide monohydrate or the potassium ferrocyanide monohydrate is 0.012 to 0.04 parts.
Optionally, the solvent is water or a mixed solution of water and ethanol; preferably, the concentration of ethanol in the mixed solution is 50-100 g/L.
Optionally, the conditions of the precipitation reaction include: the temperature is 10-40 ℃, and the reaction time is 8-24 h.
Optionally, the precipitate is subjected to centrifugal washing and vacuum drying.
Optionally, the conditions of vacuum drying I include: the temperature is 80-150 ℃; the time is 12-24 hours; preferably at 80-120 ℃ for 12-36 h.
Optionally, the coprecipitation reaction includes the steps of:
S1, mixing at least one of sodium citrate and tripotassium citrate dihydrate, ferrous salt and water to prepare uniform solution X; preferably, ferrous salt is dissolved and mixed with water, and at least one of sodium citrate and potassium citrate dihydrate is added to obtain the solution I;
S2, mixing at least one of sodium citrate, tripotassium citrate dihydrate, sodium ferrocyanide monohydrate and potassium ferrocyanide monohydrate with water to prepare uniform solution II; preferably, at least one of sodium citrate and potassium citrate dihydrate is mixed with water, and at least one of sodium ferrocyanide hydrate and potassium cyanide hydrate is added to obtain the solution II;
S3, dropwise adding the solution II into the solution I with the same volume under the protection of inert gases such as nitrogen or argon, wherein the dropwise adding speed is between 200mL/h and 800mL/h, and obtaining a precipitate containing Prussian blue analogues.
When K is contained in A, the preparation method further comprises the step of carrying out electrochemical treatment on the precipitate containing the Prussian blue analogues; the electrochemical treatment is to use a sodium salt solution as an electrolyte, a sodium sheet as a counter electrode, and the precipitate containing Prussian blue analogues is coated on an aluminum foil as an anode to assemble a half battery, and charge and discharge are carried out by constant current.
Optionally, the current density of the charging and discharging ranges from 3mA/g to 10mA/g.
Alternatively, charge and discharge two turns.
Optionally, the sodium salt solution is sodium perchlorate of 0.5-1 mol/L, the solvent is propylene carbonate fluoroacetate with the volume ratio of 1-5%, and ethylene carbonate and propylene carbonate fluoroacetate with the volume ratio of 95-99%, wherein the proportion of the ethylene carbonate to the propylene carbonate is 1:1.
The invention also provides a sodium ion battery anode material which contains the Prussian blue analogues as defined in any one of the claims; or Prussian blue analogues obtained by any one of the preparation methods.
Optionally, the Prussian blue analogues, a binder and a conductive additive are contained in a mass ratio of (7-8): (1-2): 1.
Optionally, the conductive additive is selected from at least one of carbon black, conductive graphite, acetylene black, super P.
Optionally, the binder is at least one selected from polyvinylidene fluoride, polyacrylic acid and sodium carboxymethyl cellulose.
Optionally, the positive electrode of the sodium ion battery is obtained by coating the positive electrode material on aluminum foil and drying II.
Optionally, the conditions of drying II include: 80-120 ℃ and 8-12 h.
The invention also provides a sodium ion half-cell, which comprises the positive electrode of any one of the sodium ion cells.
Optionally, the sodium ion half-cell consists of a sodium sheet and an electrolyte, wherein the positive electrode of the sodium ion cell is formed by the sodium sheet and the electrolyte;
optionally, the electrolyte is 0.5-1 mol/L sodium perchlorate solution, the solvent is 1-5% of fluoroacetate by volume ratio, 95-99% of ethylene carbonate and propylene carbonate by volume ratio, wherein the ratio of ethylene carbonate to propylene carbonate is 1:1.
The invention provides a method for synthesizing K 2-xFe[Fe(CN)6 first and then removing potassium and embedding sodium in an electrochemical mode to obtain Na 2-xFe[Fe(CN)6 so as to improve electrochemical capacity. According to the invention, the Prussian blue analogues with the size below 50nm are obtained, the synthesized material (A 2-xFe[Fe(CN)6, A is K, na or a mixture of the two) is nano particles, the A site ratio is improved from 1.53 to 1.84, the first discharge capacity is improved from 115mAh g -1 to 140mAh g -1 as a sodium ion battery positive electrode material, the coulomb efficiency is improved from 98.2% to 99% to 98.7% to 100%, and the coulomb efficiency is obviously improved. From the two plateau duty cycles of the charge-discharge curve, it can be seen that by extending the second plateau, the potassium-substituted sample has a higher specific capacity.
