CN101391816A - High energy density lithium ion secondary battery anode material and preparation method thereof - Google Patents

Abstract

The invention relates to a method for preparing positive electrode materials and oxalates thereof of lithium ion secondary batteries. The molecular formula of the materials is CrxV2O5; wherein, the x is more than zero but equal to or less than 0.1. By adopting V2O5 and Cr (NO3) 3 question mark 9H2O with the mol ratio of Cr to V between x: 2 as the raw materials, the method for preparing positive electrode materials and oxalates thereof of the lithium ion secondary batteries comprises the following steps of: adding water and C2H2O4 question mark 2H2O into the raw materials, and stirring to form gelatin; drying and grinding into powder; and sintering at the temperature between 300 and 400 DEG C, and preserving heat for 5 to 10 hours. With simple preparation method and low requirements on technique, the method for preparing positive electrode materials and oxalates thereof of the lithium ion secondary batteries is easily to be used in the industrial batch production. The compounded positive electrodes are characterized by single phases, stable structure, high energy density, large electrochemical capacity and excellent cycling performance. In addition, the electrochemical performance is more excellent under high current density.

Description

High energy density lithium ion secondary battery anode material and preparation method thereof

Technical field

The invention belongs to a kind of lithium ion battery material and preparation method thereof, be specifically related to the preparation technology of lithium ion secondary battery anode material and oxalate method thereof.

Background technology

Since the nineties in 20th century, lithium-ion secondary cell has obtained widespread use in various portable type electronic products.In recent years, the research around lithium-ion secondary cell mainly concentrates on searching voltage height, energy density height, good cycle and cheap aspects such as electrode materials.Particularly along with the needs of mixed power electric car (HEV, Hybrid Electric Vehicle) and pure electric automobile (EV, Electric Vehicle) development, the development of its core component-power accumulator has become the core missions of electric vehicle development.The electric powered motor store battery that generally adopts in the world mainly contains two kinds at present: lithium ion battery and nickel metal hydride battery.Comprehensive all multifactor considerations, lithium ion battery is generally believed it is the most promising electric powered motor store battery.Commercial widely used lithium ion secondary battery anode material is LiCoO now ₂(cobalt acid lithium), it has the voltage height, and advantages such as stable cycle performance, but because the Co element is poisonous are unfavorable to environment protection, cost an arm and a leg, and the safety problem that occurs in recent years, limited its application on more extensive.Based on LiCoO ₂Above defective, people have developed a series of novel lithium ion secondary battery anode materials, as LiMnO ₂, LiMn ₂O ₄, LiNi _1/3Mn _1/3Co _1/3O ₂And LiFePO ₄Wherein, with V ₂O ₅For the vanadium oxide positive electrode materials of representing gets most of the attention with its high energy density always.

V ₂O ₅Belong to rhombic system, have laminate structure, spacer is Pmmn.As positive electrode material, it has capacity density and energy density height, and cost is low, is easy to advantages such as preparation, but V ₂O ₅Itself, the high V of degree of crystallinity especially ₂O ₅Electrochemical properties unsatisfactory.This mainly is because of material lower electronics and ionic conductivity and material structure generation avalanche easily in charge and discharge process, thereby causes the cycle performance variation.In recent years, people adopt supercritical drying, methods such as solvent exchange, and (＜200 ℃) have prepared V at a lower temperature ₂O ₅Gas/xerogel.This class material belongs to high hole shape material, has great specific surface area, makes its Li ⁺Ion diffusion efficient increases substantially, and then has improved the high-rate charge-discharge capability of material.On the other hand, at V ₂O ₅In a small amount of Cu metallic elements such as (or) Ag that mixes, the electric conductivity of material can greatly improve (about 100-1000 times), it is more stable that the structure of material also becomes.Therefore, the pattern of doped with metal elements and control material helps improving the high-rate charge-discharge capability of lithium-ion secondary cell, when obtaining high-energy-density, improve the power density of battery, can satisfy the needs of following electric powered motor store battery development.

Summary of the invention

The objective of the invention is to synthesize a kind of novel lithium ion secondary battery anode material, and new preparation path.This synthetic method, temperature of reaction is low, reaction process is simple, is suitable for producing in batches.

The molecular formula of lithium ion secondary battery anode material of the present invention is Cr _xV ₂O ₅, 0＜x≤0.1, spacer Pmmn belongs to rhombic system, adjacent [VO ₅] trigonal bipyramid altogether prismatic become the laminate structure of prionodont.Material discharges between 2～4V and can insert 3 Li ⁺Ion, its theoretical specific capacity can reach 290mAg ^-1Add the Cr element in the material, can form new [CrO ₆] the octahedra V that connects ₂O ₅Each layer increased the three-dimensional structure stability of material, optimized the chemical property of this positive electrode material, and its space structure synoptic diagram as shown in Figure 1.

