CN117878288A - Coated modified lithium iron manganese phosphate composite positive electrode material, preparation method thereof and battery - Google Patents
Coated modified lithium iron manganese phosphate composite positive electrode material, preparation method thereof and battery Download PDFInfo
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- CN117878288A CN117878288A CN202410110076.3A CN202410110076A CN117878288A CN 117878288 A CN117878288 A CN 117878288A CN 202410110076 A CN202410110076 A CN 202410110076A CN 117878288 A CN117878288 A CN 117878288A
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- manganese phosphate
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- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical class [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 67
- 239000002131 composite material Substances 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 239000007774 positive electrode material Substances 0.000 title claims description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 44
- 229910021332 silicide Inorganic materials 0.000 claims abstract description 42
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000011159 matrix material Substances 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 25
- 239000011247 coating layer Substances 0.000 claims abstract description 17
- 239000010405 anode material Substances 0.000 claims abstract description 16
- 239000010410 layer Substances 0.000 claims abstract description 10
- 239000011572 manganese Substances 0.000 claims abstract description 10
- 239000002105 nanoparticle Substances 0.000 claims abstract description 5
- WEAMLHXSIBDPGN-UHFFFAOYSA-N (4-hydroxy-3-methylphenyl) thiocyanate Chemical compound CC1=CC(SC#N)=CC=C1O WEAMLHXSIBDPGN-UHFFFAOYSA-N 0.000 claims description 28
- 229910021355 zirconium silicide Inorganic materials 0.000 claims description 28
- 239000011248 coating agent Substances 0.000 claims description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 26
- 238000002156 mixing Methods 0.000 claims description 20
- 229910015645 LiMn Inorganic materials 0.000 claims description 19
- 238000000576 coating method Methods 0.000 claims description 19
- 239000000126 substance Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 5
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 5
- YXTPWUNVHCYOSP-UHFFFAOYSA-N bis($l^{2}-silanylidene)molybdenum Chemical compound [Si]=[Mo]=[Si] YXTPWUNVHCYOSP-UHFFFAOYSA-N 0.000 claims description 5
- 229910021344 molybdenum silicide Inorganic materials 0.000 claims description 5
- 229910021341 titanium silicide Inorganic materials 0.000 claims description 5
- 239000002086 nanomaterial Substances 0.000 claims description 4
- 238000007873 sieving Methods 0.000 claims description 4
- 239000012298 atmosphere Substances 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 3
- 229910052749 magnesium Inorganic materials 0.000 claims description 3
- 229910021334 nickel silicide Inorganic materials 0.000 claims description 3
- RUFLMLWJRZAWLJ-UHFFFAOYSA-N nickel silicide Chemical compound [Ni]=[Si]=[Ni] RUFLMLWJRZAWLJ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 239000010955 niobium Substances 0.000 claims description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 3
- 238000005245 sintering Methods 0.000 claims description 3
- 229910052715 tantalum Inorganic materials 0.000 claims description 3
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 3
- WQJQOUPTWCFRMM-UHFFFAOYSA-N tungsten disilicide Chemical compound [Si]#[W]#[Si] WQJQOUPTWCFRMM-UHFFFAOYSA-N 0.000 claims description 3
- 229910021342 tungsten silicide Inorganic materials 0.000 claims description 3
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 2
- DOCYQLFVSIEPAG-UHFFFAOYSA-N [Mn].[Fe].[Li] Chemical compound [Mn].[Fe].[Li] DOCYQLFVSIEPAG-UHFFFAOYSA-N 0.000 claims description 2
- 239000008103 glucose Substances 0.000 claims description 2
- 125000002791 glucosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)[C@H](O1)CO)* 0.000 claims description 2
- 239000011164 primary particle Substances 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 150000003017 phosphorus Chemical class 0.000 claims 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract description 9
- 238000004090 dissolution Methods 0.000 abstract description 7
- 229910052748 manganese Inorganic materials 0.000 abstract description 6
- 230000014759 maintenance of location Effects 0.000 abstract description 5
- 239000000463 material Substances 0.000 description 44
- 230000000052 comparative effect Effects 0.000 description 18
- 238000012986 modification Methods 0.000 description 12
- 230000004048 modification Effects 0.000 description 12
- 238000005303 weighing Methods 0.000 description 11
- 239000011777 magnesium Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 239000003792 electrolyte Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 6
- 238000005260 corrosion Methods 0.000 description 6
- 238000009792 diffusion process Methods 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 239000010406 cathode material Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 229910006249 ZrSi Inorganic materials 0.000 description 3
- 238000005253 cladding Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 229910001448 ferrous ion Inorganic materials 0.000 description 2