Drawings
FIG. 1 is an SEM image of a potassium-substituted sodium Prussian blue material K 1.84FeFe[(CN)6 prepared according to example 1;
FIG. 2 is an SEM image of a portion of the potassium-substituted sodium Prussian blue material K 1.85Na0.03FeFe[(CN)6 prepared in example 2;
fig. 3 is an SEM image of the prussian blue material Na 1.53FeFe[(CN)6 prepared in comparative example 1;
FIG. 4 is an XRD pattern of three of the potassium-substituted sodium Prussian blue material K 1.84FeFe[(CN)6 prepared in example 1, the partially potassium-substituted Prussian blue material K 1.85Na0.03FeFe[(CN)6 prepared in example 2, and the Prussian blue material Na 1.53FeFe[(CN)6 prepared in comparative example 1;
Fig. 5 is a first charge-discharge curve of a sodium ion battery using a prussian blue material K 1.84FeFe[(CN)6 of example 1 potassium-substituted sodium as a positive electrode;
FIG. 6 is a first charge-discharge curve of a sodium ion battery with a portion of the Prussian blue material K 1.85Na0.03FeFe[(CN)6 of example 2 potassium-substituted sodium as the positive electrode;
Fig. 7 is a first charge-discharge curve of a sodium ion battery of comparative example 1 Prussian blue material Na 1.53FeFe[(CN)6 as a positive electrode;
Fig. 8 is the coulombic efficiency of 100 cycles of charge and discharge of the sodium ion battery of example 1 potassium-substituted sodium Prussian blue material K 1.84FeFe[(CN)6 as the positive electrode;
Fig. 9 is a coulombic efficiency of 100 cycles of charge and discharge of a sodium ion battery of example 2, partially potassium-substituted sodium Prussian blue material K 1.85Na0.03FeFe[(CN)6, as a positive electrode;
Fig. 10 is a coulombic efficiency of 100 cycles of charge and discharge of the sodium ion battery of comparative example 1 Prussian blue material Na 1.53FeFe[(CN)6 as a positive electrode;
Fig. 11 is a graph showing the rate performance of a sodium ion battery using the prussian blue material K 1.84FeFe[(CN)6 as a positive electrode, which was potassium-substituted sodium in example 1.
Detailed Description
In order to facilitate understanding of the present invention, examples are set forth below. It will be apparent to those skilled in the art that the examples are merely to aid in the understanding of the present invention and should not be construed as a specific limitation thereof. The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values.
All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, definitions, will control.
In the context of this specification, any two or more aspects of the invention may be combined arbitrarily, and the resulting solution is part of the original disclosure of the specification, while also falling within the scope of the invention.
Where not explicitly indicated, all percentages, parts, ratios, etc. referred to in this specification are by weight unless otherwise indicated, as such, do not conform to the conventional wisdom of one skilled in the art.
As one of the embodiments, a method for synthesizing a potassium-substituted sodium Prussian blue analog is obtained by coprecipitation synthesis of reaction raw materials under a protective atmosphere of inert gas nitrogen.
The raw materials adopt sodium citrate, tripotassium citrate dihydrate, ferrous sulfate heptahydrate, sodium ferrocyanide hydrate and potassium ferrocyanide monohydrate, coprecipitate in water under nitrogen atmosphere, and then centrifugal washing is carried out to obtain a preliminary product, and potassium-substituted Prussian blue analogues (Na xK2-xFe[Fe(CN)6, x is less than or equal to 2) are obtained after vacuum drying, wherein the content ranges of the sodium citrate, tripotassium citrate dihydrate, ferrous sulfate heptahydrate, sodium ferrocyanide monohydrate and potassium ferrocyanide monohydrate in water are respectively as follows:
sodium citrate: 0 to 0.14g/mL;
Tripotassium citrate dihydrate: 0 to 0.16g/mL;
ferrous sulfate heptahydrate: 0.008-0.033 g/mL;
sodium ferrocyanide monohydrate: 0.01-0.04 g/mL;
Potassium ferrocyanide monohydrate: 0.012-0.048 g/mL.
