| As a traditional lithium battery anode material,graphite(theoretical capacity is 372 m Ah g-1)can no longer meet the requirements for high energy-density-batteries.Lithium（Li）metal(theoretical capacity is 3860 m Ah g-1)and silicon（Si）materials(theoretical capacity is 4200 m Ah g-1)are both good anode materials for the next-generation high-energy-density batteries,which both have the characteristics of low lithiation and delithiation potentials.However,the growth of Li dendrites and the poor stability of the solid electrolyte interphase（SEI）during cycling in the Li metal battery can cause serious safety hazards.The Si anode also faces the huge volume change during charging and discharging,and the repeated growth of the SEI leads to rapid capacity decay.Therefore,inhibiting the growth of Li dendrites and limiting the expansion of Si anodes are the key problems that these two systems need to solve urgently.Compared with the traditional planar current collector,a three-dimensional（3D）metal current collector can provide large specific surface area and sufficient ion diffusion channels and improve conductivity of the electrodes.It can also accelerate and stabilize the formation of SEI,which improves the battery safety and life.Most of the reported 3D current collector for the lithium ion battery cannot simultaneously exhibit high cycling stability,good rate performance and high loading of active materials.The high material cost and complicated synthetic technology are also obstacles for the fabrication of an excellent 3D current collector.Hence,reasonable design and synthesis of a stable 3D current collector are of great significance to the development of lithium ion batteries.In this thesis,two kinds of metal current collectors are designed for Li metal anodes and Si anodes,which provide new strategy for stabilizing anodes of lithium ion battery.On the basis of detailed structure and performance characterization of the batteries,the stabilization mechanism of 3D current collector for the two materials is systematically discussed.It has important practical significance and theoretical value for the design and construction of new anodes for high energy density lithium batteries.The main results obtained in this thesis are as follows:（1）A novel 3D current collector is built from nitridated nickel micro particles by rolling-coating method and applied in the dendrite free lithium metal anodes.The accumulated pores provide space for Li metal deposition,the nitridated nickel surface have good lithiophilicity and the 3D conductive framework can effectively decrease the local current density.Therefore,the employment of the 3D current collector effectively reduces the nucleation overpotential of Li metal deposition and induces the even Li depositon.The Coulombic efficiency of the Li-3D N-Ni is up to 98%cycling for 280cycles at 1 m Ah cm-2.When applied to the full battery system,excellent cycle performance and rate performance can be achieved.（2）The free-standing Cu-Si composite electrode is integrated by one-step sintering of milled Cu and Si nano particles without any binder and conductive reagents added.The conductive framework is closely connected with the active material,and thus keeps the structure intact before and after the cycle.Moreover,the 3D Cu-Si electrode structure promotes high loading of Si inside the metal current collector.The reasonable design of pore-channel scaffold provides a buffer for the volume expansion of Si and stabilizes the formation of the SEI.These merits render the 3D Cu-Si electrode remarkable cyclinf stability and capacity retention,which is 83%after 120 cycles at 0.5A g-1.The design of the3D composite electrode structure is facile,and the cost is relatively low,making it expandable into other anode systems. |
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