The Research Of New Carbon Materials In Aluminum/Potassiumbased Batteries

Electrochemical energy storage devices represented by lithium ion batteries are the key to the effective use of renewable energy.However,due to factors such as low energy density and high cost,the development of new high specific energy battery systems to replace lithium ion batteries has become increasingly important.Aluminum batteries(ABs),potassium ion batteries(PIB)and dual ion batteries(DIB)have attracted much attention due to their high theoretical energy density and wide range of electrode material sources.Carbon materials have the characteristics of wide source,low cost,good chemical stability,excellent conductivity,and environmental friendliness,etc.,and are widely used in the field of electrochemical energy storage.However,the application of commercial carbon materials in ABs/PIB and DIB is subject to defects such as low capacity and poor structural stability,which slows down related research and development.Reasonable structural design is very important to improve the electrochemical performance of carbon-based electrodes in ABs/PIB and DIB.This thesis uses chemical mechanical stripping,microwave radiation,chemical vapor deposition(CVD)and other methods to construct a variety of new carbon nanomaterials with special structures,study their electrochemical performance as ABs/PIB and DIB electrodes,and explore related storage Energy mechanism.The main contents are as follows:(1)Carbon nanotubes(CNT)can only be used as a conductive agent for aluminum batteries due to the lack of active insertion sites.A high-performance flexible decompressed carbon nanotube(UCNT)film with carbon nanotubes as the composite graphene nanoribbons were prepared by a simple,low-cost,and scalable chemical mechanical peeling method,and the UCNT film was used as the ABs electrode.In this structure,graphene nanoribbons provide a large number of active embedding sites to store AlCl₄^-anions and internal CNTs serve as electron transport channels,while achieving rapid transmission of electrons and ions,improving the performance of ABs.Electrochemical tests show that the constructed UCNT(positive electrode)-Al(negative electrode)battery has excellent Al Cl₄^-anion storage performance,with a specific capacity of 100 mAh g^-1 at a current density of 2000 mA g^-1;contribute a specific capacity of 75 mAh g^-1 at 5000 mA g^-1,with a cycle life of up to 5600 cycles and a capacity retention rate of 99%;it can still provide stable power supply under different degrees of bending from 0° to 180°.Electrochemical performance,morphological and structural characteristics,and spectroscopic studies show that UCNT improves the energy storage capacity of carbon nanotubes and broadens its application range.(2)Carbon nanocage has the characteristics of stable structure,high specific surface,and hollow structure,and its catalyst-free preparation has important application prospects.The catalyst-free microwave pulse radiation method can quickly convert Ketjen black into a three-dimensional interconnected carbon nanocage(CCN).The specific surface area of CCN is 1205m² g^-1,and its three-dimensional structure is conducive to the transmission of electrons.Molecular dynamics simulations show that when the interconnected CCN stores AlCl₄^-,its self-protection mechanism can avoid the collapse of the electrode structure.As the positive electrode of aluminum batteries,the interconnected CCN has a specific discharge capacity of 117 mAh g^-1 at a current density of 1000 mA g^-1;the specific capacity after 1000 cycles at a current density of 2000 mA g^-1 is still as high as 105 mAh g^-1(capacity retention rate 95%).The microwave method has the advantages of fast,non-polluting,and low cost,which reduces the experimental requirements for the preparation of CCN,can realize the rapid and large-scale preparation of CCN,and provides a feasible solution for its large-scale application in ABs and other related fields.(3)The dual-ion battery is widely concerned because of its high power density.In this work,a new aluminum dualion battery(ADIB)with Al(ClO₄)₃ as the electrolyte,metallic aluminum as the negative electrode,and three-dimensional graphene foam as the positive electrode was developed.The reaction mechanism of ADIB is that the negative electrode is electrochemically deposited and dissolved through aluminum metal during the charging and discharging process;the positive electrode achieves energy storage and releases through the insertion/de-intercalation of ClO₄^-anion in the graphite negative electrode.ADIB has the characteristics of high discharge voltage(about 1V),high rate(specific capacity of 101 mAh g^-1 at 2000 mA g^-1 current density),long cycle(over 400 cycles)and fast charge and slow discharge(Fully charged in 13 minutes,discharge for 73 minutes).Through theoretical simulation and experimental exploration,the reaction mechanism of the aluminum-based dual ion battery was verified.(4)The key to fully flexible electronic devices is flexible batteries.A flexible three-dimensional composite structure carbon material was synthesized by microwave method anchoring carbon dots on the surface of reduced graphene oxide(CDs@rGO),and its electrochemical performance and energy storage mechanism,when used as a PIB negative electrode,were explored.The CDs@rGO film has a three-dimensional composite structure and rich electron and ion transfer channels,which facilitates the rapid transfer of electrons and ions.The introduction of carbon dots brings a lot of defects and oxygen-containing functional groups,which increases the electrochemically active sites.The flexible CDs@rGO negative electrode has a high specific capacity of 310 mAh g^-1 at a current density of 100 mA g^-1,which exceeds the theoretical capacity of graphite.It has a long cycle life(840 cycle at 200 mAh g^-1)and excellent rate performance(185 mAh g^-1 at a current density of 500 m A g^-1).It provides a reference for the development of flexible electronic devices.The strategy of introducing carbon quantum dots to enhance electrochemical performance also provides new ideas and visions for other research fields.