CN102610815A - Lithium iron phosphate composite modified lithium ion battery cathode material and preparation method thereof - Google Patents
Lithium iron phosphate composite modified lithium ion battery cathode material and preparation method thereof Download PDFInfo
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- CN102610815A CN102610815A CN2012100506669A CN201210050666A CN102610815A CN 102610815 A CN102610815 A CN 102610815A CN 2012100506669 A CN2012100506669 A CN 2012100506669A CN 201210050666 A CN201210050666 A CN 201210050666A CN 102610815 A CN102610815 A CN 102610815A
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Abstract
The invention discloses a lithium iron phosphate composite modified lithium ion battery cathode material and a preparation method thereof. The chemical formula of the cathode material is LiFe1-xRExPO4-REPO4/(C+Fe2P), and a multi-phase structure with LiFe1-xRExPO4, REPO4 and Fe2P exists; REPO4, C and Fe2P are coated on the surface of the LiFe1-xRExPO4; and x ranges from 0.01 to 0.04. The method comprises the following steps of: uniformly mixing a lithium source compound, a phosphorus source compound, inorganic and organic mixed iron source compound and rare earth oxide RE2O3 so as to prepare a reaction precursor; and forging the reaction precursor so as to obtain the lithium iron phosphate composite modified lithium ion battery cathode material. The preparation method is simple and feasible and low in production cost; the prepared material has relatively high electrochemical performance and tap density; and the method is favorable for industrial production.
Description
Technical field
The invention belongs to technical field of lithium ion, specifically be meant anode material for lithium-ion batteries that a kind of LiFePO4 is composite modified and preparation method thereof.
Background technology
Lithium ion battery anode material lithium iron phosphate (LiFePO
4) have Stability Analysis of Structures, specific discharge capacity is big, security performance good, raw material cheaply is easy to get, advantage such as environmentally friendly; Its thermal stability and high temperature cyclic performance are particularly outstanding, are considered to prepare long-life, high power, high security, one of the best positive electrode of lithium-ion-power cell cheaply.
Yet; Some inherent defects of LiFePO 4 material have seriously hindered its commercialization process: one of which: the lithium ion migration rate and the electronic conductivity of this material are all on the low side; High rate during charging-discharging is relatively poor, and the battery of preparation can't satisfy high-specific-power output requirement; Its two: the theoretical tap density of material is low, causes the volumetric specific energy of material significantly to reduce, and the electrokinetic cell volume of processing is too huge, influences the practicality of battery.Therefore; Research so far mainly concentrates on electronic conductivity, the lithium ion mobility of improving material and the tap density aspect that improves material: improving lithium ion migration rate aspect mainly is the optimization through synthesis technique; The grain growth of material in the control building-up process; Have small grains and particle size distribution than the material of homogeneous to obtain, reduce the migration path that lithium ion spreads therein, thereby reach the purpose that improves the lithium ion migration rate; Improving the electronic conductivity aspect is the electronic conductivity that improves material through the conductive doped dose of mode with metal cation; The tap density aspect that improves material then mainly is to adopt crystallization control method or fuse salt method etc. through the spherical LiFePO of preparation
4Particle improves the tap density of material.Like people such as Arnold [Jourral of Power Sources, 2003,119-121:247-251] with Li
+And Fe
2+Phosphate be raw material, at N
2The LiFePO that synthesizes through coprecipitation under the atmosphere
4Under the 0.5C discharge-rate, the specific discharge capacity up to 145mAh/g is arranged; People such as K.Konstantinov [Flectrochimica Acta, 2004, (2-3): 421-426] and adopt the solution spray technology, synthesized the LiFePO that granularity is tiny, crystalline phase is single, conductivity is higher
