Iron phosphate compound anode material of lithium in a kind of lithium ion battery and preparation method thereof
Technical field
The present invention relates in a kind of lithium ion battery iron phosphate compound anode material of lithium the preparation method, belong to technical field of lithium ion.
Background technology
Along with becoming increasingly conspicuous of problems such as environmental pollution, energy crisis and shortage of resources; development of technologies such as countries in the world are more and more paid much attention to efficiently, cleaning, regenerative resource and electric automobile, electric bicycle, portable power tool, their development and electrokinetic cell are closely bound up.The electrokinetic cell that present electric vehicle is used is mainly lead-acid battery and Ni-MH battery.It has been recognized that plumbous murder by poisoning problem now, the use of lead-acid battery begins to be restricted; And the energy density of Ni-MH battery can not satisfy the fast-developing market demand, so people must reselect and development of new energy storage device.Under the promotion in markets such as the electric automobile of fast development, electric bicycle, portable power tool, emerging green power type energy storage device becomes the focus that global high-tech industry is paid close attention to.
The liquid lithium ion electrokinetic cell is the novel green energy storage device that development in recent years is got up, and lithium ion battery has caused people's extensive concern because of its high-energy-density is higher relatively, high-rate discharge ability is better.And positive electrode is a very crucial part in the lithium electricity industry, its performance and quality directly have influence on important performances such as the capacity, life-span, fail safe of lithium ion battery, therefore, research and develop more efficient, safe positive electrode, being the important channel of the power density that improves lithium ion battery, cycle performance, security performance, is to satisfy the important means that growing power-type lithium ion battery market requires battery performance.
Olivine-type LiFePO
4From 1997 by the Goodenough reported first since since its security performance good, have extended cycle life, characteristics such as raw material sources are wide, environmental friendliness, be acknowledged as the desirable positive electrode of power lithium-ion battery, also become " focus " that common people pay close attention to.Yet, LiFePO
4Remarkable shortcoming as positive electrode is that the intrinsic electronic conductivity is lower by (10
-8~10
-10S/cm) and the lithium ion diffusion rate little by (1.8 * 10
-14Cm
2/ s), thus cause this material electronics in charge and discharge process in time from electrode, not deviate from and to embed with lithium ion, cause bigger capacitive reactance, have a strong impact on its chemical property, make it be difficult to obtain practical application.At present, to LiFePO
4Research emphasis be placed on and improve on its electric conductivity, adopt on the one hand and add the electron conduction that conductive agent and ion doping improve material, the method with control material particle size, raising working temperature improves ions diffusion speed on the other hand.CN200610041396 discloses the method that a kind of carbon coats, and the product that makes is with the 0.2C rate charge-discharge, and its specific capacity reaches 147mAh/g, and 30 times the capability retention of circulating is 94.56%; CN200710173591 discloses the method that a kind of conductive network coats, and the product electronic conductivity height of gained, tap density height are suitable for high rate charge-discharge; CN200710008713 discloses a kind of P site doped method, the initial reversible capacity height of the product of gained, good cycle; CN200510132429 discloses a kind of rare earth doped method, and product cycle electric performance that makes and battery capacity have had and significantly improve; CN200810029616 discloses a kind of preparation method of nano-scale lithium iron phosphate, and the product particle of gained is tiny, even, has higher charge/discharge capacity, good high rate performance and good circulation performance.
Summary of the invention
The purpose of this invention is to provide iron phosphate compound anode material of lithium in a kind of lithium ion battery and preparation method thereof.Iron phosphate compound anode material of lithium of the present invention has excellent conducting performance, thereby improves other chemical properties such as reversible capacity, high rate performance and cycle life of battery.Method of the present invention also has simply, practical characteristics.
Purpose of the present invention is achieved through the following technical solutions:
A kind of lithium ion battery iron phosphate compound anode material of lithium of the present invention, one or both in the particle gap of lithium iron phosphate positive material filling metal nanometer line, metal oxide nano-wire; Or, fill and be coated with in metal nanometer line, the metal oxide nano-wire one or both in the particle gap of lithium iron phosphate positive material and at particle surface.
Described metal nanometer line is selected from one or both in copper nano-wire, nano silver wire, nickel nano wire, aluminium nano wire, zinc nano wire, stannum nanowire, magnesium nano wire, the titanium nano wire; Metal oxide nano-wire is selected from one or both in alumina nanowires, cupric oxide nano line, magnesia nanometer line, TiOx nano line, chromium oxide nano wire, nickel oxide nano line, zirconium oxide nano wire, the zinc oxide nanowire.
