CN102332580A

CN102332580A - Fluorinated ferric sulfate salt compound as well as preparation method and application thereof

Info

Publication number: CN102332580A
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: 2012-01-25
Anticipated expiration: 2031-07-25
Also published as: WO2012122686A1; CN102332580B

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) is 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, chemical property is stable, safe and reliable, lithium storage content is higher and voltage than advantages such as height.But this type material also exists ionic conductivity and the low shortcoming of electronic conductivity at present; At present often through reducing particle size; Methods such as carbon coating can solve low electricity preferably and lead effect of material performance, but still can't satisfy the secondary lithium battery requirements of one's work.

The existence of X-O key has important effect in the polyanionic compound.Except the stabilizing material structure, it can also improve the oxidation-reduction pair voltage of transition metal through the inductive effect of X-O key, and present 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 with 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 hope through introducing stronger atom or the group of electronegativity, such as fluorine element and than phosphate radical electronegativity strong sulfate radical, further the current potential platform of raising material stronger than oxygen element electronegativity.

Such as LiFePO ₄Middle Fe ³⁺/ Fe ²⁺Voltage 3.45V apparently higher than the 2V of general ferriferous oxide.Because the electronegativity of S element is better than the electronegativity of P element, promptly 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, be zero consideration from total valence state, need be at the lithium ion of positive monovalence, outside the transition metal ions of positive divalence and the sulfate ion of negative divalence, the ion that adds a negative monovalence is again kept charge balance.In numerous candidates, the F element is ideal, and its atomic mass is little, helps keeping the high power capacity of compound, and electronegativity is very strong, helps improving 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; Disclosing a kind of sulfur fluoride hydrochlorate of anorthic system Tavorite structure, fluoridized the ferric sulfate lithium and have electro-chemical activity, is the oxidation-reduction pair of divalent/trivalent iron equally; How much voltage do not obtain because introducing stronger sulfate radical of electronegativity and fluorine ion and promotes; The voltage platform of its 3.6V is added theoretical capacity and originally just is lower than LiFePO4 only than the high 0.15V of LiFePO4, causes not preponderating on its energy density.This explanation is not sufficient to make that only through introducing the strong ion/group of electronegativity the embedding lithium voltage of material is improved, and has only that this rule just can work (with reference to the LiFePO of Tavorite structure under the same structure ₄F is than the LiFePO that is the Tavorite structure equally ₄The high 0.7V of OH voltage).Therefore, improve the current potential platform of positive electrode, the more important thing is the material of seeking crystal structure with higher embedding lithium voltage.Triclinic in addition sulfur fluoride hydrochlorate structural stability neither be very desirable, and unit cell volume alters a great deal before and after taking off lithium, causes its cycle life shorter.Its preparation method of this in addition anorthic system sulfur fluoride hydrochlorate need adopt expensive ionic liquid, and preparation process complicacy is loaded down with trivial details, is not easy to large-scale production, has seriously limited it in the serondary lithium battery Application for Field.

Summary of the invention

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

One side of the present invention provides a kind of sulphate of iron compound of fluoridizing, and this compound is represented with following general formula (I):

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

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

x＝0.25～0.75，y＝0.25～0.75；

x+y≤1；

This compound is a 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 said preparation method who fluoridizes the sulphate of iron compound comprises the steps:

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

2), with the precursor powder hot pressed sintering, obtain the said sulphate of iron compound of fluoridizing, in sintering process, apply greater than atmospheric mechanical pressure to said 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 is formed and comprised the described sulphate of iron compound of fluoridizing.

Description of drawings

Accompanying drawing is used to provide further understanding of the present invention, and constitutes the part of specification, is used to explain the present invention with embodiments of the invention, is not construed as limiting the 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 is the monoclinic system (Li of mixed-cation occupy-place _0.6Fe _0.4) ₂SO ₄The XRD measured drawing of F;

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

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

Fig. 4-5 is 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 is 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 is 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 is 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 is 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 ₄First all charging and discharging curve figure of F;

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

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

Fig. 5-4 is the monoclinic system (Li of CNT and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄First all charging and discharging curve figure of F composite material;

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

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

Fig. 5-7 is 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 is the monoclinic system (Li of mixed-cation occupy-place _0.45Fe _0.45Zr _0.05Mg _0.05) ₂SO ₄First all charging and discharging curve figure of F;

Fig. 5-9 is the monoclinic system (Li of mixed-cation occupy-place _0.475Fe _0.45Cr _0.025Mg _0.05) ₂SO ₄First all 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 is the monoclinic system (Li of CNT and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The SEM collection of illustrative plates of F composite material;

Fig. 6-3 is 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 attitude _0.5Fe _0.5) ₂SO ₄The XRD figure spectrum 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 Figure 13-1, Figure 13-2 mix for distinct methods;

Figure 14 is the hot pressing furnace structural representation.

In conjunction with accompanying drawing, Reference numeral is following among the present invention:

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 is represented 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 promptly Li and Fe can occupy the position in lattice each other, and both can realize exchanging completely the position.For expression 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.

The research proof, the sulphate of iron of fluoridizing provided by the invention is because its specific crystal structure has better electrochemical properties.In this compound, M is a doped chemical, and the interpolation of said doped chemical can effectively improve the conductivity of compound.M is preferably one or more among element Na, K, Ca, Mg, Cr, Mn, V, Co, Ni, Zn and the Al.Shown in the 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 the existing anode material of lithium battery all can be used as the doped chemical of this compound.

