CN100551821C - Preparation method of rare earth doped lithium iron phosphate powder - Google Patents

Abstract

The invention discloses a method for preparing rare earth-doped lithium iron phosphate powder, which belongs to the technical field of preparation of electrochemical power source materials. The anode material of lithium ion battery, lithium iron phosphate, is represented by the molecular formula Li _1-x RE _x FePO ₄ , and its specific preparation method is a solid-phase method in which the dopant is mixed with the parent raw material once, and then calcined twice. That is, according to the molar ratio of lithium salt, ferrous salt, phosphate and dopant, the materials are mixed once, dried, low-temperature pre-calcined and high-temperature secondary calcined to obtain rare earth-doped lithium iron phosphate powder. With lanthanide rare earth element compounds as dopants, it is easy to achieve effective doping through traditional solid-state methods, significantly improving battery capacity and cycle electrical performance, and is of great practical value. It is commonly used in secondary lithium-ion batteries and power energy battery cathode materials The field has broad application prospects.

Description

Preparation method of rare earth doped lithium iron phosphate powder

technical field

The invention belongs to the technical field of preparation of electrochemical power source materials. In particular, it relates to a preparation method of a rare earth doped lithium iron phosphate powder used as a common secondary lithium ion battery or a modified lithium ion battery positive electrode material for power energy.

technical background

Lithium-ion battery is a new type of green high-energy rechargeable battery that appeared in the early 1990s. It has many advantages such as high voltage, high energy density, good cycle performance, small self-discharge, no memory effect, and wide operating temperature range. It is widely used in mobile Telephones, notebook computers, portable electric tools, electronic instruments, weapons and equipment, etc. also have good application prospects in electric vehicles, and have become the focus of research and development by countries all over the world. The positive electrode material is an important part of the lithium-ion battery. During the charging and discharging process of the lithium-ion battery, it is not only necessary to provide the lithium required for the reciprocal intercalation/extraction in the positive and negative lithium intercalation compounds, but also to bear the burden of forming SEI on the surface of the negative electrode material. Therefore, research and development of high-performance cathode materials have become the key to the development of lithium-ion batteries. The current research mainly focuses on lithium-containing transition metal oxides, and the transition metals are mainly cobalt, nickel, and manganese. In recent years, materials based on Fe ³⁺ /Fe ²⁺ redox couples have attracted great interest, especially lithium iron phosphate (LiFePO ₄ ), which has an olivine crystal structure, has emerged as the most promising candidate cathode for recent studies. Material.

中LiFePO₄和FePO₄两相转变发生的p-n型转变的导电机理；Shi.S.Q.，Chen，L.Q.等(物理评论B，Physical Review B，68卷，19期，195108-1页)运用第一性原理计算了微量Cr掺杂Li_1-3xCr_xFePO₄的电子态密度、费米能级，提出了基于掺杂离子3d能级与Fe、O能级杂化的导电隧道的新的导电机理；Hu，Y.Q.，Doeff，M.M.，Kostecki，R.，Finones，R.(电化学学报，Journal of theElectrochemical Society，151卷，8期，A1279页)首次运用溶胶-凝胶法制备了掺杂的Li_0.98Mg_0.01FePO₄和Li_0.96Ti_0.01FePO₄正极材料，同样提高了LiFePO₄的基础电池性能；Ni，J.F.等(材料快报，Materials Letters，59卷，18期，2361页)运用共沉淀法制备了掺Mg²⁺、Cu²⁺、Zn²⁺的LiFePO₄正极粉体，C/10倍率下放电，得到120mAh/g以上的容量。在其他正极材料中，如尖晶石锰酸锂LiMn₂O₄，彭正顺[中国稀土学报，18卷，2000年，1期：48]研究了稀土Nd，Ce替代Mn位的LiMn₂O₄正极材料；杨书廷等[中国稀土学报，21卷，2003年，4期：414]利用微波加热技术合成了稀土掺杂基LiMn_2-xRE_xO₄(RE＝Y，Nd，Gd，Ce)材料，研究了不同掺杂离子及不同掺杂量对其电化学可逆性与电化学比容量的作用规律。又如钴酸锂LiCoO₂系统中，魏进平等[JOURNAL OF RARE EARTHS，21卷，2000年，4期：466]研究了LiCo_1-xRE_xO₂(x＝0101～0.03)，RE＝Y，La，Tm和Gd系列稀土掺杂材料。再如LiNi_0.8Co_0.2O₂系统中，豆志河等[JOURNAL OF RARE EARTHS，22卷，2004年，5期：644]研究了Ce取代Co的LiNi_0.95Ce_0.05O₂材料。迄今为止，有关稀土元素对磷酸铁锂LiFePO₄的改性作用研究尚未见报道。LiFePO ₄ material has many advantages such as cheap, non-toxic, non-hygroscopic, good environmental compatibility, abundant mineral resources, high capacity, and good stability. Goodenough [J.Electrochem.Soc., 144 (1997) 1188] research group first synthesized lithium iron phosphate (LiFePO ₄ ), which has a high theoretical specific capacity (170mAh/g) as a cathode material for lithium-ion batteries , which is greater than the actual discharge specific capacity of 140mAh/g of LiCoO ₂ that has been commercialized, so it has attracted great attention of researchers. However, the electronic conductivity of this material is poor, which greatly limits the application of the material at higher current densities. The currently reported methods for improving the performance of this material mainly include mixing or coating conductive carbon ^materials or conductive metal particles on the surface to improve the electronic conductivity between the matrix material particles; Ionic conductivity; and doping a small amount of high-valent metal ions to partially replace the Li ⁺ position can improve the electronic conductivity in the matrix particle, which is an important modification method. Chung, SY, Chiang, YM, etc. (Nature·Materials Edition, Nature materials, 2003, volume 1, October, page 123) first used a small amount of high-valent metal ions Mg ²⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ²⁺ , Nb ⁵⁺ , W ⁶⁺ doped LiFePO ₄ , greatly improved the conductivity of LiFePO ₄ , so that LiFePO ₄ also has a capacity of more than 60mAh/g at high charge and discharge rates, and proposed a corresponding

