Stabilized Nanostructures For Electrochemical Energy Storage Devices And Nanoelectronic Bioprobes

With the rapid development of nanotechnology,nanomaterials and devices have created a tremendous growth potential in many research fields,such as energy storage and biochemical detection.For electrochemical energy storage,nanomaterials are advantageous in offering huge surface to volume ratios,favorable transport properties resulting from the nanoscale dimensions to enhance the energy density and rate performance.For electronic bioprobe,shrinking electronic transducer dimensions to the nanoscale can yield significant improvements in the sensitivity and minimally invasive.However,the high activity and large surface to volume ratios will also accelerate interfacial instability,structure degradation and dissolution,and significantly affect the performance of energy storage devices and bioprobes.In the present dissertation,we focus on the strategies to overcome the structural changes associated with lithium charging/discharging and dissolution under physiological conditions.We achieved lithium ion battery with high energy density,high rate performance and long lifetime,and silicon nanowire based bioprobe array with long-term,stable,large-scale cellular recording.The main contents of the present dissertation are as follows:1.To overcome poor electrochemical performance caused by crystal structural changes,lattice disorder and transformation to an inactive materials during lithium intercalation/de-intercalation,we describe a synergistic effect between crystal structure and intercalated ion by experimental characterization and ab initio calculations,based on more than 20 nanomaterials:five typical cathode materials together with their alkali metal ion intercalation compounds A-M-O?A=Li,Na,K,Rb;M=V,Mo,Co,Mn Fe-P?.We show that pre-intercalation of alkali metal ions in V-O and Mo-O yields substantial improvement in the Li-ion charge/discharge cycling and rate,compared to A-Co-O,A-Mn-O and A-Fe-P-O.Diffraction and modeling studies reveal that pre-intercalation with K-and Rb-ions yields a more stable interlayer expansion,which prevent destructive collapse of layers and allow Li ions to diffuse more freely.This study demonstrates that appropriate alkali metal ion intercalation in admissible structure can overcome the limitation of cyclability as well as rate capability of cathode materials,besides,the pre-intercalation strategy provides an effective method to enlarge diffusion channel at the technical level,and more generally,it suggests that the optimized design of stable intercalation compounds could lead to substantial improvements for applications in energy storage.2.To overcome inherent large volume variations and sluggish kinetics of conversion reaction based high energy lithium battery materials,we elaborate a self-adaptive strain-relaxed electrode through homogeneously crumpling of 3D graphene to serve as high-stretchy protective shells on metal framework.The graphene sheets are homogeneously self-assembled and deeply crumpled into pinecone-like structure through a novel constriction-strain-driven crumpling method.The as-prepared electrode exhibits good safety,high specific capacity,fast charge-discharge rate(20 A g^-1)without any capacity fading in 1000 cycles.In-situ TEM characterization and MD simulations demonstrate that homogeneously crumpled graphene have self-adaptive behavior of spontaneous unfolding-folding synchronizing with cyclic expansion-contraction volumetric variation of core materials,which can release strain and maintain good electric contact simultaneously.Our strategy leads to a novel approach and new insight for synthesis,understanding and applications of crumpled graphene as well as the self-adaptive materials.3.To realize long-term,large scale cellular recording by Si nanowire based bioprobes,we develop a new shape-controlled deterministic assembly technology and fabricate U-shaped three-dimensional nanowire bioprobe arrays containing 200individually addressable nanodevices.U-shaped Si/Al₂O₃ core/shell can be achieved by passivating the nanowire elements with ultrathin metal oxide shells Al₂O₃ and then fabricate into U-shaped nanowire field-effect transistor array.Studies of Si and Si/Al2O3 core/shell nanowires in physiological solutions show the stability of nanowires bioprobes is significantly enhanced,which could provide an opportunity of long-tern and multiplex intracellular recording by U-shaped nanowire bioprobe arrays.