Detailed description of the invention
Hereinafter the detailed description of the invention of the present invention is described in detail.It should be appreciated that detailed description of the invention described herein is merely to illustrate and explains the present invention, it is not limited to the present invention.
End points and any value of scope disclosed in this article are not limited to this accurate scope or value, and these scopes or value should be understood to the value comprised close to these scopes or value.For numerical range, between the endpoint value of each scope, between the endpoint value of each scope and single point value, and individually can obtain one or more new numerical range with combination with one another between point value, these numerical rangies should be considered the most specifically to disclose.
In the present invention, in the case of illustrating on the contrary, the FePO related to4, lithium source, carbon source and pore creating material weight all in terms of butt;The term " gram specific capacity " used refers to total electricity that the battery active material of unit mass can be released, and its value is the biggest, illustrates that the electricity that battery material can store is the biggest.
Comprise the following steps according to the method preparing LiFePO4 that the present invention provides: in the presence of pore creating material, will be containing FePO4, the raw material of lithium source and carbon source is sintered.
According to the present invention, kind and consumption to pore creating material have no particular limits, as long as the specific surface area of LiFePO4 can be promoted after distilling to obtain improving.Preferably, with FePO4Butt meter, described pore creating material and FePO4Weight ratio be 0.2-2:10 (arbitrary value as between 0.2:10,0.3:10,0.4:10,0.5:10,0.6:10,0.7:10,0.8:10,0.9:10,1:10,1.1:10,1.2:10,1.3:10,1.4:10,1.5:10,1.6:10,1.7:10,1.8:10,1.9:10,2:10 or aforementioned value).Described pore creating material is boiling point high (more than 150 DEG C) and the material easily distilled at temperature is less than 300 DEG C.Preferably, described pore creating material is provided by one or more in camphor, paracide and naphthalene.Wherein, camphor can be provided by natural camphor ball (commercially available).
According to the present invention, FePO4Can be iron phosphate pressed powder, it is preferable that FePO4By the FePO with water of crystallization4There is provided.
According to the present invention, kind and consumption to lithium source have no particular limits, as long as it can be with FePO4React and obtain LiFePO4.Preferably, in terms of elemental lithium, described lithium source and FePO4Mol ratio be 0.5-2:1 (arbitrary value as between 0.5:1,0.6:1,0.7:1,0.8:1,0.9:1,1:1,1.1:1,1.2:1,1.3:1,1.4:1,1.5:1,1.6:1,1.7:1,1.8:1,1.9:1,2:1 or aforementioned value), more preferably 0.5-1:1.Described lithium source can be various commonly used in the art containing Li+Ionic compound, it is preferable that described lithium source is one or more in lithium carbonate, Lithium hydrate and lithium nitrate.
According to the present invention, kind and consumption to carbon source have no particular limits, as long as can be coated with LiFePO4 is uniform.Preferably, with FePO4Butt meter, described carbon source and FePO4Weight ratio be 1-5:10 (arbitrary value as between 1:10,1.5:10,2:10,2.5:10,3:10,3.5:10,4:10,4.5:10,5:10 or aforementioned value), more preferably 1-2:10.Described carbon source can be one or more in monosaccharide (such as glucose), oligosaccharide (such as disaccharide) and polysaccharide (if molecular weight is the polysaccharide of 150000 to 600000).Preferably, one or more during described carbon source is glucose, sugarcane sugar and starch.
According to the present invention, in order to obtain the LiFePO4 of excellent performance, preferably, described method also includes: control before sintering the particle diameter of raw material below 300 mesh (such as 300-600 mesh), and moisture below 5 weight % (such as 0.1-5 weight %).It can be to pulverize (such as ball milling) and/or be dried (such as microwave drying and/or spray drying) that the particle diameter of control raw material and moisture meet the method for above-mentioned requirements.
According to the present invention, described sintering can be carried out under the normal condition of this area.Preferably, described sintering is carried out under an inert atmosphere, and the temperature of sintering is 300-800 DEG C, and the time of sintering is 2-13h.
It is highly preferred that the mode of sintering is 1-3h at being first placed in 300-400 DEG C, then 1-10h at being placed in 600-800 DEG C.
The method preparing LiFePO4 according to the present invention comprises the following steps:
(1) mixing is with the FePO of water of crystallization4, lithium source, carbon source and pore creating material, wherein, with FePO4Butt meter, described pore creating material and FePO4Weight ratio be 0.2-2:10, described pore creating material by camphor, paracide and naphthalene one or more provide, wherein, camphor can be provided by natural camphor ball (commercially available);In terms of elemental lithium, described lithium source and FePO4Mol ratio be 0.5-2:1, described lithium source is one or more in lithium carbonate, Lithium hydrate and lithium nitrate;Described carbon source and FePO4Weight ratio be 1-5:10, described carbon source is one or more in glucose, sugarcane sugar and starch, wherein FePO4Weight in terms of butt;
(2) carry out pulverizing and/or being dried by the mixing raw material that step (1) obtains so that mixing raw material particle diameter below 300 mesh (such as 300-600 mesh), and moisture below 5 weight % (such as 0.1-5 weight %);
(3) being placed under inert atmosphere be sintered processing, through step (2), the material that obtains, the temperature of sintering is 300-800 DEG C, and the time of sintering is 2-13h.
According to the present invention, the mode of described pulverizing can use the breaking method that this area is conventional, it is preferable that the mode of pulverizing is ball milling.It is highly preferred that described ball milling is carried out in ball grinder (such as planetary ball mill tank).The condition of ball milling can include that rotating speed is 100-200r/min, and the time is 1-10h.
