| Theoretical studies show that B-C-N materials have similar electronic structures and atomic arrangements with carbon materials,which determines that these materials have similar physical and chemical properties.B-C-N materials have important applications not only in superhard and lubricious materials,but also semiconductors and electricity.Besides,they also have great application prospects in electrochemical energy storage.Theoretical studies of graphite-like BC3 materials is a robust electrode material in lithium-ion batteries,besides,it could also be a new electrode material for next-generation batteries such as sodium ion batteries,potassium ion batteries,magnesium ion batteries,and aluminum ion batteries.Previous studies show that synthesized BC3 is mostly an amorphous phase,and now finding an effective experimental route for the synthesis of BC3 crystals is a big problem faced by this material.LiBC is another kind of layered material with graphite-like structure.Theoretical studies show that the material has a large specific capacity in lithium-ion batteries.The current electrochemical research show that LiBC material could not release any capacity.Based on the synthetic route and research of predecessors,this article continues to explore the possibility of using LiBC as the electrode material for lithium-ion batteries.The results show that LiBC is a new kind of lithium-ion battery anode material,and lithium ions can be intercalated and de-intercalated from LiBC materials reversibly.We also found that the specific capacity of LiBC is firmly related to the crystallinity of the material.The higher of the crystallinity,the smaller of the capacity.Using solid-phase method,and by changing the temperature and time of material synthesis,the specific capacity of LiBC that calcined at 800? for 10h was determined to be the highest.Meanwhile,we also found the relationship between the crystallinity and capacity,that is the higher of the crystallinity,the smaller of the capacity.Comparing the difference in capacity of LiBC that synthesized by different carbon sources,it was concluded that LiBC synthesized using amorphous carbon materials such as acetylene black(a-LiBC)has low crystallinity,small particle size,and large specific material capacity of near 500 mAh g-1,at a rate of 0.1C,the corresponding electrochemical reaction equation is LiBC(?)Li0.45BC + 0.55Li.However,LiBC that synthesized with different particles of graphite(g-LiBC)has a higher crystallinity and large particle size,but the specific capacity of the material is relative lower,as 200 mAh g-1 at a rate of 0.1C,the corresponding electrochemical reaction equation is LiBC(?)Li0.78BC + 0.22Li.Besides,there is no significant difference in the capacity of g-LiBC materials that synthesized from different particle sizes of graphite.The in-situ XRD and in-situ Raman techniques were used to characterize the charge-discharge process of a-LiBC and g-LiBC.The reason for the difference in specific capacity between a-LiBC and g-LiBC was studied.And the results show that the crystal structure of a-LiBC changes greatly during charge and discharge,while little change for g-LiBC,in-situ Raman results show the Raman vibration modes change in the same way for both two materials.The activation energy calculated through high and low temperature impedance tests reveals that the activation energy of the charge transfer part of g-LiBC was higher,indicating the electrochemical delithiation reaction is more difficult for g-LiBC than a-LiBC at the same conditions.The effect of deionized water on g-LiBC was studied.The results show that deionized water can pre-delithiate the g-LiBC material,and the specific capacity of g-LiBC after treated with deionized water can reach 400 mAh g-1,double compare with the original capacity,and the cyclic performance is better.The in-situ water treatment of XRD and Raman results show that the water molecules can remove some lithium ions from g-LiBC,and the phenomenon is same with the electrochemical delithiation process. |
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