数学模拟方法研究导电剂形貌对锂离子电池高倍率放电性能的影响

制备了正极中只含有一种导电剂(KS-6或Super-P)的锂离子电池,比较了它们的倍率放电性能并对放电过程进行了模拟。以Super-P为正极导电剂的电池15C放电容量为1C容量的84.3%,以KS-6为正极导电剂的电池15C放电容量为1C容量的21.8%,前者的倍率放电性能明显优于后者。数学模拟结果显示,以KS-6为导电剂的正极的Bruggeman系数为3.1,以Super-P为导电剂的正极的Bruggeman系数为2.76,前者明显大于后者,认为这是由于KS-6的片状形貌使其容易相互平行排列造成的。大电流放电时,以KS-6为导电剂的正极中出现了电解质耗竭而导致该区域内电化学反应停止的现象,从而导致电池放电容量急剧降低。

Effect of Conductive Agent Morphology on High Rate Discharge Capability of Li-Ion Batteries by Mathematical Simulation

Tow kinds of lithium ion batteries, using one kind of conductive agent in cathode only, KS-6 or Super-P, were prepared and their rate discharge performances were compared. Their discharge processes were simulated also. The discharge capacity of cell using Super-P as cathode conductive agent at 15C is 84.3% of that at 1C rate. The discharge capacity of cell using KS-6 as cathode conductive agent at 15C rate only holds 21.8% of that at 1C rate. The rate discharge performance of former is superior to the latter.The results of simulation demonstrate that the Bruggeman coefficient for cathode using KS-6 is 3.1, which is much larger than that for cathode using Super-P (2.76). This is ascribed to flaky shape of KS-6 since these particles are prone to stack parallel in electrode. When discharged at large current, the electrolyte in cathode using KS-6 is depleted and the electrochemical reaction in this region ceases. The discharge capacity declines steeply.