4/ C composite material has improved the chemical property of material; People [Journal of Power Sources, 2009,189:169-178] such as George Ting-Kuo Key utilization mechanical activation method is a carbon source with the malonic acid, through evaporating rheology reaction and ball milling at LiFePO
4The surface on carbon coated, gained sample 0.1C discharge can have the specific capacity of 161mAh/g; People such as Wang [Fletrochemcal Acta, 2005,50:2955-2958] have been LiFePO
4The research of mixing of Fe position, use M
2+(M=Ni, Co and Mg) replaces Fe respectively, prepared doped compound LiFe
0.9M
0.1PO
4When 5C discharged and recharged, its initial capacity reached 100mAh/g; [Journal of Power Sources, 2006,158:543-548] such as Ying Jierong is with the synthetic FePO with spherical structure of crystallization control method
4Material, and synthesized Li with spherical structure as raw material
0.97Cr
0.01FePO
4/ C material, the tap density of this material is up to 1.8g/cm
3
Though electrical property has some improvement, also there is following problems in the composite ferric lithium phosphate material that above prior art is synthesized:
1. can prepare the less powder body material of particle diameter though adopt methods such as hydrothermal synthesis method, liquid-phase coprecipitation, sol-gel process; Reduce the migration path of lithium ion; But material particle size reduce to have increased the contact area between material granule; Reduce tap density, volume and capacity ratio and the volumetric specific power of material, also had shortcomings such as equipment requirements height or complicated process of preparation simultaneously, be difficult to carry out industrialized production;
Though 2, the containing transition metal element can improve the body phase electronic conductivity of material, and is less to the grain diameter influence of material, can not improve the lithium ion diffusion rate of material, thereby very limited to the improvement effect of the chemical property of material;
3, carbon coats the electronic conductivity that not only improves material, and carbon coats material particle size is obviously reduced simultaneously, has reduced the migration path of lithium ion, and is very outstanding to the improvement effect of material electrical property, but the tap density of carbon compares LiFePO
4Low, the material that simple carbon coats has reduced volumetric specific energy, has a strong impact on the practicality of material.
Though 4, adopt crystallization control method and liquid-phase coprecipitation can synthesize spherical structure LiFePO with high-tap density
4Material, but synthesis technique needs strictness to control factors such as the temperature of reaction system, pH value, stir speed (S.S.), co-precipitation speed, operating procedure is complicated, and the industrialization difficulty is big.
Summary of the invention
The objective of the invention is provides a kind of highly electron conductive and lithium ion conduction speed, anode material for lithium-ion batteries that the LiFePO4 of high material tap density is composite modified and preparation method thereof in order to solve the problem that above-mentioned prior art exists.
The oxide (RE=La, Nd, Sm, Ce) that the present invention proposes with rare earth elements RE is a doped raw material, adopts traditional high temperature solid-state-carbo-thermal process to prepare the LiFe with heterogeneous coexisting structure
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) material in electronic conductivity that has improved material and lithium ion conduction speed, has also improved the tap density of material, has not only improved the big multiplying power discharging property of material, but also has made material have higher volume and capacity ratio.
The object of the invention is realized through following technical scheme:
The anode material for lithium-ion batteries that a kind of LiFePO4 is composite modified, this positive electrode chemical formula is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P), there is LiFe
1-xRE
xPO
4, REPO
4And Fe
2The P heterogeneous structure, REPO
4, C and Fe
2P coats LiFe
1-xRE
xPO
4The surface, x is 0.01～0.04; RE=La, Nd, Sm or Ce.
