The first generation electrolyte: PC + DME + 1M LiPF6 has poor compatibility with the negative graphite electrode and is prone to solvent co-intercalation.
The second generation electrolyte: EC + DMC (or DEC) + 1M LiPF6 has poor performance at low temperatures.
The third generation electrolyte: EC + DMC (DEC) + EMC + 1M LiPF6, the conductivity can reach 10-2S.cm-1, >50%.
Currently, most works focus on the selection of additives to improve the first charge and discharge efficiency of the battery and improve the stability of the SEI.
Liquid electrolyte solution: Lithium-ion batteries use an aprotic organic solvent dissolved in lithium salt as the electrolyte. The organic electrolyte participating in the formation of the SEI film on the surface of the negative electrode, it has a significant impact on the performance of the battery.
As an electrolyte for lithium batteriesum-ion, it must meet the following basic conditions:
① It has good chemical stability and a wide electrochemical window.
② High conductivity.
③ It has good compatibility with negative electrode materials and can form stable SEI film.
④ Wide operating temperature range (-40-60℃).
⑤ Low prices and easy to obtain materials.
⑥ Non-toxic, non-polluting.
★ Solvent part:
Aprotic organic solvent. To achieve the highest possible conductivity, binary or multi-component solvents are often used.
a. PC propylene carbonate (propylene carbonate).
b. Ethylene carbonate EC (ethylene carbonate).
c. DEC (dimethyl carbonate).
d. Propiolic acid methyl ester.
e. 1,4-Butyrolactone GBL (γ-Butyrolactone).
★ Solute part:
a. LiPF6 (mainly).
b.LiBF4.
c.LiClO4.
d. LiAsF6.
e, LiCF3SO3, etc.
A, cyclic carbonate (cyclic carbonate)
EC (ethylene carbonate) and PC (propylene carbonate) commonly used:< /p> p>< p>① Phosgene method --- Using the reaction of the diol compound ﹝glycol﹞ with phosgene
CH2OHCH2OH + COCl2 -------> (CH2O)2CO + 2 HCl
② Carbon dioxide synthesis method CH2OCH2 + CO2 -------> (CH2O)2CO
B, chain carbonate compounds
C, DMC ( dimethyl carbonate) and DEC (diethyl carbonate) commonly used:
① Carbon monoxide synthesis method: 2CH3OH + CO + 1/2 O2 -------> (CH3O)2CO + H2O
② Transesterification method: C2H5OH + (CH3O)2CO -------> CH3OCOOC2H5 + CH3OH
★ Development of polymer electrolyte (polymer electrolyte):< /p>
① Dry polymer Electrolyte: Polymer doped with lithium salt to form "polymerization" Material -lithium-ion complex".
Due to the low conductivity of lithium ions at room temperature (about 10-8s.cm-1), it is difficult to meet the application requirements
② Plasticized polymer electrolyte (plasticized polymer electrolyte): using plasticized polymer electrolyte plasticization method, the solution of organic electrolyte is added as a plasticizer into the network structure formed by the polymer matrix material (such as polymethyl methacrylate PMMA, polyacrylonitrile PAN, polyvinylidene fluoride PVDF) and fixed.
The conductivity can reach 10-4——10-3s.cm-1, which is close to the conductivity of liquid phase solution, can meet practical requirements and has been put into application practical (marketed polymer lithium ion battery).
Microbatteries can be divided into two broad categories. One type is micro alkaline batteries, including silver oxide batteries, mercury batteries, zinc-air batteries, zinc-nickel batteries, zinc-manganese batteries,cadmium-nickel, cadmium-mercury batteries, etc. ; , Including lithium manganese batteries, lithium thionyl chloride batteries, lithium chromic acid batteries, lithium iron sulfide batteries and more than a dozen types. The negative electrode of these batteries is metallic lithium, hence the name lithium battery. Some lithium batteries use organic solvents as electrolytes, such as lithium-manganese batteries; some use inorganic solvents as electrolytes, such as lithium-thionyl chloride batteries; and some use solid electrolytes, such as lithium-iodine batteries.
Micro batteries can also be divided into primary and secondary batteries, called primary micro cells and storage micro batteries, respectively. Since the liquid leakage problem of micro batteries has not been solved, the lifespan of alkaline micro batteries does not exceednot 10 years old.
The most commonly used and commonly used micro-battery is the zinc-silver oxide button cell, called a silver oxide cell. There are three types of silver oxide batteries: monovalent silver oxide (Ag2O) as the positive electrode, divalent silver oxide (AgO) as the positive electrode, and silver oxide batteries. silver button type. Its basic performance is shown in the table. Compared with silver oxide batteries, lithium batteries have a wide voltage range, good sealing, long storage time, wide operating temperature range, and are suitable for microwaves.Advantages of the slimming and slimming. The disadvantage of lithium batteries is their low current output capacity. However, due to the rapid development of ultra-large-scale integrated circuits, the power consumption of microelectronic devices has been further reduced, so this disadvantageient of lithium batteries is no longer important. Since the 1980s, lithium batteries have gradually replaced the widely used silver oxide batteries.