Study On Preparation Technology And Preformance Of Lithium-ion Battery Pack

In this paper,10 Ah nominal capacity of 186590 square aluminum test battery were prepared by choosing the LiNi_0.5Co_0.2Mn_0.3O₂ as cathode material and the Mesophase carbon microbeads?MCMB?as anode material.The preparation technology and the effect of preparation technology on the electrochemical performance of single batteries and battery pack were studied by the charge and discharge test system.The effect of cell technology on the initial discharge capacity of battery was studied.Two different cells were designed,which were the traditional negative coated positive structure and the improved positive coated negative structure respectively.It was found that the initial discharge capacity of battery with improved structure increased 0.26 Ah compared with the traditional battery at the rate of 0.2 C under the same dressing.This is because the improved cell with continuous anode flake eliminates the capacity loss caused by transition edge effect,which is produced by the intermittent anode flake in the transition cell,finally improves the assembly of cell with shell,increases electrolyte injection space and the number of transferred Li⁺.Low lithium salt concentration of electrolyte will lead to weaken the cycle stability of the battery.To solve this problem,we increased the lithium salt concentration of electrolyte,tested and compared the electrochemical performance of batteries which injected into two kinds of lithium concentration electrolyte.Compared with the battery with the low concentration of lithium salt electrolyte,the high concentration of lithium salt electrolyte injection can significantly improve cycle performance of the battery,the capacity retention rate was increased 25.17%after 500 cycles at the rate of 1 C.At the same time,the battery has better rate performance and lower self-discharge rate.Owing to the increased lithium salt concentration of the electrolyte,the number of migratory Li⁺was increased and SEI film stability was enhanced,so as to improve the electrochemical performance of battery.The consistency of the battery pack was studied.The consistency of batteries in the pack which was composed of three consistent initial performance batteries and one different battery compared with others were represented.The differential battery can reduce the available capacity of the battery pack,reduce the cycle performance and increase the inconsistency.The reason is that the initial performance of the single battery is not uniform and the process capacity fade is not synchronous.On this basis,the effect of sub-matching technology on the consistency of the 48V/10Ah battery pack for the electric bicycle was studied.With capacity,voltage,resistance of the battery as the separation conditions,different distribution programs were set by control variable method.The experiments results showed that the three parameters were selected as the separation condition of the battery pack simultaneously has the highest capacity retention rate which is 97.68%after110 cycles at the rate of 0.5 C,and the discharge capacity discrete degree of batteries in the pack is the smallest.This is because the effective sub-matching made the initial performance of the battery pack was consistent,the process capacity decay rate of the batteries in the back were reduced,effectively enhanced the consistency of the battery pack.