The conduction mechanism of the pn-type transition that occurs during the two-phase transition of LiFePO ₄ and FePO ₄ in medium; Shi.SQ, Chen, LQ et al. Calculated the electronic density of state and Fermi energy level of trace Cr-doped Li _1-3x Cr _x FePO ₄ in principle, and proposed a new conduction mechanism based on the conductive tunnel of doped ion 3d energy level hybridized with Fe and O energy levels ; Hu, YQ, Doeff, MM, Kostecki, R., Finones, R. (Acta Electrochemical Society, Journal of the Electrochemical Society, Volume 151, Issue 8, Page A1279) prepared doped Li by sol-gel method for the first time _0.98 Mg _0.01 FePO ₄ and Li _0.96 Ti _0.01 FePO ₄ cathode materials also improved the basic battery performance of LiFePO ₄ ; Ni, JF et al. LiFePO ₄ cathode powder doped with Mg ²⁺ , Cu ²⁺ , and Zn ²⁺ was used to discharge at a rate of C/10, and a capacity of more than 120mAh/g was obtained. In other positive electrode materials, such as spinel lithium manganese oxide LiMn ₂ O ₄ , Peng Zhengshun [Chinese Journal of Rare Earth, Volume 18, 2000, Phase 1: 48] studied the LiMn ₂ O ₄ positive electrode where rare earth Nd and Ce replace Mn sites Materials; Yang Shuting et al [Chinese Journal of Rare Earth, 21, 2003, 4: 414] synthesized rare earth-doped LiMn _2-x RE _x O ₄ (RE=Y, Nd, Gd, Ce) materials using microwave heating technology , studied the effect of different doping ions and different doping amounts on its electrochemical reversibility and electrochemical specific capacity. Another example is in the LiCoO ₂ system of lithium cobaltate, Wei Jinping [JOURNAL OF RARE EARTHS, 21 volumes, 2000, 4th issue: 466] studied LiCo _1-x RE _x O ₂ (x=0101～0.03), RE= Y, La, Tm and Gd series rare earth doped materials. Another example is in the LiNi _0.8 Co _0.2 O ₂ system, Dou Zhihe et al [JOURNAL OF RARE EARTHS, 22 volumes, 2004, 5 phase: 644] studied the LiNi _0.95 Ce _0.05 O ₂ material in which Ce was substituted for Co. So far, there have been no reports on the modification of rare earth elements on lithium iron phosphate LiFePO ₄ .