Preferably, the method comprises the following steps:
1) Dissolving ferrous salt in deionized water, and dissolving one or two of sodium citrate and potassium citrate dihydrate in the solution to obtain mixed salt solution;
The ferrous salt is one or more selected from ferrous chloride tetrahydrate, ferrous sulfate heptahydrate and ferrous nitrate;
2) Dissolving one or two of sodium citrate and potassium citrate dihydrate in deionized water, and dissolving one or more of sodium ferrocyanide hydrate and potassium cyanide hydrate in the solution to obtain a mixed salt solution;
3) Slowly dropwise adding the solution in the step A) into the solution in the step B) under the protection of inert gases such as nitrogen or argon, magnetically stirring in the adding process, reacting for a period of time, collecting a product A 2Fe[Fe(CN)6 (A is one or two of Na and K, and mixing), filtering, washing and drying;
Preferably, the reaction is carried out at a temperature of 10-40 ℃ for 8-24 hours;
preferably, in the drying process, the heating temperature is 80-120 ℃ and the heating time is 12-36h in a vacuum drying oven;
as one of the embodiments, the potassium-removing and sodium-inserting method of the sodium-substituted Prussian blue analog sodium-electric positive electrode material comprises the following steps:
Preparation of electrode plates: mixing the prepared positive electrode material with a conductive additive and PVDF solution in a certain proportion, adding a proper amount of solvent N-methyl pyrrolidone, grinding and mixing uniformly, uniformly coating on an aluminum foil, heating and drying the solvent to obtain a positive electrode plate, and punching the plate into a proper size; the conductive additive is one of acetylene black, carbon black, conductive graphite and Super P; preferably, the PVDF solution has a concentration of 5% -10% of N-methylpyrrolidone solution; preferably, the solid content ratio of the mixture of the positive electrode material, the conductive additive and the PVDF solution is 8:1:1, a step of; preferably, the heating temperature is 80-120 ℃ and the heating time is 8-12h.
And (3) assembling a half cell: the obtained positive electrode plate is assembled with sodium plates, electrolyte, glass fibers (Glass fibers), springs and gaskets in a glove box to form a button cell; the electrolyte is 1mol/L sodium perchlorate solution, the solvent is a mixed solution of propylene carbonate, ethylene carbonate and fluoroethylene carbonate, and the ratio of the propylene carbonate to the ethylene carbonate is 1:1, the total amount accounts for 95 to 99 percent, and the content of fluoroethylene carbonate is 1 to 5 percent;
Electrochemical potassium removal and sodium intercalation: the assembled button cell is charged and discharged under constant current to finish the potassium-removing and sodium-inserting process; and (3) carrying out potassium removal and sodium intercalation by constant current charge and discharge in a glove box, wherein the current density range is 3 mA/g-10 mA/g, and the positive electrode material of sodium Prussian blue is obtained after two circles of charge and discharge. Sodium salt electrolyte is sodium perchlorate of 0.5-1 mol/L, solvent is fluoroacetate propylene carbonate of which the volume ratio is 1-5 percent, and ethylene carbonate and propylene carbonate fluoroacetate of which the volume ratio is 95-99 percent, wherein the proportion of ethylene carbonate to propylene carbonate is 1:1. preferably, the constant current charge and discharge current is 10mA/g, and the voltage window is 2-4V.
Example 1
(1) Synthesis of Prussian blue analogues of potassium-substituted sodium
Potassium-substituted prussian blue analogues are synthesized by adopting a coprecipitation method under an inert atmosphere.
40G of tripotassium citrate dihydrate was dissolved in 500mL of water to prepare a homogeneous mixed salt solution, designated solution X.
3.34G of ferrous sulfate heptahydrate was dissolved in 200mL of solution X to prepare a uniformly mixed salt solution, designated as solution I.
200ML of solution X was further prepared, and 4.72g of potassium ferrocyanide monohydrate was dissolved therein to prepare a uniformly mixed salt solution, which was designated as solution II.
