Home > News > Small: in situ TEM study of multi-step phase transition of Mn3O4 in galvanostatic discharge mode

Small: in situ TEM study of multi-step phase transition of Mn3O4 in galvanostatic discharge mode

wallpapers News 2020-09-23

lithium-ion batteries are widely used in portable electronic devices electric vehicles. It is of great significance to fully underst the reaction mechanism during battery charging discharging to improve their energy density power density cycle life. As an anode material Mn3O4 has attracted much attention due to its low redox potential low price environmental protection non-toxic high theoretical specific capacity (936 MAH · g-1 more than twice of graphene anode). However most of the previous studies focused on the three-step electrochemical phase transition of MnO4. In situ transmission electron microscopy (in-situ TEM) has become a popular technology to study the charging discharging process of battery materials because of its atomic level spatial resolution real-time observation. However due to the limitation of TEM cavity size the micro cell constructed in the previous in-situ TEM research can only load a very small amount of active substances (usually in the order of nanogram) the current path is usually realized by using the point contact method which leads to the high impedance of the micro cell so the constant voltage charging method can only be used in the test process which makes it difficult to charge discharge the battery In order to control the electrochemical reaction the observed electrochemical reaction process often deviates from the actual condition of the battery.

team led by Professor Zhang Yuegang of Tsinghua University researcher Zhang Jinping of Suzhou Institute of nanotechnology nanobionics of Chinese Academy of Sciences has developed a new type of in-situ electrochemical TEM chip to solve this problem. The micro battery constructed by this chip can load more active materials (for example about 25 mg of Mn3O4 is loaded in this work) which can be used in the same field as conventional batteries Constant current charge discharge test electrochemical impedance test were carried out under similar conditions. The team applied a new in-situ electrochemical TEM chip to study the lithium intercalation process of Mn3O4 found that the charge discharge mode of the micro battery would affect the electrochemical reaction path. In the galvanostatic discharge mode the lithiation of Mn3O4 follows three steps: Mn3O4 Li → limn3o4 Li → MnO Li2O → Mn Li2O; it is also found that Li tends to enter Mn3O4 along the {101} crystal plane in the initial stage of galvanostatic lithium intercalation reaction. In the constant voltage mode only one step reaction was observed: Mn3O4 Li → Mn Li2O. The results show that it is very important to control the charge discharge rate charge quantity of the battery accurately. It is worth noting that this new in-situ electrochemical TEM method has strong universality can be used to study the electrochemical reaction mechanism atomic structure evolution of various electrode materials interfaces.


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