The present invention proposes to use a rare earth lanthanide compound (referred to as RE, the same below) as a doping raw material, and to prepare oxygen-site-doped lithium iron phosphate Li _1-x RE _x FePO ₄ (0<x≤0.05 ), improve the basic electrical properties of this material, so that it has a high charge and discharge capacity and good battery cycle performance.

Contents of the invention

The object of the present invention is to provide a preparation method of a rare earth-doped lithium iron phosphate powder, which is a positive electrode material for a lithium-ion battery that significantly improves the basic electrical properties of the matrix by doping with a rare-earth lanthanide compound. It is characterized in that the lithium iron phosphate lithium ion battery anode material is represented by the molecular formula Li _1-x RE _x FePO ₄ , wherein RE is a doping source element, 0<x≤0.05;

The specific method of the preparation method of the rare earth-doped lithium iron phosphate powder is as follows:

Lithium salt, ferrous salt, phosphate and rare earth dopant are mixed once at the molar ratio of element Li:Fe:P:RE=(1-x):1:1:x, and mixed with mixing media for ball milling 6 ～12 hours, after drying at 40～70℃, heat to 400～550℃ under inert atmosphere or reducing atmosphere, and keep warm for 5～10 hours for pre-calcination; drying at ~70°C, and then calcining twice at 550-850°C under an inert or reducing atmosphere to obtain rare earth-doped lithium iron phosphate Li _1-x RE _x FePO ₄ powder.

The mixed medium is at least one of deionized water, industrial alcohol and absolute ethanol.

The dopant is the oxides and hydroxides of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium other than radioactive promethium, At least one of chlorides, nitrates, sulfates, carbonates, fluorides and organic salts.

The lithium salt is at least one of Li ₂ CO ₃ , LiOH, lithium oxalate and lithium acetate.

The ferrous salt is at least one of ferrous oxalate, ferrous acetate, ferrous chloride and ferrous sulfate.

The phosphate includes at least one of ammonium phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

The inert atmosphere or reducing atmosphere is at least one of nitrogen, argon, and nitrogen-hydrogen mixed gas.

The beneficial effect of the present invention is that by using the solid-phase method that is easy for commercial production, doping various lanthanide compounds with a wide range of materials, through a simple mixing and drying process, and by controlling the temperature and time of heat treatment, a compound with good crystallization performance and composition Uniform, rare earth-doped lithium-ion battery cathode material lithium iron phosphate Li _{1- x} RE _x FePO ₄ (0<x≤0.05) powder, the first discharge specific capacity at room temperature can reach 90-140mAh/g. Compared with other metal cation doping routes, the present invention can more significantly improve the capacity and capacity cycle performance of the matrix basic battery, has obvious advantages, and is of great practical value. The field has broad application prospects.

Detailed ways

The invention provides a method for preparing a rare earth-doped lithium iron phosphate powder, which is a positive electrode material for a lithium-ion battery, by doping a rare-earth lanthanoid compound and significantly improving the basic electrical properties of the matrix. The anode material of the lithium ion battery, lithium iron phosphate, is represented by the molecular formula Li _1-x RE _x FePO ₄ , wherein RE is a doping source element, 0<x≤0.05;

The specific method of the preparation method of the rare earth-doped lithium iron phosphate powder is as follows:

Feed lithium salt, ferrous salt, phosphate and rare earth dopant at a molar ratio of element Li:Fe:P:RE=(1-x):1:1:x, then add deionized water, industrial alcohol and at least one of anhydrous ethanol as the mixing medium, mixed ball milling for 6-12 hours, and dried at 40-70°C; after drying, the powder was heated to 400-550°C in an inert atmosphere or a reducing atmosphere, and kept for 5-50°C. Pre-calcine for 10 hours; ball mill the pre-calcined material for 6-12 hours for the second time, dry it at 40-70°C, and then calcinate it again at 550-850°C under an inert or reducing atmosphere to obtain rare earth-doped phosphoric acid Lithium iron Li _1-x RE _x FePO ₄ powder.

The dopant is the oxides and hydroxides of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium other than radioactive promethium, At least one of chloride, nitrate, sulfate, carbonate, fluoride and organic salt.

The lithium salt is at least one of Li ₂ CO ₃ , LiOH, lithium oxalate and lithium acetate.

The ferrous salt is at least one of ferrous oxalate, ferrous acetate, ferrous chloride and ferrous sulfate.

The phosphate includes at least one of ammonium phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

The mixed medium is at least one of deionized water, industrial alcohol and absolute ethanol.