The preparation method of the anode material for lithium-ion batteries that said a kind of LiFePO4 is composite modified comprises the steps and process conditions:
The first step is dispersant with ethanol, is source of iron with the mixture of ironic citrate and inorganic iron compound, and source of iron, Li source compound, P source compound and dopant rare earth oxide is even through ball mill mixing, and the addition of ironic citrate is target product LiFePO
410%～45% of Theoretical Mass; Wherein the mol ratio of Li: Fe: P: Sm is (1～1.02): (0.96～1): 1: (0.01～0.05), inorganic source of iron and ironic citrate add by the amount of iron atom wherein than being (0.9～0.55): (0.1～0.45); Amount of alcohol added is 100%～300% of a raw materials mix amount;
Said Li source compound is one or more in lithium phosphate, lithium nitrate, lithium carbonate, lithium acetate and the lithium hydroxide;
Said P source compound is one or more in phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and the ferric phosphate;
Said inorganic iron source compound is one or more in di-iron trioxide, ferric phosphate and the tri-iron tetroxide;
The oxide of said rare earth element is one or more in samarium oxide, lanthana, neodymia and the cerium oxide;
Second step with mixed raw material 300～450 ℃ of down heating 5～20 hours, cooling, after grinding the reaction precursor body;
The 3rd step calcined the reaction precursor body 10～40 hours down at 600～800 ℃, promptly got LiFe after the cooling
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) the composite modified anode material for lithium-ion batteries of LiFePO4.
For further realizing the object of the invention, said amount of alcohol added is preferably 100%～200% of raw materials mix amount.
Said target product LiFePO
4Theoretical Mass is meant the structural formula according to the composite modified anode material for lithium-ion batteries of LiFePO4, and the ratio of the amount of source of iron, Li source compound, P source compound and dopant rare earth oxide adds, the quality of complete reaction products therefrom.
The time of heating is preferably 10～15 hours to said raw material down at 300～450 ℃.
The time of said calcining is preferably 20～30 hours.
Material of the present invention compared with prior art has the following advantages:
1. LiFe of the present invention
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) crystalline structure of material and pure LiFePO
4Crystalline structure basic identical, on the XRD spectra except having the drift left and the REPO of peak position
4Peak and Fe
2Outside the P, the both is basic identical.
2. at the prepared LiFe of the present invention
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) in the crystal structure of positive electrode, the part rare earth ion gets into the inside of positive electrode crystal structure, and the part rare earth ion is with REPO
4Form be present in LiFe
1-xRE
xPO
4The crystal boundary place.Because LiFe
1-xRE
xPO4 and REPO
4Two phase structure differs greatly, and two phase intergranules form bigger out-phase crystal boundary distortion district, in this distortion district, and short texture, the degree of disorder is big, and defect density is high.This out-phase crystal boundary is to Li
+The obstruction of ion migration is less, thereby has significantly improved LiFePO in the charge and discharge process
4/ FePO
4State of interface, strengthened the ionic conduction performance and the electronic conductivity of material, thereby helped Li
+Embedding and deviate from.
3. the present invention utilizes C and Fe
2P is as conductiving doping agent, Fe
2The carbon that P produces in citrate Pintsch process process and cracking produces together, it is extremely even to distribute, and has formed intergranular C+Fe
2The P conductive network has reached when reducing the amount of carbon coated between particle, does not but influence the conductive effect between material granule, when having guaranteed that material has high-rate discharge ability, maintains higher tap density, thereby makes material have high volumetric specific energy.
4. the present invention utilizes each autoreduction of the different source of iron of chemical property to form LiFePO
4The time to form granular size different; Be two interval character that distribute; Utilize granule fill bulky grain pile up in formed space improve the tap density of material; Simplified the synthesis technique that improves the material tap density greatly, be convenient to carry out industrialized production, the tap density of gained material reaches 1.2g/cm
3～2.0g/cm
3
5. the prepared LiFe of the present invention
1-xRE
xPO
4-REPO
4/ (C+Fe
2The superior performance of P) composite positive pole embedding, lithium ionic insertion/deinsertion has very high specific discharge capacity and volumetric specific energy.At room temperature, when 2.2～4.2V, its first discharge specific capacity reaches 160mAh/g to this material with the voltage range of 0.1C rate charge-discharge, and volume and capacity ratio reaches 304mAh/cm
3
4. the LiFe of the present invention preparation
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) high rate during charging-discharging of composite positive pole is superior.At room temperature, during with the 1.0C rate charge-discharge, its first discharge specific capacity reaches 150mAh/g, and volume and capacity ratio reaches 285mAh/cm
3
7. gained material synthesis of the present invention is more simple, and low cost of manufacture is convenient to carry out industrialized production.