The content of Li and Fe in the precursor: in the said general formula compound, x=0.25～0.75, y=0.25～0.75; Preferred x=0.45～0.55, y=0.45～0.55.It is shown in figure 11 that the precursor of corresponding r (wherein r=Li/Fe)=0.8,1,1.2,1.5,2 has carried out the XRD detection 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, can't see the diffraction maximum of LiF in the sample of r=1.0 and r=1.2 fully, and in the sample of r=1.5, begun 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, promptly under the situation of Fe ion excessive 25%, except LiFeSO ₄The diffraction maximum of F also exists 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 °, and these several impurity peaks also appear in other r value sample just; Just intensity weakens along with the increase of Li ratio in the presoma, to the r=1.5 sample, is difficult to identification, in the r=2.0 sample, has then disappeared, and in existing card base, element is restricted to Li; Fe, S, O; F, H judges it might is to lack FeSO under the situation of Li in view of the above 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 the presoma) presoma gained sample; With 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.

Though the rising of Li content helps reducing the dephasign in the end-product in the presoma; But correspondingly reduced the discharge capacity of material, this is not owing to Li has electro-chemical activity yet, and remaining Li has offset and 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 big, also contingent is that part iron is oxidized to ferric iron with the maintenance charge balance, so the minimizing capacity.

Further; The sulphate of iron compound of fluoridizing of the present invention is carried out X ray (CuK α) crystal powder diffraction; This compound crystal structure is following: diffraction maximum is 24.5 °～26.8 ° at 2 θ; 27.2 °～28.5 °, 29.1 °～30.6 °, 31.7 °～32.8 ° demonstrate four characteristic diffraction peaks.Diffraction maximum is that 29.1 °～30.6 ° diffraction maximum is a highest peak at 2 θ.Said 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 does

α=γ=90 °; β=119.77 (0) °;

Further, the sulphate of iron compound of fluoridizing of the present invention, its unit cell volume that takes off the lithium front and back changes less than 5% when using as cell positive material.Like (Li _xFe _1-x) ₂SO ₄F or change less than 5% at the unit cell volume that takes off before and after the lithium by its electrode material that constitutes.Preferably less than 4%.

The unit cell volume that table 1 different materials takes off before and after the lithium 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％
			Monocline 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％
Monocline phase (Li _0.5Mn _0.5) ₂SO ₄F	Do not exist	2.4％

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

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

Optional, the Fe in its formula of (I) compound can also be by Co, Mn, and the one or more replacements among Ni or the V make wherein no longer to 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 the precursor powder hot-pressing sintering, place inert atmosphere earlier or contain the inert atmosphere pre-burning 0.5～10 hour of reducing gas, said calcined temperature is 100～300 ℃.The effect of pre-burning mainly is to remove moisture in the precursor powder to be dried.The inert atmosphere that places inert atmosphere during the pre-burning of precursor powder or contain reducing gas is to be used to prevent that precursor powder (like Fe wherein) is oxidized.Said inert gas can be argon gas or nitrogen, and said reducibility gas can be hydrogen or carbon monoxide.Said pre-burning programming rate does not have particular restriction, but the programming rate that adopts usually is per hour 50～200 ℃.The direct hot pressed sintering of precursor powder that also can grinding be obtained, and the precursor powder is not carried out pre-burning, it is not carried out other dried yet.

The precursor particle size: experiment shows that the granularity of said 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 that contacts between several kinds of feed particles, thereby influences 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 then can fully to be contacted between the 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 said precursor powder generally should be D50 less than 500nm, preferably less than 300nm, like 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, and reach desired particle size and get final product precursor powder oxidation or other adverse effects.For example can adopt modes such as the 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 to carry out batch mixing and grinding.Milling time is had no particular limits, as long as can reach desired particle size.Common said 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 satisfies the precursor powder.

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

Keep mixed system (through suitable cooling provision) under the condition of normal temperature or lower temperature, in the wet method medium, implement ball milling and mix precursor, provide granularity thin as far as possible precursor powder.In specific embodiments of the present invention; 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 inside and outside courage of its ball grinder, feed the recirculated water of cooling usefulness; To avoid or to slow down material temperature rising in the process of ball milling, can be used for preparing at normal temperatures ultra-fine powder.Process of lapping is in following embodiment: the FeSO that takes by weighing mol ratio and be 1: 1 ₄7H ₂O and LiF simply mix, and zirconia mill Jie ball of the mixture of 50ml altogether and 250ml is sequentially added in the ball grinder of zirconia inner bag that capacity is 500ml, are installed on the Union Process ball mill; Add the about 100ml of ball milling media ethanol, in the ball grinder chuck, feed cooling water, carry out ball milling with the rotating speed of 3500rpm; Behind the ball milling 2.5 hours, replenish part ball milling media, again with same rotating speed ball milling 2.5 hours; The gained slurry is taken out; In air, dry naturally, the gained siccative is sieved 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, the higher 600rpm that reaches of rotating speed, and can before ball milling, feed protective gas and avoid higher material and the air reaction of causing of temperature in the mechanical milling process.Idiographic flow is: the FeSO that takes by weighing mol ratio and be 1: 1 ₄7H ₂O and LiF simply mix, with mixture and the stainless steel mill Jie ball of 15g The capacity of joining is in the stainless steel jar mill of 100ml, adds ball milling media ethanol 20ml, and lid is sealed; Utilize its air inlet/outlet to feed the ventilation of high-purity Ar gas, be installed to after the weighing quality on the Retsch PM100 ball mill, mix up counterweight; Carry out ball milling (rotating speed 600rpm, 12 hours ball milling time, every ball milling half an hour by setting the ball milling program; Stop half an hour and prevent that the ball milling jar is overheated), treat ball milling jar cooling after, slurry is poured out; 50 ℃ of bakings 12 hours, manual porphyrize promptly got precursor powder LFSF#2 with vacuum drying oven;