More preferably, the mode of ball milling is wet grinding, and water is 0.5-2:1 (arbitrary value as between 0.5:1,0.6:1,0.7:1,0.8:1,0.9:1,1:1,1.1:1,1.2:1,1.3:1,1.4:1,1.5:1,1.6:1,1.7:1,1.8:1,1.9:1,2:1 or aforementioned value) with the weight ratio mixing raw material.
According to the present invention, described dry mode can use the drying means that this area is conventional, it is preferable that dry method is microwave drying and/or spray drying.In order to before making sintering, the moisture of raw material meets above-mentioned requirements, dry actual conditions can be selected by those skilled in the art, does not repeats them here.
According to the present invention, described in be sintered in atmosphere furnace carrying out.Preferably, atmosphere furnace is tube-type atmosphere furnace.Preferably, it is provided that the noble gas of inert atmosphere is nitrogen and/or argon.
According to the invention, it is further possible to the product obtained after sintering is crushed, be suitable to prepare the LiFePO4 product of positive electrode to obtain.
The method preparing positive electrode of the present invention includes preparing LiFePO4 according to the invention described above method, and is mixed with conductive agent by the LiFePO4 obtained.
According to the present invention, kind and consumption to conductive agent have no particular limits, as long as its weight ratio that can play electric action, conductive agent and LiFePO4 can be 0.5-2:20 (arbitrary value as between 0.5:20,0.6:20,0.7:20,0.8:20,0.9:20,1:20,1.1:20,1.2:20,1.3:20,1.4:20,1.5:20,1.6:20,1.7:20,1.8:20,1.9:20,2:20 or aforementioned value).Preferably, conductive agent is white carbon black.It is highly preferred that conductive agent is little granule conductive black.
According to the present invention, described method can also include mixing the LiFePO4 obtained, conductive agent with binding agent.Described binding agent can be various polymer commonly used in the art, such as polyvinylidene fluoride (pvdf).The weight ratio of described binding agent and LiFePO4 can be 0.5-2:20 (arbitrary value as between 0.5:20,0.6:20,0.7:20,0.8:20,0.9:20,1:20,1.1:20,1.2:20,1.3:20,1.4:20,1.5:20,1.6:20,1.7:20,1.8:20,1.9:20,2:20 or aforementioned value).
According to the present invention it is possible to be further used for preparing battery by the positive electrode that said method prepares.Such as, by the LiFePO4 obtained according to the present invention, little granule conductive black (Super-P) and binding agent (such as polyvinylidene fluoride, pvdf) mixing is as positive pole, Super-P is 0.5-2:20 with the weight ratio of LiFePO4, pvdf is 0.5-2:20 with the weight ratio of LiFePO4, lithium sheet, as negative pole, makes smear button cell.This smear button cell has preferably performance, and the smear button cell prepared by the LiFePO4 prepared according to the preferred embodiment for the present invention is at 2-3.8V, room temperature (23 DEG C) 0.5C, and gram specific capacity is 156-160mAh/g;Room temperature 5C, gram specific capacity is 146-149mAh/g;2-3.8V ,-10 DEG C, 0.5C, gram specific capacity is 124-128mAh/g;Low temperature discharge-10 DEG C/23 DEG C ratio is 77.5-82%.
Hereinafter will be described the present invention by embodiment.
In following example, the method preparing smear button cell is: by LiFePO4, conductive agent Super-P, binding agent pvdf and solvent N-methyl pyrilidone (NMP) according to the proportional arrangement form slurry of 86:7:7:150, single spreading is on smooth aluminium foil, and coated side density is 100g/m2, after drying, (solvent NMP volatilization) is through roll-in, compacted density to 2g/cm3;With special piercer, pole piece is washed into the positive plate of a diameter of 14mm the most again, has weighed the weight of each positive plate with analytical balance, and recorded data;Then by positive plate and a diameter of 16mm lithium sheet and the barrier film of a diameter of 19mm, in glove box, smear button cell it is assembled into.The method of test gram specific capacity is: use the test cabinet (BTS-2) of new Weir, according to multiplying power to be tested, the electric current setting electric discharge makes smear button cell just complete electric discharge (such as in required time, when multiplying power is 5C, required time is 0.2h, when multiplying power is 0.5C, required time is 2h), i.e. can obtain the test data (weight of the electric current × required time/positive plate of gram specific capacity=setting electric discharge) of gram specific capacity.
The natural camphor ball used in following example is song spirit tablet camphor ball (camphor content is 96 weight %);Super-P is purchased from Jitian Chemical Co., Ltd. of Shenzhen;Pvdf is purchased from Xiamen Zhong Wutou Import and Export Co., Ltd.;The method of test specific surface area is: use the JW-004A dynamic adsorption instrument of precise and tiny Gao Bo, Beijing science and technology company limited, it is first turned on computer software and adsorption instrument and preheats 0.5h, then prepared LiFePO4 is added in the sample U-tube of adsorption instrument, the LiFePO4 weight that record adds, then 150 DEG C of process 0.5h in the case of helium is protected, it is cooled to room temperature (25 DEG C), turn off helium, take out sample, the weight of record sample, then U-tube is inserted in adsorption instrument, in Dewar flask, add liquid nitrogen simultaneously, and allow U-tube leaching end in liquid nitrogen, open test software, start test, after having tested, i.e. can obtain specific surface area.