The Research On Lithium Metalanode Of High Specific Energy Lithium Secondary Battery

Lithium metal is one of the anode materials which have the highest specific massenergy due to its extremely high theoretical specific capacity(3860mAh/g), and thelithium secondary battery with lithium metal anode always attracts people,s attentions.Currently it exits low cycle efficiency, lithium dendrites and security issue in thelithium secondary battery，especially security issue. The battery system generatesheat during overcharge and over discharge process, or even an explosion occurred.The most important factor which influences the performances of lithium metal anodeof battery is the solid electrolyte interphase (SEI) film on the lithium anode. Thereforehow to make lithium metal anode have a SEI film with a better performance is the keyto improve the electrochemistry performances of lithium metal anode in lithiumsecondary battery. In this paper, the solvent、lithium salt and additive were studiedrespectively in the lithium secondary battery to improve the electrochemistryperformances of lithium metal anode.The effect of the electrolyte on lithium anode is critical in the lithium secondarybattery. Existed literatures did not systematically report the effects of differentsolvents and lithium salts on lithium electrode, so the experiment was taken to studythe effect of solvents and lithium salts existed in the laboratory. The solvents andlithium salts were studied to indicate the effect on lithium electrode individually in theexperiment. The cyclic voltammetry curve、deposition curve、surface morphology、the impedance、the cycle performance and the average coulombic efficiency wereused to evaluate the effect on lithium anode. As known from the electrolytecomposition of Li-ion battery, the effect of muti-solvent and muti-salt on lithiumelectrode were studied. The experiment results showed that the cyclic alkyl carbonatecan form the good performance SEI film, and LiBOB and LiTFSI can also form theSEI film with good performance.One of the biggest problems of the lithium metal secondary battery is lithiumdendrite generated during charge and discharge process in lithium metal battery, andthe dendrites grow up to pierce the septum, and lead to contact the positive withnegative, causing short circuit, or even an explosion. We used a new theory (SHES)system to suppress the generation of lithium dendrite. The theory was tested indifferent solvents and lithium salts by a three-electrode system and button cell. Thistheory was evaluated the effect of suppression lithium dendrite by SEM、EDX、the cycle performance and the average coulombic efficiency. The experiment resultsshowed that the additives CsPF6and RbPF6played the role of suppression lithiumdendrite in the PC or EC solvents.The SHES theory was used in the water system to solve dendrite growth of themetal battery. The deposition of zinc metal with additive was studied, and theexperiment results showed that the additives can suppress the growth of zinc dendriteto some extent.