Description of drawings
Fig. 1 is the prepared LiFe of this specification embodiment 1
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) X-ray diffracting spectrum.
Fig. 2 is this specification embodiment 1 made LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) the first charge-discharge curve of the Experimental cell of composite material assembling, the charging/discharging voltage scope is 4.2～2.2V, electrolyte is 1mol/L LiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)], charge-discharge magnification is difference 0.1C, 1C.
Embodiment
Below in conjunction with embodiment, the present invention is done detailed description further, but execution mode of the present invention is not limited thereto.
Embodiment one
The first step is with 0.51mol lithium carbonate, 1mol DAP, 0.057mol ironic citrate, 0.216mol di-iron trioxide, 0.01mol samarium oxide; Adding the absolute ethyl alcohol that accounts for mixture amount 100% is dispersant, through high speed ball mill ball mill mixing (rotating speed 300r/min);
Second step placed pit furnace with mixed raw material, fed nitrogen as protective gas, was warming up to 350 ℃, constant temperature 10 hours, and the cooling back is ground and is obtained reacting precursor;
The 3rd step was put into reactor with gained reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 700 ℃, and constant temperature 24 hours after the stove cooling, grinds, and sieves, and the gained powder is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, because the chemical property of compound source of iron is different, autoreduction forms LiFePO
4The time to form granular size different, be two interval character that distribute, utilize granule fill bulky grain pile up in formed space improve the tap density of material, the tap density of utilizing the tap density appearance to measure material is 1.90g/cm
3
Fig. 1 is the prepared LiFe of this specification embodiment 1
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) X-ray diffracting spectrum can be found out LiFe among the figure
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) crystalline structure of material and pure LiFePO
4Crystalline structure basic identical, on the XRD spectra except having the drift left and the REPO of peak position
4Peak and Fe
2Outside the P, the both is basic identical, has explained that synthetic material is LiFe
1-xRE
xPO
4, REPO
4And Fe
2The P three-phase structure.
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/LLiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.Because prepared LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) in the crystal structure of positive electrode, the part rare earth ion gets into the inside of positive electrode crystal structure, and the part rare earth ion is with REPO
4Form be present in LiFe
1 -xRE
xPO
4The crystal boundary place.Because LiFe
1-xRE
xPO4 and REPO
4Two phase structure differs greatly, and two phase intergranules form bigger out-phase crystal boundary distortion district, in this distortion district, and short texture, the degree of disorder is big, and defect density is high.This out-phase crystal boundary is to Li
+The obstruction of ion migration is less, thereby has significantly improved LiFePO in the charge and discharge process
4/ FePO
4State of interface, strengthened the ionic conduction performance and the electronic conductivity of material, thereby helped Li
+Embedding and deviate from.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 160mAh/g; During with the 1.0C rate charge-discharge, its first discharge specific capacity is 150mAh/g.
Embodiment two
The first step is with 1.02mol lithium nitrate, 0.068mol phosphoric acid hydrogen ammonia, 0.028mol ironic citrate, 0.932mol ferric phosphate, 0.05mol lanthana, and the amount that adds ethanol is 200% of a mixture quality, through high speed ball mill ball mill mixing (rotating speed 400r/min);
Second step placed pit-type furnace with mixed raw material, fed argon gas as protective gas, was warming up to 250 ℃, and constant temperature 10 hours obtains the reaction precursor body after cooling, the grinding;
The 3rd step was put into reactor with the reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 800 ℃, calcining at constant temperature 32 hours, and cooling off, grind, sieve afterwards with stove, the gained powder is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, its tap density 2.0g/cm
3
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/LLiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 150mAh/g; During with the 1.0C rate charge-discharge, its first discharge specific capacity is 134mAh/g.
