| It is widely used in mobile phones,laptop computers,digital cameras and aviation power supply lithium cobalt batteries in the working process of the aging degree is difficult to identify,the service life can not be accurately estimated and so on.In order to ensure the reasonable use of the battery,it is necessary to estimate and predict the aging of the battery to extend the battery life and ensure the safe and stable operation of the battery power supply system.In this paper,the accelerated life test of lithium cobalt oxide battery under different stresses is carried out,and the aging model of lithium cobalt oxide battery is established with ambient temperature,charging cut-off voltage and discharge rate as independent variables and battery life as dependent variables.The specific work is as follows:Firstly,according to the basic characteristics of lithium cobalt oxide battery,the suitable accelerated life test method was selected.According to the battery technical parameters,design the accelerated life cycle test and standard capacity test flow of lithium cobalt oxide battery,and determine the basis of battery life termination.Then,according to the battery technical parameter manual,the standard level of each external stress under the normal operation of the battery is determined.Considering the environment temperature,charge ratio,discharge rate and charge cut-off voltage and discharge cut-off voltage five external factors impact on battery life,design stress screening test,according to the degree of stress effect on battery life size selection environment temperature,charge cut-off voltage and discharge ratio as cobalt acid lithium batteries accelerated stress accelerated life test.According to the actual working conditions of the battery and the data of stress screening test,the range of acceleration stress intensity in the accelerated life test of lithium cobalt oxide battery was determined: 20℃ < ambient temperature ≤40℃,4.2V < charging cut-off voltage ≤ 4.5V,and 1C < discharge rate ≤3C.According to the selected type of acceleration stress and the range of stress intensity,a reasonable stress gradient was designed for different acceleration stress to determine the accelerated life cycle test condition of lithium cobalt oxide battery and complete the accelerated life test scheme design.Then,the accelerated life test of lithium cobalt oxide battery was carried out according to the accelerated life test scheme and the selected accelerated stress.The experimental results show that the battery life decreases linearly with the increase of cycle times,and the sensitivity of battery life to different types of acceleration stress is different.Under the action of the same type of stress,the higher the stress level,the faster the battery capacity attenuation rate,the faster the battery aging speed,the shorter the battery life.Finally,the linear fitting analysis of accelerated life test data was carried out,and the battery aging model types suitable for lithium cobalt oxide batteries were selected.The aging model of lithium cobalt oxide batteries under the action of ambient temperature,charging cut-off voltage and discharge rate was established respectively.According to the aging model,it can be concluded that the battery life decreases by about 4% for every 1℃ increase of ambient temperature.The battery life decreases by about 2.5% for every increase of 0.01 V of charging cut-off voltage.The battery life decreases by about 3.1% for every 0.1C increase in discharge rate.The model accuracy verification experiment was carried out for the proposed lithium cobalt oxide battery aging model.By comparing and analyzing the test results with the model prediction results,the error was controlled within 3%,which proved that the aging model proposed in this paper could predict the life change of lithium cobalt oxide battery more accurately.The accelerated life test scheme for lithium cobalt oxide batteries presented in this paper can provide guidance for the study of accelerated aging methods for other types of lithium ion batteries.The aging model of lithium cobalt oxide battery can restore the life decay rule of the battery,predict the battery life accurately,and provide a theoretical basis for the reasonable use of the battery. |
