The electrolyte is composed of a variety of substances, mainly the following:
Electrolyte
Lithium used in salts of the electrolyte, that is, various lithium-containing compounds release large quantities of active lithium ions when dissolved in solvents. Commonly used lithium salts include LiPF6, LiClO4, LiBF4, LiBOB, LiTFSI, LiAsF6, etc. Among them, LiPF6 is currently a relatively mature commercial lithium salt.
These lithium salts each have their own advantages and disadvantages. In actual use, LiPF6 is often used as the main one, and other types are added in appropriate quantities to achieve their advantages and improve the performance of the electrolyte. .
Solvent
Lithium batteries generally use organic solvents. The negative electrode potential of lithium-ion batteries is very close tothat of lithium and is not sufficiently stable in aqueous solution systems. This is why organic solvents are used as ion carriers.
Common types of solvents for lithium battery electrolytes include carbonates, ethers, and hydroxy acid esters.
In order to improve the conductivity of the electrolyte, it is theoretically appropriate to choose a solvent capable of supplying as many active lithium ions as possible to the solution, i.e. the solubility of the electrolyte it contains is high, and the degree of dissociation of the solute molecules must also be high; the dielectric constant of the solvent is high and the viscosity is low. In fact, solvents with high dielectric constants also have high viscosity and should be selected based on actual conditions.
Additives
Additives refer to a small amount of substances aadded to the electrolyte other than the solute. It generally cannot store electricity. is to improve the performance of the electrolyte, improve the stability of the battery, etc.
Be sure to ensure the purity of the electrolyte before measuring it. Professional electrolyte filtration equipment can be used for filtration.
Professional electrolyte filtration equipment
Lithium battery electrolyte is an important component of the battery and has a great impact on the performance of the battery. battery.
In traditional batteries, the electrolytic system uses water as a solvent.
However, since the theoretical voltage for water decomposition is only 1.23 V, even taking into account the overpotential of hydrogen or oxygen, the maximum voltage of the battery with an electrolytic system using water as a solvent is only about 2 V (like a batterylead).
The voltage of lithium batteries reaches 3-4V. The traditional aqueous solution system is obviously no longer suitable for the needs of batteries, and a non-aqueous electrolyte system must be used as the electrolyte of lithium-ion batteries.
Lithium battery electrolytes mainly use organic solvents and electrolytes that can withstand high voltages without decomposing.
The electrolyte used in lithium-ion batteries is an ionic conductor with electrolytic lithium salt dissolved in an organic solvent.
Generally, as an organic electrolyte for practical lithium-ion batteries, it should have the following properties: (1) High ionic conductivity, which should generally reach 10-3——2*10- 3S/cm;
The migration number of lithium ions should be close to 1;
(2) The potential range of electrochemical stability is wide;
It there must bene electrochemical stability window from 0 to 5 V;
(3) Thermal Good stability, wide operating temperature range;
(4) Stable chemical properties, no chemical reaction with the current collector and mild substances in the battery;
(5) Safe and low-toxic, preferably biodegradable.
Suitable solvents should have a high dielectric constant and low viscosity. Commonly used solvents include alkyl carbonates such as PC and EC, which are highly polar and have a high dielectric constant, but have high viscosity and intermolecular forces. , lithium ions move slowly there.
Linear esters such as DMC (dimethyl carbonate) and DEC (diethyl carbonate) have a low viscosity but also a low dielectric constant. Therefore, in order to obtain high ionic conductivity, for liquid solutions, solvents mixts such as PC+. DEC and EC+DMC are generally used.
These organic solvents have some odor, but generally speaking, they can meet EU RoHS and REACH requirements. These are very toxic and environmentally friendly materials.
The currently developed inorganic anion conductive salts mainly include three categories: LiBF4, LiPF6 and LiAsF6. Their conductivity, thermal stability and oxidation resistance are in the following order: Conductivity: LiAsF6≥LiPF6>LiClO4>LiBF4 Thermal stability. : LiAsF6>LiBF4>LiPF6 Oxidation resistance: LiAsF6≥LiPF6≥LiBF4>LiClO4 LiAsF6 has very high conductivity, stability and battery charge and discharge rate, but arsenic toxicity limits its application .
Currently, the most commonly used is LiPF6.
All materials in currently commonly used lithium batteries, including electrolytes,comply with EU RoHS and REACH requirements and are environmentally friendly energy storage products.