Preparation method of the present invention, may further comprise the steps: lithium iron phosphate positive material is scattered in the organic solvent, add then and account for the nano wire that the lithium iron phosphate positive material percentage by weight is 0.2-5.0wt%, this nano wire is one or both in metal nanometer line, the metal oxide nano-wire, make its even mixing by ultrasonic agitation, subsequent drying obtains the compound lithium iron phosphate positive material of nano wire, after annealing obtains iron phosphate compound anode material of lithium.
The temperature of described annealing is 100-500 ℃, and annealing time is 1-10h.
The present invention specifically may further comprise the steps:
(1) with Li source compound, Fe source compound and P source compound in molar ratio 1~1.2: 1: 1 mixed, add carbon source more therein, with acetone or absolute ethyl alcohol is medium, with rotating speed 300-500r/min high speed ball milling 6-48h, makes mixture after 50-80 ℃ of following drying;
(2) mixture that step (1) is made is heated to 300-400 ℃ under inert atmosphere, insulation 5-20h, under inert atmosphere, be heated to 550-800 ℃ again, calcining 10-24h, calcining is finished and is taken out after the afterreaction thing naturally cools to room temperature, obtains lithium iron phosphate positive material.
(3) lithium iron phosphate positive material is scattered in the organic solvent (as ethanol, acetone), add then and account for the nano wire that the lithium iron phosphate positive material percentage by weight is 0.2-5.0wt%, this nano wire is one or both in metal nanometer line, the metal oxide nano-wire, make its even mixing by ultrasonic agitation, subsequent drying obtains the compound lithium iron phosphate positive material of nano wire, after annealing obtains iron phosphate compound anode material of lithium.
Above-mentioned nano wire is wherein one or both of metal or metal oxide nano-wire; Li source compound is lithium carbonate, lithium nitrate, lithium acetate or lithium hydroxide; Fe source compound is that oxalic acid dihydrate is ferrous, frerrous chloride, ferrous nitrate or ferrous sulfate; P source compound is ammonium dihydrogen phosphate, diammonium hydrogen phosphate or sodium phosphate; Carbon source is one or more in graphite, carbon black, glucose, the sucrose etc.; Inert atmosphere is meant nitrogen, argon gas or helium atmosphere.
Compared with prior art, the invention has the beneficial effects as follows:
Nano wire is filled in the particle gap of LiFePO4 as electric conductor, form spacial framework, reduce the impedance between the particle, make and have a large amount of spaces between the particle, help the infiltration of electrolyte, nano wire has bigger specific area simultaneously, and more active site is arranged, conductivity is big, helps Li
+With the transmission of electronics, thereby improve the chemical property (as reversible capacity, high rate performance and the cycle life of battery) of lithium ion battery.
The above-mentioned beneficial effect of the inventive method is proved in the following example.
Description of drawings
The present invention is further described below in conjunction with drawings and Examples.
Fig. 1 is the X-ray diffractogram of iron phosphate compound anode material of lithium among the embodiment 1.
Fig. 2 is the FESEM picture of iron phosphate compound anode material of lithium among the embodiment 1.
Fig. 3 is the EDS picture of iron phosphate compound anode material of lithium among the embodiment 1.
Fig. 4 is the charging and discharging curve of iron phosphate compound anode material of lithium 0.1C among the embodiment 1.
Fig. 5 is the multiplying power cycle performance of iron phosphate compound anode material of lithium among the embodiment 1.
Embodiment
Following examples are intended to illustrate the present invention rather than limitation of the invention further.
Embodiment 1
To analyze pure lithium carbonate, ferrous oxalate, ammonium dihydrogen phosphate according to stoichiometric proportion mixing in 0.5: 1: 1, and add a spot of glucose again, be medium with the absolute ethyl alcohol, and wet ball grinding 20h obtains presoma after the drying.Presoma is placed tube furnace, feeds argon shield, be warming up to 350 ℃ of insulation 5h after, be warming up to 700 ℃ of constant temperature sintering 12h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the nickel nano wire of 0.5wt%, and as dispersant, by stirring and ultrasonicly making its even mixing, after the drying, in vacuum furnace, 200 ℃ are incubated 1h, promptly get end product with ethanol.
The XRD figure of the anode material for lithium-ion batteries that makes as shown in Figure 1, SEM schemes as shown in Figure 2, EDS schemes as shown in Figure 3.As seen products therefrom is the olivine-type LiFePO4, and there is not impurity peaks in the structure complete in crystal formation in the spectrogram, and product purity is higher.Particle size is comparatively even, and particle diameter is less.Simultaneously can see that the nickel nano wire is evenly distributed between the active particle in the sample.
