Multi-element composite positive pole material for lithium secondary battery and preparation method thereof
Technical field
The present invention relates to inorganic functional material and high-energy battery technology, specifically, relate to positive electrode of multi-element metal oxide, lithium rechargeable battery and preparation method thereof.
Background technology
At present, along with the fast development of portable electric appts such as mobile phone, notebook computer, digital camera MP3, MP4 etc., energy market is increasing to reproducible, high power capacity, high power, long-life battery requirements amount.Lithium ion battery is the battery that voltage is the highest, energy density is maximum in the battery of practicability up to now, has good its development.
In the anode material for lithium-ion batteries of present industrialization, it is simple to possess production technology, and discharge capacity is big, and the advantage of good cycle has firmly occupied most lithium rechargeable battery market.But LiCoO
2Material also has following shortcoming: the one, and cobalt belongs to rare metal, and content is less in the earth's crust, and price is higher, and the 2nd, LiCoO
2Security performance also have defective, especially under the condition of overcharging (>=4.2V), material unstable easily and electrolyte react, cause battery blast on fire, be unfavorable for using the field of batteries that security performance is being had relatively high expectations; LiCoO in addition
2Theoretical capacity is 274mAh/g, but actual reversible capacity is about 145mAh/g, the further raising of restriction cell capacity.Therefore seek that cheap, environmental protection, capacity are higher, the better positive electrode of security performance has the important strategic meaning to the development of lithium ion battery.
With LiCoO
2Advantages such as material is compared, and polynary positive pole material lithium manganese cobalt nickel oxygen system has the specific capacity height, and the anti-over-charging performance is good, thermal stability is outstanding and receiving much concern.In three kinds of components of material; Various elements are different to the influence of material; Generally speaking the content of nickel element is relevant with the capacity of material; The Ni constituent content is high more, and the gram volume of whole multi-element composite material system is high more, but the cycle performance of the whole material of Ni too high levels and thermal stability will descend; Cobalt Co constituent content is relevant with the layer structure growth and the conductivity of material; The Co constituent content is high more, and whole positive electrode system conductivity is high more, and the layer structure of material is good more; But the Co too high levels will increase the preparation cost of polynary positive pole material, and the thermal stability of material also can descend simultaneously; The thermal stability of the content of manganese Mn element and material is relevant in the polynary positive pole material, and the cycle performance of the high more material of Mn content is good more, and thermal stability is high more, but the Mn element is high more, will cause material capacity to reduce, and finally can be converted into unsteadiness Mn
3+, influence the cycle performance of material system.At present respectively to these characteristics of polynary positive pole material system, commodity production the good LiNi of combination property
1/3Co
1/3Mn
1/3O
2The LiNi good with stability
0.4Co
0.2Mn
0.4O
2Material.But these two kinds of materials receive the restriction (discharging and recharging window 3-4.2V) in current battery market, and the gram specific capacity all and LiCoO
2Comparing does not have advantage even lower slightly, can not satisfy the demand that improves the material gram volume.
Nickelic (0.5≤Ni content≤1) ternary material be at present unique a kind of in 3-4.2V discharges and recharges window discharge capacity surpass LiCoO
2Material, its specific discharge capacity reaches as high as 190mAh/g, but because the more (Ni of variation of valence of Ni element
+ 2, Ni
+ 3, Ni
+ 4) particularly ionic radius is different under each valence state, cause material lattice shrinkage ratio in cyclic process bigger, thereby influence the cycle performance of material, Ni in the material in addition
3+Unstable easily and electrolyte react also be cause material cycle performance and thermal stability relatively poor main cause.At present the research of high-nickel material is mainly concentrated on and coat and above the doping means; Doping again or coating through to the ternary system material improve the material crystals structure; The reaction of barrier material body and electrolyte; In the hope of improving the chemical property of material, research at present shows doping and is coated on the cyclical stability that can improve material to a certain extent, but can not overcome the loop attenuation of material fully.The present invention is intended to start with from the improvement of the physical property of material and improves the cyclical stability and the thermal stability of material.
Summary of the invention
The object of the present invention is to provide a kind of multi-element composite positive pole material for lithium secondary battery and preparation method thereof; To overcome the defective of present polynary positive pole material capacity and stability; Improve the specific capacity of material; The pattern and the particle diameter of while control material, thus reach the purpose that improves stability of material.
To achieve these goals, technical scheme of the present invention is:
A kind of multi-element composite positive pole material for lithium secondary battery, chemical formula are LiNi
xCo
yMn
zO
2, 0.5≤x≤1,0≤y≤0.2,0≤z≤0.3, x+y+z=1, spherical in shape, particle size distribution is narrow, consistency≤0.3, tap density>=2.2g/cm
3(gram/cubic centimetre).
