CN102332580B

CN102332580B - Fluorinated ferric sulfate salt compound as well as preparation method and application thereof

Info

Publication number: CN102332580B
Application number: CN201110207643XA
Authority: CN
Inventors: 黄学杰; 孙洋; 刘磊; 张斌
Original assignee: Institute of Physics of CAS
Current assignee: Institute of Physics of CAS
Priority date: 2011-03-15
Filing date: 2011-07-25
Publication date: 2013-11-27
Anticipated expiration: 2031-07-25
Also published as: WO2012122686A1; CN102332580A

Abstract

The invention discloses a fluorinated ferric sulfate salt compound as well as a preparation method and application thereof. The fluorinated ferric sulfate salt compound is expressed by using the following general formula: (LixFeyM1-x-y)2SO4F, and in the general formula, M is one or more of elements of Na, K, Ca, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, Ag, Nb, Sn, Ta, Al, Zr and W; x ranges from 0.25 to 0.75, y ranges from 0.25 to 0.75; and the compound is in a monoclinic system and Li and Fe are mixed cation sites. Compared with the prior art, the fluorinated ferric sulfate salt compound disclosed by the invention has the advantage that the stability and electrochemical property of a material structure are remarkably improved in charge and discharge processes.

Description

Fluoridize sulphate of iron compound, Preparation method and use

Technical field

The present invention relates to material technology, relate in particular to a kind of monoclinic sulphate of iron compound, Preparation method and use fluoridized that have.

Background technology

(polyanion is expressed as (XO to contain the transistion metal compound of polyanion _y) ^Z-, X=S, P, As, Mo, W, B, Si, Ge etc.; Y=3 or 4; Z=2 or 3) be a kind of positive electrode active materials that is mainly used in serondary lithium battery.It has that the prices of raw and semifnished materials are cheap, storage is abundant, environmentally safe, stable chemical nature, safe and reliable, lithium storage content is higher and voltage than advantages of higher.But this class material also exists ionic conductivity and the low shortcoming of electronic conductivity at present, at present often by reducing particle size, the methods such as carbon coating can solve preferably low electricity and lead the impact on material property, but still can't meet the secondary lithium battery requirements of one's work.

In polyanionic compound, the existence of X-O key has very important effect.Except the stabilizing material structure, it can also improve the oxidation-reduction pair voltage of transition metal by the inductive effect of X-O key, and current generally accepted viewpoint is that the induction of polyanion has improved the right oxidation-reduction potential of electroactive transition metal.Typical example is the LiFePO of olivine structural ₄, the induction of phosphate radical is by Fe ²⁺/ Fe ³⁺The right voltage of electricity is brought up to 3.45V, makes it can be used as anode material for lithium-ion batteries.After this people wish such as than the strong fluorine element of oxygen element electronegativity and the sulfate radical stronger than phosphate radical electronegativity, further to improve the current potential platform of material by introducing stronger atom or the group of electronegativity.

Such as LiFePO ₄Middle Fe ³⁺/ Fe ²⁺Voltage 3.45V apparently higher than the 2V of general ferriferous oxide.Due to the electronegativity of S element, be better than the electronegativity of P element, namely the inductive effect of S-O key is better than the P-O key, so when containing identical oxidation-reduction pair, the voltage of sulphate cpd is higher than phosphate compounds.In containing the transition metal sulfate compound of lithium, for total valence state, be zero consideration, need to be at the lithium ion of positive monovalence, outside the transition metal ions of positive divalence and the sulfate ion of negative divalence, then add the ion of a negative monovalence to maintain charge balance.In numerous candidates, the F element is ideal, and its atomic mass is little, is conducive to maintain the high power capacity of compound, and electronegativity is very strong, is conducive to improve the voltage of material.Be that sulfur fluoride hydrochlorate capacity is high, electronegativity is strong, and material voltage is higher.

Publication No. is: WO2009FR52040, denomination of invention: the international application of Fluorosulfaes useful as electrode materials, a kind of sulfur fluoride hydrochlorate of anorthic system Tavorite structure is disclosed, fluoridize the ferric sulfate lithium and have electro-chemical activity, the oxidation-reduction pair of divalent/trivalent iron equally, how much voltage is not promoted because introduce sulfate radical that electronegativity is stronger and fluorine ion, the voltage platform of its 3.6V is only than the high 0.15V of LiFePO4, add theoretical capacity originally just lower than LiFePO4, cause not preponderating on its energy density.This explanation, only by introducing the strong ion/group of electronegativity, is not sufficient to make the embedding lithium voltage of material to be improved, and only has this rule under same structure just can work (with reference to the LiFePO of Tavorite structure ₄F is than the LiFePO that is equally the Tavorite structure ₄The high 0.7V of OH voltage).Therefore, improve the current potential platform of positive electrode, the more important thing is the material of finding the crystal structure with higher embedding lithium voltage.Triclinic sulfur fluoride hydrochlorate structural stability neither be very desirable in addition, and before and after de-lithium, unit cell volume alters a great deal, and causes its cycle life shorter.Its preparation method of this anorthic system sulfur fluoride hydrochlorate need adopt expensive ionic liquid in addition, and the preparation process complexity is loaded down with trivial details, is not easy to large-scale production, has seriously limited its application in the serondary lithium battery field.

Summary of the invention

The invention provides a kind of sulphate of iron compound of fluoridizing, it has unique crystal structure, and than prior art, stability and the chemical property of molecule significantly improve.

An aspect of of the present present invention provides a kind of sulphate of iron compound of fluoridizing, and this compound means with following general formula (I):

(Li _xFe _yM _1-x-y) ₂SO ₄F (I), and in this general formula,

M is one or more in element Na, K, Ca, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, Ag, Nb, Sn, Ta, Al, Zr and W;

x＝0.25～0.75，y＝0.25～0.75；

x+y≤1；

This compound is monoclinic system, and Li and Fe are the mixed-cation occupy-places.

Another aspect of the present invention provides the preparation method who fluoridizes the sulphate of iron compound of a kind of general formula (I).

The described preparation method who fluoridizes the sulphate of iron compound, comprise the steps:

1), the mol ratio according to each element in general formula takes Li source, ,Fu source, Fe source, SO ₄ ^2-Source and M source, mix and grind obtaining the precursor powder;

2), by the precursor powder hot pressed sintering, obtain the described sulphate of iron compound of fluoridizing, in sintering process, apply and be greater than atmospheric mechanical pressure to described precursor powder, be preferably more than or equal the pressure of 0.5MPa.

Another aspect of the present invention provides a kind of sulfur fluoride silicate material, contains the described sulphate of iron compound of fluoridizing.

Another aspect of the present invention provides a kind of ion transfer medium, comprises the described sulphate of iron compound of fluoridizing.

Another aspect of the present invention provides a kind of positive electrode, comprises the described sulphate of iron compound of fluoridizing.

Another aspect of the present invention provides a kind of electrochemical cell, and the positive electrode of electrochemical cell forms and comprises the described sulphate of iron compound of fluoridizing.

The accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms the part of specification, be used to explaining the present invention, is not construed as limiting the invention together with embodiments of the present invention.In the accompanying drawings:

Fig. 1-1, Fig. 1-2 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The structural representation of F;

Fig. 2 is the monoclinic system (Li of non-mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD fitted figure of F;

Fig. 3 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD fitted figure of F;

Fig. 4-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD measured drawing of F;

Fig. 4-2 are the monoclinic system (Li of mixed-cation occupy-place _0.6Fe _0.4) ₂SO ₄The XRD measured drawing of F;

Fig. 4-3 are the monoclinic system (Li of mixed-cation occupy-place _0.55Fe _0.45) ₂SO ₄The XRD measured drawing of F;

Fig. 4-4 are the monoclinic system (Li of carbon nano-tube and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD measured drawing of F composite material;

Fig. 4-5 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.45Mn _0.05) ₂SO ₄The XRD measured drawing of F;

Fig. 4-6 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.25Mn _0.25) ₂SO ₄The XRD measured drawing of F;

Fig. 4-7 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.475Na _0.025) ₂SO ₄The XRD measured drawing of F;

Fig. 4-8 are the monoclinic system (Li of mixed-cation occupy-place _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄The XRD measured drawing of F;

Fig. 4-9 are the monoclinic system (Li of mixed-cation occupy-place _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄The XRD measured drawing of F;

Fig. 5-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-2 are the monoclinic system (Li of mixed-cation occupy-place _0.6Fe _0.4) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-3 are the monoclinic system (Li of mixed-cation occupy-place _0.55Fe _0.45) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-4 are the monoclinic system (Li of carbon nano-tube and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The head week charging and discharging curve figure of F composite material;

Fig. 5-5 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.45Mn _0.05) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-6 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.25Mn _0.25) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-7 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.475Na _0.025) ₂SO ₄F charges and discharge first all electric curve charts;

Fig. 5-8 are the monoclinic system (Li of mixed-cation occupy-place _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 5-9 are the monoclinic system (Li of mixed-cation occupy-place _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄The head week charging and discharging curve figure of F;

Fig. 6-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The SEM collection of illustrative plates of F;

Fig. 6-2 are the monoclinic system (Li of carbon nano-tube and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The SEM collection of illustrative plates of F composite material;

Fig. 6-3 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.45Mn _0.05) ₂SO ₄The SEM collection of illustrative plates of F;

Fig. 7 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The GITT curve of F and OCV curve;

Fig. 8 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The cyclic curve measured drawing of F;

Fig. 9 is the different (Li that discharge and recharge state _0.5Fe _0.5) ₂SO ₄The XRD collection of illustrative plates of F;

Figure 10 is that the TG-DSC-MS of different grain size precursor powder analyzes;

Figure 11 is the (Li of different r values (r=Li/Fe) _xFe _y) ₂SO ₄F compounds X RD collection of illustrative plates;

Figure 12 is the (Li of different r values _xFe _y) ₂SO ₄The first all charging and discharging curves of F compound constant current;

The XRD of the presoma that mix for distinct methods Figure 13-1, Figure 13-2;

Figure 14 is the hot pressing furnace structural representation.