Sample LFSF#3 adopts the mode of manual abrasive material to pulverize and mix, and is 1: 1 FeSO with the mol ratio that amounts to about 10g ₄7H ₂The mixture of O and LiF places mortar, and hand-held pestle ground 3 hours in the direction of the clock, has both got 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 1: 1 FeSO ₄7H ₂The mixture of O and LiF places ball grinder, is 200rpm with rotating speed, and ball milling 5 hours had both got precursor powder LFSF#4.

The XRD of precursor powder LFSF#1, LFSF#2, LFSF#3, LFSF#4 characterize collection of illustrative plates like Figure 13-1 with shown in the 13-2: the presoma that is obtained by the visible first three methods of figure has identical phase, can point out to be FeSO ₄H ₂The mixture of O (JCPDS No.83-2092) and LiF (JCPDS No.78-1217), wherein more weak and wideization of the obvious intensity of the diffraction maximum of LFSF#1 explained with the presoma crystal grain of Union Process 01-HD preparation less; And strong with the LFSF#3 diffraction maximum of hand mill, halfwidth is little, and crystal grain is bigger; The strength, peak of the presoma LFSF#2 that mixes with Retsch PM100 is between the two, but is salmon pink behind the presoma ball milling, shows ferric existence; The LFSF#4 that mixes with homemade ball mill is different with above three, can it be pointed out to be FeSO ₄4H ₂The mixture of O (JCPDS No.76-0655) and LiF (JCPDS No.78-1217).

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

Through above-mentioned experiment and analysis, obtain to draw a conclusion and to explain:

1, the different polishing mode has determined the size of the particle and the crystal grain of precursor, and granular size has determined the tightness degree of presoma contact, and then the very big influence that has to reacting.

The component of the presoma that 2, ground changes, and reason is FeSO ₄7H ₂The crystallization water among the O combines tightness degree different, and wherein the first six crystallization water is prone to lose, and the activation energy of its dehydration is very low, and this also is FeSO ₄7H ₂The reason of O meeting dehydration weathering in dry air.Promptly following the variation

FeSO ₄·7H ₂O→FeSO ₄·H ₂O+6H ₂O

When presoma is ground,,, add that absolute ethyl alcohol does the ball milling media stronger water absorption is arranged, be easier in the LFSF#1 sample crystallization water and deviate from because its rotating speed is fast, energy is high for Union Process ball mill; Even with mortar hand mill, because air flow makes water section volatilize, 6 crystallizations water in the gained LFSF#3 sample can break away from voluntarily, finally obtain FeSO ₄H ₂O; What need particularly point out is that the LFSF#4 sample that in homemade ball grinder, obtains is FeSO ₄4H ₂O, this is because after the ball grinder sealing, moisture can't overflow, FeSO ₄H ₂O crystallization that absorbs water again in the process of cooling is FeSO ₄4H ₂O, promptly following process

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

Its diffraction maximum is strong higher than other three samples than obviously with the peak of the diffraction maximum of LiF, and this recrystallization process also has been described; And, then making vapour pressure less because filling rate is low for the LSFS#2 sample that Retsch PM100 handled, the ball milling energy is higher, finally also can obtain FeSO ₄H ₂O, but see that 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 handled of Retsch PM100 is salmon pink, shows ferric existence, and this explain in the process of high-energy ball milling, and is also higher in the local temperature of clashing into moment because collision energy is higher, makes FeSO ₄7H ₂O partly decomposes, and the oxygen that discharges can cause Fe ²⁺Be oxidized to trivalent and show salmon pink, equation is following:

2FeSO ₄→Fe ₂O ₃+SO ₂+SO ₃

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

The heat analysis of presoma: LSFS#1 and two kinds of presomas of LSFS#3 are carried out 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; Simultaneously can the test sample mass change; The mass spectrum of the heat absorption heat release and the gas that produces, be the TG-DSC-MS analysis of different grain size precursor powder like Figure 10: wherein LFSF#1 precursor powder D50 is less than 200nm; Wherein LFSF#3 precursor powder D50 is 600nm-50 μ m.Granularity like the visible precursor powder of Figure 10 has directly influenced reaction speed, and the precursor powder that less precursor powder (D50 is less than 200nm) is compared big (D50 is 600nm-50 μ m) reaction speed is fast.

