Accurate Design And Electrochemical Performance Study Of Multi-stage Substructure Carbon Skeletons For Lithium Batteries

As energy storage devices put forward higher requirements of energy density,the development of high-performance electrode materials for lithium batteries has become one of the current research hotspots in the field of energy storage.As a key component of lithium batteries,anode materials play a significant role in improving the energy density of lithium batteries.Therefore,high-capacity alloy anode materials(silicon,phosphorus,germanium,tin,etc.)and lithium metal anodes have become the focus of research on anode materials for lithium batteries at present.The composite structure modulation of anode materials will effectively improve their electrochemical lithium storage performance,which is an effective way to realize electrochemical memory devices with both high energy density and high power density.In this paper,we focus on the research of lithium battery anode materials to achieve the significant improvement of the electrochemical lithium storage performance of anode materials through the precise regulation of the multi-level carbon skeleton structure,and investigate the conformational relationship between the multi-level carbon structure and its electrochemical lithium storage performance by using different characterization and testing methods to investigate the microstructure regulation and electrochemical performance of the materials.The main research contents are as follows.(1)With the new requirements for the energy density of lithium batteries in the development of power batteries and other fields,silicon anode(Li₁₅Si₄:3579 m Ah g^-1)with high theoretical specific capacity has become one of the most promising anode materials.However,during charging and discharging,the huge volume change leads to the chalking of the material structure,which causes rapid capacity decay and poor cycle life,which greatly limits the commercialization process.Based on the above problems,this paper adopts a nanostructure engineering strategy to build an integrated electrode structure using silicon nanoparticles,polyacrylonitrile and graphene oxide,combined with low-temperature annealing to realize a cyclized polyacrylonitrile-bridged silicon nanoparticle and reduced graphene oxide electrode structure to build a three-dimensional multi-level carbon skeleton,analogous to a reinforced concrete structure.The strategy effectively improves the stability of the electrode structure and establishes efficient electron and lithium ion(charge)transport networks,which not only effectively improves the stability of the electrode structure,but also achieves a significant improvement of the multiplicative performance through the construction of efficient charge transport networks.The prepared Si/r GO/c PAN electrodes exhibit good overall performance,including excellent mechanical properties,good cycling stability and high areal capacity.This novel electrode design concept is expected to promote the practical application of silicon anode and open up new avenues for the development of high-capacity anodes for other high-performance batteries.(2)Lithium metal is considered as the"holy grail"of next-generation rechargeable batteries with 10 times the theoretical specific capacity of graphite anode(3960 m Ah g^-1)and the lowest redox potential(-3.04 V),However,due to the uneven deposition of lithium and uncontrolled growth of lithium dendrites,there are not only serious safety hazards such as thermal runaway,fire and even working battery explosion,but also the freshly exposed lithium will continuously consume the electrolyte,resulting in poor cycle stability,which seriously hinders the practical application of lithium metal anode in rechargeable batteries.In order to solve the above mentioned problems of lithium metal anode,we constructed a multi-stage three-dimensional carbon cloth collector using waste cotton cloth as a lithium metal host to alleviate the volume change of lithium metal anode during long cycle,mainly for the following reasons:firstly,there are a large number of nucleation sites on the surface of carbon cloth fiber,which can induce uniform deposition of lithium metal and inhibit the generation of dendrites to prevent the short circuit of the battery;furthermore,the porous structure of carbon fibers and the excellent electrical conductivity of carbon fibers allow the deposition of lithium metal not only on the surface,but also to the interior of the fibers,which makes the porous 3D collector we prepared can serve as a stable host for high lithium loading,which is conducive to reducing the volume change,lowering the volume fluctuation,and improving the safety of lithium metal batteries.Benefiting from the excellent structural design,the electrode not only achieves stable cycling at low current densities,but also exhibits excellent electrochemical lithium storage performance at high current densities as well as ultra-high surface capacities.This novel electrode design concept not only helps to accelerate the application process of lithium-metal anode,but also promotes the research on the application of waste biomass carbon valorization.