The inert atmosphere or reducing atmosphere is at least one of nitrogen, argon, and nitrogen-hydrogen mixed gas.

Rare earth-doped lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride are uniformly ground according to the mass ratio of (9-16): (0.875-2.2): 1, and then coated on the aluminum sheet of the current collector to make an electrode sheet. The metal lithium sheet is used as the negative electrode, 1.0mol/L LiPF ₆ is dissolved in the solvent of ethyl carbonate and dimethyl carbonate mixed at a volume ratio of 1:1 as the electrolyte, and the polypropylene microporous film is used as the diaphragm, and the assembly is Simulates a lithium-ion rechargeable battery.

The charging and discharging system of the assembled corresponding battery is: constant current charging and discharging at a cut-off voltage of 2.5V-4.2V at a rate of 0.05-0.2C.

Below by embodiment, further illustrate outstanding feature and remarkable progress of the present invention, only in order to illustrate the present invention and in no way limit the present invention.

Example 1

Add 0.0975 moles of lithium hydroxide LiOH·H ₂ O, 0.1 moles of ferrous oxalate Fe(C ₂ O ₄ )·2H ₂ O, 0.1 moles of ammonium dihydrogen phosphate NH ₄ H ₂ PO ₄ and 0.00125 moles of lanthanum oxalate nonahydrate La ₂ (C ₂ O ₄ ) ₃ 9H ₂ O was mixed and added to the polyester tank, 70ml of absolute alcohol was added, after sealing, ball milled and mixed on a planetary ball mill for 10 hours, and after drying, the material was dried under a nitrogen atmosphere of 0.3 liters/minute , raised to 400°C at a heating rate of 5°C/min, held for 8 hours, and cooled to room temperature with the furnace to obtain pre-fired material, which was ball-milled with industrial alcohol for 6 hours, and dried in 0.3 liters/min of nitrogen after discharge. Under the atmosphere, the temperature was raised to 700°C at a rate of 4°C/min, held for 8 hours, and then cooled to room temperature with the furnace to obtain the positive electrode material Li _0.975 La _0.025 FePO ₄ .

Weigh 0.9g of the above-mentioned positive electrode material powder, add 0.19g of carbon black, 0.096g of polyvinylidene fluoride, use absolute ethanol as a dispersant, and ultrasonically oscillate and mix for 30 minutes to make it fully mixed. After drying at 80°C, add N-formazan The base pyrrolidone was prepared into a slurry, which was evenly coated on the current collector aluminum foil, dried at 80°C, and flattened on a roller press to make a positive electrode film with a thickness of about 200 μm. Punch out a 1 cm ² disc on the positive electrode film, weigh it, dry it in vacuum at 140°C for more than 12 hours, and use it as a spare electrode after cooling naturally in a vacuum box. Electrolyte adopts 1mol/L LiPF ₆ ethyl carbonate EC: dimethyl carbonate DMC = 1: 1 mixed solution; polypropylene microporous film is used as diaphragm; metal lithium sheet is used as negative electrode. The battery was packaged in an argon atmosphere glove box, aged for 6 hours, charged to 4.2 volts at a rate of 20 mA/g (calculated as the positive electrode), and discharged to 2.5 volts. The first reversible discharge specific capacity was about 117 mAh/g. After 20 cycles, the discharge specific capacity remains above 118mAh/g.

Example 2

Mix 0.04975 moles of lithium carbonate Li ₂ CO ₃ , 0.1 moles of ferrous acetate Fe(CH ₃ COO) ₂ 2H ₂ O, 0.1 moles of ammonium phosphate (NH ₄ ) ₃ PO ₄ and 0.00025 moles of lanthanum oxide La ₂ O ₃ , add Add 100ml of industrial alcohol to the polyester tank, seal it and mix it on a planetary ball mill for 6 hours. After the material is dried, raise the temperature to 430°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/min. After 7.5 hours, cool down to room temperature with the furnace to obtain the pre-fired material, take water as the medium ball mill for 10 hours, discharge and dry the mixture under a nitrogen-hydrogen mixed atmosphere of 0.3 liters/minute (nitrogen: hydrogen = 9: 1, volume ratio) , raised to 720°C at a heating rate of 4°C/min, held for 7 hours, and cooled down to room temperature with the furnace to obtain the positive electrode material Li _0.995 La _0.005 FePO ₄ .

