The importance of the cycle performance of
a lithium ion battery without
saying; additional terms of the macro, longer cycle life means less consumption
of resources. Thus, the factors that affect the performance of lithium-ion
battery cycle, every problem associated with lithium industry personnel have
had to consider. The following are a few that may affect cell cycle performance
factors, for your reference.
Material
Type:
The choice of materials is the first factor
affecting the performance of lithium-ionbatteries. Select a poor cycle performance materials, processes and then
reasonable to prepare for further improvement, batteries can not be guaranteed
circulation is bound; choose a better material, even made a slight problem
follow the cycle of poor performance may not too outrageous (once played grams
of lithium cobalt oxide is only about 135.5mAh / g and analysis of lithium batteries, 1C although hundreds
of times diving but 0.5C, 500 times more than 90%; anode batteries have open
after a black graphite particles batteries, the cycle performance of normal).
From the material point of view, the performance of a full cycle of the
battery, the positive electrode and the electrolyte solution cycle
characteristics after the match, the cycle properties of the electrolyte and
the negative electrode after the two match, the less one to decide. Poor
cycling performance, one may change the crystal structure of the cycle can not
proceed so fast lithium deintercalation one hand, since the active substance
may be unable to generate the corresponding electrolyte membrane caused by
dense, homogeneous active substance SEI side reactions with the electrolyte
leaving prematurely excessive consumption thereby affecting electrolyte
circulation. In the design of the batteries, if the material is poor cycle
performance of a selection electrode is recognized, the other electrode is
preferably no need to select the cycle performance material waste.
Positive
and negative compaction:
Positive and negative high
compaction, although the energy density of batteries, but also to reduce the
cycling performance to some extent. From the theoretical analysis, the greater
the compaction, the greater the equivalent structural damage to the material,
the structure of the material is the basis for a lithium-ion battery can be used;
addition, the positive and negative high compaction is difficult to ensure than
the batteries the high liquid retention amount, and the amount of fluid is
guaranteed to complete the normal cycle batteries or more cyclic basis.
Moisture:
Excessive moisture will be positive and negative electrode active
material and side reaction occurs, and thus affect the structure of the
destruction cycle, while too much water is not conducive to the formation of
the SEI film. However, while difficult to remove traces of water, traces of
water can be guaranteed to some extent, the performance of batteries.
Coated
film density:
Consider the impact of a single variable
density film cycle is almost an impossible task. Film density inconsistencies
or differences in the capacity to bring either batteries or winding difference
laminated layers. With the same capacity of the same material type batteries,
the lower the density of the film corresponds to an increase or a wound layer
or layers laminated layers, corresponding to the increase of the electrolyte
membrane can absorb more to ensure circulation. Considering the thinner the
film density can be increased rate performance of batteries, and the bare core
pole piece of baking will be easier to remove water, of course, the density of
the coating film is too thin, the error may be difficult to control when the
active substance large particles may also be coated, rolled a negative impact,
more layers means more foil and diaphragm, in turn means higher costs and lower
energy density. Therefore, when assessing the need to balance considerations.
Negative
excess:
Excess addition causes a negative initial
irreversible capacity to consider the impact of the deviation and the coating
film density than the impact on the cycle performance is also a consideration.
For lithium cobalt oxide and graphite system, the negative cycle of graphite
become "short board" one of the more common. If negative excess is
not sufficient, batteries may not analyzed before cycling lithium, but hundreds
of times the loop structure is minimal but the positive and negative changes in
the structure was severely damaged but not completely positive reception thus
providing lithium-ion analysis of lithium, resulting in over-capacity early
fall.
Electrolyte
volume:
Produce insufficient amounts of electrolyte
circulation affect three main reasons, one less than the amount of fluid
injection, the second injection fluid volume is adequate, but despite the lack
of time or aging infusion due to the positive and negative electrodes and other
causes excessive compaction is not sufficient, the third is with cycle
batteries inside the electrolyte is consumed. Note inadequate and insufficient
fluid volume fluid volume Paul wrote, "electrolyte deficiencies on the
performance of batteries" before and therefore not repeat them. On the
third point, the negative electrode and the positive and negative electrolyte
particular microscopic matching dense and stable performance of SEI formation
and performance of the visible eye, both for circulation of the electrolyte
during the consumption rate. Incomplete SEI film on the one hand and the
electrolyte can not effectively prevent the occurrence of negative side effects
and thus consume the electrolyte, while the SEI film with defective parts will
be re-circulated in order to generate the SEI film and electrolyte depletion
reversible lithium source . Whether circulating hundreds or even thousands of
times the batteries or both diving for dozens of batteries, the electrolyte is
sufficient and if the first cycle after cycle has been consumed electrolyte,
the electrolyte increased ownership is likely to be some enhance the cycle
performance degree.
Test
objective conditions:
Testing during
charge-discharge rate, cut-off voltage, the charging cut-off current, tests
overcharge and over discharge, the test room temperature, the sudden
interruption during the test, the test point and the contact resistance of
batteries and other external factors that will or less impact cycle performance
test results. In addition, the sensitivity of different materials to the above
objective factors varies, uniform testing standards and understand the
characteristics of the common and important materials should be sufficient
daily use.
To
sum up:
The same principle as the barrel, the
factors affecting the performance of batteries circulation among many, the
ultimate decisive factor is a number of factors in the shortest board.
Meanwhile, among these factors, but also have a reciprocal influence. In the
same materials and made capacity, the higher the circulation, often
means lower energy density, to find exactly the point of integration to meet
customer needs, try to ensure the consistency of
batteries made of party is the most important task lies .
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