- 238000005087 graphitization Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910015118 LiMO Inorganic materials 0.000 description 1
- 229910013275 LiMPO Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 229910016006 MoSi Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910008484 TiSi Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 241000234314 Zingiber Species 0.000 description 1
- 235000006886 Zingiber officinale Nutrition 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 235000008397 ginger Nutrition 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910021437 lithium-transition metal oxide Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000010951 particle size reduction Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
The invention belongs to the technical field of anode materials, and particularly discloses a coated modified lithium iron manganese phosphate composite anode material, a preparation method thereof and a battery, wherein the surface of lithium iron manganese phosphate nano particles is sequentially coated with a carbon layer and a silicide coating layer from inside to outside; the carbon layer accounts for 0.5-2wt% of the lithium iron manganese phosphate matrix; the silicide coating layer accounts for 0.5-2.5wt% of the lithium iron manganese phosphate matrix. The method can solve the technical problems of low conductivity, low discharge capacity, poor rate capability, poor cycle retention rate, high manganese dissolution rate and the like of the conventional lithium iron manganese phosphate anode material.
Description
Technical Field
The invention belongs to the technical field of electrode materials, and particularly relates to a coated modified lithium iron manganese phosphate composite anode material, a preparation method thereof and a battery.
Background
The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.
LiMPO with high thermal stability, cycle stability, safety performance and low cost was introduced for the first time in 1997 from Goodenough et al 4 (m=mn, fe, co, and Ni) lithium ion battery cathode materials to replace conventional layered lithium transition metal oxide LiMO that has been widely studied 2 Since then. Wherein LiFePO 4 (LFP) positive electrode materials have been successfully prepared, developed and commercially applied to the field of Electric Vehicles (EV) or power grid energy storage on a large scale. But its low operating voltage (3.4V) results in its relatively low energy density, which limits its battery application in the high energy domain.
Research has found that LiMnPO 4 (LMP) has a higher energy density than LFP material, due to its operating voltage of 4.1V, which can be increased by about 10-20%. However, LMP has very poor electrochemical properties due to its inherent low electron and ion conductivity, unstable Mn elution caused by ginger-taylor distortion effect, and the like. It was found that the kinetic limitations of LMP materials can be overcome by particle size reduction with external conductive carbon coatings and internal cationic substitution, particularly iron Mn site substitution. Namely LiMn 1-x Fe x PO 4 A solid solution system that combines the advantages of LFP with relatively high conductivity and LMP with relatively high operating voltage. It can not only enhance the conductivity of electron pair material, but also alleviate the effect of ginger Taylor. However, the conductivity, lithium diffusion and high Wen Meng dissolution of the material under the system have limited improvement effect, and the dissolved manganese element can damage the structure of the electrolyte, so that the cycle performance of the battery is degraded, and the electrochemical performance of the material is difficult to fully play.
In order to improve the conductivity of the material, the material is prepared from LiMn 1-x Fe x PO 4 And coating a carbon layer on the surface of the material to prepare the carbon-coated nano-particle LMFP material. However, the presence of the carbon coating layer prevents diffusion channels of lithium ions, the particle nano-sized LMFP material generally has large surface area and lower compaction density, and finally the low volume energy density and processing performance are deteriorated, so that the defects are greatThe development and the wide application of the lithium iron manganese phosphate anode material are limited.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a coated modified lithium manganese iron phosphate composite positive electrode material, a preparation method thereof and a battery, so as to solve the technical problems of low conductivity, low discharge capacity, poor rate capability, poor cycle retention rate, high manganese dissolution rate and the like of the conventional lithium manganese iron phosphate positive electrode material.
In order to achieve the above object, the present invention is realized by the following technical scheme:
in the first aspect, the invention provides a coated modified lithium iron manganese phosphate composite anode material, wherein the surface of lithium iron manganese phosphate nano particles is sequentially coated with a carbon layer and a silicide coating layer from inside to outside;
the carbon layer accounts for 0.5-2wt% of the lithium iron manganese phosphate matrix;
the silicide coating layer accounts for 0.5-2.5wt% of the lithium iron manganese phosphate matrix.