By reference to the accompanying drawings, in the present invention, Reference numeral is as follows:

1-heating chamber 2-heater 3-hot pressing die

4-pressure apparatus 5-die cavity

Detailed Description Of The Invention

One aspect of the invention provides a kind of sulphate of iron compound of fluoridizing, and this compound means with following general formula (I):

(Li _xFe _yM _1-x-y) ₂SO ₄F (I), in this general formula,

x＝0.25～0.75，y＝0.25～0.75；

x+y≤1；

Li and Fe are the mixed-cation occupy-places, and namely Li and Fe can occupy the position in lattice each other, and both can realize exchanging completely position.For meaning Li and the mutual occupy-place relation of Fe, adopted general formula (Li here _xFe _yM _1-x-y) ₂SO ₄The form of F, it also can be expressed as (Li _xFe _yM _1-x-y) (Fe _yLi _xM _1-x-y) SO ₄F.

Studies have shown that the sulphate of iron of fluoridizing provided by the invention, due to its specific crystal structure, has better electrochemical properties.In this compound, M is doped chemical, and the interpolation of described doped chemical can effectively improve the conductivity of compound.M is preferably one or more in element Na, K, Ca, Mg, Cr, Mn, V, Co, Ni, Zn and Al.Shown in above general formula, the ratio of M in above-claimed cpd, i.e. 1-x-y, can be in 0～0.5 scope, as 0～0.2 or 0～0.1.For example the Mn scope can be 0.02-0.2; The Na scope can be 0.01-0.05; The Mg scope can be 0.03-0.10; The Zr scope can be 0.03-0.07; The Cr scope can be 0.01-0.10.It will be understood by those skilled in the art that other doped chemicals of using in existing anode material of lithium battery all can be used as the doped chemical of this compound.

The content of Li and Fe in precursor: in described general formula compound, x=0.25～0.75, y=0.25～0.75; Preferred x=0.45～0.55, y=0.45～0.55.The precursor of corresponding r (wherein r=Li/Fe)=0.8,1,1.2,1.5,2 has carried out the XRD detection as shown in figure 11 respectively, along with the increase of r value, can find out:

1, the diffraction maximum of LiF is increasing by force: at r=0.8, in the sample of r=1.0 and r=1.2, can't see the diffraction maximum of LiF fully, and in the sample of r=1.5, started to occur the diffraction maximum of LiF, the diffraction maximum of LiF further strengthens in the sample of r=2;

2, the weakening and disappear of impurity peaks: in the sample of r=0.8, namely in the situation of Fe ion excessive 25%, except LiFeSO ₄The diffraction maximum of F, also exist excessive Fe SO ₄H ₂The FeSO that the O dehydration forms ₄Diffraction maximum, and other several main impurity peaks, lay respectively at 16.0 °, 26.1 °, 30.3 °, 32.3 °, these impurity peaks also appear in other r value sample just, and just intensity weakens along with the increase of Li ratio in presoma, are difficult to identification to the r=1.5 sample, in the r=2.0 sample, disappear, in existing card base, element is restricted to Li, Fe, S, O, F, H, judgement is likely in the situation that lack Li FeSO accordingly ₄H ₂A kind of cenotype that O forms.

Figure 12 is the (Li of different r values _xFe _y) ₂SO ₄The first all charging and discharging curves of the constant current of F compound, contrast the performance of different r values (being the molar ratio of Li ion and Fe ion in presoma) presoma gained sample, take r=1 and r=2 is example, multiplying power with 0.05C is carried out constant current charge-discharge, the first discharge capacity that 63mAh/g is arranged in week of the sample of r=1, and the sample of r=2 only has the discharge capacity of 39mAh/g.

Although in presoma, the rising of Li content is conducive to reduce the dephasign in end-product, but also correspondingly reduced the discharge capacity of material, this is because Li does not have electro-chemical activity, remaining Li has offset and has fluoridized the discharge capacity that the sulphate of iron compound ratio transformation improves contribution, and the existence of Li has hindered the conduction of electronics and ion, also make polarization become large, also contingent is that part iron is oxidized to ferric iron to keep charge balance, so the minimizing capacity.

Further, the sulphate of iron compound of fluoridizing of the present invention is carried out to X ray (CuK α) crystal powder diffraction, this compound crystal structure is as follows: diffraction maximum is 24.5 °～26.8 ° at 2 θ, 27.2 °～28.5 °, 29.1 °～30.6 °, 31.7 °～32.8 ° present four characteristic diffraction peaks.The diffraction maximum that diffraction maximum is 29.1 °～30.6 ° at 2 θ is highest peak.Described X-ray diffraction peak position of fluoridizing the sulphate of iron compound presents the systematicness skew with unit cell dimension, but trend is constant relatively.

Further, this compound is: (Li _xFe _1-x) ₂SO ₄F.Preferred this compound is: (Li _0.5Fe _0.5) ₂SO ₄F (LiFeSO ₄F).(Li _0.5Fe _0.5) ₂SO ₄The diffraction maximum of F is 26.2 °, 27.8 °, 29.7 °, 31.5 ° at 2 θ and four characteristic diffraction peaks occur.(Li _0.5Fe _0.5) ₂SO ₄The structure cell of F is a(

)=13.0401; B(

)=6.3914; C(

)=9.8499; α=γ=90 °; β=119.766 °; Volume (

)=712.56.

Further, the sulphate of iron compound of fluoridizing of the present invention, the unit cell volume variation when using as cell positive material before and after its de-lithium is less than 5%.As (Li _xFe _1-x) ₂SO ₄F or change and be less than 5% by the unit cell volume of its electrode material formed before and after de-lithium.Preferably be less than 4%.

Unit cell volume before and after the de-lithium of table 1 different materials changes

?	Experiment value (X-ray diffraction)	Calculated value (density functional theory)
			LiFePO ₄	6.8%	4.3%
Three monoclinic phase LiFeSO ₄F	10.1%	7.0%
			Monoclinic phase (Li _0.5Fe _0.5) ₂SO ₄F	2.8%	2.2%
LiMnPO ₄F	9.0%	6.2%
			Three monoclinic phase LiMnSO ₄F	Do not exist	9.1%
Monoclinic phase (Li _0.5Mn _0.5) ₂SO ₄F	Do not exist	2.4%

Compare LiFePO ₄, three monoclinic phase LiFeSO ₄F and monoclinic phase (Li _0.5Fe _0.5) ₂SO ₄The change in volume of F, as (Li as seen from Table 1 _0.5Fe _0.5) ₂SO ₄The F lithium ion is deviate from and embeds front and back unit cell volume variation to be less than 4%, and little than LiFePO4 and anorthic system sulfur fluoride silicate material, in the battery charging and discharging circulation, electrode structure is stable, has extended cycle life.

Fig. 9 is the different (Li that discharge and recharge state _0.5Fe _0.5) ₂SO ₄The XRD collection of illustrative plates of F, the XRD diffraction maximum (mainly having used four main peaks here) that discharges and recharges the stage from difference can find out, the change in volume of this compound in charge and discharge process is very little, and peak position does not have skew substantially.This is the mutual occupy-place character due to this compound, and skeleton is not easy to change more.

Optionally, the Fe in its formula of (I) compound can also be by Co, Mn, and the one or more replacements in Ni or V, make and wherein no longer contain Fe.

Another aspect of the present invention also provides a kind of general formula preparation method that (I) fluoridizes the sulphate of iron compound.

Alternatively, before precursor powder hot-pressing sintering, first be placed in inert atmosphere or contain the inert atmosphere pre-burning 0.5～10 hour of reducing gas, described calcined temperature is 100～300 ℃.The effect of pre-burning is mainly to remove moisture in the precursor powder to be dried.The inert atmosphere that is placed in inert atmosphere during the pre-burning of precursor powder or contains reducing gas is oxidized be used to preventing precursor powder (as Fe wherein).Described inert gas can be argon gas or nitrogen, and described reducibility gas can be hydrogen or carbon monoxide.Described pre-burning programming rate is not particularly limited, but the programming rate usually adopted is per hour 50～200 ℃.The direct hot pressed sintering of precursor powder that also grinding can be obtained, and the precursor powder is not carried out to pre-burning, it is not carried out to other dry processing yet.

The precursor particle size: experiment shows that the granularity of described precursor powder has material impact to end product.The size of the particle diameter of precursor powder has determined the specific area of feed particles, and the tightness degree contacted between several feed particles, thereby affects above-mentioned hot pressed sintering solid phase reaction process.The excessive feed particles that directly causes of precursor powder particle can't fully contact, and it is incomplete that reaction is carried out; Particle is less can fully be contacted between feed particles, has promoted course of reaction, makes reaction more complete, and then has improved product purity.In preparation method of the present invention, the granularity of described precursor powder generally should be D50 and is less than 500nm, preferably is less than 300nm, as 10～200nm, is 10～50nm in certain embodiments.Can adopt any known Ginding process to obtain sizeable precursor powder, as long as in process of lapping, prevent precursor powder oxidation or other adverse effects, and reach desired particle size and get final product.Such as adopting the modes such as ball mill Union Process 01-HD type high energy ball mill or the Retsch PM100 type high energy ball mill of refrigerating function (as have), hand lapping, carry out batch mixing and grinding.Milling time is had no particular limits, as long as can reach desired particle size.Common described milling time is 0.5～12h.When grind adopting ball mill, the particle diameter of ball-milling medium can be 0.1mm～10mm, or is 1～10mm, with the demand of the particle diameter that meets the precursor powder.