Weigh 1.125g of positive electrode material powder, add 0.169g of carbon black, 0.12g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 10mA/g (in terms of positive electrodes), and discharge To 2.5 volts, the first reversible discharge specific capacity of the battery is about 120mAh/g. After 20 cycles, the discharge specific capacity remains above 120mAh/g.

Example 3

Mix 0.099 mol of lithium acetate Li(CH ₃ COO), 0.1 mol of ferrous chloride FeCl ₂ , 0.1 mol of diammonium hydrogen phosphate and 0.0005 mol of cerium oxalate nonahydrate Ce ₂ (C ₂ O ₄ ) ₃ 9H ₂ O, add Add 75ml of anhydrous alcohol to the polyester tank, seal it and mix it on a planetary ball mill for 7 hours. After the material is dried, under a nitrogen atmosphere of 0.3 liters/min, the temperature rises to 450°C at a rate of 5°C/min. Insulate for 9 hours, cool down to room temperature with the furnace to obtain pre-fired material, use industrial alcohol as a medium for ball milling for 10 hours, and after drying, heat up to 700 at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min. ℃, kept at this temperature for 8 hours, and then cooled down to room temperature with the furnace to obtain the positive electrode material Li _0.99 Ce _0.01 FePO ₄ .

Weigh 1.02g of positive electrode material powder, add 0.184g of carbon black, 0.096g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 10mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is about 137mAh/g. After 20 cycles, the discharge specific capacity remains above 130mAh/g.

Example 4

Mix 0.0475 moles of lithium carbonate, 0.1 moles of ferrous sulfate FeSO ₄ ·7H ₂ O, 0.1 moles of diammonium hydrogen phosphate and 0.005 moles of cerium sulfate Ce(SO ₄ ) ₂ ·2H ₂ O, add to the polyester tank, add 100ml of Water alcohol, sealed and mixed on a planetary ball mill for 11 hours, after the discharge is dried, in a nitrogen atmosphere of 0.3 liters/min, the temperature is raised to 480°C at a rate of 5°C/min, kept for 5 hours, and cooled to At room temperature, the pre-fired material was obtained, ball milled with water for 5 hours, and after the discharge was dried, it was heated to 680°C at a rate of 4°C/min in an atmosphere of 0.3 liters/min of ammonia decomposition gas, and kept at this temperature for 11 Hours, the temperature was lowered to room temperature with the furnace, and the positive electrode material Li _0.95 Ce _0.05 FePO ₄ was obtained.

Weigh 0.9g of positive electrode material powder, add 0.16g of carbon black, 0.096g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method of Example 1, charge to 4.2 volts at a rate of 10mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 137mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 130mAh/g.

Example 5

Mix 0.099 mol of lithium hydroxide, 0.1 mol of ferrous chloride, 0.1 mol of ammonium dihydrogen phosphate and 0.001 mol of praseodymium chloride PrCl ₃ into a polyester tank, add 55ml of industrial alcohol, seal and mix on a planetary ball mill for 6.5 Hours, after discharging and drying, under a nitrogen atmosphere of 0.3 liters/min, the temperature was raised to 400°C at a rate of 5°C/min, kept at a temperature of 8.5 hours, and cooled to room temperature with the furnace to obtain pre-fired material. After ball milling for 5.5 hours, the material was dried and then heated to 700°C at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain the positive electrode material Li _0.99 Pr _0.01 FePO ₄ .

Weigh 0.537g of positive electrode material powder, add 0.066g of carbon black, 0.036g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 34mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 100mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 100mAh/g.

Example 6

Mix 0.0498 moles of lithium carbonate, 0.1 moles of ferrous oxalate, 0.1 moles of ammonium phosphate and 0.0004 moles of neodymium fluoride NdF ₃ , add to a polyester tank, add 130ml of water, seal and mix on a planetary ball mill for 6 hours, discharge and dry After drying, under a nitrogen atmosphere of 0.3 liters/min, raise the temperature to 400°C at a rate of 5°C/min, keep it warm for 8 hours, and cool to room temperature with the furnace to obtain pre-fired material, use water as the medium for ball milling for 8 hours, and discharge After drying, under a nitrogen-hydrogen mixed atmosphere of 0.3 liters/min (nitrogen: hydrogen = 9:1, volume ratio), the temperature rises to 700°C at a rate of 4°C/min, and is kept at this temperature for 8 hours, and the temperature is lowered with the furnace. to room temperature, the positive electrode material Li _0.996 Nd _0.004 FePO ₄ was obtained.

