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Lithium-ion battery lithium branch formation cause, how to find early lithium latenses in the battery? Lithium derinating crystals refers to a dendrite metal, which is formed when the lithium ion reduction is reduced by a lithium ion battery using a liquid electrolyte. The reason why metal lithium is not used as an negative electrode active material is due to the crystallization of metal lithium in the negative electrode to form a dendritic metal lithium - "Lithium Grind Crystal". "Lithium Grinding Crystals" will pierce the diaphragm to a certain extent, resulting in short circuit inside the lithium ion battery, seriously threatening personal safety.
Lithium-ion battery lithium lactary crystal formation (1) The surface of the electrode is uneven: the cause of the surface of the electrode is uneven: the single electrode coating is uneven, the two pole weight difference is large, the active substance contains impurities, etc. The larger the surface roughness, the more it is conducive to the formation of lithium dendrites. (2) In the discharge process, the negative electrode lithium ion concentration has gradually increased, and the positive electrode lithium ion concentration is slowly smaller.
When the depth is discharged, the amount of lithium ion is limited since the negative electrode is limited, so the remaining lithium ions will freely Extreme surface, and precipitate. (3) Lithium ion concentration gradient and distribution: lithium ions take out from the positive electrode material, pass through the electrolyte and diaphragm, embedding the negative electrode. During charging, the concentration of the positive electrode lithium ion is continuously increased, and the negative electrode lithium ion concentration gradually decreases, and the ion concentration can be regarded as 0 in the dilute solution having a large current density, indicating that the negative electrode is partially charged, and the branch, branches The growth rate of crystalline structure and the ion offset rate in the electrolyte.
How to find early lithium latenses in the battery? In order to capture the dendritic structure, the lithium ion battery is mounted on a high-definition video microscope, and it can be monitored to monitor the voltage between the dendrites growth and the two electrodes, which changes during charging and discharging cycles. The observation of the electrode - dendritic crystal growth or contracted, and the general degradation state-voltage measurement results, then link the voltage mode to a particular dendrite activity. 1.
Hydrogen capture method Detection of lithium branch growth has built an in situ optical observation and H2 gas capture platform, demonstrating the principle of using H2 gas capture detection of lithium branch growth. Sealed the gas that appears in the glass bottle to enter the gas chromatograph and automatically detect, and the optical microscope can be used to simultaneously recording the formation behavior of the dendrites. Normally, the lithium ion is removed from the positive electrode and embedded in the graphite negative in the form of LiC6.
Lithium lactary crystals start in a lithium-saturated portion of the graphite negative electrode under overcharge or rapid charging conditions, and reacting hydrogen is formed with a polymer binder. 2. When there is no polymer binder, the in situ detection of lithium derinates in order to exclude interference of electrolyte reduction and other substances, assembled an additional two lithium ion batteries (LIFEPO4-CU and LIFEPO4-graphite batteries), without any polymerization Material binder.
Regarding the Lifepo4-graphite battery, lithium branch growth is observed at 1080s, and the battery voltage is about 3.6V. In the LifePo4-Cu battery, lithium ions are plated directly on the surface of the copper foil to form lithium metal.
However, due to the limitations of optical microscopy observation, lithium branch growth is observed at around 120s, and the battery voltage is about 3.6V. The dendritic is a small, hard tree structure, which will grow in a lithium ion battery, and the portion of its needle-like protrudes is called dendrites.
Both things can cause huge damage, can penetrate the diaphragm inside the battery, just like weeds can penetrate the cement terrace or paved the same. Moreover, such materials also add new electrolytes and lithium adverse reactions, accelerate battery failure. The energy density of the lithium metal battery is higher than the commonly used lithium ion battery, but the dendritic and dendritic crystal have hindered the popularity of lithium metal batteries.
In the long-term circulation charging, the formation of lithium dendrites is one of the lithium ion batteries used in our daily lives, which limits its application in many applications. Lithium dendrites must overcome the thermodynamic critical radius to have sufficient energy-shaped cores; a single crystal core must be greater than the kinetic critical radius can grow, otherwise the crystal nucleation disappears. .
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