The TG-DSC test shows that also the precursor powder has tangible endothermic peak and weightlessness at 280 ℃, loses the crystallization water and causes; Tangible endothermic peak and weightlessness occurring at 420～450 ℃, is SO ₄ ^2-Decomposition, cause SO ₂(m/z=64) overflow.So the hot pressed sintering temperature that the present invention suits is 300～450 ℃, preferably 360～420 ℃, be more preferably 370～390 ℃; Programming rate is not had particular restriction, but the programming rate that adopts usually is per hour 50～200 ℃; The time of said hot pressed sintering is decided 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 is meant and reaches predetermined sintering temperature among this paper, the time of sintering under this predetermined temperature.

Hot pressed sintering: the hot pressed sintering step can be carried out in hot pressing furnace, the hot pressing furnace structural representation of Figure 14 for using in one embodiment of the invention.The Packed heating chamber 1 of said hot pressing furnace is provided with heater 2 and hot pressing die 3, the said heater 2 optional electric heating elements of using in the heating chamber 1.Hot pressing die 3 links to each other 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, is used to hold the precursor powder.Hot pressing die 3 has a piston mobile to link to each other with pressure apparatus 4.Therefore when the pressure that receives from pressure apparatus 4, the piston of this hot pressing die 3 passes to pressure in the precursor powder that is contained in the die cavity 5.To place hot pressing die 3 without pre-burning or with the precursor powder after the pre-burning during operation.In order to guarantee being heated evenly of hot pressed sintering, the good and material that the precursor powder is inertia of preferred thermal conductivity is 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 said hot pressing die 3 is inner to communicate with heating chamber 1 gas.Heated sealed chamber 1 is charged into inert atmosphere or is evacuated to 10 ^-1～10 ^-3Pa can prevent effectively that low valence metal ion is oxidized (like Fe ²⁺Oxidized).Exert pressure to hot pressing die 3 through pressure apparatus 4, make that the piston forward body powder applied pressure of this hot pressing die 3 is 0.5～100MPa, or 2～50MPa, or 5～20MPa, suitable pressure can prevent or reduce SO in addition ₄ ^2-Decompose, help improving the purity of reactant, improve chemical reaction velocity simultaneously.

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

Optional, can the precursor powder just not applied 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 like 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 helps the carrying out of the solid phase reaction of air-sensitive, is well suited for the reaction that presoma is this type of LiF stable compound.

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

Compare with traditional method for preparing solid phase; Hot pressed sintering method for preparing solid phase of the present invention can carry out under relatively low temperature; Thereby can obtaining particle size, less (for example D50 is less than 600nm; Or D50 is less than 500nm, and D50 is less than 400nm in certain embodiments) formula (I) compound particle gather thing, so saidly fluoridize that the sulphate of iron compound need not or only need simple grinding to use after cooling.

Raw material: raw material mainly comprises Li source, Fe source, fluorine source, M source and SO in the preparation process ₄ ^2-The source.Described Li source is one or more in lithium fluoride, lithium sulfate, lithium acetate, lithium carbonate, lithium citrate, lithium nitrate and the lithium oxalate; Said fluorine source is one or more in lithium fluoride, hydrofluoric acid, ammonium fluoride, ammonium acid fluoride and the hydrogen fluoride lithium; Said M source is one or more in sulfate, acetate, carbonate, citrate, nitrate and the oxalates that contains M; Said SO ₄ ^2-The source be metal in the general formula (I) (Li, Fe and/in M) sulfate, sulfuric acid, ammonium sulfate and the hydrogen sulfate ammonia one or more.The Fe source is one or more in the inferior salt of ferrous sulfate, ferrous acetate, ferrous citrate and oxalic acid.Be appreciated that said 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 said general formula (I) fluoridizes the sulphate of iron compound.Optional, also can contain conductive agent in the said sulfur fluoride silicate material, said conductive agent accounts for the 1-30wt% of this material total weight, and said conductive agent can be in carbon black, graphite and the CNT 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 said general formula (I) fluoridize the sulphate of iron compound and comprise positive electrode that the material of this compound processes and, electrochemical cell, promptly; The active component of said positive electrode is perhaps processed by this compound from the aforementioned sulphate of iron compound of fluoridizing fully; Because 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 the present invention also provides the purposes that the sulphate of iron compound is used to prepare positive electrode of fluoridizing of said general formula (I), and, saidly fluoridize the purposes that the sulphate of iron compound is used for preparing the ion transfer medium of battery electrode.

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

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

The present invention also provides a kind of electrochemical cell; The positive electrode of this electrochemical cell form comprise said general formula (I) fluoridize the sulphate of iron compound; Can be the composite material that comprises said sulfur fluoride silicate material, also can be the material that has 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, contains the sulfur fluoride hydrochlorate in this material at least, 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 among Nb or the Zr;

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

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

M and B are not with a kind of element simultaneously;

C, a, m, b, z, n, f represent mol ratio respectively, 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 said 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 demonstrates 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 said 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 said general formula (II) has nucleocapsid structure, and the shell material 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, magnesia, titanium oxide, polypyrrole, polyaniline or polythiophene shell thickness be 1nm-500nm to said shell material.

Further, said 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 said 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 said 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 said 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 said general formula (II) can contain micropore, mesoporous or macropore, and the aperture is 2nm-500nm.