Precursor mixes: hybrid mode is not specifically limited, and is standard so that precursor material reaches abundant contact, for example, can mix in the following way presoma:

Maintain mixed system (by suitable cooling provision) under the condition of normal temperature or lower temperature, in the wet method medium, implement ball grinding stirring mixing precursor, provide granularity thin as far as possible precursor powder.In the specific embodiment of the invention scheme, sample LFSF#1 adopts Union Process 01-HD type high energy ball mill to carry out batch mixing, be characterized in adopting the wet method medium stirring mill to pulverize and mixed material, rotating speed is fast, energy is high, can between the inner-outer tube of its ball grinder, pass into the recirculated water of cooling use, to avoid or to slow down the temperature rising of material in the process of ball milling, can be for preparing at normal temperatures ultra-fine powder.Process of lapping is in following embodiment: take mol ratio and be the FeSO of 1: 1 ₄7H ₂O and LiF simply mix, the zirconia of the mixture of 50ml altogether and 250ml mill Jie ball is sequentially added in the ball grinder of zirconia inner bag that capacity is 500ml, be installed on Union Process ball mill, add the about 100ml of ball milling medium ethanol, in the ball grinder chuck, pass into cooling water, rotating speed with 3500rpm carries out ball milling, after ball milling 2.5 hours, supplement part ball milling medium, again with same rotating speed ball milling 2.5 hours, the gained slurry is taken out, in air, naturally dry, the gained siccative is screened out to mill Jie ball with the standard screen of 200 purposes, obtain presoma powder LFSF#1,

Sample LFSF#2 adopts Retsch PM100 type high energy ball mill mixing presoma, and it adopts planetary type ball-milling, and rotating speed is than Gao Keda 600rpm, and can before ball milling, pass into protective gas and avoid higher material and the air reaction of causing of temperature in mechanical milling process.Idiographic flow is: take mol ratio and be the FeSO of 1: 1 ₄7H ₂O and LiF simply mix, by the mixture of 15g and stainless steel mill Jie ball The capacity of joining is in the stainless steel jar mill of 100ml, add ball milling medium ethanol 20ml, by sealing of lid, utilize its air inlet/outlet to pass into the ventilation of high-purity Ar gas, after the weighing quality, be installed on Retsch PM100 ball mill, mix up counterweight, by setting the ball milling program, carry out ball milling (rotating speed 600rpm, Ball-milling Time 12 hours, every ball milling half an hour, stop half an hour and prevent that the ball milling jar is overheated), after the ball milling jar is cooling, slurry is poured out, dried 12 hours at 50 ℃ with vacuum drying oven, manual porphyrize namely obtains precursor powder LFSF#2;

Sample LFSF#3 adopts the mode of manual abrasive material pulverize and mix, and by the mol ratio that amounts to about 10g, is the FeSO of 1: 1 ₄7H ₂The mixture of O and LiF is placed in mortar, and hand-held pestle ground 3 hours in the direction of the clock, has both obtained presoma LFSF#3;

Sample LFSF#4 and second sample mix mode are similar, and different is that the balls grinding machine is the WL-IA type particle sphere grinding machine that bright source, Tianjin electric equipment Co., Ltd produces.The employing capacity is the agate jar of 200ml, and mill Jie ball is agate mill Jie ball

The mol ratio that amounts to about 15g is the FeSO of 1: 1 ₄7H ₂The mixture of O and LiF is placed in ball grinder, is 200rpm by rotating speed, and ball milling 5 hours had both obtained precursor powder LFSF#4.

The XRD of precursor powder LFSF#1, LFSF#2, LFSF#3, LFSF#4 characterizes collection of illustrative plates as shown in Figure 13-1 and 13-2: the presoma that obtains of first three methods has identical phase as seen from the figure, can point out as FeSO ₄H ₂The mixture of O (JCPDS No.83-2092) and LiF (JCPDS No.78-1217), wherein weak the and broadening of the obvious intensity of the diffraction maximum of LFSF#1, illustrate that the presoma crystal grain prepared with Union Process 01-HD is less; And strong by the LFSF#3 diffraction maximum of hand mill, halfwidth is little, and crystal grain is larger; The strength, peak of the presoma LFSF#2 mixed with Retsch PM100 is between the two, but is salmon pink after the presoma ball milling, shows ferric existence; The LFSF#4 mixed with domestic ball mill is different from above three, it can be pointed out as FeSO ₄4H ₂The mixture of O (JCPDS No.76-0655) and LiF (JCPDS No.78-1217).

SEM photo by sample also can find out, the particle size minimum of LFSF#1, be floccule mass and get together; LFSF#2, the heterogeneity that the particle size of LFSF#3 becomes, and become successively large; The particle of LFSF#4 is larger, and corner angle are clearly arranged, and shows its product of water suction after crystallization of attaching most importance to, and this has also supported the conclusion of front.

By above-mentioned experiment and analysis, obtain drawing a conclusion and explaining:

1, different lapping modes has determined the size of particle and the crystal grain of precursor, and granular size has determined the tightness degree of presoma contact, and then having a significant impact reaction.

The component of the presoma 2, ground changes, and reason is FeSO ₄7H ₂The crystallization water in O is in conjunction with the tightness degree difference, and wherein the first six crystallization water more easily loses, and the activation energy of its dehydration is very low, and this is also FeSO ₄7H ₂The reason of O meeting dehydration weathering in dry air.It is following variation

FeSO ₄·7H ₂O→FeSO ₄·H ₂O+6H ₂O

When presoma is ground, for Union Process ball mill, because its rotating speed is fast, energy is high, add that absolute ethyl alcohol does the ball milling medium stronger water absorption is arranged, be easier to the crystallization water in the LFSF#1 sample and deviate from; Even with mortar hand mill, because Air Flow makes the water section volatilization, 6 crystallizations water in gained LFSF#3 sample can break away from voluntarily, finally obtain FeSO ₄H ₂O; It needs to be noted, the LFSF#4 sample obtained in domestic ball grinder is FeSO ₄4H ₂O, this is that moisture can't overflow, FeSO due to after the ball grinder sealing ₄H ₂The O crystallization that again absorbs water in cooling process is FeSO ₄4H ₂O, i.e. following process

FeSO ₄·7H ₂O→FeSO ₄·H ₂O+6H ₂O→FeSO ₄·4H ₂O+3H ₂O

Its diffraction maximum is strong than obviously higher than other three samples with the peak of the diffraction maximum of LiF, and this recrystallization process also has been described; And, for the LSFS#2 sample that Retsch PM100 processed, because filling rate is low, making vapour pressure less, the ball milling energy is higher, finally also can obtain FeSO ₄H ₂O, but from the result of XRD, there are following relation in method for mixing and crystallite dimension:

LSFS#3 (hand mill)>LSFS#2 (Retsch PM100)>LSFS#1 (Union Process)

3, the LSFS#2 sample processed of Retsch PM100 is salmon pink, shows ferric existence, and this illustrate in the process of high-energy ball milling, because collision energy is higher, also higher in the local temperature of shock moment, makes FeSO ₄7H ₂O partly decomposes, and the oxygen discharged can cause Fe ²⁺Be oxidized to trivalent and aobvious salmon pink, equation is as follows:

2FeSO ₄→Fe ₂O ₃+SO ₂+SO ₃

Fe ₂O ₃Can't point out out from XRD spectra, illustrate that this dephasign amount is less or crystallization is bad, presoma is heat-treated to 600 ℃, in the gained catabolite, also contain Fe ₂O ₃.

The heat analysis of presoma: LSFS#1 and two kinds of presomas of LSFS#3 are carried out to the TG-DSC-MS analysis.This TG-DSC test is carried out sample in high-purity Ar gas, programming rate with 10 ℃/min is tested, can detect simultaneously sample quality changes, the mass spectrum of heat absorption heat release and the gas that produces, the TG-DSC-MS that is the different grain size precursor powder as Figure 10 analyzes: wherein LFSF#1 precursor powder D50 is less than 200nm; Wherein LFSF#3 precursor powder D50 is 600nm-50 μ m.The granularity of precursor powder has directly affected reaction speed as shown in Figure 10, and the precursor powder that less precursor powder (D50 is less than 200nm) is compared large (D50 is 600nm-50 μ m) reaction speed is fast.

The TG-DSC test also shows that the precursor powder has obvious endothermic peak and weightlessness at 280 ℃, loses the crystallization water and causes; At 420～450 ℃, obvious endothermic peak and weightlessness occurring, is SO ₄ ^2-Decomposition, cause SO ₂(m/z=64) overflow.So the suitable hot pressed sintering temperature of the present invention is 300～450 ℃, preferably 360～420 ℃, be more preferably 370～390 ℃; Programming rate is not particularly limited, but the programming rate usually adopted is per hour 50～200 ℃; The time of described hot pressed sintering is determined by the differential responses thing, and hot pressing time is shorter usually, and (for example 0.1～0.5 hour) got final product sufficient reacting in 0.1～2 hour.When hot pressed sintering, can disposablely be warming up to required sintering temperature, also can adopt the mode of ladder-elevating temperature.After the hot pressed sintering time refers to and reaches predetermined sintering temperature herein, the time of sintering under this predetermined temperature.

