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As shown in Fig. 2.4, mechanical tensions might arise within the active material
particles. They form cracks within the particles and their pulverization. As a result,
individual active material particles are no longer electrically connected. This type
of stress and its effects are detailed in .
Another aging process is the result of the expansion of the active materials
by mechanical strain during the intercalation of the lithium ions and it leads to a
change in particle volume. As shown in Fig. 2.5, this might cause the separation of
Fig. 2.4 Aging processes in the active material of the positive electrode during cycling 
Fig. 2.5 Aging processes in the active material of the positive electrode during cycling. Sep
aration of electrical conduction paths 
2 Lithium-ion battery overview19
the electrical conduction paths (Specific electrical conduction paths are supplied
between the particles and the current collector. This is done by means of carbon
black, a special carbon conductor.) This entails that the active material particles are
no longer electrically connected to the current collectors.
This aging process can become manifest at both the positive and the negative
electrodes. Further aging processes are discussed in detail in . The lifetime of
the battery cells depends on the operating conditions, the materials applied, the
electrolyte composition, and the quality of the production process. It differs in relation to the application, the design of the lithium-ion battery cell, and the operating
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