Summary of the invention
The present invention is intended to effectively to overcome lithium manganate having spinel structure and stratiform cobalt acid lithium and the stratiform lithium nickelate limitation separately as the positive source material, and provide a kind of excellent combination property, with low cost, capacity is high, the little lithium rechargeable battery of capacity attenuation under the Heat stability is good, good heavy current, high temperature.
For achieving the above object, according to a kind of lithium rechargeable battery of the present invention, comprise positive pole, negative pole, electrolyte and barrier film, it is characterized in that, the active material of described positive pole is gone up substantially by lithium manganate having spinel structure and tertiary cathode material and is formed, and the ratio of described lithium manganate having spinel structure and tertiary cathode material is 1~9: 9~1 scope.
According to lithium rechargeable battery of the present invention, the chemical formula of described lithium manganate having spinel structure is Li
1+XMn
2-yM
xO
4, wherein M is element M g, Ca, and Sr, Ba, Ti, Cr, Fe, Co, Ni, Cu, at least a among the Al, the value of X is-0.15~0.15, the value of Y is 0~0.5.
According to lithium rechargeable battery of the present invention, the chemical formula of described tertiary cathode material is LiNi
yMn
yCo
1-2yO
2, the value of Y is greater than 0 less than in 0.5 the scope, described tertiary cathode material is preferably LiNi
0.1Mn
0.1Co
0.8O
2, LiNi
0.2Mn
0.2Co
0.6O
2, LiNi
1/3Mn
1/3Co
1/3O
2, most preferably be LiNi
1/3Mn
1/3Co
1/3O
2
According to lithium rechargeable battery of the present invention, the mixed proportion of described lithium manganate having spinel structure and tertiary cathode material is 3~7: 7~3, and the particle grain size scope of lithium manganate having spinel structure and tertiary cathode material is between 5~40 μ m.
According to lithium rechargeable battery of the present invention, the active material of described positive pole also comprises adhesive, conductive agent and solvent.
According to lithium rechargeable battery of the present invention, described adhesive is selected from the group of being made up of fluororesin, polyethylene, polyvinyl alcohol; Described conductive agent is selected from material with carbon elements such as carbon black, graphite; Described solvent is selected from the group of being made up of N-methyl pyrrolidone, dimethylformamide, absolute ethyl alcohol.
According to lithium rechargeable battery of the present invention, spinelle shape LiMn2O4 is 1.5~8 with the average grain diameter ratio of tertiary cathode material, and preferred average grain diameter ratio is 2~6.
According to a kind of anode active material composition of the present invention, basically form by lithium manganate having spinel structure and tertiary cathode material, the ratio of described lithium manganate having spinel structure and tertiary cathode material is 1~9: 9~1 scope, the chemical formula of wherein said lithium manganate having spinel structure are Li
1+XMn
2-yM
xO
4, wherein M is element M g, Ca, and Sr, Ba, Ti, Cr, Fe, Co, Ni, Cu, at least a among the Al, the value of X is-0.15~0.15, the value of Y is 0~0.5; The chemical formula of described tertiary cathode material is LiNi
yMn
yCo
1-2yO
2, the value of Y greater than 0 less than 0.5 scope in.
According to a kind of method of making the positive plate of lithium rechargeable battery of the present invention, may further comprise the steps:
Anode active material composition is provided, described composition is made up of lithium manganate having spinel structure and tertiary cathode material basically, the ratio of described lithium manganate having spinel structure and tertiary cathode material is 1~9: 9~1 scope, the chemical formula of wherein said lithium manganate having spinel structure are Li
1+XMn
2-yM
xO
4, wherein M is element M g, Ca, and Sr, Ba, Ti, Cr, Fe, Co, Ni, Cu, at least a among the Al, the value of X is-0.15~0.15, and the value of Y is 0~0.5, and the chemical formula of described tertiary cathode material is LiNi
yMn
yCo
1-2yO
2, the value of Y greater than 0 less than 0.5 scope in;
Add adhesive, conductive agent and solvent;
Mix, apply, oven dry, compressing tablet, obtain the positive plate of lithium rechargeable battery.
