The electrolyte in lithium batteries is an important component of the battery and has a significant impact on battery performance. In traditional batteries, the electrolytic system uses water as a solvent. However, since the theoretical voltage of water decomposition is only 1.23 V, even taking into account the overpotential of hydrogen or oxygen, the maximum voltage of a battery with an electrolytic system using water as a solvent is only about 2V (like a lead acid battery). acid battery). 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, generally reaching 10-3~2*10-3S/cm lithium ion; the migration number should be close to 1;
(2) The potential range of electrochemical stability is wide; there should be an electrochemical stability window of 0~5V;
(3) Good thermal stability, wide operating temperature range;
(4) Chemical properties are stable and do not react chemically with the current collector and mild substances present in the battery;
(5) Safe and low toxic, preferably biodegradable.
Suitable solvents should have a high dielectric constant and low viscosity. Common solventsnt used 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 a solution with high ionic conductivity, they are generally used PC+DEC, EC+DMC. and other mixed solvents. These organic solvents have some odor, but generally speaking, they can meet EU RoHS and REACH requirements. They are very toxic, environmentally friendly and environmentally friendly materials.
The currently developed inorganic anion conductive salts mainly include three categories: LiBF4, LiPF6 and LiAsF6. Their electrical conductivity, their stabilitythermal energy and their resistance to oxidation are in the order:
Conductivity: LiAsF6≥LiPF6. >LiClO4>LiBF4
Thermal stability: LiAsF6>LiBF4>LiPF6
Oxidation resistance: LiAsF6≥LiPF6≥LiBF4>LiClO4
LiAsF6 has conductivity and very high stability and charge and discharge rates of batteries, but its application is limited due to arsenic toxicity. Currently, LiPF6 is most commonly used.
All materials of currently commonly used lithium batteries, including electrolytes, comply with EU RoHS and REACH requirements and are environmentally friendly energy storage products.
Cylinders for lithium-ion battery electrolyte. The lithium battery electrolyte is the transport medium for ions in the battery. Composed of lithium salt and organic solvent. The electrolyte plays a role in the conduction of ions between the positive electrodes andnegative of lithium batteries, which ensures that lithium-ion batteries obtain the advantages of high voltage and high specific energy. The electrolyte is generally prepared from high purity organic solvents, lithium salts of electrolyte, necessary additives and other raw materials under certain conditions and in certain proportions. It is best to use a steel bottle, which can also be protected from light.