Design Of Bacterial Cellulose Composite Separator And Its Performance Of Lithium Battery

As one of the most important and promising energy storage technologies,lithium battery has been widely used in the past decades.Separator is an important part of lithium battery,and its structure and properties also determine the final performance of lithium battery.Currently,polyolefin separator is widely used in lithium batteries.However,polyolefin cannot meet the requirements of high-performance lithium batteries in the future due to its shortcomings.Polyolefin materials from petroleum are non renewable and non degradable.Cellulose has many excellent properties.At the same time,the use of cellulose helps to reduce the dependence on fossil energy and the threat of environmental pollution.It is one of the most potential high-performance separator materials.However,there are still some problems,such as the pure cellulose separator is not flame retardant,the pore is not uniform,and has no inhibitory effect on lithium dendrite.In this paper,cellulose composite inorganic nano materials will be used to prepare separator and apply in lithium-ion battery system.The specific research contents are as follows（1）Molecular sieve nanoparticles were compounded on cellulose based separator（ZCM）by vacuum assisted filtration.The separator has many and uniform pores,and has better electrolyte affinity than polyolefin PP separator.The thermal stability test shows that the separator has excellent thermal stability and maintains dimensional stability at 180℃.The electrochemical performance test showed that the molecular sieve nanoparticles had better ionic conductivity,interface compatibility and excellent cycle rate performance than the polyolefin PP separator.Meanwhile,the linear sweep voltammetry test showed that the separator had better reaction kinetics,in the cycle stability test with the polarization voltage（0.01 V）lower than the polarization voltage above 0.1 V of PP separator.（2）Furthermore,three-layer separator（NP/SiC/NP）with heat-resistant framework was prepared by using heat-resistant SiC nanowires.There are nano pores on the separator surface,and nano cellulose with polar groups on the separator surface improves the wettability of the separator to electrolyte.In the combustion test,after being fully burned by an alcohol lamp with a flame temperature close to 500℃,the separator still keeps its original size,and its properties are stable in the range of 0～300℃.At the same time,it has excellent ionic conductivity,interface compatibility and cycling rate performance.In the cycle stability test,the polarization voltage of NP/SiC/NP separator is only 0.01 V after 385 hours cycle,which is lower than that of polyolefin PP separator（4.1 V）.（3）A three-layer separator（SiC/NP/SiC）with SiC nanowires as functional layers.The results show that the prepared separator has good wettability,excellent thermal stability and dimensional stability at 180℃.Meanwhile,the interface resistance of the separator with SiC nanowire functional layer is 70Ω,while the interface resistance of Si O₂/BC and molecular sieve/Si O₂/BC systems are all over 100Ω.In the cycle stability test of the lithium symmetrical battery,it shows long cycle and low polarization voltage（0.6V）.