In some embodiments, the carbon layer comprises 0.5 to 1.8wt% of the lithium iron manganese phosphate matrix.
In some embodiments, the silicide is selected from one or a combination of titanium silicide, cobalt silicide, zirconium silicide, tantalum silicide, molybdenum silicide, tungsten silicide, nickel silicide, or niobium silicide.
Preferably, the silicide is zirconium silicide.
Preferably, the silicide coating layer accounts for 0.5-1.5wt% of the lithium iron manganese phosphate matrix.
In some embodiments, the lithium iron manganese phosphate is doped with an element M selected from one of Mg, ca, al, sc, ti, V, cr, co, ni, cu, Y, nb, mo, tc, rh, pd, ag, la, ta, re, ir, pt, au or a combination thereof.
Preferably, the element M is Mg.
Further preferably, the lithium manganese iron phosphate doped with the element M has the formula Li r Mn x Fe 1-x-y M y P z O 4 Which is provided withWherein x is more than 0 and less than 1,0.001, y is more than or equal to 0.04,0.96, z is more than or equal to 1.06,0.97, and r is more than or equal to 1.07.
Still more preferably, 0.005 < y.ltoreq.0.025.
In a second aspect, the invention provides a preparation method of the coated modified lithium manganese iron phosphate composite positive electrode material, which comprises the following steps:
uniformly mixing a nano-scale silicide coating source and a carbon-coated lithium manganese iron phosphate nano material, and sintering in an inert atmosphere at 500-700 ℃ for 1-5h to obtain LiMn x Fe 1-x-y M y PO 4 @ silicide/C.
The inert atmosphere may be a combination of one or more of nitrogen, argon, helium.
In some embodiments, the method further comprises the steps of cooling, grinding, and sieving the sintered product.
Preferably, the LiMn after sieving x Fe 1-x-y M y PO 4 The @ silicide/C has a primary particle diameter of 50nm to 350nm, an average particle diameter D50 of 0.3 μm to 1.8 μm, and a specific surface area of 21.0.+ -. 6.0m 2 /g。
In some embodiments, the carbon source of the carbon-coated lithium manganese iron phosphate nanomaterial is selected from at least one of amorphous carbon, graphitized carbon, carbon-containing organic matter, or carbon-containing inorganic matter.
Preferably, the carbon source is glucose.
In some embodiments, the silicide-coated source is selected from one or a combination of titanium silicide, cobalt silicide, zirconium silicide, tantalum silicide, molybdenum silicide, tungsten silicide, nickel silicide, or niobium silicide.
The inventors have tried to employ "TiCl" during the test 4 "isochloride and" SiH 4 "as a raw material for silicide," it was found that the following problems exist with this indirect synthesis method: the method has higher requirements on equipment; the method is easy to generate the interference effect of Cl element, so that the product generates impurity phase; the reaction of the raw materials is incomplete by adopting the method, so that the utilization rate is low, and the production cost is increased; the residual chlorides such as titanium tetrachloride are nonconductive and tend to be empty during storageContact of gas with water tends to lead to dangerous chemical reactions and the formation of corrosive substances, which in turn lead to a decrease in the electrochemical properties of the material.
The invention adopts silicide as a cladding source, has simple process and easy realization, and is more suitable for industrial production.
Preferably, the silicide is zirconium silicide.
In a third aspect, the invention provides a battery, the positive electrode of which is prepared from the coated modified lithium manganese iron phosphate composite positive electrode material.
The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:
in the invention, coating modification is carried out on the lithium iron manganese phosphate material, and magnesium and other elements doped lithium iron manganese phosphate are adopted as a coating matrix, wherein the Mg and other elements cannot directly participate in the electrochemical reaction process, thereby improving the structural support of the lithium iron manganese phosphate, the conductivity and Li of the lithium iron manganese phosphate + The effect of conductivity can not lead to the voltage platform of the lithium iron manganese phosphate to be reduced, and the stable electrochemical performance of the matrix material is ensured.