Weigh 1.325g of positive electrode material powder, add 0.263g of carbon black, 0.12g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 10mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 94mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 90mAh/g.

Example 7

Mix 0.099 mol of lithium acetate, 0.1 mol of ferrous oxalate, 0.1 mol of ammonium dihydrogen phosphate and 0.0005 mol of samarium oxide (Sm ₂ O ₃ ), add it to a polyester tank, add 80ml of absolute alcohol, seal it and put it on a planetary ball mill Mix for 7 hours, and after discharging and drying, raise the temperature to 400°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/minute, keep it warm for 8 hours, and cool down to room temperature with the furnace to obtain pre-fired material. Media ball milled for 6 hours, and after the discharge was dried, in a nitrogen atmosphere of 0.3 liters/min, the temperature was raised to 700°C at a rate of 4°C/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain the positive electrode material Li _0.99 Sm _0.01 FePO ₄ .

Weigh 0.45g of positive electrode material powder, add 0.078g of carbon black, 0.032g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 20mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 123mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 120mAh/g.

Example 8

Mix 0.097 moles of lithium hydroxide, 0.1 moles of ferrous oxalate, 0.1 moles of diammonium hydrogen phosphate and 0.0015 moles of europium oxalate Eu ₂ (C ₂ O ₄ ) ₃ ·10H ₂ O, add to polyester tank, add 60ml of absolute alcohol , after sealing, mix it on a planetary ball mill for 6 hours, and after drying the material, raise the temperature to 420°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/minute, keep it warm for 9 hours, and then cool it down to room temperature with the furnace. The calcined material was obtained, ball milled for 6 hours with industrial alcohol as the medium, and after the discharge was dried, it was raised to 700°C at a heating rate of 3°C/min under an ammonia decomposition gas atmosphere of 0.3 liters/min, and kept at this temperature for 7 Hours, the temperature was lowered to room temperature with the furnace, and the positive electrode material Li _0.97 Eu _0.03 FePO ₄ was obtained.

Weigh 0.45g of positive electrode material powder, add 0.0448g of carbon black, 0.032g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 34mA/g (in terms of positive electrodes), and discharge to 2.5 volts, and the first reversible discharge specific capacity of the battery is 121mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 120mAh/g.

Example 9

Mix 0.048 mol of lithium carbonate, 0.1 mol of ferrous oxalate, 0.1 mol of ammonium dihydrogen phosphate and 0.004 mol of gadolinium nitrate Gd(NO ₃ ) ₃ into a polyester tank, add 60ml of absolute alcohol, seal it and put it on a planetary ball mill Mix for 7 hours, discharge and dry, then raise the temperature up to 400°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/min, keep it warm for 8 hours, and cool down to room temperature with the furnace to obtain pre-fired material. It is a medium ball mill for 6 hours, and after the discharge is dried, it is raised to 750°C at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain the positive electrode material Li _0.96 Gd _0.04 FePO ₄ .

Weigh 0.45g of positive electrode powder, add 0.06g of carbon black, 0.032g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 25mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 111mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 109mAh/g.

Example 10

Mix 0.096 mol of lithium acetate, 0.1 mol of ferrous acetate, 0.1 mol of ammonium phosphate and 0.001 mol of terbium oxide (Tb ₄ O ₇ ), add to a polyester tank, add 80ml of absolute alcohol, seal and mix on a planetary ball mill for 7 Hours, after discharging and drying, under a nitrogen atmosphere of 0.3 liters/min, the temperature rises to 400°C at a rate of 5°C/min, and is kept at this temperature for 8 hours. Water was used as the medium for ball milling for 6 hours, and after the discharge was dried, the temperature was raised to 700°C at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain a positive electrode Material Li _0.96 Tb _0.04 FePO ₄ .

Weigh 0.45g of positive electrode material powder, add 0.078g of carbon black, 0.032g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 30mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 123mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 120mAh/g.

Example 11

Mix 0.0499 moles of lithium carbonate, 0.1 moles of ferrous chloride, 0.1 moles of ammonium dihydrogen phosphate and 0.0002 moles of dysprosium chloride _DyCl3 , add to a polyester tank, add 80ml of absolute alcohol, seal and mix on a planetary ball mill for 7 Hours, after discharging and drying, under a nitrogen atmosphere of 0.3 liters/min, the temperature rises to 400°C at a rate of 5°C/min, and is kept at this temperature for 8 hours. Water was used as the medium for ball milling for 6 hours, and after the discharge was dried, the temperature was raised to 700°C at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain a positive electrode Material Li _0.998 Dy _0.002 FePO ₄ .