Below the lithium iron phosphate positive material that makes is used for the making of Experimental cell electrode:
Active material iron phosphate powder, conductive agent acetylene black and binding agent Kynoar (PVDF) are mixed in an amount of solvent N-methyl pyrrolidone (NMP) by mass ratio at 8: 1: 1, stir ultrasonic dispersion.Again slurry is coated on the positive plate uniformly, puts into the vacuum drying chamber oven dry.In the argon gas atmosphere dry glove box, be to electrode with metal lithium sheet, barrier film is Celgard2400, electrolyte is ethylene carbonate (EC)+dimethyl carbonate (DMC)+1MLiPF
6, be assembled into the button cell test performance.The charge-discharge performance test of battery is at room temperature carried out, and carries out the constant current charge-discharge loop test with Shenzhen new prestige BTS series high accuracy battery combination property detection system, and charging/discharging voltage is 2.3-4.2V.
The first charge-discharge curve chart of the Experimental cell 0.1C that is made by the anode material for lithium-ion batteries of embodiment 1 preparation is seen Fig. 3, and as seen its first charge-discharge specific capacity is 165mAh/g.The rate charge-discharge performance of embodiment 1 as shown in Figure 4, the battery capacity when discharge-rate is 5C is 126mAh/g, circulates that capability retention is 90.6% after 190 times, shows that the multiplying power discharging property of material is good.
Embodiment 2
To analyze pure lithium carbonate, ferrous oxalate, ammonium dihydrogen phosphate according to stoichiometric proportion mixing in 0.5: 1: 1, and add a spot of sucrose again, be medium with the absolute ethyl alcohol, and wet ball grinding 24h obtains presoma after the drying.Presoma is placed tube furnace, feeds argon shield, be warming up to 350 ℃ of insulation 10h after, be warming up to 700 ℃ of constant temperature sintering 20h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the alumina nanowires of 1wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in argon gas atmosphere, 220 ℃ of insulation 1h promptly get end product.
Embodiment 3
To analyze pure cerium hydroxide lithium, ferrous oxalate, ammonium dihydrogen phosphate according to stoichiometric proportion mixing in 1.05: 1: 1, and add a spot of glucose again, be medium with the absolute ethyl alcohol, and wet ball grinding 18h obtains presoma after the drying.Presoma is placed tube furnace, feeds nitrogen protection, be warming up to 300 ℃ of insulation 6h after, be warming up to 750 ℃ of constant temperature sintering 15h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the nickel oxide nano line of 0.3wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in nitrogen atmosphere, 300 ℃ of insulation 30min promptly get end product.
Embodiment 4
To analyze pure phosphoric acid dihydro lithium, ferrous oxalate according to stoichiometric proportion mixing in 1: 1, and add a spot of carbon black again, be medium with the absolute ethyl alcohol, and wet ball grinding 15h obtains presoma after the drying.Presoma is placed tube furnace, feeds nitrogen protection, be warming up to 400 ℃ of insulation 5h after, be warming up to 800 ℃ of constant temperature sintering 18h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the zirconium oxide nano wire of 2wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in nitrogen atmosphere, 220 ℃ of insulation 1h promptly get end product.
Embodiment 5
To analyze pure lithium carbonate, frerrous chloride, diammonium hydrogen phosphate according to stoichiometric proportion mixing in 0.5: 1: 1, and add a spot of carbon black again, be medium with the absolute ethyl alcohol, and wet ball grinding 24h obtains presoma after the drying.Presoma is placed tube furnace, feeds argon shield, be warming up to 350 ℃ of insulation 10h after, be warming up to 700 ℃ of constant temperature sintering 15h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the aluminium nano wire of 3wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in argon gas atmosphere, 200 ℃ of insulation 1h promptly get end product.
Embodiment 6
To analyze pure lithium nitrate, ferrous nitrate, diammonium hydrogen phosphate according to stoichiometric proportion mixing in 1.1: 1: 1, and add a spot of graphite again, be medium with the absolute ethyl alcohol, and wet ball grinding 30h obtains presoma after the drying.Presoma is placed tube furnace, feeds the helium protection, be warming up to 400 ℃ of insulation 10h after, be warming up to 750 ℃ of constant temperature sintering 10h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the copper nano-wire of 3wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in helium atmosphere, 400 ℃ of insulation 30min promptly get end product.
Embodiment 7
To analyze pure cerium hydroxide lithium, frerrous chloride, ammonium dihydrogen phosphate according to stoichiometric proportion mixing in 1.05: 1: 1, and add a spot of sucrose again, be medium with the absolute ethyl alcohol, and wet ball grinding 48h obtains presoma after the drying.Presoma is placed tube furnace, feeds argon shield, be warming up to 300 ℃ of insulation 10h after, be warming up to 650 ℃ of constant temperature sintering 20h again, cool to room temperature with the furnace.Adding mass fraction in above-mentioned product is the magnesia nanometer line of 2wt%, adds ethanol then as dispersant, and vigorous stirring mixes it, and after the drying, in argon gas atmosphere, 200 ℃ of insulation 1h promptly get end product.