CN1948138A

CN1948138A - High temperature solid phase method of ferrosodium flurophosphate for sodium ion battery

Info

Publication number: CN1948138A
Application number: CNA2006100968747A
Authority: CN
Inventors: 王先友; 何建平; 唐敏; 何平; 张传香; 赵桂网
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2006-10-23
Filing date: 2006-10-23
Publication date: 2007-04-18

Abstract

The present invention relates to a high-temperature solid phase method for preparing sodium ferrous fluophosphate for sodium ion battery, belonging to the preparation method of secondary cell positive electrode material in energy source material. Said method includes the following steps: mixing sodium carbonate, sodium fluoride, ferrous oxalate and ammonium dihydrogen phosphate according to the ratio of 0.5 mol:1mol:1Mol:1mol, using absolute ethyl alcohol as medium, ball-grinding for 4 hr, vacuum drying at 80 deg.C for 8 hr, prefiring at 300 deg.C for 3 hr in tubular furnace under the protection of argon gas, taking out, tabetting, continuously calcining at 650-850 deg.C under the condition of argon gas protection, heat-insulating for 6 hr, cooling to room temperature, grinding so as to obtain the invented product.

Description

The high temperature solid-state method of ferresodium flurophosphate for sodium ion battery

One, technical field

The high temperature solid-state method of the ferresodium flurophosphate for sodium ion battery of this invention belongs to the preparation method of the secondary battery positive electrode material in the energy and material.

Two, technical background

It is low that sodium-ion battery has material cost, and therefore characteristics such as safety performance excellence are considered to substitute lithium ion battery as moving the better selection that reaches electrical source of power.In recent years, the research of external sodium-ion battery negative material is flourish, it is reported that materials such as treated graphite, carbon black, hard carbon all have higher reversible capacity (more than the 300mAh/g).With respect to the obtained good progress of negative material, the optional leeway of positive electrode current material is less, and specific discharge capacity lower (being lower than 90mAh/g).Therefore, can the research of positive electrode material make a breakthrough, and is the key point of development sodium-ion battery.

At home, the research work of sodium-ion battery positive electrode material does not appear in the newspapers as yet, for seeking good sodium-ion battery positive electrode material, has occurred some significant research work abroad.Bach etc. have studied under the sodium ion low temperature has the Mn of spinel structure _2.2Co _0.27O ₄Embedded performance in the material is found to discharge and recharge with the electric current of C/8 multiplying power, and capacity is held in the discharge in the 15th week still 95mAh/g.Concrete research document is [S.Bach, M.Millet, J.P.Periera-Ramos, L.Sanchez, P.Lavela, and J.L.Tirado, Electrochemical and Solid-State Letters, 2 (1999) 545].The loading capacity of this material and cyclical stability are still not fully up to expectations, and the performance under middle high temperature is unsatisfactory.U.S. Valence Technology, the research that the Barker of Incorporated etc. carry out transistion metal compound, they find NaVPO ₄The better performances of F cooperates with hard carbon material and to make sodium-ion battery, and battery operated voltage is 3.7V, and is very consistent with lithium ion battery, and the capacity of positive electrode material is 82mAh/g, after 30 charge and discharge cycles cell container be the 1st time 50%.Concrete work is [J.Barker, M.Y.Saidi, and J.L.Swoyer, A Sodium-Ion Cell Based on theFluorophosphate Compound NaVPO ₄F, Electrochemical and Solid-State Letters, 6 (2003) A1-A4].Though NaVPO ₄F can obtain comparatively stable sparking voltage, but its loading capacity and stable circulation performance still have much room for improvement.

High temperature solid-state method is the common method of composite electrode material, and it has obtained widespread use in the preparation of anode material for lithium-ion batteries, as the synthetic stratiform LiMn that contains Al of the hot solid phase method of usefulness such as Ammundsen _0.95Al _0.05O ₂[Ammundsen B, Paulsen J, Davidson I, et al.Local structure and first cycle redox mechanism oflayered Li _1.2Cr _0.4Mn _0.4O ₂Cathode material[J] .Journal of the Electrochemical Society, 2002,149 (4): A431-A436].This invention applies to high temperature solid-state method in the preparation of sodium-ion battery positive electrode material, obtains having the hexafluorophosphoric acid Naferon positive electrode material that sodium ion takes off the embedding performance, will promote the development of sodium-ion battery technology energetically.

Three, summary of the invention

The objective of the invention is at the deficiencies in the prior art, propose the ferresodium flurophosphate for sodium ion battery preparation methods that a kind of energy preparation has higher specific discharge capacity and stable circulation performance.

This invention makes that by rational more secondary clacining process prepared material crystals growth is more abundant, and particle is more even, has bigger sodium ion embedded quantity in the hope of making it, thereby improves the capacity of battery.Moreover this invention use technology temperature condition is controlled, and reaction and operating process are easy, helps the industrialization operation in enormous quantities of material preparation, will further promote the practicalization of low-cost and high-performance energy storage material.