The method according to this invention, wherein said adhesive is selected from the group of being made up of fluororesin, polyethylene, polyvinyl alcohol; Described conductive agent is selected from material with carbon elements such as carbon black, graphite; Described solvent is selected from the group of being made up of N-methyl pyrrolidone, dimethylformamide, absolute ethyl alcohol, described spinelle shape LiMn2O4 is 1.5~8 with the average grain diameter ratio of tertiary cathode material, be preferably 2~6, the particle grain size scope of described lithium manganate having spinel structure and tertiary cathode material is between 5~40 μ m.
Contribution of the present invention is, it has overcome lithium manganate having spinel structure and the stratiform cobalt acid lithium basic unit shape lithium nickelate limitation separately as the positive source material.The tertiary cathode material that expands when lithium manganate having spinel structure that when charging shunk, expands during discharge and charging, shrinks during discharge mix use after, except can when discharging and recharging, forming the complementation on the change in volume, active material is interionic to be dissociated thereby reduce, keep outside the higher current collecting efficiency, tertiary cathode material can also suppress the overdischarge on the LiMn2O4 particle effectively, thereby suppresses the generation of the Jahn-Teller effect of lithium manganate having spinel structure.In addition, lithium manganate having spinel structure can play inhibitory action to the orientation trend of tertiary cathode material.So just can obtain with low cost, capacity is high, the little nonaqueous lithium ion secondary cell of capacity attenuation under the Heat stability is good, good heavy current, high temperature.
Embodiment
Below by embodiment the present invention being further explained and illustrating that these embodiment are used for illustrative purposes, is not the restriction to protection scope of the present invention.
The invention provides a kind of lithium rechargeable battery, this battery comprises positive pole, negative pole, electrolyte and barrier film, it is characterized in that, the active material of described positive pole is gone up substantially by lithium manganate having spinel structure and tertiary cathode material and is mixed, its purpose mainly is, lithium manganate having spinel structure and tertiary cathode material can form the complementation on the change in volume when discharging and recharging, thereby reduce dissociating between active material particle, keep higher current collecting efficiency.In addition, because the tertiary cathode material electron conductivity is than lithium manganate having spinel structure height, therefore overdischarge at first occurs on the tertiary cathode material particle, this tertiary cathode material can effectively suppress the overdischarge on the LiMn2O4 particle like this, thereby suppresses the generation of the Jahn-Teller effect of lithium manganate having spinel structure; Moreover lithium manganate having spinel structure can play inhibitory action to the orientation trend of tertiary cathode material.
To achieve these goals, lithium manganate having spinel structure and tertiary cathode material are by the mixed of 1~9: 9~1 (weight portions), and its preferred proportion is 3~7: 7~3.
In use, because the lithium manganate having spinel structure specific discharge capacity is lower, and tap density is slightly little, thereby causes lithium manganate having spinel structure hierarchy number specific capacity very low.In order to satisfy the capacity requirement of battery, when using mixed cathode active material, must increase the anode dressing amount, thereby need more anode dressing density, need bigger pressure to come compressing tablet during the positive plate film-making.If the lithium manganate having spinel structure average grain diameter is less than the tertiary cathode material average grain diameter, just can't the orientation trend of tertiary cathode material under the high pressure be suppressed, tertiary cathode material takes place parallel-oriented with respect to collector body, the channel parallel of lithium ion migration is in collector body, and the electrolyte impregnability is not high, cause the difficulty of lithium ion migration, this problem is especially outstanding when heavy-current discharge.
If the average grain diameter of lithium manganate having spinel structure is greater than the average grain diameter of tertiary cathode material, spinelle shape LiMn2O4 just can suppress the orientation of tertiary cathode material, promptly when applying big pressure, the pressure between lithium manganate having spinel structure and the tertiary cathode material will suitably be disperseed.
It is 1.5~8 that the present invention requires the lithium manganate having spinel structure and the average grain diameter ratio of tertiary cathode material, and its preferred average grain diameter ratio is 2~6.
