Separator-free battery? Envision's new patent is published, battery energy density increased by 8%

In everyone's understanding, lithium-ion batteries generally consist of a positive electrode, a negative electrode, a separator and an electrolyte.

The positive electrode sheet is mainly formed by coating lithium cobalt oxide, lithium iron phosphate and other materials on the aluminum foil current collector and rolling it. The negative electrode sheet is mainly formed by coating graphite material on the surface of the copper foil current collector and rolling it. The diaphragm, as one of the key internal components of the battery, is mainly used to separate the positive and negative electrodes of the battery to prevent short circuits. At the same time, it must have a certain degree of permeability to allow electrolyte ions and electrons to pass gently when needed. The main materials are PE and PP.

Do batteries without separators exist?

As the public's requirements for lithium battery life increase, major battery manufacturers are constantly innovating in positive and negative electrode materials and electrolytes. Thinning the diaphragm is also a means.

Currently, the main process for diaphragm thinning is to thin the base film or coating of the isolation membrane. After thinning, the permeability of the electrolyte can be improved, but its puncture ability is reduced, and its resistance to thermal shrinkage is reduced, which can easily lead to greater battery cell safety risks.

On July 5, Envision Power disclosed an invention patent titled "Diaphragmless Electrochemical Devices and Electronic Devices", which isolates the positive and negative electrodes and conducts ions by setting a porous heat-resistant coating between them to replace conventional diaphragms. The synergistic effect of the porous heat-resistant coating aramid and the solid electrolyte can enhance the ion transmission function while isolating electrons. At the same time, it has good thermal stability and meets the safety performance requirements of electrochemical devices.

Compared with conventional PE and PP separators, the thickness of the porous heat-resistant coating in the positive and negative electrodes is very small, which can further improve the energy density of the battery.

How much can it be improved? The experimental data in the patent shows that this process can increase the battery energy density by about 8%. At the same time, the thermal shock pass rate of the battery at 130°C is also greatly improved.

An 8% improvement may not seem like much, but this is only achieved through improvements in one direction of the diaphragm. Envision Power has grown rapidly in recent years, and its battery installed capacity often ranks among the top 10 in the world. Moreover, its main "zero-carbon battery" has been recognized by many European and American giants. Not long ago, it reached a cooperation with Mercedes-Benz and will provide power batteries for the Mercedes-Benz EQ electric vehicle series.