Weigh 0.843g of positive electrode powder, add 0.078g of carbon black, 0.062g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 40mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 113mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 110mAh/g.

Example 12

Mix 0.0994 mole of lithium hydroxide, 0.1 mole of ferrous oxalate, 0.1 mole of diammonium hydrogen phosphate and 0.0003 mole of holmium oxide Ho ₂ O ₃ , add to a polyester tank, add 50ml of water alcohol, seal and mix on a planetary ball mill for 7 Hours, after discharging and drying, under a nitrogen atmosphere of 0.3 liters/min, the temperature was raised to 400°C at a rate of 5°C/min, kept at a temperature of 8 hours, and cooled to room temperature with the furnace to obtain a pre-fired material. After ball milling for 6 hours, the material was dried and then heated to 700°C at a rate of 4°C/min in an atmosphere of ammonia decomposition gas at 0.3 liters/min, kept at this temperature for 8 hours, and then cooled to room temperature with the furnace to obtain the positive electrode material Li _0.994 Ho _0.006 FePO ₄ .

Weigh 0.624g of positive electrode material powder, add 0.09g of carbon black, 0.052g of polyvinylidene fluoride, make electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 20mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 148mAh/g. After 20 cycles, the displayed discharge specific capacity remains above 135mAh/g.

Example 13

Mix 0.0493 moles of lithium carbonate, 0.1 moles of ferrous oxalate, 0.1 moles of ammonium phosphate and 0.0007 moles of erbium oxide (Er ₂ O ₃ ), add to a polyester tank, add 80ml of absolute alcohol, seal and mix on a planetary ball mill for 7 Hours, after discharging and drying, under a nitrogen atmosphere of 0.3 liters/min, the temperature was raised to 400°C at a rate of 5°C/min, kept at a temperature of 8 hours, and cooled to room temperature with the furnace to obtain a pre-fired material. After ball milling for 6 hours, the material was dried and then heated to 700°C at a rate of 4°C/min under a nitrogen atmosphere of 0.3 liters/min, kept at this temperature for 8 hours, and cooled to room temperature with the furnace to obtain the positive electrode material Li _0.986 Er _0.014 FePO ₄ .

Take by weighing 0.734g of positive electrode material powder, add 0.085g of carbon black, 0.052g of polyvinylidene fluoride, manufacture electrode sheet and assemble battery by the method of Example 1, charge to 4.2 volts with the rate of 20mA/g (calculated as positive electrode), discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 118mAh/g. After 20 cycles, the displayed discharge specific capacity remains above 120mAh/g.

Example 14

Mix 0.098 mol of lithium acetate, 0.1 mol of ferrous oxalate, 0.1 mol of ammonium dihydrogen phosphate and 0.002 mol of thulium chloride TmCl ₃ into a polyester tank, add 80ml of absolute alcohol, seal and mix on a planetary ball mill for 7 hours , after discharging and drying, in the atmosphere of 0.3 liters/min of ammonia decomposition gas, the temperature was raised to 400 °C at a rate of 3 °C/min, kept for 7 hours, and the temperature was lowered to room temperature with the furnace to obtain pre-burned material. It is a medium ball mill for 6 hours, and after the discharge is dried, it is raised to 750°C at a rate of 4°C/min in an atmosphere of ammonia decomposition gas at 0.3 liters/min, kept at this temperature for 6 hours, and cooled to room temperature with the furnace to obtain The cathode material is Li _0.98 Tm _0.02 FePO ₄ .

Take by weighing 0.45g of positive electrode material powder, add 0.078g of carbon black, 0.042g of polyvinylidene fluoride, manufacture electrode sheet and assemble battery according to the method of Example 1, charge to 4.2 volts with the rate of 20mA/g (calculated as positive electrode), discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 123mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 120mAh/g.

