Development Of Lithium Ion Batteries For ETC Application

With the rapid development of the national highway network,the contradiction among the artificial semi-automatic toll collection mode and the gradually increasing traffic flow as well as the vehicle traffic efficiency has become increasingly prominent.The drawbacks of low efficiency of the traditional charging model is exposed day by day.The highway electronic toll collection system(ETC)has become increasingly popular,resulting in the frequent occurrence of ETC failures using lithium-ion batteries.The drawbacks of a lithium battery have become increasingly prominent,and it has become urgent to find alternative batteries.Lithium-ion batteries are characterized by high relative energy,long cycle life,high single-cell voltage,light weight,low self-consumption rate,wide temperature range,no memory effect,and environmental friendly.They are widely used in smartphones,notebook computers,and Bluetooth devices.Therefore,lithium-ion batteries have become the preferred choice for replacing lithium batteries on automotive ETCs.Because the lithium iron phosphate battery is with stable discharge platform,the superior high temperature performance,the excellent safety performance,the wide material source,and the economical cost,which can fully satisfy the requirements of the vehicle ETC for the power battery.In this paper,the battery performance requirements are determined by the current usage of the vehicle ETC,the ambient temperature used,and the battery safety requirements.By analyzing and comparing the existing cathode material system,lithium iron phosphate cathode;artificial graphite anode,EC\DMC\DEC\VC 1 mol lithium salt electrolyte,0.02 mm thick wet diaphragm,carbon coated aluminum foil,cylindrical steel shell,etc.Materials,developed a high performance 14200Fe100 lithium iron phosphate battery that meets the requirements of ETC use.The specific content and results of this study are as follows:(1)Through the analysis of the discharge voltage platform of lithium iron phosphate battery,the relation between open circuit voltage and capacity is obtained.When the charge is in the 70-90%charged region,the battery voltage does not change;10%-70%is charged when the battery is open.The voltage is 3.217-3.313 V,the voltage difference is 0.096 V,and the linear characteristic of voltage and charge percentage is not obvious;when the charge is below 10%,the state of charge is linear with voltage.Using the regression method,the relationshipbetweenvoltageandchargepercentageis C=0.1972V~3-1.5137V~2+3.8928V-3.3501,(R~2=0.9991);the relationship between charge percentage and voltage is V=-11424C~3+2891.3V~2-316.9V+2.6671,(R~2=0.9997).Using this result,a charge of about 2%is selected in the production process,and the voltage is about 2.9V,which enables rapid and effective self-consumption screening by voltage difference.(2)By optimizing the design,the standard deviation of the internal resistance of the battery is only 2%,the internal resistance is good;95%discharges 103%of the electricity,and the high temperature performance is good;70 degrees storage 28 days,the recovery is 93%,70 degrees The storage is increased by only 20%in 84 days,the storage performance is stable;the cycle capacity is not attenuated for 500 weeks,and the cycle performance is good;3C10V overcharge is incombustible and non-explosive,and the safety is high;the battery monopole replaces the bipolar ear,and the production operation is simple,greatly Provides high manufacturing efficiency.It has been widely recognized by the market.