And (3) placing a magneton in the solution I, magnetically stirring, introducing nitrogen, and slowly dropwise adding the solution II into the solution I under the protection of the nitrogen, wherein the dropwise adding speed is 300mL/h. The reaction was stirred for 12h and was carried out at room temperature. Filtering and washing the obtained product, putting the product into a vacuum drying oven, heating to 120 ℃, and keeping the temperature for 12 hours to obtain the Prussian blue analog (sample No. 1) of potassium-substituted sodium.
Sample 1# was characterized for morphology by Scanning Electron Microscopy (SEM), as shown in fig. 1, and the visible material was a stack of nanoparticles with a nanoparticle size below 50 nm.
The crystal structure of sample 1# was characterized by X-ray diffraction (XRD), as shown in fig. 4, it was seen that the material had a different crystal structure from sodium-based prussian blue, and the ratio of the peak intensity of the diffraction peak at 23 to 25 ° to the peak intensity of the diffraction peak at 16 to 18 ° was 1.08. In addition, the diffraction peak appears to be broadened because of particle nanocrystallization. The content of potassium and iron in sample 1# was determined by inductively coupled plasma atomic emission spectrometry (ICP), and the data result is K 1.84FeFe[(CN)6.
(2) Preparation of sodium ion battery positive plate
Sample 1# synthesized above was mixed with carbon black and PVDF solution (5% by mass solution, nitrogen methyl pyrrolidone as solvent) in a mass ratio of 8:1:1, adding 2 to 3 times (mass) of azomethine pyrrolidone into the mixture, uniformly mixing, coating the mixture on an aluminum foil with the thickness of 200 mu m, vacuum drying the mixture at the temperature of 100 ℃, and punching the electrode plate into a wafer with the thickness of 0.8 to 1.2cm 2 after 8 hours to obtain the positive electrode plate.
(3) Assembly and testing of sodium ion batteries
The assembly of the sodium ion battery is carried out in nitrogen filled with nitrogen, and the required materials are sodium sheets (serving as a counter electrode), electrolyte, springs, gaskets, glass Fiber separators (Glass fibers) and the positive electrode sheets. The electrolyte uses 1mol/L sodium perchlorate solution, and the solvent is a mixed solution of propylene carbonate (volume of 47.5% of the total solvent), ethylene carbonate (volume of 47.5% of the total solvent) and fluoroethylene carbonate (volume of 5% of the total solvent). The 2035 button cell was assembled and the resulting cell was tested for constant current charge and discharge in a 30 ℃ incubator. The voltage range is 2-4V, the current is 10mA/g, the sodium-based Prussian blue Na 1.84FeFe[(CN)6 is obtained after two cycles, and the current of the later cycle test is 100mA/g. The conditions for the rate performance test are: after 10mA/g charge-discharge activation for three circles, the charging current was set to 20mA/g, and the discharging current was respectively 20mA/g,50mA/g,100mA/g,200mA/g.
Fig. 5 shows the first charge-discharge curves of the potassium-removing and sodium-inserting process, and it can be seen that the contribution of the first plateau and the second plateau to the capacity is 36% and 64% respectively during the charging process, i.e. the potassium-removing process, which is significantly different from the comparative example octasodium-based prussian blue, the plateau of the high voltage range is widened.
FIG. 8 shows the coulombic efficiency of material Na 1.84FeFe[(CN)6 at 100mA/g after potassium and sodium removal, and it can be seen that the coulombic efficiency is above 98.7% in 100 cycles.
Fig. 11 shows the rate performance, and the battery performs constant current charge and discharge at rates of 0.1C, 0.2C, 0.5C, 1C, and 2C (1c=100 mA), respectively, and the material shows good rate performance, and can still maintain the capacity of 40mAh g -1 at the rate of 2C.
Example 2
(1) Synthesis of Prussian blue analogues with partial potassium substitution of sodium
Prussian blue analogues with partial potassium substituted sodium are synthesized by adopting a coprecipitation method under inert atmosphere.
40G of tripotassium citrate dihydrate was dissolved in 500mL of water to prepare a homogeneous mixed salt solution, designated solution X.