Hot pressed sintering: the hot pressed sintering step can be carried out in hot pressing furnace, and Figure 14 is the hot pressing furnace structural representation used in one embodiment of the invention.The Packed heating chamber 1 of described hot pressing furnace, be provided with heater 2 and hot pressing die 3 in heating chamber 1, the optional electric heating element of using of described heater 2.Hot pressing die 3 is connected with pressure apparatus 4, and this pressure apparatus 4 can be hydraulic means or other wirking pressure devices, and it is exerted pressure to hot pressing die 3.Hot pressing die 3 has die cavity 5, be used to holding the precursor powder.Hot pressing die 3 have one movably piston with pressure apparatus 4, be connected.Therefore when the pressure that is subject to from pressure apparatus 4, the piston of this hot pressing die 3 passes to pressure in the precursor powder be contained in die cavity 5.During operation, will be placed in hot pressing die 3 without pre-burning or by the precursor powder after pre-burning.In order to guarantee being heated evenly of hot pressed sintering, preferred thermal conductivity is good and the precursor powder is to the material of inertia as hot pressing die.For example can use graphite jig or metal die (as: stainless steel mould, aluminum alloy mould), or this area other hot pressing dies commonly used.Then hot pressing die 3 is placed in the heating chamber 1 of sealing, the die cavity of described hot pressing die 3 is inner to communicate with heating chamber 1 gas.Heated sealed chamber 1 is filled with to inert atmosphere or is evacuated to 10 ^-1～10 ^-3Pa, can prevent effectively that low valence metal ion is oxidized (as Fe ²⁺Oxidized).By pressure apparatus 4, exert pressure to hot pressing die 3, making the piston forward body powder applied pressure of this hot pressing die 3 is 0.5～100MPa, or 2～50MPa, or 5～20MPa, and suitable pressure can prevent or reduce SO in addition ₄ ^2-Decompose, be conducive to improve the purity of reactant, improve simultaneously chemical reaction velocity.

Optionally, when hot pressed sintering, the gas pressure in the heating chamber 1 of sealing can be also normal pressure, low pressure, or high pressure, and be filled with inert gas.

Optionally, can the precursor powder just not applied to above-mentioned mechanical pressure, and directly in high-pressure inert gas, carry out hot pressed sintering.The pressure of inert gas can be at 0.5～50MPa, or 2～20MPa, or 5～10MPa.

The hot pressing furnace that the present invention adopts is preferably vacuum hotpressing stove, and as the ZT-20-15Y type vacuum hotpressing stove that Shanghai China in morning electric furnace Co., Ltd builds, its maximum pressure that carries out solid phase reaction is 5 tons, and rated temperature is 1500 ℃, and hot final vacuum is 6.67 * 10 ^-2Pa, such vacuum high-pressure environment is conducive to the carrying out of the solid phase reaction of air-sensitive, is well suited for the reaction that presoma is this class stable compound of LiF.

Shape of product, granularity: the sulphate of iron compound of fluoridizing of the present invention compares with existing sulfur fluoride hydrochlorate the impact that chemical property is not vulnerable to scantling, the sulphate of iron compound of fluoridizing of the present invention can be made into powdered granule material, filamentary material or flaky material and all can give play to good chemical property, and then meets job requirement.

With traditional method for preparing solid phase, compare, hot pressed sintering method for preparing solid phase of the present invention can carry out at relatively low temperature, thereby can obtaining particle size, less (for example D50 is less than 600nm, or D50 is less than 500nm, D50 is less than 400nm in certain embodiments) formula (I) compound particle gather thing, therefore described, fluoridize the sulphate of iron compound after cooling without or only need simple grinding to use.

Raw material: mainly comprise Li source, ,Fu source, Fe source, M source and SO at the preparation process Raw ₄ ^2-Source.Described Li source is one or more in lithium fluoride, lithium sulfate, lithium acetate, lithium carbonate, lithium citrate, lithium nitrate and lithium oxalate; Described fluorine source is one or more in lithium fluoride, hydrofluoric acid, ammonium fluoride, ammonium acid fluoride and hydrogen fluoride lithium; Described M source is one or more in sulfate, acetate, carbonate, citrate, nitrate and the oxalates that contains M; Described SO ₄ ^2-Source be metal in general formula (I) (Li, Fe and/one or more in M) sulfate, sulfuric acid, ammonium sulfate and hydrogen sulfate ammonia.The Fe source is one or more in the inferior salt of ferrous sulfate, ferrous acetate, ferrous citrate and oxalic acid.Be appreciated that described each raw material can provide more than one source simultaneously.

Another aspect of the present invention provides a kind of sulfur fluoride silicate material, and what contain described general formula (I) fluoridizes the sulphate of iron compound.Optionally, also can contain conductive agent in described sulfur fluoride silicate material, described conductive agent accounts for the 1-30wt% of this material total weight, and described conductive agent can be in carbon black, graphite and carbon nano-tube one or more.Conductive agent can improve the electronic conductance of material effectively, thereby has increased the capacity of material, has reduced polarization, and improves the cyclicity of material.

Another aspect of the present invention also provide utilize described general formula (I) fluoridize the sulphate of iron compound and comprise positive electrode that the material of this compound makes and, electrochemical cell, namely, the active component of described positive electrode is fluoridized the sulphate of iron compound or by this compound, is made fully from aforementioned, due to the improvement of positive electrode, make that battery charging and discharging voltage is high, energy density is high, and material relative size is little, structural stability is good, and the life-span is long.

So what the present invention also provided described general formula (I) fluoridizes the purposes of sulphate of iron compound for the preparation of positive electrode, and, the described purposes of sulphate of iron compound for the preparation of the ion transfer medium of electrode in battery of fluoridizing.

A kind of ion transfer medium, what comprise described general formula (I) fluoridizes the sulphate of iron compound.

Positive electrode provided by the invention, what comprise described general formula (I) fluoridizes the sulphate of iron compound.In a specific embodiments, described positive electrode is the composite material that comprises described sulfur fluoride silicate material.Further in embodiment, described positive electrode has the coating layer formed by fluoridizing the sulphate of iron compound.

The present invention also provides a kind of electrochemical cell, the positive electrode of this electrochemical cell form comprise described general formula (I) fluoridize the sulphate of iron compound, can be the composite material that comprises described sulfur fluoride silicate material, can be also the material had by fluoridizing the coating layer that the sulphate of iron compound forms.

Another aspect of the present invention provides a kind of sulfur fluoride silicate material, in this material, contains at least the sulfur fluoride hydrochlorate, and its chemical formula can be expressed as general formula (II): Li _cA _aM _mB _bSO _zN _nF _f(II), wherein:

A is Na, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, W, Ag, at least a in Nb or Zr;

M is Fe, Co, Mn, at least a in Ni or V;

B is Li, Na, K, Ca, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, Ag, Nb, at least a in Zr or W;

It when M is different from B, is the same element;

C, a, m, b, z, n, f mean respectively mol ratio, 0.9≤c≤2,0≤a≤0.1,0.5≤m≤1,0≤b≤0.5,3≤z≤4,0≤n≤1,1≤f≤3.

Further, the sulfur fluoride silicate material of described general formula (II) has monocline, when carrying out X ray (CuK α) crystal powder diffraction, this material has following crystal structure: its diffraction maximum is 24.5-26.8 at 2 θ, 27.2-28.5,29.1-30.6 31.7-32.8 presents four characteristic diffraction peaks; Li _cA _aM _mB _bSO _zN _nF _fThe X-ray diffraction peak position of material presents the systematicness skew with unit cell dimension, but trend is constant relatively.

Further, the sulfur fluoride silicate material of described general formula (II) has nucleocapsid structure, and core material layer is Li _xA _aM _mB _bSO _zN _nF _f.

Further, the sulfur fluoride silicate material of described general formula (II) has nucleocapsid structure, and Shell Materials is Li _xA _aM _mB _bSO _zN _nF _f, shell thickness is 1nm-5 μ m.

Further, to be preferably carbon, copper, silver, aluminum fluoride, aluminum phosphate, aluminium oxide, magnesium oxide, titanium oxide, polypyrrole, polyaniline or polythiophene shell thickness be 1nm-500nm to described Shell Materials.

Further, described core material layer is the material with layer structure, and its chemical formula is LiMO ₂, be preferably LiCoO ₂, LiNiO ₂, LiMn ₂O ₄, Li (MnNi) _1/2O ₂, Li (MnNiCo) _1/3O ₂Perhaps described core material layer is the material of spinel structure, and its chemical formula is LiM ₂O ₄, be preferably LiMn ₂O ₄, LiNi _0.5Mn _1.5O ₄Perhaps described core material layer is the olivine structural material, and its chemical formula is LiMPO ₄, be preferably LiFePO ₄, LiMnPO ₄, LiFe _cMn _1-cPO ₄, LiCo _cMn _1-cPO ₄, 0<c≤1 wherein.

Further, the sulfur fluoride silicate material of described general formula (II) can be powdery granule material, filamentary material or flaky material, and wherein the minimum diameter of granular materials is 5nm-10 μ m.

Further, the sulfur fluoride silicate material of described general formula (II) can contain micropore, mesoporous or macropore, and aperture is 2nm-500nm.

