Currently, the electrolyte is an organic solvent, which cannot bear a high voltage greater than 4.5V. Also, it can easily decompose and produce gas, and lead to battery swell, rupture, or explode.
In addition, the positive and negative materials are very active in the charging state. For example, positive electrode materials such as lithium cobalt oxide are more likely to structural collapse when overcharged or heated. At the same time, there will be obvious thermal effects, and the negative electrode of lithiated graphite containing organic solvents is easier to burn when exposed to air.
The polar organic solvent electrolyte cannot guarantee the safety of lithium ion batteries. In addition, the electrochemical window of current ionic liquids is not wide enough and the relative molecular mass and viscosity are too large. So, they cannot completely replace organic solvents. The fundamental measure to improve battery safety is to develop low solvent or solvent-free polymer electrolytes, inorganic-organic composite electrolytes or inorganic solid electrolytes.
Currently, lithium ion batteries use graphite-based materials as the negative electrode, which is close to the intercalation of the lithium. It is easy to cause lithium dendrites and lithium powder to precipitate during rapid charging, lithium dendrites will cause a short circuit inside the battery, and lithium powder will accelerate the decomposition of the electrolyte or burn in contact with air.
Therefore, the safety and cycle life of lithium ion batteries can be effectively improved by increasing the lithium intercalation of the negative electrode. Materials such as hard carbon, silicon, tin, lithium titanate can better increase the electrode potential than graphite-based anode materials.
When the temperature rises to a certain level, the positive and negative separator materials will automatically dissolve to prevent the lithium ion batteries from passing through and stop the internal charge and discharge reaction.
Unqualified binders will produce powder and cause burrs to puncture the diaphragm. Also, there will be short-circuited inside, and eventually cause lithium ion batteries to explode. Therefore, qualified binders have to be used.