Exfoliated Graphite and Copper Oxide Hybrid Anode for High Capacity and Stable Li Ion Battery
Authors: Cho Sanghun , Yoo Jeeyoung , Ahn Yong-keon , You Duck-Jae , Chung Sung Yun , Kim Youn Sang 
Published: February 2020

Lithium-ion batteries (LIBs) have become one of the most-attractive storage systems with many outstanding features including high energy density, no memory effect, low maintenance, and little self-discharge. Recently, LIBs researches are focused on high capacity and stable cycle stability in order to use energy storage system and electric vehicles. To make high capacity and stable LIBs, the two electrodes (cathode and anode) as Lithium ion source and storage medium have significantly important role.[1]

In conventional LIB cell, lithium–transition metal oxide (LiCoO2, LiFePO4) used as cathode materials. As apply the various transition metals alloy (Ni, Mn, etc.) and structure development, cathode materials have continuous progress for high capacity and stable cycle property. In addition, anode materials have researched various materials such as graphite, alloy metal, transition metal oxide, carbon nanotube (CNT) and graphene. Graphite is commercially utilized due to the cheap and relatively stable materials. However, the graphite has some disadvantages such as low theoretical capacity, low exposed edge plane and Li ion intercalation strain during the charging-discharging process.[2] It induces deficient actual capacity of graphite and inefficient energy loss. To make high capacity anode, the metal oxide, alloy metal, CNT and graphene are strongly proposed to future high capacity materials but these materials have serious problems for practical LIBs. CNT and graphene have complex manufacturing process using of strong acid and long processing time. Alloy metal (Si, Sn) and transition metal (Fe3O4, MnO2, CuO) shows extremely unstable cycle stability, which caused by cracking of active material.[3]Consequently, new anode materials are required for advanced stable and high capacity LIBs.
Herein, we introduce exfoliated graphite and Copper oxide (CuO) hybrid anode using Cu ion-organic complex decomposition. Exfoliated graphite has important advantages such as large exposed edge plane and small strain materials. To make exfoliated graphite, we apply Cu ion-organic complex and decomposition process. Decomposition of Cu ion-organic complex makes the expanded layer spacing of graphite, because process of decomposition produce the hydrogen (H2) gas and carbon dioxide gas (CO2), which is widely utilized to graphene exfoliate gas. As product of Cu ion-organic complex decomposition, CuO is valuable anode materials by conversion reaction. Therefore, the exfoliated graphite and CuO hybrid anode is effective cycle stable and high capacity materials.
The proposed hybrid anode has been prepared by commercialized graphite and Cu ion-organic complex mixing process. The homogeneous mixed graphite and Cu ion-organic complex are sintered at 350 oC for 8h. The exfoliated graphite and formed CuO material property is verified by XRD, TEM and Raman spectrum and cyclic voltammetry test. In particular, the cyclic voltammetry test and Raman spectrum can be explained as good evidence of graphite expanded layer spacing. The test for LIBs performance of prepared hybrid anode was conducted. The charge-discharge test and retention test exhibit the enhanced battery performance. In addition, the ratio control of Cu ion-organic complex and graphite results show proportional capacity increasing and layer expansion phenomenon. These results describe that prepared anode form the exfoliated graphite and CuO for high capacity and long cycle stability of LIBs performance. In conclusion, we believe that the proposed hybrid anode is a promising anode for LIBs and it applies future Electric vehicle and Energy storage system.

References

[1] Hao Bin Wu, Jun Song Chen, Huey Hoon Hng and Xiong Wen Lou Nanoscale, 2012, 4, 2526–2542
[2] T. Tran and K. Kinoshita J. Electroanal. Chem., 1995, 386, 221-224
[3] M. V. Reddy, G. V. Subba Rao, B. V. R. Chowdari Chem. Rev.
2013, 13, 5364-5457

Figure 1