The invention adopts the silicide such as zirconium silicide to carry out cladding modification on the lithium iron manganese phosphate material, and the silicide such as zirconium silicide not only has the advantages of good conductivity, acid and alkali corrosion resistance, oxidation resistance and the like, but also has the characteristics of higher melting point and high mechanical strength. The composite coating layer is formed by heat treatment of silicide such as zirconium silicide and a matrix at a specific temperature, and a small amount of carbon coating layer on the surfaces of the zirconium silicide and the lithium iron manganese phosphate, so that the structure of the finally obtained composite anode material is more stable.
The strong acid and alkali corrosion resistance of the silicide such as zirconium silicide can also effectively inhibit the dissolution of manganese element in the coated positive electrode material, effectively avoid the direct contact corrosion reaction between the surface of the lithium iron manganese phosphate electrode and electrolyte, reduce the side reaction of the electrolyte and improve the cycling stability of the material.
Oxidation resistance of silicides such as zirconium silicide further avoids reduction of material capacity caused by oxidation of ferrous ions and manganese divalent ions in the positive electrode material in the heat treatment process, the post treatment process and the electrolyte.
When the carbon content is low, a complete and uniform coating layer cannot be formed on the surface of the lithium manganese iron phosphate, and enough conductive performance cannot be obtained, but as the carbon content is increased, the coating layer is thickened, so that the tap density of an active substance is reduced and Li is blocked + Is provided.
The main purpose of carbon-coated lithium iron phosphate in industry is to inhibit excessive growth of particles to prevent diffusion of lithium ions, increase conductivity of materials and prevent iron from oxidizing into Fe 3+ Etc., but the degree of graphitization of amorphous carbon produced by decomposition of the conventional organic carbon source is relatively low, resulting in unsatisfactory conductivity.
In the present invention, the silicide such as zirconium silicide has excellent conductivity and Li + The conductivity can be improved, the graphitization degree of amorphous carbon can be increased, and the conductivity of the material is greatly improved. Therefore, the use of the silicides such as zirconium silicide reduces the coating amount of carbon, so that the coated lithium iron manganese phosphate composite positive electrode material not only has excellent conductive performance, but also further dredges Li on the surface of the positive electrode material + The diffusion channel of the material is improved, and the capacity loss of the modified material is reduced.
Based on the structure, the particle size distribution of the material is uniform, the conductivity and Li + Higher diffusion capability, lower charge transfer resistance, better crystallinity and stability. When the lithium ion battery is used as a positive electrode material of a lithium ion battery, the multiplying power performance of the battery is better, the first coulombic efficiency and capacity are higher, the manganese dissolution rate is lower, and the cycle life is longer.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is an SEM image of the surface morphology of a sample according to example 1 of the present invention;
FIG. 2 is an XRD diffraction pattern of a sample of example 1 of the present invention;
FIG. 3 is a graph showing the first charge and discharge performance of button cells of example 1 and comparative example 1 of the present invention at 25℃and 0.1C/0.1C magnification;
FIG. 4 is a graph showing charge-discharge cycle performance of button cells of example 1 and comparative example 1 of the present invention at 45℃and 1C/1C magnification.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The invention is further illustrated below with reference to examples.
Example 1
Commercial carbon-coated nanoscale lithium iron manganese phosphate matrix material is custom purchased from Hunan Mo Runxin energy battery material Co., ltd, and the chemical formula of the material can be LiMn x Fe 1-x-y M y PO 4 The cathode material is sintered and synthesized, and has a proper amount of carbon coated on the surface, and can be directly used without further treatment.
The chemicals (AR grade) in each step were purchased from chinese medicine chemicals.