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

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

3) behind the ball milling, obtain precursor powder;

4) with precursor powder in tube furnace, at inert atmosphere or contain pre-burning in the inert atmosphere of reducibility gas, natural cooling;

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

6) with the hand lapping of sintering gained solid.

Further, said carbon source is selected from least a in pitch, native graphite, electrographite, superfine graphite powder, acetylene black, carbon black, the CNT.

Further, said carbon source can be carbon black; CNT; Mol ratio is 1: 1 graphite and a carbon black; Or mol ratio is 1: 1 pitch and acetylene black; Or mol ratio is 1: 1 electrographite and superfine graphite powder; Or mol ratio is 2: 1: 3 pitch, graphite and acetylene black.

Further, the said ball milling time is 2～10 hours, and the particle diameter of ball-milling medium is 1mm～10mm; The temperature of said pre-burning is between 150 ℃～300 ℃, and the pre-burning time is 1-10 hour; The temperature of said 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 the lithium oxalate; Villiaumite is selected from one or more of ammonium fluoride, hydrofluoric acid, ammonium acid fluoride, hydrogen fluoride lithium, and said transition metal salt (for example iron) is selected from its sulfate, one or more in acetate, carbonate, citrate, nitrate and the oxalates; The salt of said doped chemical is selected from the fluoride of doped chemical, sulfate, acetate, carbonate, one or more in citrate, nitrate and the oxalates; Said inert atmosphere is argon gas or nitrogen, and said 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 cell positive material; Perhaps with the clad material of sulfur fluoride silicate material, perhaps sulfur fluoride silicate material and other material are formed and mixed collocation mutually and make and be used for forming anode as original anode.

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

In addition, the hot-pressing sintering method of aforementioned preparation general formula (I) compound is applicable to preparation 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 a kind of monoclinic system that has first, cation mixes occupy-place, space group is C12/c ₁Fluoridize the sulphate of iron compound, a kind of during it is compared with existing sulfur fluoride silicate material and mainly has 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, is higher than the 3.4V of LiFePO4, is higher than anorthic system sulfur fluoride silicate material 3.6V, and 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 ₁The sulphate of iron compound of fluoridizing mix occupy-place because of metal ion; Lithium ion is deviate from and embeds the front and back unit cell volume to change less than 5%; Change in volume is little than LiFePO4 and anorthic system sulfur fluoride silicate material, and electrode structure is stable in the battery charging and discharging circulation, has extended cycle life;

3), preparation technology is simple: the present invention is through selecting suitable reaction precursor body and reaction condition, with simple solid phase reaction method 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, sintering temperature is low, sintering time is short and advantage of low energy consumption;

4), sulfur fluoride phosphate compounds provided by the invention can directly use in serondary lithium battery as positive electrode active materials; The advantage that also can utilize its macroion electricity to lead as clad material, coats 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 with the ion transfer medium of this compound as electrode in the battery; Because this compound itself has electro-chemical activity; The conduction velocity of ion can be improved, in the high rate performance that improves battery, the energy density of electrode can also be improved in electrode interior.

5), the secondary lithium battery of application sulfur fluoride phosphate compounds preparation provided by the invention has remarkable advantages such as power density is big, energy density is high, capacity is big; This type serondary lithium battery is applicable to that various mobile electronic devices maybe need move the equipment of 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 is like electric tool, electric automobile, PHEV and accumulation power supply etc.

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

Embodiment

For making the object of the invention, technical scheme and advantage clearer; To combine the accompanying drawing in the embodiment of the invention below, the technical scheme in the embodiment of the invention carried out clear, intactly description, obviously; Described embodiment is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the present invention's protection.

Embodiment 1

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

(Li _0.5Fe _0.5) ₂SO ₄F prepares through following steps: at first take by weighing LiF and FeSO at 1: 1 according to mol ratio ₄7H ₂O (or FeSO ₄H ₂O), adopt Union Process 01-HD type high energy ball mill ball milling to obtain the precursor powder that D50 is 30nm after 5 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, rotating speed is 2000 rev/mins; With the pre-burning 5 hours under the high-purity Ar gas shiled of this precursor powder, said calcined temperature is 200 ℃ (pre-burning programming rates be 1 hour from room temperature be warming up to 200 ℃ with this precursor powder), cools off afterwards to drop to room temperature in 10 hours; With grinding 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.

Sintering gained solid abrasive is pulverized the back just can obtain monoclinic (Li _0.5Fe _0.5) ₂SO ₄The F positive electrode.The parsing of product compound structure and performance measurement:

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

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 is visible with Fig. 3, two XRD figure spectrum main distinctions 20 ° go out the peak situation.In the XRD figure shown in Figure 2 spectrum, some stronger characteristic peaks occur at this place, are illustrated in that Li is fixed on separately position accordingly with Fe in the structure cell.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; It is thus clear that (the Li of the present invention's preparation _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 identical basically, and from the monocline 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 are all less than 5%, it is thus clear that (the Li of the present invention's preparation _0.5Fe _0.5) ₂SO ₄The structure of F is identical.Deducibility goes out the prepared (Li of present embodiment thus _0.5Fe _0.5) ₂SO ₄The atom occupy-place of Li and Fe is interchangeable mixing occupy-place among the F.In the case, find on the fixed position of the fixed position of Li and Fe that in structure cell the probability of Li atom equates, and equal in this compound Li with respect to the mol ratio of Li+Fe; Equally, find on the fixed position of the fixed position of Li and Fe that in structure cell the probability of Fe atom equates, and equal in this compound Fe with respect to the mol ratio of Li+Fe.Monoclinic system (Li by the visible mixed-cation occupy-place of Fig. 1-1,1-2,4-1 and table 2 _0.5Fe _0.5) ₂SO ₄The space group of F is C12/c1 (crowd number 15), and each crystallography primitive unit cell comprises the (Li of eight molecular formula _0.5Fe _0.5) ₂SO ₄F.Lattice parameters?