3.34G of sodium ferrous sulfate heptahydrate was dissolved in 200mL of solution X to prepare a uniformly mixed salt solution, designated as solution I.
Then, 200mL of solution X was taken, and 3.94g of sodium ferrocyanide monohydrate was dissolved therein to prepare a uniformly mixed salt solution, which was designated as solution II.
And (3) placing a magneton in the solution I, magnetically stirring, introducing nitrogen, slowly dropwise adding the solution II into the solution I under the protection of the nitrogen, stirring and reacting for 12 hours, wherein the dropwise adding speed is 300mL/h, and reacting is carried out at room temperature. Filtering and washing the obtained product, putting the product into a vacuum drying oven, heating to 120 ℃, and keeping the temperature for 12 hours to obtain the Prussian blue analogue (sample # 2) with partial potassium substituted sodium. The morphology of the prepared sample No.2 is characterized by a Scanning Electron Microscope (SEM), and as shown in FIG. 2, the morphology of the material is similar to that of the sample No. 1, and the material is formed by stacking nano particles with the particle size of less than 50 nm. The crystal structure of sample 2# was characterized by X-ray diffraction, as shown in fig. 4, and it was seen that the material 1# had a crystal structure consistent with that of the material, and the ratio of the peak intensities of the diffraction peaks at 23 to 25 ° to the peak intensities of the diffraction peaks at 16 to 18 ° was 1.07. The content of sodium, potassium and iron in sample 2# was determined by inductively coupled plasma atomic emission spectrometry (ICP), and the data result is K 1.85Na0.03FeFe[(CN)6.
(2) Preparation of sodium ion battery positive plate
Sample 2# synthesized above was mixed with carbon black and PVDF solution (5% by mass solution, solvent was azamethylpyrrolidone) at a mass ratio of 8:1:1, adding 2 to 3 times (mass) of azomethine pyrrolidone into the mixture, uniformly mixing, coating the mixture on an aluminum foil with the thickness of 200 mu m, vacuum drying the mixture at the temperature of 100 ℃, and punching the electrode plate into a raw plate with the thickness of 0.8 to 1.2cm 2 after 8 hours to obtain the positive electrode plate.
(3) Assembly and testing of sodium ion batteries
The assembly of the sodium ion battery is carried out in nitrogen filled with inert gas, and the required materials are sodium sheet (as a counter electrode), electrolyte, spring, gasket, glass Fiber membrane (Glass Fiber) and the positive electrode sheet. The electrolyte uses 1mol/L sodium perchlorate solution, and the solvent is a mixed solution of propylene carbonate (volume of 47.5% of the total solvent), ethylene carbonate (volume of 47.5% of the total solvent) and fluoroethylene carbonate (volume of 5% of the total solvent). The 2035 button cell was assembled and the resulting cell was tested for constant current charge and discharge in a 30 ℃ incubator. The voltage range is 2-4V, the current is 10mA/g, the sodium-based Prussian blue Na 1.88FeFe[(CN)6 is obtained after two cycles, and the current of the later cycle test is 100mA/g.
Fig. 6 is a first-pass charge-discharge electrochemical curve of the sample potassium-removed sodium-intercalated. It can be seen that the first plateau and the second plateau of the first charge process have contributions to capacity of 42% and 58%, respectively, and the first discharge capacity is 118mAh g -1. Similar to sample 1# the capacity contribution of the high voltage platform was broadened.
FIG. 9 shows the coulombic efficiency of the material at 100mA/g after potassium and sodium removal, and it can be seen that the coulombic efficiency is above 98.5% in the first cycle, except for the 100 cycles.
Comparative example 1
(1) Synthesis of sodium Prussian blue analogues
Sodium Prussian blue analogues are synthesized by adopting a coprecipitation method under an inert atmosphere.
40G of sodium citrate was dissolved in 500mL of water to prepare a homogeneous mixed salt solution, designated solution X.
3.34G of ferrous sulfate heptahydrate was dissolved in 200mL of solution X to prepare a uniformly mixed salt solution, designated as solution I.
Then, 200mL of solution X was taken, and 3.94g of sodium ferrocyanide hydrate was dissolved therein to prepare a uniformly mixed salt solution, which was designated as solution II.