A kind of multi-element composite positive pole material for lithium secondary battery preparation method:
The first step; In ratio in the chemical formula; Salting liquid with nickel, cobalt, manganese is a raw material, adopts the technology of crystallization control to be settled out shape, the narrow consistency of particle size distribution and the satisfactory Ni-Mn-Co sediment of tap density, and this sediment makes presoma through washing, drying;
Second step; In ratio in the chemical formula, the lithium compound of presoma and respective amount is together added in the agitator, add deionized water simultaneously; After Liquid Phase Diffusion is evenly mixed; Adopt spray-dired mode dry mixed material, mix in the crystal grain rank to guarantee two kinds of materials, and can prevent batch mixing the time to the destruction of material pattern;
In the 3rd step, material that drying is good dress burns boat goes into kiln and carries out once sinteredly, and the intact back of sintering material obtains stage material just through broken classification;
In the 4th step, the product dress that the 3rd step was obtained burns boat goes into kiln once more and carries out double sintering, double sintering accomplish the back material through sieve, classification acquisition finished product multi-element composite positive pole material for lithium secondary battery.
In the above-mentioned first step, crystallization control technology is in the ternary agitated reactor of band flow turbine circulation, under the protection of nitrogen or other inert gases,, to control sedimentary crystallization and grow up with the mode of batch operation as precipitation reagent with solubility alkali lye.Said solubility alkali lye is a kind of among hydroxide NaOH, KOH, the LiOH, or carbonate Na
2CO
3, NH
4HCO
3, K
2CO
3, (NH
4)
2CO
3In a kind of and ammoniacal liquor, the concentration of alkali has considerable influence to the speed of transition metal raw material deposition and sedimentary granularity and pattern, total concentration is controlled between the 1.5-5mol/L (mol).Said coprecipitation reaction temperature is 40-70 ℃, and the mixing speed of blender is 200-600r/min (gram/minute) during reaction, and the coprecipitation reaction time is 24-48 hour, and the pH value is controlled between the 10-12.
In the above-mentioned first step, cobalt salt is cobalt nitrate Co (NO
3)
2, cobalt chloride CoCl
2Or cobaltous sulfate CoSO
4In a kind of, nickel salt is nitric acid nickel (NO
3)
2, nickel chloride NiCl
2Or nickelous sulfate NiSO
4In a kind of, manganese salt is manganese nitrate Mn (NO
3)
2, manganese chloride MnCl
2Or manganese sulfate MnSO
4In a kind of, the concentration of salting liquid is 1.0-4.0mol/L.
In above-mentioned second step, lithium compound is that the organic salt, inorganic salts of lithium is (like lithium carbonate Li
2CO
3, lithium nitrate LiNO
3) or lithium hydroxide LiOH in any one, Li and metal Ni+Mn+CO mol ratio are 1.0-1.05, the deionized water addition be solid volume 3-5 doubly, mixing time is 3-8 hour.
In above-mentioned the 3rd step, once sintered temperature is 450-600 ℃, and sintering time is 4-112 hour.
In above-mentioned the 4th step, the double sintering temperature is 700-1000 ℃, and sintering time is 6-24 hour.
After adopting such scheme; The present invention utilizes each element ratio of the polynary mixed system of optimization particularly to improve the specific capacity that the Ni constituent content improves material; Adopt the means of physics to come the pattern and the particle diameter of control material simultaneously, thereby reach the purpose that improves stability of material.Selected crystallization control coprecipitation method, drying process with atomizing and two-step sintering means all are the special process of setting in order to guarantee material to obtain best pattern in the manufacture of materials process in addition.
The invention has the advantages that: in special reaction vessel; The crystallization effect of control precipitation process; Can synthesis of densified spherical, the narrow presoma product of particle size distribution; This technology can strictness be controlled the ratio of Ni, Co, three kinds of elements of Mn in addition, and guarantees that Ni, Co, three kinds of elements of Mn reach molecular level and mix.Adopt the spray-dired batch mixing means of liquid-phase mixing not only to guarantee the degree that mixes of Li compound and presoma, also avoided the presoma pattern to be damaged simultaneously.Adopt the mode of double sintering; In sintering process through the maximum fine powder content in the control material of multiple fractionation; Improve the homogeneity that material particle size distributes, can also improve the structure cell of material in addition and grow, guaranteed that material possesses good physics and chemical property.