Satisfying under the prerequisite of above-mentioned size ratio; if the average grain diameter of lithium manganate having spinel structure is little; then the particle of tertiary cathode material can be littler; in order to obtain the positive plate of satisfactory dressing density; need to use bigger pressure; thereby the orientation of tertiary cathode material is increased, and can cause the infiltration difficulty of electrolyte.If the average grain diameter of lithium manganate having spinel structure is excessive, then the particle of tertiary cathode material also needs corresponding increase, and this can cause the specific area of material to reduce, and reduces with the contact area of electrolyte, is unfavorable for battery performance.The particle grain size scope is between 5~40 μ m in the positive electrode of the present invention.
The chemical formula of the lithium manganate having spinel structure of mentioning among the present invention is Li
1+xMn
2-yM
yO
4, wherein, M is at least a among element M g, Ca, Sr, Ba, Ti, Cr, Fe, Co, Ni, Cu, the Al, and the value of x is-0.15~0.15, and the value of y is 0~0.5.This shows that the structure of lithium manganate having spinel structure is not limited to LiMn
2O
4Structure, the material that above-mentioned chemical formula is contained all can use, thereby improves the chemical property of this positive electrode, for example specific discharge capacity, normal temperature, high temperature cyclic performance, memory property, security performance or the like.
The chemical formula of the tertiary cathode material of mentioning among the present invention is LiNi
yMn
yCo
1-2yO
2, the material that said structure is contained all can use, the preferred LiNi of tertiary cathode material
0.1Mn
0.1Co
0.8O
2, LiNi
0.2Mn
0.2Co
0.6O
2, LiNi
1/3Mn
1/3Co
1/3O
2, LiNi most preferably
1/3Mn
1/3Co
1/3O
2Thereby, improved the chemical property of this positive electrode, for example specific discharge capacity, normal temperature, high temperature cyclic performance, memory property, security performance or the like.
In one embodiment, the active material of positive pole of the present invention is to be mixed by lithium manganate having spinel structure and tertiary cathode material, and add adhesive, conductive agent and solvent after mix, apply, oven dry, compressing tablet make.
Adhesive is fluororesin, polyethylene, polyvinyl alcohol etc.; Conductive agent is material with carbon elements such as black carbon, graphite; Solvent is N-methyl pyrrolidone, alkane ketone, dimethyl formamide, absolute ethyl alcohol etc.Adhesive, conductive agent and solvent that in this area other are suitable for also can use.
Lithium rechargeable battery according to the present invention comprises: positive pole, negative pole, electrolyte, barrier film.Described negative pole utilizes prior art, wherein this negative pole is coated on the collector body and oven dry by negative active core-shell material and corresponding binder, dispersant, solvent, compressing tablet makes, and described negative active core-shell material can use lithium metal, the lithium alloy material of doped lithium ion etc. that maybe can mix/go.Material as the doped lithium ion that can mix/go, example is a carbonaceous material, as the product and the chalcogenide of native graphite, Delanium, carbon black organic polymer, for example, it can be mix/go under the current potential lower in than the positive pole oxide and the sulfide of doped lithium ion.Adhesive can be fluorine resin and polyethylene, polyvinyl alcohol; Dispersant can be a cellulose; Solvent can be N-methyl pyrrolidone, dimethyl formamide, absolute ethyl alcohol.As the collector body that is used for negative pole, can be Copper Foil, stainless steel foil etc.But shape mesh-like, paper tinsel shape.This electrolyte is non-aqueous electrolyte, can use any suitable electrolyte of the prior art.Electrolyte in the electrolyte, the electrolytic salt that can use common nonaqueous electrolytic solution to use, for example LiPF
6, LiBF
4, LiAsF
6Deng lithium salts, consider from the oxidation stability angle, preferably select LiPF for use
6, LiBF
4Used solvent is an organic solvent in the electrolyte, can be in vinyl carbonate, ethylene carbonate, the diethyl carbonate one or more.Described barrier film can be nonwoven fabrics, synthetic resin microporous barrier, preferably uses the synthetic resin microporous barrier, is excellent with polyolefin microporous film again wherein, specifically has: polyethene microporous membrane, microporous polypropylene membrane, polyethylene polypropylene composite micro porous film.