And (3) placing a magneton in the solution I, magnetically stirring, introducing nitrogen, slowly dropwise adding the solution II into the solution I under the protection of the nitrogen, stirring and reacting for 12 hours, wherein the dropwise adding speed is 300mL/h, and reacting is carried out at room temperature. Filtering and washing the obtained product, putting the product into a vacuum drying oven, heating to 120 ℃, and keeping the temperature for 12 hours to obtain the final product.
The prepared sample is characterized by a Scanning Electron Microscope (SEM), and as shown in figure 3, the microscopic morphology is a cube composition with side length of 0.3-1.5 mu m. The crystal structure is characterized by X-ray diffraction, as shown in FIG. 4, the comparison sample has good crystallinity, and the peak intensity ratio of diffraction peaks of 23-25 DEG to 16-18 DEG is 0.30. Sodium and iron contents were determined by inductively coupled plasma atomic emission spectrometry (ICP), and the data result is Na 1.53FeFe[(CN)6.
(2) Preparation of sodium ion battery positive plate
Mixing the synthesized Prussian blue analog material with carbon black and PVDF (5% solution, wherein the solvent is nitrogen methyl pyrrolidone) according to a mass ratio of 8:1:1, adding 2 to 3 times of nitrogen methyl pyrrolidone of the mass of a sample, uniformly mixing, coating the mixture on an aluminum foil, vacuum drying at 100 ℃ for 8 hours, and punching the electrode plate into a wafer with the area of 0.8 to 1.2cm 2 to obtain the positive electrode plate.
(3) Assembly and testing of sodium ion batteries
The assembly of the sodium ion battery is carried out in nitrogen filled with inert gas, and the required materials are sodium sheet (as a counter electrode), electrolyte, spring, gasket, glass Fiber membrane (Glass Fiber) and the positive electrode sheet. The electrolyte uses 1mol/L sodium perchlorate solution, and the solvent is a mixed solution of propylene carbonate (47.5%), ethylene carbonate (47.5%) and fluoroethylene carbonate (5%). The 2035 button cell was assembled and the resulting cell was tested for constant current charge and discharge in a 30 ℃ incubator. The voltage range is 2-4V, the activation current is 10mA/g, and the current of the cyclic test is 100mA/g.
Fig. 7 shows charge and discharge curves at a current density of 10mA/g, a first discharge capacity of 115mAh g -1, and a capacity contribution ratio of the first charging plateau and the second charging plateau of 70% and 30%, respectively, and it can be seen that the capacity contribution of the high voltage plateau is smaller compared to the first and second embodiments.
Fig. 10 shows the coulombic efficiency of the material at 100mA/g for the cycle after potassium and sodium removal, and it can be seen that the coulombic efficiency is between 98.2% and 99% for the first cycle, except for the 100 cycles.
The embodiments of the present invention are only used to illustrate the detailed process equipment and process flow of the present invention, but the present invention is not limited to the detailed process equipment and process flow, i.e., the present invention can be implemented without depending on the steps described in the embodiments. In summary, any modifications to the present invention, including the substitution of materials and additives described herein, the selection of particular embodiments, etc., would be within the scope of the invention and the disclosure.
Claims (10)
1. Prussian blue analogues, characterized by having a structure represented by formula I;
A 2-x Fe[Fe(CN)6 ], formula I;
A is at least one of K, na; x is more than 1.82 and less than 2.
2. Prussian blue analogues according to claim 1, wherein,
The particle size of primary particles of the Prussian blue analogues is less than or equal to 50nm;
And/or the peak intensity ratio of 23-25 DEG peak intensity of the X-ray diffraction peak of the crystal structure of the Prussian blue analog to 16-18 DEG peak intensity is between 1.0 and 1.2.
3. A process for the preparation of Prussian blue analogues according to claim 1 or 2, characterised in that,
The mixed materials undergo coprecipitation reaction in nitrogen atmosphere to obtain precipitate containing Prussian blue analogues; the mixed material contains the following components in percentage by mass:
sodium citrate or tripotassium citrate dihydrate: 0.04 to 0.16 part;
ferrous salt: 0.008-0.033 part;
sodium ferrocyanide monohydrate or potassium ferrocyanide monohydrate: 0.01 to 0.048 portion;
1 part of solvent.