A kind of above-mentioned general formula (II) for preparing is Li _cA _aM _mB _bSO _zN _nF _fThe method of sulfur fluoride silicate material, be specially:

1) according to mol ratio, weigh up lithium salts, villiaumite, the salt of transition metal sulfate, doping metals, nitrogenous source and carbon source, put into ball grinder in the lump, then starts ball milling;

3) after ball milling, obtain precursor powder;

4) by precursor powder in tube furnace, at inert atmosphere or pre-burning in containing the inert atmosphere of reducibility gas, naturally cooling;

5) the pre-burning product is ground and puts into tube furnace, at the inert atmosphere high temperature sintering, then naturally cooling;

6) by the hand lapping of sintering gained solid.

Further, described carbon source is selected from least a in pitch, native graphite, electrographite, superfine graphite powder, acetylene black, carbon black, carbon nano-tube.

Further, described carbon source can be carbon black; Carbon nano-tube; Mol ratio is graphite and the carbon black of 1: 1; Or mol ratio is pitch and the acetylene black of 1: 1; Or mol ratio is electrographite and the superfine graphite powder of 1: 1; Or mol ratio is pitch, graphite and the acetylene black of 2: 1: 3.

Further, described Ball-milling Time is 2～10 hours, and the particle diameter of ball-milling medium is 1mm～10mm; The temperature of described pre-burning is between 150 ℃～300 ℃, and the pre-burning time is 1-10 hour; The temperature of described high temperature sintering is between 300 ℃～700 ℃, and the high temperature sintering time is 0.01-20 hour.

Further, described lithium salts is derived from lithium fluoride, lithium sulfate, one or more in lithium acetate, lithium carbonate, lithium citrate, lithium nitrate and lithium oxalate; Villiaumite is selected from one or more of ammonium fluoride, hydrofluoric acid, ammonium acid fluoride, hydrogen fluoride lithium, and described transition metal salt (for example iron) is selected from its sulfate, one or more in acetate, carbonate, citrate, nitrate and oxalates; The salt of described doped chemical is selected from the fluoride of doped chemical, sulfate, acetate, carbonate, one or more in citrate, nitrate and oxalates; Described inert atmosphere is argon gas or nitrogen, and described reducibility gas is hydrogen or carbon monoxide.

The application of sulfur fluoride silicate material in serondary lithium battery of a kind of general formula (II), the sulfur fluoride silicate material directly is used as to cell positive material, the perhaps clad material using the sulfur fluoride silicate material as original anode, or sulfur fluoride silicate material and other material are formed to mix mutually arrange in pairs or groups and make to form anode.

The application of sulfur fluoride silicate material in serondary lithium battery of a kind of general formula (II), using the ion transfer medium of sulfur fluoride silicate material electrode in battery.

In addition, the aforementioned hot-pressing sintering method for preparing general formula (I) compound is applicable to prepare general formula (II) compound too.

The invention provides sulfur fluoride silicate material, the Preparation method and use of a kind of general formula (I), disclose first a kind of monoclinic system that has, cation mixes occupy-place, space group is C12/c ₁Fluoridize the sulphate of iron compound, its a kind of in comparing with existing sulfur fluoride silicate material and mainly having the following advantages at least:

1), high charge-discharge voltage: it is 3.9V that monoclinic system of the present invention is fluoridized sulphate of iron compound voltage platform, and higher than the 3.4V of LiFePO4, higher than anorthic system sulfur fluoride silicate material 3.6V, monoclinic system, space group are C12/c ₁The sulphate of iron compound of fluoridizing be the polyanion positive electrode, have higher ionic conductance;

2), Stability Analysis of Structures, monoclinic system disclosed by the invention, space group are C12/c ₁Fluoridize the sulphate of iron compound because of the mixed occupy-place of metal ion, lithium ion is deviate from and embeds front and back unit cell volume variation to be less than 5%, change in volume is little than LiFePO4 and anorthic system sulfur fluoride silicate material, and in the battery charging and discharging circulation, electrode structure is stable, has extended cycle life;

3), preparation technology is simple: the present invention is by selecting suitable precursors and reaction condition, the simple solid phase reaction method of take prepared a kind of comprise have monoclinic system, space group is C12/c ₁Fluoridize the sulphate of iron compound.Realized that preparation technology is simple, the advantage that sintering temperature is low, sintering time is short and energy consumption is low;

4), sulfur fluoride phosphate compounds provided by the invention can directly be used in serondary lithium battery as positive electrode active materials; The advantage that also can utilize its macroion electricity to lead, as clad material, coat existing positive electrode skin, plays the effect of protection; Because it self has electro-chemical activity, so energy density that can sacrificial electrode when coating protection; Also can form and mix collocation use mutually with other material; In addition can also be using the ion transfer medium of this compound electrode in battery, because this compound itself has electro-chemical activity, the conduction velocity of ion in electrode interior can be improved, when improving the high rate performance of battery, the energy density of electrode can also be improved.

5), the secondary lithium battery for preparing of application sulfur fluoride phosphate compounds provided by the invention has the remarkable advantages such as power density is large, energy density is high, capacity is large, this class serondary lithium battery is applicable to the equipment that various mobile electronic devices maybe need mobile driven by energy, for example mobile phone, notebook computer, portable video recorder and electronic toy, the equipment that particularly needs the high power electrokinetic cell, as electric tool, electric automobile, hybrid electric vehicle and accumulation power supply etc.

In compound provided by the invention, lithium atom and transition metal atoms mix and occupy two different symmetry positions in structure cell, this point is electrode material different from the past fully, normally by lithium atom and transition metal atoms, occupies respectively the different symmetry of structure cell position in existing electrode material structure.And the result of density Functional Calculation shows, this structure sulfur fluoride hydrochlorate embedding lithium voltage of other transition metals (manganese, cobalt, nickel etc.) correspondence is general phosphate higher than anorthic system sulfur fluoride hydrochlorate and olivine structural also.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment in the present invention, those of ordinary skills, not making under the creative work prerequisite the every other embodiment obtained, belong to the scope of protection of the invention.

Embodiment 1

Monoclinic system (the Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄F

(Li _0.5Fe _0.5) ₂SO ₄Prepared by following steps by F: at first according to mol ratio, take LiF and FeSO at 1: 1 ₄7H ₂O (or FeSO ₄H ₂O), adopt Union Process 01-HD type high energy ball mill ball milling after 5 hours, to obtain the precursor powder that D50 is 30nm, ball-milling medium particle diameter 0.1mm-10mm wherein, rotating speed is 2000 rev/mins; By the pre-burning 5 hours under high-purity Ar gas protection of this precursor powder, described calcined temperature is 200 ℃ (pre-burning programming rates be this precursor powder from room temperature was warming up to 200 ℃ in 1 hour), drops to room temperature in cooling 10 hours afterwards; To grind precursor powder after pre-burning hot pressed sintering 0.25 hour under 380 ℃ of (programming rate be 2 hours be warming up to 380 ℃ from room temperature) constant temperature, hot pressed sintering pressure is 10MPa, is cooled to room temperature.The heating chamber internal pressure is 10 ^-2Pa.

After being pulverized, sintering gained solid abrasive just can obtain monoclinic (Li _0.5Fe _0.5) ₂SO ₄The F positive electrode.The parsing of product compound structure and performance measurement:

Adopt crystal structure, pattern, discharge capacity and the head of XRD, SEM, the above-mentioned product of constant current charge-discharge instrument test week to put rate, as in Figure 6-1, its average grain diameter, discharge capacity, first all efficiency data are referring to table 4 for the electromicroscopic photograph of gained compound sample.

Fig. 2 is the monoclinic system (Li of non-mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD fitted figure of F; Fig. 3 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD fitted figure of F.Comparison diagram 2 and Fig. 3 are visible, two XRD collection of illustrative plates main distinctions 20 ° go out the peak situation.In XRD collection of illustrative plates shown in Figure 2, some stronger characteristic peaks occur at this place, are illustrated in Li and Fe in structure cell and are fixed on corresponding position separately.And at (Li of the present invention shown in Figure 3 _0.5Fe _0.5) ₂SO ₄In the XRD match collection of illustrative plates of F, do not have characteristic peak to occur at this place, expression Li and Fe shared position in structure cell can't be distinguished, that is to say that both mix occupy-place.

Fig. 4-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD measured drawing of F; (Li prepared by visible the present invention _0.5Fe _0.5) ₂SO ₄The XRD measured drawing of F and Fig. 3 are the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The XRD fitted figure of F is substantially identical, and from the monoclinic phase (Li of table 3 mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The cell parameter of F and theoretical experimental data error amount all are less than 5%, (Li prepared by visible the present invention _0.5Fe _0.5) ₂SO ₄The structure of F is identical.Deducibility goes out the prepared (Li of the present embodiment thus _0.5Fe _0.5) ₂SO ₄In F, the Occupation of Li and Fe is interchangeable mixing occupy-place.In the case, in structure cell, find on the fixed position of the fixed position of Li and Fe that the probability of Li atom equates, and equal in this compound Li with respect to the mol ratio of Li+Fe; Equally, in structure cell, find on the fixed position of the fixed position of Li and Fe that the probability of Fe atom equates, and equal in this compound Fe with respect to the mol ratio of Li+Fe.By Fig. 1-1,1-2,4-1 and the monoclinic system (Li of mixed-cation occupy-place as seen from Table 2 _0.5Fe _0.5) ₂SO ₄The space group of F is C12/c1 (group number 15), and each crystallography primitive unit cell comprises the (Li of eight molecular formula _0.5Fe _0.5) ₂SO ₄F.Cell parameter

β=119.77 °.Wherein lithium atom and Fe atom mix and occupy two different 8f positions, and 50% occupation probability is respectively arranged.By two 8f for being labeled as position 1 and position 2.Crystal structure is as shown in Fig. 1-1,1-2, octahedron centered by Li1/Fe1 limit altogether is connected to form the one-dimensional chain (Fig. 1-1) along (101) direction, and the octahedron centered by Li2/Fe2 limit altogether is connected to form the one-dimensional chain (Fig. 1-2) along (010) direction.Forming two kinds of octahedral coordination anions is all four oxygen atoms and two fluorine atoms, and connects that limit is octahedral altogether and be the oxygen of alternately arranging-Huo Fu-Fu limit, oxygen limit.The isolated sulfate radical distributed links together these two kinds of octahedra chains, forms the crystal structure of a three-dimensional.