For solid state reaction, fs be on crystal grain boundary or the reactant lattice of near interface in generate the nucleus of target product, this step is difficulty relatively, because the nucleus that generates is different with the structure of reactant, need be by the rearranging of reactant interface structure, comprising the fracture and the recombine of zwitterion key.Omission will be deviate from, spread and be entered to ion in the reactant lattice, help the carrying out of these processes under the high temperature, also help the generation of nucleus.Equally, the crystal growth that is further implemented on the nucleus also is the comparison difficulty, and the ion in the raw material will the crystalline growth response could take place across the diffusion at a plurality of interfaces on nucleus, and the product layer between the raw material interface is thickened.Therefore the controlled step that can see the decision reaction is the diffusion of reactant ion in the lattice, and elevated temperature helps the diffusion of lattice intermediate ion, thereby obviously helps promoting reaction.

Reaction raw materials is respectively Na ₂CO ₃, NaF, (NH ₄) H ₂PO ₄And FeC ₂O ₄2H ₂O is according to 0.5mol: 1mol: 1mol: the 1mol ratio, with these four kinds of raw materials with dehydrated alcohols as medium, ball milling 4 hours.80 ℃ of vacuum-dryings are after 8 hours; in tube furnace in the argon gas atmosphere in 300 ℃ of following pre-burnings 3 hours; take out; make disk shape (φ 20mm, thickness 5mm) with tabletting machine, continue under 650 ℃～850 ℃ temperature range argon shield, to calcine; be incubated 6 hours; cool to room temperature with the furnace, grind, so can obtain comparatively satisfied positive electrode material through twice calcining.

Show that by experiment hexafluorophosphoric acid Naferon positive electrode material of the present invention has higher charging platform and lower discharge platform, and still have the reversible capacity of 60mAh/g, circulate after 20 times, capacity attenuation is 51.1mAh/g, and capability retention can reach 85.17%.

Four, description of drawings

Fig. 1 is the hexafluorophosphoric acid Naferon SEM figure of high temperature solid-state method preparation

Fig. 2 is the first charge-discharge curve of hexafluorophosphoric acid Naferon

Fig. 3 is the discharge cycles capacity of hexafluorophosphoric acid Naferon

Five, specific embodiments

Now provide with next specific embodiment, utilize high temperature solid-state method to obtain hexafluorophosphoric acid Naferon positive electrode material.Present technique is calcined for the first time mainly by the batch mixing ball milling, and several steps of secondary clacining are formed.

1. batch mixing ball milling

Use electronic analytical balance to take by weighing the yellow soda ash of 0.005mol and Sodium Fluoride, Ferrox, each 0.01mol of primary ammonium phosphate of each 0.01mol, mix, the 200ml dehydrated alcohol is as medium, and be poured in the ball grinder, the ball grinder symmetry is placed, ball milling 4 hours takes out mixture, 80 ℃ of vacuum-drying 8 hours.

2. first calcining

The mixture powder that previous step is handled well uses tabletting machine to be pressed into the disk shape, and pressure is 15MPa, and 3 minutes (φ 20mm, thickness 5mm) keep-ups pressure.Disk is placed in the tube furnace, is in 99.99% argon stream in purity, and 750 ℃ of calcining 6h cool to room temperature with the furnace.

3. secondary clacining

With agate mortar disk shape mixture is ground to form 20 minutes, powdered, purity is the following 750 ℃ of calcinings of 99.999% argon stream in tube furnace again, is incubated 6 hours, cools to room temperature with the furnace and can get product.

In order to study the structure and the chemical property of the prepared hexafluorophosphoric acid Naferon of present technique, we take following experimental technique.

Hexafluorophosphoric acid Naferon to high temperature solid-state method preparation carries out scanning electron microscopic observation, and as shown in Figure 1, when synthesis temperature reached 750 ℃, particle was comparatively even, grain diameter at 5 μ m between the 10 μ m.The sample of preparation is assembled into Experimental cell as positive active material, with the 20mA/g constant current charge-discharge, the first charge-discharge curve of gained is sample first charge-discharge curve as shown in Figure 2, at this moment material has had better electrochemical activation, we can obviously observe a more oblique discharge platform between 2.2V～3.0V, initial discharge capacity reaches 60mAh/g.Sample charging and discharging circulation reversibility energy has at room temperature carried out repeatedly the charge and discharge cycles test to Experimental cell, and the specific discharge capacity of hexafluorophosphoric acid Naferon positive electrode material and relation such as Fig. 2 of cycle index are shown in 3.Though under this charge-discharge velocity, higher (charging) platform and the platform of lower (discharge) have appearred in solid phase method synthetic hexafluorophosphoric acid Naferon material, but material still has the bigger reversible capacity of 60mAh/g, circulating, capacity attenuation is 51.1mAh/g after 20 times, and capability retention is 85.17%.

Claims

1. the high temperature solid-state method of a ferresodium flurophosphate for sodium ion battery; it is characterized in that; yellow soda ash; Sodium Fluoride; Ferrox; four kinds of raw materials of primary ammonium phosphate are in 0.5mol: 1mol: 1mol: the 1mol ratio with dehydrated alcohol as medium; ball milling 4 hours; through 80 ℃ of vacuum-dryings after 8 hours; in tube furnace, take out after 3 hours in 300 ℃ of following pre-burnings in the argon gas atmosphere; make the disk shape with tabletting machine; calcine under the argon shield of continuation in 650～850 ℃ of scopes; be incubated 6 hours; cool to room temperature with the furnace, grind, so obtain the ferresodium flurophosphate for sodium ion battery positive electrode material through twice calcining.