Do you know anything about lithium batteries, electrolytes?

The electrolyte of a lithium battery is the interaction between the electrolyte and the electrode material in the battery. It has its own decomposition reaction and participates in almost all reaction processes that occur inside the battery. At present, the electrolytes contained in lithium-ion batteries are mostly organic systems. In the state of overcharge, overdischarge, short circuit, and thermal impact, the battery temperature increases rapidly, and flammable problems are common in electrolytes, often leading to batteries. Fire, even explosion. At present, the most prominent obstacle to the commercialization of high-capacity powered lithium-ion batteries is the safety issue. Therefore, choosing the appropriate electrolyte system is also one of the keys to obtaining high-energy, long-cycle and safe lithium secondary batteries.

Electrolytes are an important part of batteries. They act as transport ions and conduction currents between positive and negative poles. From the phase point of view, lithium ion battery electrolytes can be divided into liquid, solid and molten salt electrolytes. Starting from the actual requirements of internal mass transfer of lithium ion batteries, electrolytes must meet the following basic requirements:

(1) Ion conductivity: The electrolyte does not have electron conductivity, but it must have good Ionic conductivity. In the general temperature range, the conductivity of the electrolyte is between 1 × 10-3 ~ 2 × 10-3S / cm.

(2) Ion migration number: The transport of charge dependent ions inside the battery, high ion transport number can reduce the concentration polarization during the electrode reaction, so that the battery produces a high energy density and power density. The ideal lithium-ion migration number should be as close as possible to 1.

(3) Stability: When the electrolyte is in direct contact with the electrode, side reactions should be avoided as much as possible. This requires that the electrolyte has a certain degree of chemical stability and thermal stability.

(4) Mechanical strength: Electrolytes need to have sufficient mechanical strength to meet the mass production and packaging process of batteries. Li et al. used trimethylphosphate Ester(TMP) as an additive to Gaodianya electrolytes and used Li1 .2 Mn 0.54 Ni0 .13 Co0 .13O2 as the positive electrode of the battery and tested it. The results showed that adding 1 % TMP to the electrolyte can significantly improve the battery. Multiplication performance and cycling performance.

In order to avoid the safety problems such as leakage, flammability, and explosive in conventional lithium batteries, the electrolyte system of lithium secondary batteries is developing into a solid state. Solid electrolytes, also known as fast ion conductors, require electrolytes to have higher Ionic conductivity, low electron conductivity, and low activation energy. The solid electrolytes currently studied by scientists include inorganic solid electrolytes, solid polymer electrolytes, and solid-liquid composite electrolytes. In inorganic solid electrolytes, Li + is in flux and is transported through holes and/or gaps in the electrolyte.

The conduction of all-solid polymer electrolytes depends on the chain movement of polymers and the migration of lithium ions. It can completely avoid the use of liquid plasticizers and is considered to be one of the best ways to solve the safety problems of lithium ion batteries. Solid polymer electrolyte with crosslinked structure polyethylene / polyethylene oxide has high Ionic conductivity(at 25 °C & GT; 1.0 × 10-4S / cm) and superior dendritic growth capability. The composite of MFC(micro-fibrillatedcellulose) nanofibers with allyl methylalanine all-solid polymer dielectric membranes showed excellent mechanical properties, and the overall electrochemical properties of the material were not damaged. It is expected to be applied to flexible all-solid lithium secondary batteries.

The page contains the contents of the machine translation.