β = 119.77 °.Wherein lithium atom occupies two different 8f positions with the mixing of Fe atom, and 50% occupation probability is respectively arranged.With two 8f for being labeled as position 1 and position 2.Crystal structure is that the octahedron at center is connected to form the one-dimensional chain (Fig. 1-1) along (101) direction in the limit altogether with Li1/Fe1 shown in Fig. 1-1,1-2, is that the octahedron at center is connected to form the one-dimensional chain (Fig. 1-2) along (010) direction in the limit altogether with Li2/Fe2.Constituting two kinds of octahedral coordination anions all is four oxygen atoms and two fluorine atoms, is the oxygen-oxygen limit or the fluoro-fluorine limit of alternately arranging and connect common limit octahedral.The isolated sulfate radical that distributes 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 ₄Atom occupy-place in the structure cell of F

Monocline 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 ₄First all charging and discharging curve figure of F; It is thus clear that the monoclinic system (Li that 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; It is thus clear that 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; By figure visible through reaching 12 hours leave standstill the OCV curve display (Li that the gained equilibrium potential is linked to be _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 characteristic 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; By the visible open circuit voltage curve of figure tangible platform area is arranged near 3.9V.Polarization curve has then demonstrated a kind of special regularity, and promptly in charging process, polarization is to reduce after becoming greatly earlier, and then increases gradually; And in discharge process, similar rule being arranged, i.e. diminishing after change earlier is big becomes big again.Like this in the state of close lithium content, polarization big or small just the opposite.

Fig. 9 is the different (Li that discharge and recharge attitude _0.5Fe _0.5) ₂SO ₄The XRD figure spectrum of F, visible with its charging and discharging process by figure, diffraction maximum does not have obvious skew can prove (the Li that present embodiment is prepared _0.5Fe _0.5) ₂SO ₄F unit cell volume in charge and discharge process changes little, only has about 3% through calculating.

Embodiment 2

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

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

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

Embodiment 3

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

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

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

Embodiment 4

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

Monoclinic system (the Li of CNT of the present invention and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The F composite material can at first take by weighing LiF, FeSO according to mol ratio through the following steps preparation at 1: 1 ₄.7H ₂O; Add the CNT of 10wt%, then they are put in the alcohol solvent in the lump (ball-milling medium particle diameter 1mm-10mm behind the mechanical 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).Sintering gained solid abrasive is pulverized the monoclinic system (Li that the back just can obtain CNT and mixed-cation occupy-place _0.5Fe _0.5) ₂SO ₄The F composite material.

Adopt XRD, SEM, its crystal structure of constant current charge-discharge appearance test, pattern, discharge capacity and head week to put rate; The XRD measured drawing of gained composite sample and first all charging and discharging curve figure are shown in Fig. 4-4 and 5-4; The electromicroscopic photograph of gained material sample is shown in Fig. 6-2, and its average grain diameter, discharge capacity, first all efficiency data are referring to table 4.It is thus clear that the interpolation of CNT 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 ₄F at first takes by weighing LiF, FeSO according to mol ratio through the following steps preparation 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; With the pre-burning 1 hour under the high-purity Ar gas shiled of this precursor powder, said calcined temperature is 250 ℃ (pre-burning programming rates be 2 hours from room temperature be warming up to 200 ℃ with this precursor powder), and cooling afterwards drops to room temperature; Precursor powder after the grinding pre-burning is placed 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.

Sintering gained solid abrasive is pulverized the back just can obtain monoclinic (Li _0.5Fe _0.45Mn _0.05) ₂SO ₄The F positive electrode.Adopt XRD, SEM, its crystal structure of constant current charge-discharge appearance test, pattern, discharge capacity and head week to put rate; The XRD measured drawing of gained compound sample and first all charging and discharging curve figure are shown in Fig. 4-5 and 5-5; The SEM collection of illustrative plates is 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 ₄F at first takes by weighing LiF, FeSO according to mol ratio through the following steps preparation 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; With the pre-burning 5 hours under the high-purity Ar gas shiled of this precursor powder, said calcined temperature is 200 ℃, cools off afterwards to drop to room temperature in 10 hours; Precursor powder after the grinding pre-burning is placed graphite jig, and said 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 through hydraulic press, and hot pressed sintering pressure is 50MPa, is cooled to room temperature.

Sintering gained solid need not to grind the back just can obtain monoclinic (Li _0.5Fe _0.25Mn _0.25) ₂SO ₄The F positive electrode.Adopt XRD, its crystal structure of constant current charge-discharge appearance test, discharge capacity and head week to put rate; With shown in the 5-6, its average grain diameter, discharge capacity, first all efficiency data are referring to table 4 like Fig. 4-6 for the XRD measured drawing of gained compound sample and first all charging and discharging curve figure.

