New insights on ultrafast Na[solv]^(+) coinserted graphite driven by an electric field

电场驱动下的超快Na[solv]^(+)共嵌入石墨的新见解

Sodium ions(Na+) and ether electrolyte coinserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na^(+) ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g^(-1), and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg^(-1)and an output energy density of 103 W h kg^(-1)(relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.

钠离子和醚电解质共嵌入的石墨呈现明显的体积膨胀效果,无法对其稳定性做出合理的解释.本文中,我们发现共插入反应在大电流条件下受到施加电场的洛伦兹力影响,钠离子被分离出来,乙二醇二甲醚(DME)分子保留在石墨层之间.此见解为这种材料的非凡稳定性提供了合理解释.原位XRD和DFT计算证实了Na+的脱出.根据该结果,未改性的商品石墨以高达10 A g^(-1)的电流密度稳定地循环了6400次,容量保持率高达97.2%.在实验室组装的全电池最大输出功率为14,846 W kg^(-1),输出能量密度为103 W h kg^(-1)(相对于阳极和阴极活性材料的重量).该新机理为大规模储能提供了新的设计思路.