Embodiment three
The first step is with 1mol lithium phosphate, 0.127mol ironic citrate, 0.281mol tri-iron tetroxide, 0.04mol neodymia, and the amount that adds ethanol is 200% of a mixture quality, through high speed ball mill ball mill mixing (rotating speed 400r/min);
Second step placed pit furnace with mixed raw material, fed nitrogen as protective gas, was warming up to 400 ℃, constant temperature 5 hours, and the cooling back is ground and is obtained reacting precursor;
The 3rd step was put into reactor with gained reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 500 ℃, and constant temperature 40 hours after the stove cooling, grinds, and the gained powder that sieves is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, its tap density 1.2g/cm
3
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/L LiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 150mAh/g; During with the 1.0C rate charge-discharge, its first discharge specific capacity is 132mAh/g.
Embodiment four
The first step is with 1.02mol lithium acetate, 0.08mol ironic citrate, 0.45mol di-iron trioxide, 1mol phosphoric acid, 0.03mol cerium oxide, and the amount that adds ethanol is 250% of a mixture quality, through high speed ball mill ball mill mixing (rotating speed 350r/min);
Second step placed pit furnace with mixed raw material, fed argon gas as protective gas, was warming up to 300 ℃, constant temperature 20 hours, and the cooling back is ground and is obtained reacting precursor;
The 3rd step was put into reactor with gained reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 650 ℃, and constant temperature 10 hours after the stove cooling, grinds, and the gained powder that sieves is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, its tap density 1.4g/cm
3
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/LLiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 151mAh/g; During with the 1.0C rate charge-discharge, its first discharge specific capacity is 144mAh/g.
Embodiment five
The first step is with 1mol lithium hydroxide, 0.08mol ironic citrate, 0.3mol di-iron trioxide, 0.1mol tri-iron tetroxide, 1mol phosphoric acid ammonia, 0.005mol samarium oxide; The amount that adds ethanol is 280% of a mixture quality, through high speed ball mill ball mill mixing (rotating speed 350r/min);
Second step placed pit furnace with mixed raw material, fed nitrogen as protective gas, was warming up to 300 ℃, constant temperature 15 hours, and the cooling back is ground and is obtained reacting precursor;
The 3rd step was put into reactor with gained reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 600 ℃, and constant temperature 12 hours after the stove cooling, grinds, and the gained powder that sieves is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, its tap density are 1.3g/cm
3
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/LLiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 149mAh/g; During with the 1.0C rate charge-discharge, its first discharge specific capacity is 135mAh/g.
Embodiment six
The first step is with 0.5mol lithium hydroxide, 0.5mol lithium nitrate, 0.08mol ironic citrate, 0.3mol di-iron trioxide, 0.3mol ferric phosphate, 0.2mol phosphoric acid ammonia, 0.5mol ammonium di-hydrogen phosphate, 0.03mol samarium oxide, 0.02mol lanthana; The amount that adds ethanol is 250% of a mixture quality, through high speed ball mill ball mill mixing (rotating speed 3500r/min);
Second step placed pit furnace with mixed raw material, fed nitrogen as protective gas, was warming up to 300 ℃, constant temperature 20 hours, and the cooling back is ground and is obtained reacting precursor;
The 3rd step was put into reactor with gained reaction precursor body, placed pit-type furnace, fed nitrogen as protective gas, was warming up to 650 ℃, and constant temperature 18 hours after the stove cooling, grinds, and the gained powder that sieves is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) composite doping modification positive electrode, its tap density are 1.6g/cm
3
Above-mentioned composite doping modification positive electrode is processed cathode film as positive active material, cathode film consist of m
Active material: m
Acetylene black: m
Polytetrafluoroethylene=85: 10: 5, thickness≤0.1mm processed positive plate with the cathode film roll extrusion on stainless (steel) wire; With metal lithium sheet as negative pole; Barrier film is import microporous polypropylene membrane (Celgard2300); Electrolyte is 1mol/LLiPF
6/ [ethylene carbonate (EC)+dimethyl carbonate (DMC) (volume ratio 1: 1)] is assembled into Experimental cell in the glove box of applying argon gas, at room temperature carry out charge-discharge test, and the charging/discharging voltage scope is 2.2～4.2V.When this material discharged and recharged with the 0.1C multiplying power, its first discharge specific capacity reached 151mAh/g, and during with the 1.0C rate charge-discharge, its first discharge specific capacity is 140mAh/g.