Monoclinic system (the Li of table 2 mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄Occupation in the structure cell of F

Monoclinic phase (the Li of table 3 mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The cell parameter of F and theoretical experimental data error

Fig. 5-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The head week charging and discharging curve figure of F; Monoclinic system (the Li that visible the present embodiment is prepared _0.5Fe _0.5) ₂SO ₄The voltage platform of F is 3.9V.

Fig. 6-1 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The SEM collection of illustrative plates of F; Visible its particle diameter is below 500nm.

Fig. 7 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The GITT curve of F and OCV curve; Through reaching 12 hours standing, the OCV curve that the gained equilibrium potential is linked to be shows (Li as seen from the figure _0.5Fe _0.5) ₂SO ₄The most doff lithium of F zone is at 3.9V, and the substantially invariable platform of this magnitude of voltage is the feature of two phase reaction.

Fig. 8 is the monoclinic system (Li of mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The cyclic curve measured drawing of F; The open circuit voltage curve has obvious platform area near 3.9V as seen from the figure.Polarization curve has presented a kind of special rule, and namely in charging process, polarization is to reduce after first becoming greatly, and then increases gradually; And in discharge process, similar rule is arranged, i.e. after first change is large, diminishes and become again large.In the state of close lithium content, the size of polarization is just the opposite like this.

Fig. 9 is the different (Li that discharge and recharge state _0.5Fe _0.5) ₂SO ₄The XRD collection of illustrative plates of F, as seen from the figure with its process discharged and recharged, diffraction maximum does not have obvious skew can prove (the Li that the present embodiment is prepared _0.5Fe _0.5) ₂SO ₄F unit cell volume in charge and discharge process changes little, and 3% left and right is only arranged as calculated.

Embodiment 2

Monoclinic system (the Li of mixed-cation occupy-place _0.6Fe _0.4) ₂SO ₄F

(Li _0.6Fe _0.4) ₂SO ₄Prepared by following steps by F, at first according to mol ratio, take LiF and FeSO at 1.2: 0.8 ₄7H ₂O (or FeSO ₄H ₂O), then adopt the method identical with embodiment 1 to obtain the monoclinic (Li of mixed-cation occupy-place _0.6Fe _0.4) ₂SO ₄The F positive electrode.

Adopt XRD, constant current charge-discharge instrument to test its crystal structure, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-2 and 5-2, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 3

Monoclinic system (the Li of mixed-cation occupy-place _0.55Fe _0.45) ₂SO ₄F

(Li _0.55Fe _0.45) ₂SO ₄Prepared by following steps by F, at first according to mol ratio, take LiF and FeSO at 1.1: 0.9 ₄7H ₂O (or FeSO ₄H ₂O), then adopt the method identical with embodiment 1 to obtain monoclinic (Li _0.55Fe _0.45) ₂SO ₄The F positive electrode.

Adopt XRD, constant current charge-discharge instrument to test its crystal structure, pattern, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-3 and 5-3, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 4

Embodiment: the monoclinic system (Li of carbon nano-tube and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The F composite material.

Monoclinic system (the Li of carbon nano-tube of the present invention and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄Can prepare by following steps by the F composite material, at first according to mol ratio, take LiF, FeSO at 1: 1 ₄.7H ₂O, the carbon nano-tube that adds 10wt%, then put in the lump them in alcohol solvent, (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling, rotating speed is 2000 rev/mins, 5 hours) hot pressed sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 380 ℃ of constant temperature 0.25 hour, hot pressed sintering pressure is 1MPa, afterwards with dropping to room temperature in 10 hours).After being pulverized, sintering gained solid abrasive just can obtain the monoclinic system (Li of carbon nano-tube and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The F composite material.

Adopt XRD, SEM, constant current charge-discharge instrument to test its crystal structure, pattern, discharge capacity and head and week put rate, the XRD measured drawing of gained composite sample and first all charging and discharging curve figure are as shown in Fig. 4-4 and 5-4, the electromicroscopic photograph of resulting materials sample is as shown in Fig. 6-2, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.The interpolation of visible carbon nano-tube can significantly improve the chemical property of material.

Embodiment 5

Monoclinic system (the Li of mixed-cation occupy-place _0.5Fe _0.45Mn _0.05) ₂SO ₄F

(Li _0.5Fe _0.45Mn _0.05) ₂SO ₄Prepared by following steps by F, at first according to mol ratio, take LiF, FeSO at 1: 0.9: 0.1 ₄7H ₂O and MnSO ₄H ₂O (or MnSO ₄7H ₂O), hand lapping obtains the precursor powder that D50 is about 200nm after 5 hours; By the pre-burning 1 hour under high-purity Ar gas protection of this precursor powder, described calcined temperature is 250 ℃ (pre-burning programming rates be this precursor powder from room temperature was warming up to 200 ℃ in 2 hours), the cooling room temperature that drops to afterwards; Precursor powder after the grinding pre-burning is placed in to stainless steel mould, to stainless steel mould pressurization 5MPa, hot pressed sintering is 0.15 hour under 390 ℃ of (programming rate be 3 hours be warming up to 390 ℃ from room temperature) constant temperature, and hot pressed sintering pressure is 5MPa, naturally cools to room temperature.

After being pulverized, sintering gained solid abrasive just can obtain monoclinic (Li _0.5Fe _0.45Mn _0.05) ₂SO ₄The F positive electrode.Adopt XRD, SEM, constant current charge-discharge instrument to test its crystal structure, pattern, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-5 and 5-5, the SEM collection of illustrative plates is as shown in 6-3, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.The interpolation of doped chemical can effectively improve the conductivity of compound.

Embodiment 6

Monoclinic system (the Li of mixed-cation occupy-place _0.5Fe _0.25Mn _0.25) ₂SO ₄F

(Li _0.5Fe _0.25Mn _0.25) ₂SO ₄Prepared by following steps by F, at first according to mol ratio, take LiF, FeSO at 1: 0.5: 0.5 ₄7H ₂O and MnSO ₄H ₂O (or MnSO ₄7H ₂O), mechanical ball milling obtains the precursor powder that D50 is 100nm after 5 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, and rotating speed is 2000 rev/mins; By the pre-burning 5 hours under high-purity Ar gas protection of this precursor powder, described calcined temperature is 200 ℃, drops to room temperature in cooling 10 hours afterwards; Precursor powder after the grinding pre-burning is placed in to graphite jig, and described graphite jig is inner to communicate with the hot pressing furnace chamber, will seal the hot pressing furnace chamber and be evacuated to 10 ^-2Pa, to the graphite jig 20MPa that pressurizes, hot pressed sintering is 0.25 hour under 380 ℃ of constant temperature by hydraulic press, and hot pressed sintering pressure is 50MPa, is cooled to room temperature.

Sintering gained solid just can obtain monoclinic (Li without after grinding _0.5Fe _0.25Mn _0.25) ₂SO ₄The F positive electrode.Adopt XRD, constant current charge-discharge instrument to test its crystal structure, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-6 and 5-6, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 7

Monoclinic system (the Li of mixed-cation occupy-place _0.5Fe _0.475Na _0.025) ₂SO ₄F

(Li _0.5Fe _0.475Na _0.025) ₂SO ₄Prepared by following steps by F, at first according to mol ratio, take LiF, FeSO at 1: 0.95: 0.05 ₄7H ₂O and NaF, grind after 5 hours and obtain the precursor powder that D50 is 200nm, ball-milling medium particle diameter 0.1mm-10mm wherein, and rotating speed is 2000 rev/mins; By the pre-burning 3 hours under high-purity Ar gas protection of this precursor powder, described calcined temperature is 250 ℃ (pre-burning programming rates be this precursor powder from room temperature was warming up to 250 ℃ in 3 hours), drops to room temperature in cooling 10 hours afterwards; To grind precursor powder after pre-burning hot pressed sintering 1 hour under 400 ℃ of (programming rate be 3 hours be warming up to 400 ℃ from room temperature) constant temperature, hot pressed sintering pressure is 0.5MPa, drops to room temperature in cooling 12 hours.

