1. High specific energy electrolyte
Seeking high specific energy is the biggest research direction of lithium-ion batteries, especially when mobile devices occupy more and more proportions in people's lives, battery life has become the most critical function of batteries.
As shown in the figure, the development of high-energy density batteries in the future must be high-voltage anodes and silicon anodes. The negative electrode silicon has a huge gram capacity and is valued by people, but due to its own swelling purpose, it cannot be used. In recent years, the research direction has been changed to silicon carbon negative electrode, which has relatively high gram capacity and small volume change. The film-forming additives have different recycling uses in the silicon-carbon anode.
2. High-power electrolyte
At present, it is difficult for commercial lithium electronic batteries to complete high-rate continuous discharge. The main reason is that the battery tabs heat up severely, and the internal resistance causes the overall temperature of the battery to be too high, which is prone to thermal runaway. Therefore, the electrolyte should be able to restrain the battery from heating up too fast while maintaining high conductivity. Regarding power lithium-ion batteries, completing fast charging is also an important direction for electrolyte development.
High-power batteries not only require high solid phase dispersion, nanometerization to make ion migration paths short, control electrode thickness and compaction and other requirements for electrode materials, but also higher requirements for electrolyte: 1. High dissociation electrolyte Salt; 2. Solvent recombination-lower viscosity; 3. Interface manipulation-lower membrane resistance.
3. Wide temperature electrolyte
The battery is prone to differentiation of the electrolyte itself and the intensification of side reactions between materials and electrolyte components at high temperatures; at low temperatures, there may be electrolyte salt separation and negative SEI film impedance doubled. The so-called wide temperature electrolyte is to enable the battery to have an increasingly extensive working environment. The following figure shows the boiling point comparison chart and the solidification comparison chart of various solvents.
4. Safety electrolyte
The safety of the battery is currently burnt or even blasted. The battery itself is flammable. Therefore, when the battery is overcharged, over-discharged, short-circuited, when it receives external needles, kneading, and when the external temperature is too high, All may lead to safety accidents. Therefore, flame retardant is a primary direction for research on safe electrolytes.
The flame-retardant function is obtained by adding flame-retardant additives in the conventional electrolyte. Generally, phosphorus-based or halogen-based flame retardants are used. The flame-retardant additives are required to be reasonably priced and do not harm the electrolyte function. In addition, the use of room temperature ionic liquids as electrolytes has also entered the research stage, which will completely eliminate the use of flammable organic solvents in batteries. In addition, ionic liquids have the characteristics of extremely low vapor pressure, good thermal stability/chemical stability, and non-flammability, which will greatly improve the safety of lithium-ion batteries.
5. Long-circulation electrolyte
Due to the large technical difficulties in the recovery of lithium-ion batteries, especially power lithium-ion batteries, improving battery life is a way to alleviate this situation.
There are two main points in the research thinking of long-circulation electrolyte. One is the stability of the electrolyte, which contains thermal stability, chemical stability, and voltage stability; the other is the stability of other materials, which requires stable film formation with the electrode. There is no oxidation between the barrier and the collector, and no corrosion with the current collector.