The method of the synthetic employing of lithium ion secondary battery anode material of the present invention is an oxalate method, and detailed process is: with Vanadium Pentoxide in FLAKES (V ₂O ₅), oxalic acid (C ₂H ₂O _{4 2}H ₂O), chromium nitrate (Cr (NO ₃) ₃9H ₂O) be raw material, Vanadium Pentoxide in FLAKES is joined in the oxalic acid solution, stir down until forming transparent blue solution at 60～100 ℃, dropwise add the chromium nitrate solution that concentration is 1～3mol/L then, the control mol ratio is Cr:V=x:2, and under this temperature range, stir transpiring moisture to the pasty state gel, form the oxalic acid ligand; Then the oxalic acid ligand is dried down at 100～120 ℃, grind to form powdery and form presoma, in muffle furnace,, be incubated 5～10 hours, last naturally cooling, gained lithium ion secondary battery anode material Cr of the present invention at 300～400 ℃ of following sintering _xV ₂O ₅, 0＜x≤0.1.

The XRD spectrum of this material shows the V with rhombic system ₂O ₅Structure is identical, there is no other phase diffracted ray and exists, and shows that material structure is complete, and inclusion-free exists mutually.

Description of drawings

Fig. 1: positive electrode material Cr of the present invention _xV ₂O ₅The space structure synoptic diagram of (0＜x≤0.1);

The Cr of Fig. 2: embodiment 1 preparation _0.05V ₂O ₅The X-ray diffraction of powdered material (XRD) collection of illustrative plates;

The Cr of Fig. 3: embodiment 1 preparation _0.05V ₂O ₅The first charge-discharge graphic representation of powdered material under different current densities, wherein current density is respectively 29,150,300mAg ^-1, voltage range 2.0～3.8V;

The Cr of Fig. 4: embodiment 2 preparations _0.1V ₂O ₅The X-ray diffraction of powdered material (XRD) collection of illustrative plates

The Cr of Fig. 5: embodiment 2 preparations _0.1V ₂O ₅The first charge-discharge graphic representation of powdered material under different current densities, wherein current density is respectively 29,150,300mAg ^-1, voltage range 2.0～3.8V;

The Cr of Fig. 6: embodiment 1 and embodiment 2 preparations _0.05V ₂O ₅And Cr _0.1V ₂O ₅The cycle performance figure of powdered material; Wherein charging and discharging currents density be respectively 29,150,300mAg ^-1, voltage range 2.0～3.8V.

Embodiment

Embodiment 1:

Choose commercially available molecular weight and be 181.88 V ₂O ₅, molecular weight is 126.07 C ₂H ₂O ₄2H ₂O, molecular weight are 400.15 Cr (NO ₃) ₃9H ₂O is as raw material reagent.V ₂O ₅And Cr (NO ₃) ₃9H ₂The consumption of O is respectively 0.01mol, 0.0005mol, and corresponding Cr:V mol ratio is 0.025:1.

Vanadium Pentoxide in FLAKES is joined in the oxalic acid solution, under 80 ℃ of constant temperature, stir, dropwise add the chromium nitrate solution that concentration is 1mol/L then, be stirred to the pasty state gel, form the oxalic acid ligand until forming transparent blue solution.

The oxalic acid ligand is put into electrothermostat, and constant temperature is 12 hours under 100 ℃ of conditions, makes the oxalic acid ligand continue to shrink and expands, and reaches abundant explosion puffing drying, and grind into powder forms presoma.Under air ambient, under 400 ℃ temperature, carry out sintering then, be incubated 10 hours, promptly get lithium ion secondary battery anode material Cr of the present invention _0.05V ₂O ₅

As shown in Figure 2, the XRD of this material spectrum is shown as and V ₂O ₅Identical Pmmn structure, unit cell parameters is:

We can see from figure does not have other phase diffracted ray to exist, and shows that material structure is complete, and inclusion-free exists mutually.

In order to measure the chemical property of preparation sample, with the electroactive substance Cr that is synthesized _xV ₂O ₅, acetylene black and PVDF (polyvinylidene difluoride (PVDF)) be according to the mixed form slurry of mass ratio 75:15:10, evenly be coated on the aluminum substrates, to dry in the vacuum drying oven of electrode slice under 120 ℃ that obtain, under 6MPa pressure, compress, the square sheets that then aluminium foil is cut into fixed size is as anodal (containing the active substance about 3mg) on each thin slice, with the metallic lithium is negative pole (diameter is about 1cm, and thickness is the disk about 3mm), with 1mol/l LiPF ₆EC (NSC 11801)+DMC (methylcarbonate) (volume ratio 1:1) is an electrolytic solution, and (content of water and oxygen is less than 1PPM) is assembled into Experimental cell in being full of the glove box of argon gas.Experimental cell is tested by being subjected to computer-controlled auto charge and discharge instrument to carry out charge and discharge cycles.Charging and discharging currents density is 29,150,300mAg ^-1, charging/discharging voltage is 2.0～3.8V.