Example 15

Mix 0.04825 moles of lithium carbonate, 0.1 moles of ferrous oxalate, 0.1 moles of ammonium dihydrogen phosphate and 0.00175 moles of ytterbium oxide (Yb ₂ O ₃ ), add to a polyester tank, add 80ml of absolute alcohol, seal and place on a planetary ball mill Mix for 7 hours, discharge and dry, then raise the temperature to 400°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/minute, keep the temperature at this temperature for 8 hours, and cool down to room temperature with the furnace to obtain a calcined material. After 6 hours of ball milling with water as the medium, after the discharge is dried, in a nitrogen atmosphere of 0.3 liters/min, the temperature rises to 730°C at a rate of 4°C/min, keeps at this temperature for 8 hours, and then cools down to room temperature with the furnace. The positive electrode material Li _0.965 Yb _0.035 FePO ₄ was obtained.

Weigh 0.45g of positive electrode material powder, add 0.078g of carbon black, 0.032g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 20mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 122mAh/g. After 20 cycles, the displayed discharge specific capacity remains above 125mAh/g.

Example 16

Mix 0.0975 mol of lithium acetate, 0.1 mol of ferrous oxalate, 0.1 mol of ammonium dihydrogen phosphate and 0.0025 mol of lutetium nitrate Lu(NO ₃ ) ₃ into a polyester tank, add 80ml of absolute alcohol, seal and place on a planetary ball mill Mix for 6 hours, and after discharging and drying, raise the temperature to 400°C at a rate of 5°C/min under a nitrogen atmosphere of 0.3 liters/minute, keep the temperature at this temperature for 8 hours, and cool down to room temperature with the furnace to obtain a calcined material. After ball milling with anhydrous alcohol as the medium for 6 hours, after the discharge is dried, in a nitrogen atmosphere of 0.3 liters/minute, the temperature rises to 700°C at a rate of 4°C/min, and is kept at this temperature for 8 hours, and the temperature is lowered with the furnace. At room temperature, the positive electrode material Li _0.975 Lu _0.025 FePO ₄ was obtained.

Weigh 0.45g of positive electrode material powder, add 0.078g of carbon black, 0.032g of polyvinylidene fluoride, manufacture electrode sheets and assemble batteries according to the method in Example 1, charge to 4.2 volts at a rate of 20mA/g (in terms of positive electrodes), and discharge to 2.5 volts, the first reversible discharge specific capacity of the battery is 123mAh/g. After 20 cycles, the discharge specific capacity exhibited by the corresponding material remains above 120mAh/g.

Claims (5)

1. the preparation method of a rare earth doped iron lithium phosphate powder is characterized in that, is used for the described iron lithium phosphate molecular formula Li of anode material for lithium-ion batteries _1-xRE _xFePO ₄Expression, wherein 0＜x≤0.05; RE is the element of rare-earth dopant, and the element of this rare-earth dopant is by the rare earth lanthanide compound: the oxide compound of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, oxyhydroxide, muriate, nitrate, vitriol, carbonate, fluorochemical or organic salt are adulterated;

Concrete preparation method is as follows:

Lithium salts, ferrous salt and phosphoric acid salt and rare-earth dopant are pressed element Li: Fe: P: RE=(1-x): 1: 1: the mol ratio of x is once reinforced, adds the mix grinding medium, and 6～12 hours ball milling time is 40～70 ℃ of oven dry down; Oven dry back powder is heated to 400～550 ℃ under inert atmosphere or reducing atmosphere, be incubated 5～10 hours and carry out precalcining; Secondary ball milling 6～12 hours, 40～70 ℃ of oven dry down, under inert atmosphere or reducing atmosphere, 550～850 ℃ of secondary clacinings obtain rear-earth-doped iron lithium phosphate Li then _1-xRE _xFePO ₄Powder.

2. according to the preparation method of the described rare earth doped iron lithium phosphate powder of claim 1, it is characterized in that described lithium salts is Li ₂CO ₃, at least a in lithium oxalate and the Lithium Acetate.

3. according to the preparation method of the described rare earth doped iron lithium phosphate powder of claim 2, it is characterized in that described lithium salts substitutes with LiOH.

4. according to the preparation method of the described rare earth doped iron lithium phosphate powder of claim 1, it is characterized in that described ferrous salt is at least a in Ferrox, Iron diacetate, iron protochloride and the ferrous sulfate.

5. according to the preparation method of the described rare earth doped iron lithium phosphate powder of claim 1, it is characterized in that described phosphoric acid salt is at least a in ammonium phosphate, Secondary ammonium phosphate and the primary ammonium phosphate.