1. Weighing a proper amount of outsourcing carbon-coated and uniformly dispersed nanoscale lithium manganese iron phosphate anode matrix A (a conductive carbon layer is coated on the surface of a lithium manganese iron material in the sintering process, so that excessive growth of particles is inhibited, and the conductivity is reduced, wherein the carbon content is specially customized to be enough to inhibit the growth of particles, the conductivity is improved to a small extent), and the chemical formula is LiMn 0.6 Fe 0.38 Mg 0.02 PO 4 The surface carbon coating content is 0.7wt%;
2. weighing a nanoscale zirconium silicide coating agent accounting for 1.0wt% of the material A, adding the nanoscale zirconium silicide coating agent into the base material A obtained in the step 1, and uniformly mixing by using a high-speed mixer to obtain a mixed precursor material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃;
3. putting the mixed material B prepared in the step 2 into a tube furnace, heating to 550 ℃ at a speed of 3 ℃/min under nitrogen atmosphere, preserving heat for 2.0h, cooling, grinding and sieving to obtain the embodiment of the invention1 lithium manganese iron phosphate composite anode material LiMn with composite coating modification 0.6 Fe 0.38 Mg 0.02 PO 4 @ZrSi 2 /C。
FIG. 1 is a SEM illustration of the finished product, wherein the particles are uniformly distributed without obvious agglomeration; figure 2 is an XRD diffractogram of the material with no significant impurity generation compared to the standard card.
Example 2
1. Weighing a substrate A according to the operation in the step 1 of the example 1;
2. weighing a nanoscale titanium silicide coating agent accounting for 1.0wt% of the material A, adding the nanoscale titanium silicide coating agent into the matrix material A obtained in the step 1, and uniformly mixing by using a high-speed mixer to obtain a mixed material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃; this example 2 differs from example 1 in that the silicide capping agent is different.
3. Finally, the preparation is carried out according to the operation in the step 3 of the example 1 to obtain the lithium manganese iron phosphate composite anode material LiMn with composite coating modification in the example 2 0.6 Fe 0.38 Mg 0.02 PO 4 @TiSi 2 /C。
Example 3
1. Weighing a substrate A according to the operation in the step 1 of the example 1;
2. weighing a nanoscale molybdenum silicide coating agent accounting for 1.0wt% of the material A, adding the nanoscale molybdenum silicide coating agent into the base material A obtained in the step 1, and uniformly mixing by using a high-speed mixer to obtain a mixed material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃; this example 3 differs from example 1 in that the silicide capping agent is different.
3. Finally, the preparation of the lithium iron manganese phosphate composite anode material LiMn with composite coating modification is carried out according to the operation in the step 3 of the example 1 0.6 Fe 0.38 Mg 0.02 PO 4 @MoSi 2 /C。
Example 4
1. Weighing matrix A, which has the chemical formula LiMn, according to the procedure of example 1, step 1 06 Fe 038 Ni 002 PO 4 The method comprises the steps of carrying out a first treatment on the surface of the This example 4 andexample 1 differs in that the doping elements in the tailored matrix material are different.
2. Weighing a nanoscale zirconium silicide coating agent accounting for 1.0wt% of the material A, adding the nanoscale zirconium silicide coating agent into the base material A obtained in the step 1, and uniformly mixing by using a high-speed mixer to obtain a mixed precursor material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃;
3. finally, the preparation is carried out according to the operation in the step 3 of the example 1 to obtain the lithium manganese iron phosphate composite anode material LiMn with composite coating modification in the example 4 0.6 Fe 0.38 Ni 0.02 O 4 @ZrSi 2 /C。
Comparative example 1
1. Weighing matrix A, which has the chemical formula LiMn, according to the procedure of example 1, step 1 0.6 Fe 0.4 PO 4 The method comprises the steps of carrying out a first treatment on the surface of the This comparative example 1 differs from example 1 in that: the customized matrix material is free of doping elements and silicide cladding agents are not used;
2. adding the matrix A obtained in the step 1 into a high-speed mixer, uniformly mixing by using the high-speed mixer to obtain a mixed material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃;
3. finally, the preparation was carried out according to the procedure of step 3 of example 1 to obtain a lithium iron manganese phosphate positive electrode material LiMn with carbon coating according to comparative example 1 of the present invention 0.6 Fe 0.4 PO 4 @C。
Comparative example 2
1. Weighing matrix A, which has the chemical formula LiMn, according to the procedure of example 1, step 1 0.6 Fe 0.4 PO 4 The method comprises the steps of carrying out a first treatment on the surface of the This comparative example 2 differs from example 1 in that the tailored base material does not contain doping elements;
2. next, a lithium iron manganese phosphate positive electrode material LiMn with composite coating modification according to comparative example 2 of the present invention was prepared by the operations in steps 2 to 3 of example 1 0.6 Fe 0.4 O 4 @ZrSi 2 /C。
Comparative example 3
1. The chemical weighing of the matrix A was carried out as in step 1 of example 1Is LiMn 0.6 Fe 0.38 Mg 0.02 PO 4 ；
2. Adding the matrix A obtained in the step 1 into a high-speed mixer, uniformly mixing by using the high-speed mixer to obtain a mixed material B, wherein the rotating speed of the high-speed mixer is 1000rpm, the mixing time is 50min, and the mixing temperature is 25-45 ℃; this comparative example 2 differs from example 1 in that no silicide capping agent was added in step 2;
3. finally, the preparation was carried out according to the procedure of step 3 of example 1 to obtain a lithium iron manganese phosphate positive electrode material LiMn with composite coating modification according to comparative example 3 of the present invention 0.6 Fe 0.38 Mg 0.02 PO 4 @C。
Comparative example 4
The difference from example 1 is that: the nano-scale lithium iron manganese phosphate anode matrix A has no surface carbon coating layer.
