Preparation Of Basswood Carbon Enzymolysis By Bacillus Licheniformis And Its Electrochemical Performance As Anode Materials For Sodium-ion Batteries

The increasing demand for batteries in the world leads to the rapid consumption of lithium resources and the rapid rise of lithium price,so it is imperative to find rechargeable batteries to replace lithium-ion batteries.Sodium and lithium belong to the same main group of elements and have similar physical and chemical properties.However,sodium is highly abundant and widely distributed in the Earth’s crust.Therefore,sodium-ion batteries have broad application prospects in the field of large-scale energy storage.However,the traditional graphite cannot alloy with sodium,and cannot achieve efficient and stable storage of sodium.In addition,the large radius and mass of sodium-ions cause great damage to the structure when the electrode is unembedded.In the traditional powder electrode,the mass transfer kinetics of sodium-ions in the material is slow,so its magnification performance is often poor.Therefore,the development of new high performance anode materials is of great significance for the development and practical application of sodium ion batteries.Biomass materials have the advantages of a wide range of sources and diverse intrinsic structures.Biomass-based derived hard carbon materials show the advantages of high reversible capacity,low sodium storage potential,stable structure and so on,showing great potential in sodium-ion storage.The self-supported biomass-derived carbon material has a three-dimensional conductive skeleton and vertical natural channels,which can alleviate the volume expansion during the charging and discharging process,maintain a good stable structure and realize the rapid transmission of sodium ions.Plant biomass is mainly composed of cellulose,lignin,hemicellulose and other carbon source components.The structural components of biomass precursors are closely related to the electrochemical activity of hard carbon after pyrolysis.In order to prepare biomass derived carbon anode materials for sodium-ion batteries with high specific capacity and good rate performance,we carried out the following work:(1)With basswood as a precursor,the use of bacillus culture process middle enzyme on cellulose,hemicellulose,lignin for selective enzymatic hydrolysis,improve the proportion of cellulose,cellulose proportion to improve the high temperature treatment of carbon materials with more short range ordered microcrystalline stone ink structure,conducive to sodium-ion in the interlayer embedment.The study found that basswood precursor after bacillus licheniformis enzymolysis,cellulose proportion increase,microfiber fragments produced by enzymolysis covered part of the pore,through 1300 ℃high temperature carbonization of basswood derived carbon material has low specific surface area and high conductivity,Bacillus enzymolysis treatment increased the formation of short range ordered graphite microcrystalline structure,The irreversible reaction in the initial charge-discharge process is reduced,the charge-transfer resistance in the reaction process is reduced,and a stable reversible capacity is generated.Under the current density of 60 m A/g,the initial coulomb efficiency of basswood carbon material enzymic hydrolysis by Bacillus reached 93.1%,the specific capacity of 100 cycles can reach 306.1 m A h/g,and the capacity retention rate is 97.5%.At 300 m A/g current density,compared with the untreated basswood carbon capacity retention rate(64.8%),Bacillus enzymatic hydrolysis of basswood carbon capacity retention rate increased to 84.8%,the rate performance improved.Meanwhile,compared with the fungal treatment(120 days),the treatment time of bacillus was only 3 days.The bacillus had fast growth and rapid enzyme production,which improved the pretreatment efficiency of precursor by 40 times.(2)The Bacillus enzymolysis basswood in the air for pre-oxidation,and then it soaked in phytic acid solution,the use of phytic acid phosphate groups and cellulose in the hydroxyl esterification reaction to achieve phosphorus doping,and then through high temperature carbonization to get phosphorus doping Bacillus enzymolysis basswood carbon.Phosphorus doping can increase the layer spacing of carbon materials(0.40 nm)and produce a large number of active sites,thus speeding up the transport of sodium ions and improving the storage capacity of sodium materials.When the concentration of phytic acid solution is 5%,the material has a large active specific surface area and pore structure,and the sodium-ion can be transported quickly in the electrode material.At the current density of 60 m A/g,the specific capacity of the enzymic hydrolysis of basswood carbon by Bacillus phospho-doped bacteria was 348.4 m A h/g in 77 cycles.After phosphorus doping treatment,the capacity retention rate of the material at 300 m A/g current density is 91.1%,and the magnification performance of the material is further improved.