Description of drawings
Fig. 1 is the LiNi that the embodiment of the invention 1 provides
0.5Co
0.2Mn
0.3O
2The X diffracting spectrum of positive electrode;
Fig. 2 is the LiNi that the embodiment of the invention 1 provides
0.5Co
0.2Mn
0.3O
2The particle size distribution figure of positive electrode;
Fig. 3 is the LiNi that the embodiment of the invention 1 provides
0.5Co
0.2Mn
0.3O
2The SEM figure (Scanning electron microscope sem observation figure) of positive electrode;
Fig. 4 is the LiNi that the embodiment of the invention 1 provides
0.5Co
0.2Mn
0.3O
2The charging and discharging curve figure of positive electrode (potential region: 3-4.2V, 1C multiplying power), abscissa is charging and discharging capacity (mAh/g), ordinate is charging/discharging voltage scope (V);
Fig. 5 is the LiNi that the embodiment of the invention 1 provides
0.5Co
0.2Mn
0.3O
2Capacity-the cycle graph of positive electrode (potential region: 3-4.2V, 1C multiplying power), abscissa is a cycle-index, ordinate is discharge capacity (mAh).
Embodiment
Embodiment 1:
With Mn (NO
3)
2, Co (NO
3)
2, Ni (NO
3)
2Mn in molar ratio
2+/ Co
2+/ Ni
+=3: 2: 5 mixed, be dissolved in the deionized water, be made into [Mn
2++ Co
2++ Ni
+] the metal ion total concentration is the mixing salt solution of 2.0mol/L, configuration concentration is the NaOH solution of 4mol/L, configuration concentration is the 6.0mol/L ammonia spirit.To mix the ternary agitated reactor that three kinds of solution (salting liquid, NaOH solution and ammonia spirit) and stream slowly are added dropwise to the circulation of band flow turbine; Under the protection of nitrogen or other inert gases; Control sedimentary crystallization and grow up with the mode of batch operation, control reaction temperature is 50 ℃, and mixing speed is 600r/min; The pH value is 11, and the reaction time is 48 hours.Reaction accomplish the back use deionized water repeatedly washing reaction product to the pH value of filtrating be neutrality, 100 ℃ of dryings of warp obtained compact crystallization (tap density>=2.2g/cm in 12 hours again
3), spherical morphology, the presoma of granularity narrow (consistency is 0.2).
According to the metal ion mol ratio is that the ratio of Li/ (Co+Ni+Mn)=1.05 takes by weighing Li
2CO
3With nickel cobalt manganese presoma, will weigh up material and put into mixer, add and 3: 1 deionized water of solid material volume ratio simultaneously; Open paddle; Mixed material behind 6 hours even batch mixings of Liquid Phase Diffusion, carries out spray drying with mixed slurry suction spray dryer; Guaranteeing that two kinds of materials mix in the crystal grain rank, and can prevent batch mixing the time to the destruction of material pattern.
The dried material burning boat of packing into is sent the tunnel kiln sintering to, is warmed up to 700 ℃ with 5 ℃/min, is incubated 10 hours, and cooling obtains stage material just then, first stage material is broken, sieve, classification (these are ripe production technologies) obtains primary product.With the primary product burning boat of packing into once more; Send tunnel kiln to and carry out double sintering, be warmed up to 950 ℃, be incubated 15 hours with 5 ℃/min; Cooling obtains the double sintering product then, the double sintering product through sieve, classification obtains the prepared multi-element composite positive pole material for lithium secondary battery of the present invention.
Adopt thermoelectric (the Thermo Elemental U.S.A) inductively coupled plasma atomic emission of the U.S. to measure the content of metal ion in the product, confirm that it consists of LiNi
0.5Co
0.2Mn
0.3O
2X-ray diffractometer (the Cu K that adopts German Brooker company to produce
aRadiation, λ=1.5406) characterize product structure, its XRD test result is as shown in Figure 1, and product is the single a-NaFeO of crystalline phase
2Structure LiNi
0.5Co
0.2Mn
0.3O
2, layer structure material is usually with R=(I
006+ I
102)/I
101Come the chemical property of exosyndrome material, generally speaking the performance of the electrical property of the more little material of R value is good more, and is through calculating embodiment 1 prepared product R=0.3995, less relatively.The particle size distribution that adopts Britain Ma Erwen laser particle size distribution instrument to test product, test result is as shown in Figure 2, and particle size distribution is very narrow, and consistency is 0.2.The pattern of material that adopted the FDAC scanning electron microscope test, the result is as shown in Figure 3, and material granule is a regular spherical, D
Min>=4 μ m (micron) do not have the small chip of fine powder and other to exist.