Of the present invention focusing on, the active material that this is anodal basic composition is lithium manganate having spinel structure and tertiary cathode material, mixed proportion is 1~9: 9~1 (weight portions), and the average grain diameter of lithium manganate having spinel structure and tertiary cathode material ratio is 1.5~8: 1.The preferred LiNi of tertiary cathode material
1/3Mn
1/3Co
1/3O
2
In order to prepare the positive pole of lithium rechargeable battery provided by the invention, preparation or purchase obtain lithium manganate having spinel structure and tertiary cathode material according to known method, according to aforementioned proportion with the two mixing and add adhesive, conductive agent and solvent, mix, coating, oven dry, compressing tablet makes positive pole.Wherein mixing speed is controlled to be 300-6000rpm, and mixing time is controlled to be 0.2-10 hour, and described adhesive can be fluorine resin and polyethylene such as polytetrafluoroethylene, Kynoar, polyvinyl alcohol; Conductive agent is carbon black, graphite-like material with carbon element, and solvent is N-methyl pyrrolidone, dimethylformamide, absolute ethyl alcohol.
The preparation of lithium manganate having spinel structure sees also " fine-chemical intermediate ", 34 2 phases of volume, " different manganese dioxide prepare the research of lithium manganate having spinel structure " of Peng Aiguo etc.The preparation of tertiary cathode material can be adopted existing method, and for example, high temperature solid-state method, wet chemistry method also can be purchased, for example Shenzhen proud son of heaven scientific and technological development Co., Ltd from the market in conjunction with high temperature solid-state method, hydro thermal method and ion-exchange etc.
According to the following example, technical conceive that the present invention may be better understood and advantage.
Embodiment 1
At first getting structural formula is LiMn
2O
4Lithium manganate having spinel structure and tertiary cathode material LiNi
1/3Mn
1/3Co
1/3O
2The average grain diameter of control lithium manganate having spinel structure is 18 μ m, and the average grain diameter of tertiary cathode material is 9 μ m, and the size ratio of the two is 2: 1.
The lithium manganate having spinel structure of getting 8 parts (weight) mixes as positive electrode active materials mutually with 1 part of (weight) tertiary cathode material.Adopting the PVDF of 4% (weight) is adhesive, and (weight) acetylene black of 2% is conductive agent, and the NMP of surplus is a solvent.Under the speed of 300-6000rpm, stirred 0.2-10 hour, make it abundant mixing.Through coating, dry then, compressing tablet obtains the positive plate material.Wherein mix, be coated with, dry three processes and all need carry out under vacuum environment, the positive plate material that obtains behind the compressing tablet obtains positive plate according to specified size through after the cutting.
Adopt the prior art for preparing negative pole.With carbon dust and 2% (weight) acetylene black of 92% (weight) is conductive agent, and the NMP of surplus is that stirring solvent mixes, is coated with, oven dry, and compressing tablet makes negative plate after being cut into the size of appointment.
Adopt said method to make positive plate, negative plate, electrolyte are LiPF
6, solvent is a vinyl carbonate, ethylene carbonate, and the mixed organic solvents of diethyl carbonate, concentration is 1 mol, and diaphragm paper is a polyethylene, and polypropylene composite diaphragm paper makes lithium rechargeable battery of the present invention by common process.
With above-mentioned positive pole, negative pole, the lithium rechargeable battery that electrolyte and barrier film are assembled into, have with low cost, capacity height, Heat stability is good, good heavy current, the little advantage of capacity attenuation under the high temperature.The test result of concrete technical indicator is referring to table 1.
Embodiment 2~embodiment 7 has provided the example of the different mixing ratio of lithium manganate having spinel structure and tertiary cathode material, and the test result of its technical indicator sees Table 1.
Embodiment 2
The mixed proportion of lithium manganate having spinel structure and tertiary cathode material (weight portion) is that 7: 3 other processes are with embodiment 1 in this example.
Embodiment 3
The mixed proportion of lithium manganate having spinel structure and tertiary cathode material (weight portion) is that 5: 5 other processes are with embodiment 1 in this example.