This Cr _0.05V ₂O ₅The first charge-discharge curve of positive electrode material under different current densities, as shown in Figure 3.The Li of every mole of active substance ⁺The insertion amount is respectively 1.6,1.1 and 0.8, and corresponding current density is 29,150,300mAg ^-1Mean energy density and power density corresponding under each current density are as shown in table 1.

Table 1: Cr under the different current densities _0.05V ₂O ₅Mean energy density and power density

Embodiment 2:

Preparation oxalic acid ligand, the technological process of presoma, preparation condition are identical with embodiment 1.Different is the mole proportioning of starting raw material.

Starting raw material V ₂O ₅And Cr (NO ₃) ₃9H ₂The consumption of O is respectively 0.01mol, 0.001mol, and corresponding Cr:V mol ratio is 0.05:1.

Synthesizing molecular formula is Cr _0.1V ₂O ₅Positive electrode material.The XRD spectrum of gained material is identical with the material of embodiment 1, does not have impurity to exist mutually.Unit cell parameters is:

Just the XRD peak of material broadens, and shows that the degree of crystallinity of material decreases, as shown in Figure 4.

The preparation process of electrode and Experimental cell, charging and discharging currents and charging/discharging voltage are interval identical with embodiment 1.This Cr _0.1V ₂O ₅The first charge-discharge curve of positive electrode material under different current densities, as shown in Figure 5.The Li of every mole of active substance ⁺The insertion amount is respectively 1.8,1.3 and 1.1, and corresponding current density is 29,150,300mAg ^-1Mean energy density and power density corresponding under each current density are as shown in table 2.Although discharge and recharge experiment under higher current density, material is influenced by polarization phenomena, and capacity descends to some extent, along with the increase of Cr doping, and the chemical property of material, especially the constant current charge-discharge performance under high magnification improves a lot.The doping that this has shown metallic element Cr is to improve lithium ion secondary battery anode material V ₂O ₅A kind of efficient and simple method of chemical property.

Table 2: Cr under the different current densities _0.1V ₃O ₅Mean energy density and power density

Comparing embodiment 1:

Mix to positive electrode material V in order to further specify Cr ₂O ₅The influence of chemical property, we compare the cycle performance of the constant current charge-discharge of two kinds of materials among embodiment 1 and the embodiment 2 50 times, as shown in Figure 6.

The positive electrode material Cr of embodiment 2 _0.1V ₂O ₅All show better cycle ability under each current density, the first discharge specific capacity of this material is respectively 271,196,157mAhg ^-1, corresponding current density is 29,150,300mAg ^-1, being respectively 70.1%, 85.7%, 73.9% at 50 circulation back specific discharge capacity conservation rates, this positive electrode material shows superior cycle performance, and particularly the cycle performance under high current density is better.

Claims (3)

1, lithium ion secondary battery anode material is characterized in that: molecular formula is Cr _xV ₂O ₅, 0＜x≤0.1, spacer Pmmn belongs to rhombic system.

2, the preparation method of the described lithium ion secondary battery anode material of claim 1 is characterized in that: adopt the oxalate method preparation.

3, the preparation method of lithium ion secondary battery anode material as claimed in claim 2 is characterized in that: with Vanadium Pentoxide in FLAKES V ₂O ₅, oxalic acid C ₂H ₂O ₄2H ₂O, chromium nitrate Cr (NO ₃) ₃9H ₂O is a raw material, Vanadium Pentoxide in FLAKES is joined in the oxalic acid solution, stir down until forming transparent blue solution at 60～100 ℃, dropwise add the chromium nitrate solution that concentration is 1～3mol/L then, mol ratio is Cr:V=x:2, and under this temperature range, stir transpiring moisture to the pasty state gel, form the oxalic acid ligand; Then with the oxalic acid ligand 100～120 ℃ of down oven dry, grind to form powdery and form presoma, again in muffle furnace at 300～400 ℃ of following sintering, be incubated 5～10 hours; To carry out compressing tablet at the powder behind the sintering under the said temperature at last, last naturally cooling promptly obtains lithium ion secondary battery anode material Cr _xV ₂O ₅, 0＜x≤0.1.

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