Performance for the anode material for lithium-ion batteries of testing present embodiment preparation.Get 91 parts of the products of present embodiment preparation; Conductive agent Super P:2.5 part and KS-6:2.5 part; Kynoar PVDF:4 part adds processes slurry after an amount of N-methyl pyrrolidone mixes, and processes pole piece through the coating machine coating, in argon circulation glove box, their same diaphragm papers, charcoal negative pole and electrolyte is assembled into Experimental cell then; Its charge/discharge capacity of test and cycle performance on new prestige cell tester, its Electrochemical results such as Fig. 4, shown in Figure 5.Test result: products therefrom is in the 3-4.2V interval, and 1C discharges and recharges, current density 150mA/cm
2, reversible specific capacity is 158.3mAh/g first, 100 times circulation back capability retention is that 97.2%, 300 circulation volume conservation rate is 96.1%.
Embodiment 2:
With Mn (NO
3)
2, Co (NO
3)
2, Ni (NO
3)
2Mn in molar ratio
2+/ Co
2+/ Ni
+=2: 2: 6 mixed in dissolving and the deionized water, is made into [Mn
2++ Co
2++ Ni
+] the metal ion total concentration is the mixing salt solution of 1.5mol/L, configuration concentration is the NaOH solution of 3mol/L, configuration concentration is the 5mol/L ammonia spirit.Three kinds of solution and stream slowly are added dropwise to the ternary agitated reactor that band flow turbine circulates; Under the protection of nitrogen or other inert gases; Control sedimentary crystallization and grow up with the mode of batch operation, control reaction temperature is 60 ℃, and mixing speed is 400r/min; The pH value is 11.5, and the reaction time is 36 hours.Reaction accomplish the back use deionized water repeatedly washing reaction product to the pH value of filtrating be neutrality, 100 ℃ of dryings of warp obtained compact crystallization in 12 hours, spherical morphology, the presoma that particle size distribution is good again.
Batch mixing-drying process is with embodiment 1, do not do at this and gives unnecessary details.
The dried material burning boat of packing into is sent the tunnel kiln sintering to, is warmed up to 600 ℃ with 5 ℃/min, is incubated 10 hours, and cooling obtains stage material just then, first stage material is broken, sieve, classification obtains primary product.With the primary product burning boat of packing into once more; Send tunnel kiln to and carry out double sintering, be warmed up to 900 ℃, be incubated 15 hours with 5 ℃/min; Cooling obtains the double sintering product then, the double sintering product through sieve, classification obtains the prepared multi-element composite positive pole material for lithium secondary battery of the present invention.
Detection means is with embodiment 1: the present embodiment product is the a-NaFeO of single crystalline phase through XRD test product
2, R=0.4124; Detect through inductively coupled plasma atomic emission spectrometer ICP-AES, confirm that it consists of LiNi
0.6Co
0.2Mn
0.2O
2Through the laser particle analyzer analysis, the particle size distribution consistency is 0.2; Through sem analysis, material granule is regular spherical, no fine particle and chip; Material discharges and recharges in the 3-4.2V interval, current density 150mA/cm
2, reversible specific capacity is 165.5mAh/g first, 100 times circulation back capability retention is that 95.8%, 300 circulation volume conservation rate is 91.6%.
Embodiment 3
With Mn (NO
3)
2, Co (NO
3)
2, Ni (NO
3)
2Mn in molar ratio
2+/ Co
2+/ Ni
+=2: 1: 7 mixed in dissolving and the deionized water, is made into [Mn
2++ Co
2++ Ni
+] the metal ion total concentration is the mixing salt solution of 1.8mol/L, configuration concentration is the NaOH solution of 2.5mol/L, configuration concentration is the 5mol/L ammonia spirit.Three kinds of solution and stream slowly are added dropwise to the ternary agitated reactor that band flow turbine circulates; Under the protection of nitrogen or other inert gases; Control sedimentary crystallization and grow up with the mode of batch operation, control reaction temperature is 60 ℃, and mixing speed is 300r/min; The pH value is 11, and the reaction time is 36 hours.Reaction accomplish the back use deionized water repeatedly washing reaction product to the pH value of filtrating be neutrality, 100 ℃ of dryings of warp obtained compact crystallization in 12 hours, spherical morphology, the presoma that particle size distribution is good again.
Batch mixing-drying process is with embodiment 1, do not do at this and gives unnecessary details.
The dried material burning boat of packing into is sent the tunnel kiln sintering to, is warmed up to 450 ℃ with 5 ℃/min, is incubated 10 hours, and cooling obtains stage material just then, first stage material is broken, sieve, classification obtains primary product.With the primary product burning boat of packing into once more; Send tunnel kiln to and carry out double sintering, be warmed up to 800 ℃, be incubated 20 hours with 5 ℃/min; Cooling obtains the double sintering product then, the double sintering product through sieve, classification obtains the prepared lithium rechargeable battery composite positive pole of the present invention.