After being pulverized, sintering gained solid abrasive just can obtain monoclinic (Li _0.5Fe _0.475Na _0.025) ₂SO ₄The F positive electrode.Adopt XRD, constant current charge-discharge instrument to test its crystal structure, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-7 and 5-7, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 8

Monoclinic system (the Li of mixed-cation occupy-place _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄F

(Li _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄Prepared by following steps by F, at first according to mol ratio 0.9: 0.9: 0.1: 0.1 takes LiF, FeSO ₄7H ₂O, ZrSO ₄4H ₂O and MgSO ₄7H ₂O, ball milling obtain the precursor powder that D50 is 30nm after 10 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, and rotating speed is 3000 rev/mins; Then by precursor powder hot pressed sintering 2 hours under 370 ℃ of (programming rate be 1.5 hours be warming up to 370 ℃ from room temperature) constant temperature, hot pressed sintering pressure is 5MPa, the cooling room temperature that drops to.

After being pulverized, sintering gained solid abrasive just can obtain monoclinic (Li _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄The F positive electrode.Adopt XRD, constant current charge-discharge instrument to test its crystal structure, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-8 and 5-8, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 9

Monoclinic system (the Li of mixed-cation occupy-place _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄F

(Li _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄Prepared by following steps by F, at first according to mol ratio 0.95: 0.9: 0.05: 0.1 takes LiF, FeSO ₄7H ₂O, Cr ₂(SO ₄) ₂6H ₂O and MgSO ₄6H ₂O, mechanical ball milling obtains the precursor powder that D50 is less than 35nm after 15 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, rotating speed is 2000 rev/mins; By the pre-burning 5 hours under high-purity Ar gas protection of this precursor powder, described calcined temperature is 200 ℃ (pre-burning programming rates be this precursor powder from room temperature was warming up to 200 ℃ in 1 hour), drops to room temperature in cooling 10 hours afterwards; To grind precursor powder after pre-burning 400 ℃ of (programming rate be 2 hours be warming up to 400 ℃ from room temperature) constant temperature lower sheeting hot pressed sinterings 0.1 hour, the hot pressed sintering temperature is 0.5MPa, drops to room temperature in cooling 10 hours.

After being pulverized, sintering gained solid abrasive just can obtain monoclinic (Li _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄The F positive electrode.Adopt XRD, constant current charge-discharge instrument to test its crystal structure, discharge capacity and head and week put rate, the XRD measured drawing of gained compound sample and first all charging and discharging curve figure are as shown in Fig. 4-9 and 5-9, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.

Embodiment 10-20

The monoclinic system of mixed-cation occupy-place is fluoridized ferric sulfate lithium (Li _xFe _yM _1-x-y) ₂SO ₄F.

Adopt the hot-pressing sintering method similar to embodiment 1-9: the mol ratio according to each element in general formula takes Li source, ,Fu source, Fe source, SO ₄ ^2-Source and M source, mix and grind obtaining the precursor powder; By the precursor powder hot pressed sintering, obtain in table 4 fluoridizing the sulphate of iron compound shown in 10-20, its average grain diameter, discharge capacity, first all efficiency data are also referring to table 4.

The principal character of table 4 monoclinic crystal phase fluorination sulfate material

Embodiment 21

Sulfate material Li is fluoridized in this doping of nitrogen for serondary lithium battery of preparation _1.2FeSO _3.8N _0.2F.

Li for serondary lithium battery _1.2FeSO ₄N _0.2Can prepare by following steps by the F positive electrode, at first according to mol ratio 1: 0.2: 1: 0.3 takes LiF, Li ₃N, FeSO ₄.7H ₂O and carbon black; (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling; rotating speed is 2000 rev/mins; 5 hours); by the pre-burning under high-purity Ar gas protection of this mixture (step of pre-burning is: with 1 hour from room temperature be warming up to 200 ℃, 200 ℃ of constant temperature 5 hours; afterwards with dropping to room temperature in 10 hours); after hand lapping is pulverized; mixture again sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 300 ℃ of constant temperature 0.25 hour, afterwards with dropping to room temperature in 10 hours).After being pulverized, the hand lapping of sintering gained solid just can obtain Li _1.2FeSO ₄N _0.2The F positive electrode.Its average grain diameter, discharge capacity, first all efficiency data are referring to table 5.

Embodiment 22

Oxygen room sulfur fluoride silicate material LiFeSO for the preparation of serondary lithium battery _3.98F.

LiFeSO _3.98Can prepare by following steps by the F positive electrode, at first according to mol ratio 1: 0.99: 0.01: 0.3 takes LiF, FeSO ₄.7H ₂O; FeS and carbon black; (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling; rotating speed is 2000 rev/mins; 5 hours); by the pre-burning under high-purity Ar gas protection of this mixture (step of pre-burning is: with 1 hour from room temperature be warming up to 200 ℃, 200 ℃ of constant temperature 5 hours; afterwards with dropping to room temperature in 10 hours); after hand lapping is pulverized; mixture again sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 300 ℃ of constant temperature 0.25 hour, afterwards with dropping to room temperature in 10 hours).After being pulverized, the hand lapping of sintering gained solid just can obtain LiFeSO _3.98The F positive electrode.Its average grain diameter, discharge capacity, first all efficiency data are referring to table 5.

Embodiment 23-67

The sulfur fluoride silicate material 7-51 with brand new for the preparation of serondary lithium battery

Preparation method and embodiment 21-22 are similar, and difference is to have prepared the Li doped MSO that contains different doped chemicals and ratio ₄F basis material, and the LiMSO of oxygen-containing vacancy ₄The F basis material.General formula Li _cA _aM _mB _bSO _zN _nF _fMean the silicate material of the sulfur fluoride for serondary lithium battery of the present invention, wherein, A is Na, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, W, Ag, at least a in Nb or Zr; M is Fe, Co, Mn, at least a in Ni or V; B is Li, Na, K, Ca, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, Ag, Nb, at least a in Zr or W; It when M is different from B, is the same element; X, a, m, b, z, n mean respectively mol ratio, 0.9≤c≤2,0≤a≤0.1,0.5≤m≤1,0≤b≤0.5,3≤z≤4,0≤n≤1,1≤f≤3; Its average grain diameter, discharge capacity, first all efficiency data are referring to table 5.

Table 5 has the principal character of the sulfur fluoride silicate material of monocline

Embodiment 68

With AlF ₃For the shell clad material of nucleocapsid structure, for the preparation of serondary lithium battery with LiFeSO ₄F is core, AlF ₃The positive electrode with nucleocapsid structure for shell.

For serondary lithium battery with LiFeSO ₄F is core, AlF ₃For can prepare by following steps by the positive electrode with nucleocapsid structure of shell, at first according to mol ratio, take LiF, FeSO at 1: 1: 0.1 ₄.7H ₂O and AlF ₃Put in the lump in alcohol solvent; (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling; rotating speed is 2000 rev/mins; 5 hours); by the pre-burning under high-purity Ar gas protection of this mixture (step of pre-burning is: with 1 hour from room temperature be warming up to 200 ℃, 200 ℃ of constant temperature 5 hours; afterwards with dropping to room temperature in 10 hours); after hand lapping is pulverized; mixture again sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 300 ℃ of constant temperature 0.25 hour, afterwards with dropping to room temperature in 10 hours).After being pulverized, the hand lapping of sintering gained solid just can obtain with LiFeSO ₄F is core, AlF ₃The positive electrode with nucleocapsid structure for shell.

Embodiment 69

With LiFeSO ₄F is the shell clad material of nucleocapsid structure, prepare of the present invention for serondary lithium battery with LiCoO ₂For core, LiFeSO ₄F is the positive electrode with nucleocapsid structure of shell.

For serondary lithium battery with LiCoO ₂For core, LiFeSO ₄F is can prepare by following steps by the positive electrode with nucleocapsid structure of shell, at first according to mol ratio, takes LiF, FeSO at 0.1: 0.1: 1 ₄.7H ₂O and LiCoO ₂Put in the lump in alcohol solvent; (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling; rotating speed is 2000 rev/mins; 5 hours); by the pre-burning under high-purity Ar gas protection of this mixture (step of pre-burning is: with 1 hour from room temperature be warming up to 200 ℃, 200 ℃ of constant temperature 5 hours; afterwards with dropping to room temperature in 10 hours); after hand lapping is pulverized; mixture again sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 300 ℃ of constant temperature 0.25 hour, afterwards with dropping to room temperature in 10 hours).After being pulverized, the hand lapping of sintering gained solid just can obtain with LiCoO ₂For core, LiFeSO ₄F is the positive electrode with nucleocapsid structure of shell.

Embodiment 70

Take citric acid and carbon black is carbon source, for the preparation of the LiFeSO with meso-hole structure of serondary lithium battery ₄The F positive electrode.

The LiFeSO with meso-hole structure for serondary lithium battery ₄Can prepare by following steps by the F positive electrode, at first according to mol ratio 1: 1: 0.15: 0.15 takes LiF, FeSO ₄.7H ₂O; citric acid and carbon black are put in alcohol solvent in the lump; (ball-milling medium particle diameter 1mm-10mm after the machinery ball milling; rotating speed is 2000 rev/mins; 5 hours); by the pre-burning under high-purity Ar gas protection of this mixture (step of pre-burning is: with 1 hour from room temperature be warming up to 200 ℃, 200 ℃ of constant temperature 5 hours; afterwards with dropping to room temperature in 10 hours); after hand lapping is pulverized; mixture again sintering (sintering step is: with 2 hours from room temperature be warming up to 300 ℃, 300 ℃ of constant temperature 0.25 hour, afterwards with dropping to room temperature in 10 hours).After being pulverized, the hand lapping of sintering gained solid just can obtain having the LiFeSO of meso-hole structure ₄The F positive electrode.