Embodiment 4
The mixed proportion of lithium manganate having spinel structure and tertiary cathode material (weight portion) is that 3: 7 other processes are with embodiment 1 in this example.
Embodiment 5
The mixed proportion of lithium manganate having spinel structure and tertiary cathode material (weight portion) is that 1: 8 other process is with embodiment 1 in this example.
Comparative Examples 1~4 provided positive electrode be respectively lithium manganate having spinel structure and tertiary cathode material the experiment comparing result its results are shown in Table 1.
Comparative Examples 1
Positive electrode uses lithium manganate having spinel structure in this example, and other process is with embodiment 1.
Comparative Examples 2
Positive electrode uses tertiary cathode material in this example, and other process is with embodiment 1.
Comparative Examples 3
Positive electrode uses the mixed proportion (weight portion) 15: 1 of lithium manganate having spinel structure and tertiary cathode material in this example, and other process is with embodiment 1.
Comparative Examples 4
Positive electrode uses the mixed proportion (weight portion) 1: 15 of lithium manganate having spinel structure and tertiary cathode material in this example, and other process is with embodiment 1.
Battery performance test
Battery to embodiment and comparative example carries out performance, and is specific as follows:
Specific discharge capacity: after the battery charge, discharge into discharge capacity/positive electrode active materials quality of 3.0V with the electric current of 0.5C first from 4.2V, unit is mAh/g.
Circulation: be called a circulation to 4.2V and then with the 1C current discharge to 3.0V with the 1C current charges, the discharge capacity of acquisition is the capacity of this circulation, and unit is mAh.
High temperature circulation: under 60 ℃, be called a circulation to 4.2V and then with the 1C current discharge to 3.0V with the 1C current charges.
The discharge capacity that obtains is the capacity of this circulation, and unit is mAh.
100 circulation volume conservation rates: (the 100th time the circulation specific discharge capacity/specific discharge capacity first circulates) 100%, unit is %.
100 high temperature circulation capability retentions: (the 100th high temperature circulation specific discharge capacity/high temperature circulation specific discharge capacity) first 100%, unit is %.
High-rate performance: respectively with 1C, the 3C electric current discharges to battery, and relatively the size of its discharge capacity is labeled as 3C/1C, and unit is %.
Thermal stability: the battery that will be charged to 4.2V is dissected, and takes out positive plate, after the drying positive plate is taken off, and carries out the thermogravimetric experiment under air atmosphere, obtains the decomposition temperature of this material, and unit is ℃.
Test result is as shown in table 1.
Table 1
Sequence number | The mixed proportion of lithium manganate having spinel structure and tertiary cathode material (weight portion) | Specific discharge capacity/mAh/g | 100 circulation volume conservation rate/% | 100 high temperature circulation capability retention/% | High-rate performance 3C/1C/% | Thermal stability/℃ |
Embodiment 1 | 8∶1 | 95 | 90 | 77 | 79 | 280 |
Embodiment 2 | 7∶3 | 117 | 91 | 82 | 78 | 262 |
Embodiment 3 | 5∶5 | 125 | 91 | 88 | 78 | 238 |
Embodiment 4 | 3∶7 | 133 | 91 | 87 | 78 | 225 |
Embodiment 5 | 1∶8 | 127 | 91 | 88 | 75 | 217 |
Comparative Examples 1 | 1 | 105 | 89 | 55 | 73 | 295 |
Comparative Examples 2 | 0 | 145 | 97 | 90 | 52 | 302 |
Comparative Examples 3 | 15∶1 | 108 | 89 | 56 | 73 | 281 |
Comparative Examples 4 | 1∶15 | 142 | 93 | 85 | 75 | 203 |
As can be seen from Table 1, the mass ratio of lithium manganate having spinel structure and tertiary cathode material is 1~9 among the present invention: between 9~1, be preferably 3~7: between 7~3, battery has superior comprehensive electrochemical properties.Its specific discharge capacity is greatly improved with respect to the lithium manganate having spinel structure material, and (60 ℃) capacity attenuation is little under the high temperature, and high-rate performance is good, and positive electrode active materials charging back decomposition temperature improves a lot with respect to tertiary cathode material, and security performance is better.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.