The composite positive electrode materials obtained in examples 1 to 4 and comparative examples 1 to 4 were used as positive electrode materials for batteries, respectively, to prepare button cells for electrochemical performance test. The manufacturing method comprises the following steps:
a. the lithium iron manganese phosphate materials prepared in the examples and the comparative examples are prepared according to the following positive electrode material powder: conductive agent (SP): adhesive (PVDF) =90: 5:5, uniformly dispersing anode slurry formed by proportional stirring, and carrying out coating, sheet punching and vacuum drying on the slurry; taking a metal lithium sheet as a cathode material of a battery, and taking a polypropylene film with micropores as a battery diaphragm; 1mol/L LiPF of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) with a solvent volume ratio of 1:1 6 As an electrolyte, a 2032 type button cell was assembled in a glove box filled with dry high purity argon and left to stand for 8 hours;
b. the coin cells after standing were charged and discharged at an ambient temperature of 25℃under a current of 2.5 to 4.5V at a rate of 0.1C, and the electrochemical performance of examples 1 to 4 and comparative examples 1 to 4 was measured. And calculates the first discharge efficiency, namely: first effect = first discharge specific capacity/first charge specific capacity 100%.
c. The cycle performance test was performed at 45℃at 2.5-4.5V at 1C charge/1C discharge for examples 1-4 and comparative examples 1-4, and the capacity retention after 100 cycles was calculated as follows: capacity retention = 100% of the 100 th discharge specific capacity/first discharge specific capacity.
For specific test data, please refer to table 1.
TABLE 1
As can be seen from the above Table 1, compared with comparative example 1, the electrical properties (initial efficiency and specific discharge capacity) and cycle properties of the composite modified cathode material prepared in each example of the present invention are significantly improved. The charge-discharge curve in the graph shows that the sample of the comparative example 1 has larger polarization, and the charge-discharge capacity, the first effect and the cycle retention rate are lower; example 1 also exhibited good cycle performance at 45 ℃ and 1C magnification, also demonstrating improved magnification performance and manganese dissolution appearance.
The reason for the effects achieved by the above embodiment is as follows: the invention adopts zirconium silicide to carry out coating modification on the lithium iron manganese phosphate material, and the zirconium silicide has the characteristics of good conductivity, acid and alkali corrosion resistance, oxidation resistance and other chemical stability, higher melting point and high mechanical strength. The zirconium silicide and the matrix are subjected to heat treatment at a specific temperature, a small amount of carbon on the surfaces of the zirconium silicide and the lithium iron manganese phosphate is coated to form a composite coating layer, so that the structure of the finally obtained composite anode material is more stable, the dissolution of manganese element in the coated anode material can be effectively inhibited due to the strong acid and alkali corrosion resistance of the zirconium silicide, the direct contact reaction corrosion of the surface of the lithium iron manganese phosphate electrode and electrolyte is effectively avoided, the side reaction of the electrolyte is reduced, and the cycling stability of the material is improved. The oxidation resistance of zirconium silicide also further avoids the reduction of material capacity caused by oxidation of ferrous ions and manganese divalent ions in the anode material in the heat treatment process, the post treatment process and the electrolyte; in addition, since the use of zirconium silicide having excellent conductivity reduces the coating amount of carbon, since a complete and uniform coating layer cannot be formed on the surface of lithium manganese iron phosphate when the carbon content is low, sufficient conductivity cannot be obtained, but as the carbon content is increased, the coating layer becomes thicker, not only does vibration of the active material decreaseSolid density and hinder Li + In the zirconium silicide invention, since zirconium silicide is not only an excellent conductor but also has a certain Li + The conductivity ensures that the coated lithium iron manganese phosphate composite positive electrode material not only has excellent conductivity, but also further dredges Li on the surface of the positive electrode material + The diffusion channel of the material is improved, and the capacity loss of the modified material is reduced.