Embodiment 71

LiFeSO for serondary lithium battery ₄F and C/LiFeSO ₄The electrochemical measurement of F composite material

Will be for the LiFeSO of serondary lithium battery ₄F or carbon nano-tube LiFeSO ₄The n-formyl sarcolysine base pyrrolidone solution of F composite material and acetylene black and 5% Kynoar (PVDF) is mixed to form slurry (active material: acetylene black: PVDF=80: 10: 10) at normal temperatures and pressures, evenly be coated on aluminum substrates, then 100 ℃ of vacuumizes after 5 hours, the film of gained is compressed under 10MPa pressure, the film thickness of gained is about 100 μ m, is cut into the positive pole of the electrode slice of 1 * 1cm as simulated battery.

The negative pole of simulated battery is used the lithium sheet, and electrolyte is 1mol LiPF ₆Be dissolved in the mixed solvent of 1L EC and DMC (volume ratio 1: 1).Two kinds of positive poles are assembled into to simulated battery with negative pole, electrolyte, barrier film respectively in the glove box of argon shield.

The electro-chemical test step of simulated battery: with the multiplying power of C/10 by simulated battery charge to 4.5V then with identical multiplying power current discharge to 2.2V.Under the C/10 multiplying power, the capacity of emitting is with LiFeSO ₄The Mass Calculation of F reaches 120mAh/g.The effect coated in order to contrast carbon, contrast does not have the compound LiFeSO of Non-carbon black ₄F, carbon black LiFeSO ₄F composite material and carbon nano-tube LiFeSO ₄F composite material chemical property, in relatively large electric current 1C situation, carbon nano-tube LiFeSO ₄The capacity of F composite material is the highest, and the compound LiFeSO of Non-carbon black ₄The F capacity is minimum.

Embodiment 72: of the present invention for serondary lithium battery with LiFeSO ₄F is as the electrochemical measurement of electrode ion transmission medium in battery

By commodity LiMn ₂O ₄Material, the LiFeSO for serondary lithium battery of the present invention ₄F, the n-formyl sarcolysine base pyrrolidone solution of acetylene black and 5% Kynoar (PVDF) is mixed to form slurry (active material: ion transfer medium: acetylene black: PVDF=80: 5: 5: 10) at normal temperatures and pressures, evenly be coated on aluminum substrates, then 100 ℃ of vacuumizes after 5 hours, the film of gained is compressed under 10MPa pressure, the film thickness of gained is about 100 μ m, is cut into the positive pole of the electrode slice of 1 * 1cm as simulated battery.

The electro-chemical test step of simulated battery: with the multiplying power of C/10 by simulated battery charge to 4.5V then with identical multiplying power current discharge to 2.2V.The capacity that can find battery does not add LiFeSO ₄F is enhanced.Energy content of battery density has reached 200Wh/kg.

Finally it should be noted that: above embodiment only, in order to technical scheme of the present invention to be described, is not intended to limit; Although with reference to previous embodiment, the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme that aforementioned each embodiment puts down in writing, or part technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the spirit and scope of various embodiments of the present invention technical scheme.

Claims

1. fluoridize the sulphate of iron compound for one kind, it is characterized in that, this compound means with following general formula (I):

(Li _xFe _yM _1-x-y) ₂SO ₄F(I), and in this general formula,

x=0.25～0.75，y=0.25～0.75；

x+y≤1；

2. compound according to claim 1, is characterized in that, in described general formula compound, and x=0.45～0.55, y=0.45～0.55.

3. compound according to claim 1, is characterized in that, described M is one or more in element Na, K, Ca, Mg, Cr, Mn, V, Co, Ni, Zn and Al.

4. according to the described compound of claim 1-3 any one, it is characterized in that, its crystal structure is as follows: diffraction maximum is 24.5 °～26.8 ° at 2 θ, and 27.2 °～28.5 °, 29.1 °～30.6 °, 31.7 °～32.8 ° present four characteristic diffraction peaks.

5. compound according to claim 1, is characterized in that, this compound means with following general formula: (Li _xFe _1-x) ₂SO ₄F.

6. compound according to claim 5, is characterized in that, this compound is: (Li _0.5Fe _0.5) ₂SO ₄F.

7. compound according to claim 6, is characterized in that described (Li _0.5Fe _0.5) ₂SO ₄The crystal structure of F is as follows: diffraction maximum is 26.2 °, 27.8 °, 29.7 °, 31.5 ° at 2 θ and presents four characteristic diffraction peaks.

8. compound according to claim 7, is characterized in that described (Li _0.5Fe _0.5) ₂SO ₄The structure cell of F is a( )=13.0401; B(

)=6.3914; C(

)=9.8499; α=γ=90 °; β=119.766 °; Volume (

)=712.56.

9. the sulphate of iron compound of fluoridizing according to claim 1, is characterized in that, its unit cell volume variation before and after de-lithium is less than 5% when as cell positive material, using.

10. one kind prepares the method that following general formula (I) is fluoridized the sulphate of iron compound, (Li _xFe _yM _1-x-y) ₂SO ₄F(I), and in this general formula,

x=0.25～0.75，y=0.25～0.75；

x+y≤1；

This compound is monoclinic system, and Li and Fe are the mixed-cation occupy-places;

Described method comprises the steps:

1), the mol ratio according to each element in general formula takes Li source, ,Fu source, Fe source, SO4 ^2-Source, M source, mix and grind obtaining the precursor powder;

2), by the precursor powder hot pressed sintering, obtain the described sulphate of iron compound of fluoridizing, in sintering process, apply and be greater than atmospheric mechanical pressure to described precursor powder.

11. preparation method according to claim 10, is characterized in that, before precursor powder hot-pressing sintering, first is placed in inert atmosphere or contains the inert atmosphere pre-burning 0.5～10 hour of reducing gas, described calcined temperature is 100～300 ℃.

12. preparation method according to claim 10, is characterized in that, the particle diameter D50 of described precursor powder is less than 500nm.

13. according to the described preparation method of claim 10-12 any one, it is characterized in that, the described mechanical pressure that precursor powder is applied is more than or equal to 0.5MPa.

14. according to the described preparation method of claim 10-12 any one, it is characterized in that, described sintering temperature is 300-450 ℃.

15. preparation method according to claim 13, is characterized in that, described sintering temperature is 300-450 ℃.

16. the preparation method according to claim 14, is characterized in that, described sintering temperature is 370-390 ℃.

17. according to the described preparation method of claim 10-12 any one, it is characterized in that, described sintering time is 0.1～2 hour.

18. preparation method according to claim 13, is characterized in that, it is characterized in that, described sintering time is 0.1～2 hour.

19. preparation method according to claim 14, is characterized in that, it is characterized in that, described sintering time is 0.1～2 hour.

20. according to the described preparation method of claim 15-16 any one, it is characterized in that, it is characterized in that, described sintering time is 0.1～2 hour.

21. according to the described preparation method of claim 10-12 any one, it is characterized in that, described sintering is 10 at inert atmosphere or vacuum degree ^-1～10 ^-3Under pa pressure, carry out.

22. preparation method according to claim 13, is characterized in that, described sintering is 10 at inert atmosphere or vacuum degree ^-1～10 ^-3Under pa pressure, carry out.

23. preparation method according to claim 14, is characterized in that, described sintering is 10 at inert atmosphere or vacuum degree ^-1～10 ^-3Under pa pressure, carry out.

24. according to the described preparation method of claim 15-16 any one, it is characterized in that, described sintering is 10 at inert atmosphere or vacuum degree ^-1～10 ^-3Under pa pressure, carry out.

25. preparation method according to claim 17, is characterized in that, described sintering is 10 at inert atmosphere or vacuum degree ^-1～10 ^-3Under pa pressure, carry out.

26. preparation method according to claim 10, is characterized in that, described Li source is one or more in lithium fluoride, lithium sulfate, lithium acetate, lithium carbonate, lithium citrate, lithium nitrate and lithium oxalate.

27. preparation method according to claim 10, is characterized in that, described fluorine source is one or more in lithium fluoride, ammonium fluoride, hydrofluoric acid, ammonium acid fluoride and hydrogen fluoride lithium.

28. preparation method according to claim 10, is characterized in that, described M source is one or more in sulfate, acetate, carbonate, citrate, nitrate and the oxalates that contains M.

29. preparation method according to claim 10, is characterized in that, described SO ₄ ^2-Source is one or more in sulfate, sulfuric acid, ammonium sulfate and the hydrogen sulfate ammonia of metal in general formula (I).

30. preparation method according to claim 10, is characterized in that, described Fe source is one or more in the inferior salt of ferrous sulfate, ferrous acetate, ferrous citrate and oxalic acid.

31. a sulfur fluoride silicate material, is characterized in that, in described material, contains the described sulphate of iron compound of fluoridizing of claim 1-9 any one.

32. according to the described material of claim 31, it is characterized in that, in described material, also contain and account for total weight 1～30wt% conductive agent.

33. according to the described material of claim 32, it is characterized in that, described conductive agent be in carbon black, graphite and carbon nano-tube one or more.

34. an ion transfer medium, is characterized in that, comprises the described sulphate of iron compound of fluoridizing of claim 1～9 any one claim.

35. a positive electrode, is characterized in that, comprises the described sulphate of iron compound of fluoridizing of claim 1～9 any one claim.

36. positive electrode according to claim 35, is characterized in that, the unit cell volume variation before and after de-lithium is less than 5%.

37. an electrochemical cell, is characterized in that, the positive electrode of described electrochemical cell forms and comprises the described sulphate of iron compound of fluoridizing of claim 1-9 any one claim.