School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
Nano Lett. 2014 Aug 13;14(8):4700-6. doi: 10.1021/nl5018139. Epub 2014 Jul 7.
Improving battery capacity and power is a daunting challenge, and in Li-ion batteries positive electrodes often set the limitation on both properties. Layered transition-metal oxides have served as the mainstream cathode materials for high-energy batteries due to their large theoretical capacity (∼ 280 mAh/g). Here we report a significant enhancement of cathode capacity utilization through a novel concept of material design. By embedding Li(Ni0.5Co0.2Mn0.3)O2 in the single wall carbon nanotube (CNT) network, we created a composite in which all components are electrochemically active. Long-term charge/discharge stability was obtained between 3.0 and 4.8 V, and both Li(Ni0.5Co0.2Mn0.3)O2 and CNT contribute to the overall reversible capacity by 250 and 50 mAh/g, respectively. The observed improvement causes significant depolarization within the electrodes through the CNT network system. Additionally, the depolarization provides the ideal template to understand the solid reaction mechanism of Li(Ni0.5Co0.2Mn0.3)O2 by demonstrating well-defined two-stage delithiation kinetics consistent with first-principle calculations, which would be otherwise impossible. These results deliver new insights on both practical designs and fundamental understandings of battery cathodes.
提高电池容量和功率是一项艰巨的挑战，在锂离子电池中，正极通常对这两个性能都有限制。层状过渡金属氧化物因其具有较大的理论容量（约 280 mAh/g）而被用作高能电池的主流阴极材料。在这里，我们通过一种新颖的材料设计理念，报告了对阴极容量利用率的显著提高。通过将 Li(Ni0.5Co0.2Mn0.3)O2 嵌入单壁碳纳米管 (CNT) 网络中，我们创造了一种所有组件都具有电化学活性的复合材料。在 3.0 和 4.8 V 之间获得了长期的充放电稳定性，Li(Ni0.5Co0.2Mn0.3)O2 和 CNT 分别贡献了 250 和 50 mAh/g 的总可逆容量。观察到的改进通过 CNT 网络系统在电极内部引起显著的去极化。此外，去极化提供了理想的模板，通过展示与第一性原理计算一致的明确两阶段脱锂动力学，来理解 Li(Ni0.5Co0.2Mn0.3)O2 的固相反响机制，否则这是不可能的。这些结果为电池阴极的实际设计和基础理解提供了新的见解。
