多孔石墨烯纳米片阵列的制备与储钾性能研究

Study on Preparation and Potassium Storage Properties of Porous Graphene Nanosheet Arrays

摘要:

石墨烯钾离子电池（PIBs）具有原料储量丰富及与锂离子电池接近的标准电位的优势，在储能领域受到广泛关注。快速储能特性对于钾离子电池的应用具有重要意义。石墨烯具有良好的导电性及较短的离子电子扩散路径，是钾离子电池负极材料的理想选材之一。与离子插层相比，石墨烯基于吸脱附机制的储能更有利于快速充放电，且具有较长的电极寿命。不同于石墨烯的结构调控、掺杂及无序化等改性方法，制备多孔石墨烯有利于增加更多的缺陷活性位点及更大的比表面积，进而提升其基于吸脱附机制的快速储能性能。首先将少层石墨烯纳米片阵列（GNS）负载超细ZnO纳米颗粒，然后采用碳热还原法制备出多孔石墨烯纳米片阵列的电极（P-GNS），并将其用于钾离子电池。结果表明，P-GNS可有效地提升钾离子电池的倍率性能，在较大电流密度（3 A·g^-1）下的容量达到181.6 mAh·g^-1，在电流密度1 A·g^-1下经1 000次循环后的容量保持率仍有80.6%，表现出优异的循环性能。全电池在1 A·g^-1电流密度下也表现出较好的大倍率性能，循环50次后的容量仍有87.4 mAh·g^-1。储能机理研究表明，石墨烯电极造孔可使基于吸脱附电容性储能的活性位点明显增多，进而有效地提升了电池大倍率充放电性能。另外，基于脱吸附的储钾过程不会破坏材料，有利于石墨烯维持结构的稳定，进而大幅提升了电池的循环寿命。本研究为构建石墨烯基快速储能材料，以及发展大倍率长寿命钾离子电池提供了参考。

Abstract:

Compared with lithium-ion batteries， potassium-ion batteries （PIBs） have received extensive attention in the field of energy storage due to their abundant potassium resources and standard electrode potential close to lithium. The fast energy storage characteristics are of great significance for the practical application of potassium ion batteries. Graphene， with its large specific surface area and good electrical conductivity， is an ideal choice for the negative electrode of fast potassium-ion batteries. The storage mechanism of graphene for potassium is divided into ion intercalation and defect/edge adsorption. Among them， the adsorption storage mechanism is usually conducive to fast energy storage and longer electrode life. Therefore， this paper aims to improve its fast potassium storage performance by modifying graphene. Specifically， few-layered graphene nanosheet （GNS） arrays were first loaded with ultrafine ZnO particles， and porous graphene nanosheet （P-GNS） array electrodes were prepared through the carbothermal reduction method， which were applied in PIBs. Experimental results show that this material can effectively improve the rate performance of PIBs. The capacity of P-GNS can reach 181.6 mAh·g^-1 at a high current density of 3 A·g^-1. After 1 000 cycles at 1 A·g^-1， the capacity retention is as high as 80.6%， showing excellent cycle performance. In addition， the full cell also displays good high-rate performance， the capacity is still 87.4 mAh·g^-1 at a current density of 1 A·g^-1 after 50 cycles. The energy storage mechanism study revealed that the porous graphene electrode can significantly increase the active sites for adsorption/desorption capacitive energy storage， thereby effectively improving the high-rate charge-discharge performance； in addition， the adsorption/desorption potassium storage process will not destroy the material structure， which is beneficial to graphene. Maintaining structural stability can greatly improve the cycle life. This work provides a reference for constructing graphene-based fast energy storage materials and developing high-rate and long-life PIBs.