锂离子电池的优点

锂离子电池的优点

1）能量密度高。能量密度可达460-600Wh/kg，其能量密度是铅酸电池的6-7倍；

2）相对较高的平均输出电压值。常用的锂离子电池单体平均工作电压约为3.7V，约为镍-隔电池或者镍-氢电池的3倍

3）可以高功率输出，在电动汽车的磷酸铁锂离子电池可以达到15-30C充放电能量，有利于启动加速；

4）相对较小的自放电率，无记忆效应，锂电池的自放电率为镍-隔电池或者镍-氢电池的一半甚至更小。记忆效应指的是电池在充放电循环过程中容量减小的现象，而锂离子电池在循环过程中不出现明显地容量衰减现象；

5）使用寿命长，在正常条件下，锂离子电池使用寿命可达6年，循环次数超过1000次。（6）可快速充电，使用额定电压为4.2 V的充电器只需1~2小时即可充满

（7）使用温度范围宽，通常可在-30～+45℃温度范围内使用，通过调整电解液甚至可以在更宽温度范围内使用；

（8）绿色电池，对环境友好，无论生产、使用和报废，都不存在镉、铅、汞等对环境有污染的元素；

Figure 4b shows the typical charge−discharge voltage profiles of the S@CNTs/Co3S4−NBs, S@Co3S4−NBs and S@CNTs electrodes at 0.2 C (1.0 C = 1,675 mAh g−1). The S@CNTs/ Co3S4−NBs electrode exhibits two typical discharge plateaus at 2.35 and 2.08 V (vs Li+/Li), originated from the reduction of S8 to soluble long-chain polysulfides (Li2Sx, 4 ≤ x ≤ 8) and the formation of insoluble short-chain polysulfides (Li2S/Li2S2), respectively. The single charge plateau of S@CNTs/Co3S4−NBs between 2.25−2.36 V is ascribed to the oxidation of Li2S/ Li2S2 to Li2Sx and eventually S8. These charge and discharge plateaus are consistent with corresponding CV curves (Figure S5). Notably, the S@CNTs/Co3S4−NBs electrode exhibits lower potential hysteresis and higher sulfur utilization ratio than those of the S@Co3S4−NBs and S@CNTs, mainly attributed to the strong chemical affinity of polar Co3S4−NBs with polysulfides and the interconnected CNT network.

图4b 显示了S@CNTs/Co3S4−NBs、S@Co3S4−NBs 和S@CNTs 电极在0.2 c (1.0 c = 1675 麻将g−1)上的典型charge−discharge 电压剖面。S@CNTs/Co3S4−NBs电极展示两个典型的放电高原在 2.35 和 2.08 V (vs li +/李), 起源于 S8 的减少到可溶性长链多硫化物 (Li2Sx, 4 ≤ x ≤ 8) 和形成不溶性短链多硫化物 (Li2S/Li2S2),分别.2.25−2.36 V 之间

S@CNTs/Co3S4−的单电荷高原归因于Li2S/Li2S2 对Li2Sx 和最终S8 的氧化作用。这些电荷和放电高原与相应的CV 曲线一致(图S5)。值得注意的是, S@CNTs/Co3S4−NBs电极具有比S@Co3S4−NBs和 S@CNTs 更低的潜在滞后率和较高的硫利用率,主要归因于极Co3S4−NBs与多硫化物的强烈化学亲和性和互联的碳纳米管网络。

The rate capability comparison of S@CNTs/Co3S4−NBs,S@Co3S4−NBs, S@CNTs, and S@mixed-CNTs&Co3S4−NBs(the sulfur composite of simply mixed CNTs and Co3S4−NBs)is shown in Figure 4d and Figure S6. When cycled at 0.2, 0.5,1.0, 2.0, and 5.0 C, the S@CNTs/Co3S4−NBs cathode candeliver impressive discharge capacities of 1330, 1165, 988, 859,and 702 mAh g−1, respectively. As the current density turnsback to 1.0 C, the discharge capacity of S@CNTs/Co3S4−NBsrestores to 958 mAh g−1, indicating good structural stability athigh rate. In contrast, the discharge capacities of S@Co3S4−NBs cathode fades sharply from 1240 to 268 mAh g−1 when therate increases from 0.2 to 2.0 C. What is more, the dischargecapacity of S@CNTs fades dramatically to 37 mAh g−1 whenthe current rate increases to 5.0 C. It is clear that the S@CNTs/Co3S4−NBs cathode exhibits much higher ratecapabilities than those of S@Co3S4−NBs and S@CNTs. Thegalvanostatic charge−discharge voltage profiles of