As above tell, can realize the present invention preferably.
The foregoing description is a preferred implementation of the present invention; But execution mode of the present invention is not restricted to the described embodiments; Change, the modification that other are any not to deviate under the principle of the invention to be made, substitute, combination, simplify, all should be the substitute mode of equivalence, be included among protection scope of the present invention.
Claims (6)
1. the anode material for lithium-ion batteries that LiFePO4 is composite modified is characterized in that, this positive electrode chemical formula is LiFe
1-xRE
xPO
4-REPO
4/ (C+Fe
2P), there is LiFe
1-xRE
xPO
4, REPO
4And Fe
2The P heterogeneous structure, REPO
4, C and Fe
2P coats LiFe
1-xRE
xPO
4The surface, x is 0.01～0.04; RE=La, Nd, Sm or Ce.
2. the preparation method of the composite modified anode material for lithium-ion batteries of the said a kind of LiFePO4 of claim 1 is characterized in that comprising the steps and process conditions:
The first step is dispersant with ethanol, is source of iron with the mixture of ironic citrate and inorganic iron compound, and source of iron, Li source compound, P source compound and dopant rare earth oxide is even through ball mill mixing, and the addition of ironic citrate is target product LiFePO
410%～45% of Theoretical Mass; Wherein the mol ratio of Li: Fe: P: Sm is (1～1.02): (0.96～1): 1: (0.01～0.05), inorganic source of iron and ironic citrate add by the amount of iron atom wherein than being (0.9～0.55): (0.1～0.45); Amount of alcohol added is 100%～300% of a raw materials mix amount;
Said Li source compound is one or more in lithium phosphate, lithium nitrate, lithium carbonate, lithium acetate and the lithium hydroxide;
Said P source compound is one or more in phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and the ferric phosphate;
Said inorganic iron source compound is one or more in di-iron trioxide, ferric phosphate and the tri-iron tetroxide;
The oxide of said rare earth element is one or more in samarium oxide, lanthana, neodymia and the cerium oxide;
Second step with mixed raw material 300～450 ℃ of down heating 5～20 hours, cooling, after grinding the reaction precursor body;
The 3rd step calcined the reaction precursor body 10～40 hours down at 600～800 ℃, promptly got LiFe after the cooling
1-xRE
xPO
4-REPO
4/ (C+Fe
2P) the composite modified anode material for lithium-ion batteries of LiFePO4.
3. according to the preparation method of the composite modified anode material for lithium-ion batteries of the said a kind of LiFePO4 of claim 2, it is characterized in that: said amount of alcohol added is 100%～200% of a raw materials mix amount.
4. according to the preparation method of the composite modified anode material for lithium-ion batteries of the said a kind of LiFePO4 of claim 2, it is characterized in that: said target product LiFePO
4Theoretical Mass is meant the structural formula according to the composite modified anode material for lithium-ion batteries of LiFePO4, and the ratio of the amount of source of iron, Li source compound, P source compound and dopant rare earth oxide adds, the quality of complete reaction products therefrom.
5. according to the preparation method of the composite modified anode material for lithium-ion batteries of the said a kind of LiFePO4 of claim 2, it is characterized in that: the time of heating is 10～15 hours to said raw material down at 300～450 ℃.
6. according to the preparation method of the composite modified anode material for lithium-ion batteries of the said a kind of LiFePO4 of claim 2, it is characterized in that: the time of said calcining is 20～30 hours.
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