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 ₄F at first takes by weighing LiF, FeSO according to mol ratio through the following steps preparation at 1: 0.95: 0.05 ₄7H ₂O and NaF grind and obtain the precursor powder that D50 is 200nm after 5 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, and rotating speed is 2000 rev/mins; With the pre-burning 3 hours under the high-purity Ar gas shiled of this precursor powder, said calcined temperature is 250 ℃ (pre-burning programming rates be 3 hours from room temperature be warming up to 250 ℃ with this precursor powder), cools off afterwards to drop to room temperature in 10 hours; With grinding 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, cools off to drop to room temperature in 12 hours.

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

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 ₄F is through following steps preparations, and at first according to mol ratio 0.9: 0.9: 0.1: 0.1 takes by weighing 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; With 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 then, and cooling drops to room temperature.

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

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 ₄F is through following steps preparations, and at first according to mol ratio 0.95: 0.9: 0.05: 0.1 takes by weighing LiF, FeSO ₄7H ₂O, Cr ₂(SO ₄) ₂6H ₂O and MgSO ₄6H ₂O, mechanical ball milling obtain the precursor powder of D50 less than 35nm after 15 hours, ball-milling medium particle diameter 0.1mm-10mm wherein, and rotating speed is 2000 rev/mins; With the pre-burning 5 hours under the high-purity Ar gas shiled of this precursor powder, said calcined temperature is 200 ℃ (pre-burning programming rates be 1 hour from room temperature be warming up to 200 ℃ with this precursor powder), cools off afterwards to drop to room temperature in 10 hours; With grinding precursor powder after the 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, cools off to drop to room temperature in 10 hours.

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

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 with embodiment 1-9: the mol ratio according to each element in the general formula takes by weighing Li source, Fe source, fluorine source, SO ₄ ^2-Source and M source mix and grind obtaining the precursor powder; With the precursor powder hot pressed sintering, obtain in the table 4 fluoridizing the sulphate of iron compound shown in the 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

Preparation originally is used for nitrogen doping the fluoridizing sulfate material Li of serondary lithium battery _1.2FeSO _3.8N _0.2F.

The Li that is used for serondary lithium battery _1.2FeSO ₄N _0.2The F positive electrode can be through following steps preparations, and at first according to mol ratio 1: 0.2: 1: 0.3 takes by weighing LiF, Li ₃N, FeSO ₄.7H ₂O and carbon black, (ball-milling medium particle diameter 1mm-10mm, rotating speed are 2000 rev/mins behind the mechanical ball milling; 5 hours); With the pre-burning under the high-purity Ar gas shiled 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 once more 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).The back is pulverized in 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

Preparation is used for the oxygen room sulfur fluoride silicate material LiFeSO of serondary lithium battery _3.98F.

LiFeSO _3.98The F positive electrode can be through following steps preparations, and at first according to mol ratio 1: 0.99: 0.01: 0.3 takes by weighing LiF, FeSO ₄.7H ₂O, FeS and carbon black, (ball-milling medium particle diameter 1mm-10mm behind the mechanical ball milling; Rotating speed is 2000 rev/mins, 5 hours), with the pre-burning under the high-purity Ar gas shiled 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 once more 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).The back is pulverized in 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

Preparation is used for the sulfur fluoride silicate material 7-51 with brand new of serondary lithium battery

Preparation method and embodiment 21-22 are similar, and different 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 _fRepresent the sulfur fluoride silicate material that is used 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 among Nb or the Zr; M is Fe, Co, Mn, at least a among Ni or the V; B is Li, Na, K, Ca, Mg, Ti, V, Cr, Cu, Mn, Co, Ni, Zn, Ga, In, Ge, Ag, Nb, at least a among Zr or the W; M and B are not with a kind of element simultaneously; X, a, m, b, z, n represent mol ratio respectively, 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 ₃Be the shell clad material of nucleocapsid structure, the preparation be used for serondary lithium battery with LiFeSO ₄F is a core, AlF ₃Positive electrode for shell with nucleocapsid structure.

Be used for serondary lithium battery with LiFeSO ₄F is a core, AlF ₃For the positive electrode with nucleocapsid structure of shell can at first take by weighing LiF, FeSO according to mol ratio through the following steps preparation at 1: 1: 0.1 ₄.7H ₂O and AlF ₃Put in the lump in the alcohol solvent, (ball-milling medium particle diameter 1mm-10mm, rotating speed are 2000 rev/mins behind the mechanical ball milling; 5 hours); With the pre-burning under the high-purity Ar gas shiled 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 once more 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).The back is pulverized in the hand lapping of sintering gained solid just can be obtained with LiFeSO ₄F is a core, AlF ₃Positive electrode for shell with nucleocapsid structure.

Embodiment 69

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

Be used for serondary lithium battery with LiCoO ₂Be core, LiFeSO ₄F is that the positive electrode with nucleocapsid structure of shell can at first take by weighing LiF, FeSO according to mol ratio through the following steps preparation at 0.1: 0.1: 1 ₄.7H ₂O and LiCoO ₂Put in the lump in the alcohol solvent, (ball-milling medium particle diameter 1mm-10mm, rotating speed are 2000 rev/mins behind the mechanical ball milling; 5 hours); With the pre-burning under the high-purity Ar gas shiled 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 once more 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).The back is pulverized in the hand lapping of sintering gained solid just can be obtained with LiCoO ₂Be core, LiFeSO ₄F is the positive electrode with nucleocapsid structure of shell.

