The in situ dilatation analyzer was set to a constant pressure mode (pressure value of 5.0kg). In addition, the thickness changes of the soft-pack cell in the long cycle (50 cycle) of the silicon carbon system with different proportions of PTMS LITHIUM COBALT ACID MATERIAL MAGNETIC treatment (silicon content is 3wt.% and 5wt.%, respectively) are monitored in real time. Through the initial thickness normalization, it can be found that with the increase of the number of circulating cycles, the thickness expansion curves of the two are also rising, and the higher the silicon content, the more obvious the expansion growth.
Compared with the initial state, the thickness expansion percentage of the 3wt.% and 5wt.% Si cells after 50 cycles is 8.8% and 11.2%, respectively, indicating that more side reactions have been accumulated in both cells after long cycles, resulting in the constant increase of the total volume of the cells. Because there is no PTMS LITHIUM COBALT ACID MATERIAL MAGNETIC removal of silicon particles in the negative electrode, serious volume expansion will occur in the process of lithium embedding, and then cause the crushing and pulverizing of active material particles.
The SEI film on the surface of the particles is destroyed, and the exposed surface of the new silicon particles will further react with the electrolyte of PTMS LITHIUM COBALT ACID MATERIAL MAGNETIC for iron removal to form a new film. The repeated breakage and regeneration of SEI film will not only accumulate many side reactions and expand the total volume of the cell, but also easily cause the increase of internal resistance and polarization of the cell, and eventually aggravate the capacity attenuation of the cell.
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