Detection means is with embodiment 1, and the present embodiment product is the a-NaFeO of single crystalline phase through XRD test product
2, R=0.4286; Detect through ICP-AES, confirm that it consists of LiNi
0.7Co
0.1Mn
0.2O
2Through the laser particle analyzer analysis, the particle size distribution consistency is 0.2; Through sem analysis, material granule is regular spherical, no fine particle and chip; Material discharges and recharges in the 3-4.2V interval, current density 150mA/cm
2, reversible specific capacity is 178.9mAh/g first, 100 times circulation back capability retention is that 94.5%, 300 circulation volume conservation rate is 89.2%.
Comparative Examples 1
Except settling apparatus being changed into the common response still, other experimental procedures are with embodiment 1.Experiment shows: deposition is accomplished disposed slurry and is gluey, is difficult to washing and separates, and adopts sem analysis in addition, is precipitated as irregular reunion shape particle, and the particle size distribution consistency is very poor.The final products electric performance test is the result show, material discharges and recharges in the 3-4.2V interval, current density 150mA/cm
2, reversible specific capacity is 148.7mAh/g first, 100 times circulation back capability retention is that 84.5%, 300 circulation volume conservation rate is 72.1%.
Comparative Examples 2
It is medium that presoma and lithium compound hybrid mode are changed into alcohol, stirring ball-milling 2 hours, and bake drying, all the other steps are with embodiment 1.Experiment shows, because the mechanical milling process ball has than the havoc effect granular precursor, is destroyed through the spherical morphology of sem analysis material, has more chip and particulate to mix and is attached to particle gap and particle surface, and the particle size distribution consistency is relatively poor.The final products electric performance test is the result show, material discharges and recharges in the 3-4.2V interval, current density 150mA/cm
2, reversible specific capacity is 153.6mAh/g first, 100 times circulation back capability retention is that 92.6%, 300 circulation volume conservation rate is 86.6%.
Comparative Examples 3
Deposition and mixing procedure are with embodiment 1, and sintering process changes into, is warmed up to 900 ℃ with 5 ℃/min, is incubated 20 hours, cooling then, and material sieves, classification obtains product.Experiment shows that raw meal particle size distribution and pattern are slightly poor than embodiment 1 product, and there are some chips in the product particle surface.Through XRD test product is the a-NaFeO of single crystalline phase
2But, R value more greatly 0.4546; The final products electric performance test is the result show, material discharges and recharges in the 3-4.2V interval, current density 150mA/cm
2, reversible specific capacity is 143mAh/g first, 100 times circulation back capability retention is that 93.5%, 300 circulation volume conservation rate is 85.6%.
With the chemical composition of the foregoing description and Comparative Examples, electro-chemical test condition, discharge capacity, 100 circulation volume conservation rates, 300 circulation volume conservation rates tabulations first as follows:
The composition of table 1 electrode material and chemical property
The sample title |
Chemical composition |
The electro-chemical test condition |
Discharge capacity (mAh/g) first |
100 circulation volumes keep (%) |
300 circulation volumes keep (%) |
Embodiment 1 |
LiNi
0.5Co
0.2Mn
0.3O
2 |
3-4.2V, 1C |
158.3 |
97.2 |
96.1 |
Embodiment 2 |
LiNi
0.6Co
0.2Mn
0.2O
2 |
3-4.2V, 1C |
165.5 |
95.8 |
91.6 |
Embodiment 3 |
LiNi
0.7Co
0.1Mn
0.2O
2 |
3-4.2V, 1C |
178.9 |
94.5 |
89.2 |
Comparative Examples 1 |
LiNi
0.5Co
0.2Mn
0.3O
2 |
3-4.2V, 1C |
148.7 |
84.5 |
72.1 |
Comparative Examples 2 |
LiNi
0.5Co
0.2Mn
0.3O
2 |
3-4.2V, 1C |
153.6 |
92.6 |
86.6 |
Comparative Examples 3 |
LiNi
0.5Co
0.2Mn
0.3O
2 |
3-4.2V, 1C |
143 |
93.5 |
85.6 |
Visible by last table, material specific capacity height provided by the invention and good stability.Through improvement, the optimization of the present invention to ternary material pattern and composition, obviously improved the reversible capacity of ternary material, overcome the relaxation phenomenon of material capacity in cyclic process simultaneously, obviously improve the cycle life of material.