Embodiment 70

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

The LiFeSO that is used for serondary lithium battery with meso-hole structure ₄The F positive electrode can be through following steps preparations, and at first according to mol ratio 1: 1: 0.15: 0.15 takes by weighing LiF, FeSO ₄.7H ₂O; Citric acid and carbon black are put in the alcohol solvent in the lump, and (ball-milling medium particle diameter 1mm-10mm, rotating speed are 2000 rev/mins behind the mechanical ball milling; 5 hours); With the pre-burning under the high-purity Ar gas shiled 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 once more 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).The LiFeSO that the back just can obtain having meso-hole structure is pulverized in the hand lapping of sintering gained solid ₄The F positive electrode.

Embodiment 71

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

The LiFeSO that will be used for serondary lithium battery ₄F or CNT LiFeSO ₄The F composite material mixes formation slurry (active material: acetylene black: PVDF=80: 10: 10) at normal temperatures and pressures with the n-formyl sarcolysine base pyrrolidone solution of acetylene black and 5% Kynoar (PVDF); Evenly be coated on the aluminum substrates; Then 100 ℃ of vacuumizes after 5 hours; The film of gained is compressed under 10MPa pressure, and 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 uses 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 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 with 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 being emitted is with LiFeSO ₄The Mass Calculation of F reaches 120mAh/g.In order to contrast the effect that carbon coats, contrast does not have the compound LiFeSO of carbon black ₄F, carbon black LiFeSO ₄F composite material and CNT LiFeSO ₄F composite material chemical property, under relatively large electric current 1C situation, CNT LiFeSO ₄The capacity of F composite material is the highest, and does not have the compound LiFeSO of carbon black ₄The F capacity is minimum.

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

Commodity are used LiMn ₂O ₄Material, the LiFeSO that is used 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 formation slurry (active material: ion transfer medium: acetylene black: PVDF=80: 5: 5: 10) at normal temperatures and pressures; Evenly be coated on the aluminum substrates,, the film of gained compressed under 10MPa pressure then 100 ℃ of vacuumizes after 5 hours; 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 with 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.

What should explain at last is: above embodiment is only in order to explaining technical scheme of the present invention, but not to its restriction; Although with reference to previous embodiment the present invention has been carried out detailed explanation, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, and perhaps part technical characterictic wherein is equal to replacement; And these are revised or replacement, do not make the spirit and the scope of the essence disengaging various embodiments of the present invention technical scheme of relevant art scheme.

Claims

1. fluoridize the sulphate of iron compound for one kind, it is characterized in that, this compound is represented 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. according to the said compound of claim 1, it is characterized in that, in the said general formula compound, x=0.45～0.55, y=0.45～0.55.

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

4. according to each described compound of claim 1-4, it is characterized in that its crystal structure is following: diffraction maximum is 24.5 °～26.8 ° at 2 θ, and 27.2 °～28.5 °, 29.1 °～30.6 °, 31.7 °～32.8 ° demonstrate four characteristic diffraction peaks.

5. compound according to claim 1 is characterized in that this compound is represented 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. according to the said compound of claim 6, it is characterized in that said (Li _0.5Fe _0.5) ₂SO ₄The crystal structure of F is following: diffraction maximum is 26.2 °, 27.8 °, 29.7 °, 31.5 ° at 2 θ and demonstrates four characteristic diffraction peaks.

8. according to the said compound of claim 7, it is characterized in that said (Li _0.5Fe _0.5) ₂SO ₄The structure cell of F does

α=γ=90 °; β=119.77 (0) °;

9. the sulphate of iron compound of fluoridizing according to claim 1 is characterized in that, it changes less than 5% at the unit cell volume that takes off the lithium front and back when using as cell positive material.

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 a monoclinic system, and Li and Fe are the mixed-cation occupy-places;

Said method comprises the steps:

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

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

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

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

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

14., it is characterized in that said sintering temperature is 300-450 ℃ according to each described preparation method of claim 10-13.

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

16., it is characterized in that said sintering time is 0.1～2 hour according to each described preparation method of claim 10-15.

17., it is characterized in that said sintering is 10 at inert atmosphere or vacuum degree according to each described preparation method of claim 10-16 ^-1～10 ^-3Carry out under the pa pressure.

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

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

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

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

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

23. a sulfur fluoride silicate material is characterized in that, contains each described sulphate of iron compound of fluoridizing of claim 1-9 in the said material.

24. according to the said material of claim 23, it is characterized in that, also contain in the said material and account for total weight 1～30wt% conductive agent.

25. according to the said material of claim 24, it is characterized in that, said conductive agent be in carbon black, graphite and the CNT one or more.

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

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

28. positive electrode according to claim 27 is characterized in that, changes less than 5% at the unit cell volume that takes off the lithium front and back.

29. an electrochemical cell is characterized in that, the positive electrode of said electrochemical cell is formed and is comprised the described sulphate of iron compound of fluoridizing of any claim of claim 1-9.