一些金属氧化物因具有理论容量高，电极电势低和廉价等优点成为锂离子电池负极材料的研究热点。如NiO、Cr2O3、Co3O4、ZnO，其理论容量分别为718、1080、892、978 mA h g-1，远远高于常用的石墨等碳负极材料（370 mA h g-1)。但是，由于金属氧化物在充放电过程中体积形变比较大，容量衰减很快，循环性能较差，因而限制其在实际中的应用。为解决此问题，可以将碳材料作为载体来缓解电极材料在充放电过程中体积变化带来的机械应力，从而提高其电化学性能。像CMK-3和CMK-8这样的多孔碳材料常用来负载金属氧化物，以改变金属氧化物的电化学性能。然而，由于金属氧化物含量的增多，CMK-3和CMK-8的结构有可能会破坏，而且还有一些颗粒会聚集在孔道外，这样就会导致容量的衰减和降低循环的稳定性。因此，本次研究先通过二步法合成了CMK-3和CMK-8金属氧化物（ZnO、Co3O4），再利用静电吸引作用制得石墨烯包覆的多孔碳基金属氧化物（ZnO、Co3O4）。与单纯的金属氧化物和多孔碳基金属氧化物相比，包覆的样品表现出了更好的电池性能。此外，石墨烯的引入可在充放电的过程中稳定CMK-3和CMK-8的结构，提高整体电极的导电性，均有利于提高多孔碳金属氧化物的电化学性能。本文选取了一种具有良好导电性能的二维单层薄片碳材料——石墨烯做壳层，以介孔碳CMK-3或CMK-8为骨架，研究它们对金属氧化物ZnO、Co3O4负极材料在锂离子电池中的电化学性能的影响。首先，以SBA-15和KIT-6为模板，合成了介孔碳材料CMK-3和CMK-8，并向其孔道内填充金属氧化物，得到多孔碳基金属氧化物（CMK3-ZnO、CMK8-ZnO和CMK3-Co3O4）。同时，通过Hummers 方法制备氧化石墨烯（GO)，调节GO和介孔碳基金属氧化物悬浮液的pH值，使二者通过静电引力结合，再通过水热还原方法将氧化石墨烯（GO）还原为石墨烯，制备石墨烯包覆的多孔碳基氧化锌和四氧化三钴复合材料。生成的石墨烯通过XRD，FT-IR，XPS表征，多孔碳基及包覆的样品的结构通过SEM和TEM表征。恒电流测试发现包覆后的材料的循环性能和倍率性能均有很大提高，EIS阻抗测试表明石墨烯包覆可以减小材料的电阻，增强其导电性能，从而提高多孔碳基金属氧化物的电化学性能。

Metal oxides have attracted widespread attention as anode materials for lithium ion battery due to their advanced properties such as low electrode potential, high theoretical capacities and low cost. For instance, the theoretical capacities of NiO, Cr2O3, Co3O4 and ZnO are 718, 1080, 892 and 978 mA h g–1, respectively, much higher than that of the commonly used LiC6 anodes (370 mA h g–1). However, many metal oxides show rapid capacity fading and poor cycling behaviors because of the dramatic volume change during the charge-discharge process. Some methods have been adopted to alleviate the volume changes and improve the cycling stability for metal oxides such as fabrication of carbon-coated metal oxide composites. The carbon shell can effectively buffer the strain from the volume change of metal oxides during the charge-discharge process and maintain the high electrical conductivity of electrode. ZnO-loaded porous carbon composites were synthesized by decomposition of zinc nitrate inside the pores of CMK-3 or CMK-8, and showed enhanced electrochemical properties than pure ZnO nanoparticles. A high content of ZnO is desirable in terms of the theoretical capacity of ZnO-containing composites, which results in partial destruction of the mesostructure of porous carbon, the formation of some large ZnO particles on the surface of porous carbons, and thereby the capacity fading. Therefore, the ZnO-loaded porous carbon composites were wrapped by graphene nanosheets to further improve their electrochemical performances.Graphene is a novel two-dimensional carbon matrix that exhibits superior properties such as high electrical conductivities, unique mechanical properties and large surface areas. Herein, we described a novel strategy to prepare graphene-encapsulated porous carbon metal oxide composites by a stepwise heterocoagulation method, and the electrochemical performance of those composites was also investigated. Porous carbon CMK-3 and CMK-8 were synthesized using SBA-15 and KIT-6 as templates. GO was synthized by a modified Hummers method. ZnO (Co3O4)-loaded porous carbons (CMK-3 or CMK-8) are prepared by a two-step method and exhibit better electrochemical properties than pure ZnO (Co3O4) particles. ZnO (Co3O4) nanoparticles are separated inside the pores of porous carbons, which limit the growth of ZnO crystals and accommodate their volume variation during cycles. Moreover, to further improve their electrochemical performances, these composites are further wrapped by graphene nanosheets through a stepwise heterocoagulation method. Compared to uncoated porous carbon-ZnO (Co3O4), graphene-encapsulated porous carbon-ZnO (Co3O4) composites exhibited higher reversible capacities, better cycle performances and rate capabilities. The superior performances of graphene-encapsulated composites may be attributed to graphene encapsulation, which enhances the electrical conductivity of the overall electrode, avoids the aggregation of porous carbon-ZnO (Co3O4) particles and even stabilizes the mesostructure of porous carbon during cycles.