According to the invention, the LMFP composite positive electrode material is prepared by a solid phase method and adopting zirconium silicide and amorphous carbon composite coating modification, and the preparation method has the advantages of simple process, controllable conditions, high crystallinity, less crystal impurity phase and uniform product particle size. At the same time, it is also cost-effective, environmentally friendly and easy to commercially expand.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A coated modified lithium iron manganese phosphate composite positive electrode material is characterized in that: the surface of the lithium iron manganese phosphate nanoparticle is sequentially coated with a carbon layer and a silicide coating layer from inside to outside;
the carbon layer accounts for 0.5-2wt% of the lithium iron manganese phosphate matrix;
the silicide coating layer accounts for 0.5-2.5wt% of the lithium iron manganese phosphate matrix.
2. The coated modified lithium manganese iron phosphate composite positive electrode material according to claim 1, characterized in that: the carbon layer accounts for 0.5-1.8wt% of the lithium iron manganese phosphate matrix.
3. The coated modified lithium manganese iron phosphate composite positive electrode material according to claim 1, characterized in that: the silicide is selected from one or a combination of titanium silicide, cobalt silicide, zirconium silicide, tantalum silicide, molybdenum silicide, tungsten silicide, nickel silicide or niobium silicide;
preferably, the silicide is zirconium silicide;
preferably, the silicide coating layer accounts for 0.5-1.5wt% of the lithium iron manganese phosphate matrix.
4. The coated modified lithium manganese iron phosphate composite positive electrode material according to claim 1, characterized in that: the lithium iron manganese phosphate is doped with an element M, wherein M is selected from one or a combination of Mg, ca, al, sc, ti, V, cr, co, ni, cu, Y, nb, mo, tc, rh, pd, ag, la, ta, re, ir, pt, au;
preferably, the element M is Mg.
5. The coated modified lithium manganese iron phosphate composite positive electrode material according to claim 4, wherein: the chemical formula of the lithium iron manganese phosphate doped with the element M is Li r Mn x Fe 1-x-y M y P z O 4 Wherein x is more than 0 and less than 1,0.001, y is more than or equal to 0.04,0.96, z is more than or equal to 1.06,0.97, and r is more than or equal to 1.07;
preferably, y is more than 0.005 and less than or equal to 0.025.
6. The preparation method of the coated modified lithium iron manganese phosphate composite positive electrode material according to any one of claims 1 to 5, which is characterized by comprising the following steps: the method comprises the following steps:
uniformly mixing a nano-scale silicide coating source and a carbon-coated lithium manganese iron phosphate nano material, and sintering in an inert atmosphere at 500-700 ℃ for 1-5h to obtain LiMn x Fe 1-x-y M y PO 4 @ silicide/C.
7. The method for preparing the coated and modified lithium iron manganese phosphate composite positive electrode material according to claim 6, which is characterized in that: the method further comprises the steps of cooling, grinding and sieving the sintered product.
8. The coated modified phosphorus of claim 7The preparation method of the acid manganese iron lithium composite anode material is characterized by comprising the following steps of: sieved LiMn x Fe 1-x-y M y PO 4 The @ silicide/C has a primary particle diameter of 50nm to 350nm, an average particle diameter D50 of 0.3 μm to 1.8 μm, and a specific surface area of 21.0.+ -. 6.0m 2 /g。
9. The method for preparing the coated and modified lithium iron manganese phosphate composite positive electrode material according to claim 6, which is characterized in that: the carbon source of the carbon-coated lithium iron manganese phosphate nano material is at least one of amorphous carbon, graphitized carbon, carbon-containing organic matters or carbon-containing inorganic matters;
preferably, the carbon source is glucose.
10. A battery, characterized in that: the anode is prepared from the coated modified lithium manganese iron phosphate composite anode material in any one of claims 1-5.
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