4. A process according to claim 3, wherein,
The ferrous salt is at least one selected from ferrous chloride tetrahydrate, ferrous sulfate heptahydrate and ferrous nitrate;
and/or, 0.04 to 0.14 part of sodium citrate or tripotassium citrate dihydrate;
And/or 0.012-0.04 parts of sodium ferrocyanide monohydrate or potassium ferrocyanide monohydrate;
And/or the solvent is water or a mixed solution of water and ethanol; preferably, the concentration of ethanol in the mixed solution is 50-100 g/L;
and/or, the conditions of the precipitation reaction include: the temperature is 10-40 ℃ and the reaction time is 8-24 h;
and/or, the precipitate is treated by centrifugation, washing and vacuum drying;
Preferably, the conditions for vacuum drying I include, temperature: 80-150 ℃; the time is 12-24 hours; preferably at 80-120 ℃ for 12-36 h.
5. The method according to claim 3 or 4, wherein,
The coprecipitation reaction includes the steps of:
S1, mixing at least one of sodium citrate and tripotassium citrate dihydrate, ferrous salt and water to prepare uniform solution X; preferably, ferrous salt is dissolved and mixed with water, and at least one of sodium citrate and potassium citrate dihydrate is added to obtain the solution I;
S2, mixing at least one of sodium citrate, tripotassium citrate dihydrate, sodium ferrocyanide monohydrate and potassium ferrocyanide monohydrate with water to prepare uniform solution II; preferably, at least one of sodium citrate and potassium citrate dihydrate is mixed with water, and at least one of sodium ferrocyanide hydrate and potassium cyanide hydrate is added to obtain the solution II;
S3, dropwise adding the solution II into the solution I with the same volume under the protection of inert gases such as nitrogen or argon, wherein the dropwise adding speed is between 200mL/h and 800mL/h, and obtaining a precipitate containing Prussian blue analogues.
6. The process according to claim 3, 4 or 5,
When K is contained in A, the preparation method further comprises the step of carrying out electrochemical treatment on the precipitate containing the Prussian blue analogues;
Preferably, the electrochemical treatment is to use a sodium salt solution as an electrolyte, a sodium sheet as a counter electrode, the precipitate containing Prussian blue analogues is coated on an aluminum foil as an anode, and the semi-cell is assembled by constant current for charge and discharge;
Preferably, the current density of the charge and discharge ranges from 3mA/g to 10mA/g;
and/or, charging and discharging two circles;
preferably, the sodium salt solution is sodium perchlorate of 0.5-1 mol/L, and the solvent is propylene carbonate fluoroacetate of which the volume ratio is 1-5 percent, ethylene carbonate and propylene carbonate fluoroacetate of which the volume ratio is 95-99 percent, wherein the ratio of the ethylene carbonate to the propylene carbonate is 1:1.
7. A sodium ion battery positive electrode material characterized by comprising the prussian blue analogue according to claim 1 or 2; or comprises the Prussian blue analogues obtained by the preparation method of any one of claims 3 to 6.
8. The positive electrode material for sodium ion battery according to claim 7, wherein,
The sodium ion battery anode material contains Prussian blue analogues, a binder and a conductive additive in a mass ratio of (7-8): (1-2): 1;
Preferably, the conductive additive is at least one selected from carbon black, conductive graphite, acetylene black and Super P; and/or the binder is at least one selected from polyvinylidene fluoride, polyacrylic acid and sodium carboxymethyl cellulose; and/or, coating the positive electrode material on an aluminum foil, and drying II to obtain the positive electrode of the sodium ion battery; preferably, the conditions for drying II include: 80-120 ℃ and 8-12 h.
9. A sodium ion half cell comprising the positive electrode of a sodium ion cell according to claim 7 or 8.
10. The sodium ion half cell of claim 9, wherein the positive electrode of the sodium ion half cell consists of a sodium sheet and an electrolyte;
Preferably, the electrolyte is 0.5-1 mol/L sodium perchlorate solution, the solvent is 1-5% of fluoroacetate by volume ratio, 95-99% of ethylene carbonate and propylene carbonate by volume ratio, wherein the ratio of ethylene carbonate to propylene carbonate is 1:1.
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