锂离子电解液的介绍英文PPT

Face these challenges, what we can do?
LiBOB or LiPF6 , which is suitable?
Since a new lithium salt-lithium bis(oxalate)borate was disclosed by Lischka 1999 firstly , and it was successfully syntheticed by the united states air force laboratory in 2000. A novel lithium salt, (LiBOB), which possesses good film-forming property and high thermal stability, is becoming the most potential salt to replace commercial LiPF6 for lithium-ion battery electrolytes in recent years.
Solute
LiPF6 ,LiBF4,LiClO4,LiAsF6,LiCF3SO. Conductivity: LiAsF6> LiPF6 >LiClO4>LiBF4 Thermal stability: LiAsF6>LiBF4 > LiPF6 Resistnce to oxidation: LiAsF6 > LiPF6 >LiBF4 >LiClO4
Characteristics of salt
Electrolyte salt LiClO4 advantages High conductivity disadvantages Strong oxidant Bad high temperature Performance and unsafe Toxic, high cost Bad thermal stability Sensitive to water Bad thermal stability
2、On the solid electrolyte interface It is possible to modify the anode surface chemistry by using active additives in solutions, whose reduction may form higly compact insoluble films. Eg: PC-based electrolyte Vinylene Carbonate to form a stable SEI layer.
1. Organic Solvent 2. Electrolyte Salt 3. Electrolyte Additives 4. Current development situation
Electrolyte additives – three primary functions
1、on the conductivity Freezing point, viscosity, dielectric constant and donating number of solvent. Eg: LiPF6 ,LiBF4,LiClO4,LiAsF6,LiCF3SO. DMC ,DEC , EMC`````
DMC It has completed the insulating or resistant to high temperatures, high flash point, low freezing point. It can works between long-term 5℃ ~ 80℃, excellent water resistence. Non-toxic, insipidity.
Vinylene Carbonate to form a stable SEI layer.
Q↑
C↑
ξ↑
Add VC quantity and circulation performance relationship
0.3C
1C
Add VC additives and different temperature discharge properties
1.on the conductivity
Salt(1mol/L) Co-sovent Specific conductivity(ms/cm)
Li(CF3SO2)2N
DMC DEC MP
9.2 6.5 8.8 11.2 7.8 10.3
LiPF6
DMC DEC MP
Electrolyte additives – three primary functions
Face these challenges what we can do?
Electrolyte additives are one of significant measurements for safety currently recognized of lithium batteries. You can improve the all kinds of performance by adding different additives.
1 2
EC+DEC+DMC (3.5:2.5:2.5) EC+DMC+EMC+ DEC (4:2:3:1) EC+DEC+DMC (1:1:0.8) EC+EMC+DMC (1.1:0.9:2.1) EC+DMC (1:1.5)
344 355
3
93.64
623
98.4
94.4
79.3
397
4
91.93
Two salts, have each their preponderance
Two salts, have each their preponderance
Room temperature
65℃
LiBOB
LiBOB formed a good crystalline phase and as show in XRD patterns, the impurity reduced. The conductivity of LiBOB based electrolyte is the half of that of LiPF6 counterpart from 0℃to 80℃ .In half cell, LiBOB has a superior chargedischarge capacity at elevated temperature than that of LiPF6
solvent
PC (PropyleneCarbonate) C4H6O3 EC (EthyleneCarbonate) C3H4O3 DEC (DimethylCarbonate) (key to SEI) DMC (Dimethyl cyclosiloxane)
DMC today's synthetic organic "new foundation".
LiAsF6 LiPF6 LiBF4
High conductivity Good thermal stability High conductivity High conductivity
At present LiPF6 is the common lithium salt which uses in commodity lithium-ion batteries. LiPF6 has poor hydrolysis stability and thermal stability and the hydrolysis product HF would adversely affected the performance of battery. The effective SEI film formed in the surface of the negative electrode only when LiPF6 and ethylene carbonate (EC) combining used. But high melt point (37℃) of EC become the limitation of the using of batteries at lower temperature.
The influence of solvent composition of the capacity holding rate and cycle characteristics of Li-ion battery
N O Composition of solvent(V/V) Capacity holding rate(%) 92.92 93.16 0.2C Capacity /mAh 632 639` 0.5C Capacity ratio/% 98.6 98.5 1C Capacity ratio/% 96.3 94.5 2C Capacity ratio/% 85.1 78.7 Cycle life
Tip Of The Iceberg for Electrolytes
CATALOGUE
1. Organic Solvent 2. Electrolyte Salts 3. Electrolyte Additives 4. Current development situation
Electrolytes are one of four key material （ cathode, anode, electrolyte material and separator ） and called as blood of Li-ion batteries .they are in proportion of preparation of high concentration organic solvent, electrolyte salt and other raw materials. in given conditions.