以钠金属为对电极的纽扣半电池通常被用来评价钠离子电池电极材料的电化学性能。本工作揭示了在低温环境下,钠金属半电池在商业化酯类电解液中用于评价电极材料电化学性能存在局限性,这是因为钠金属电极在低温下具有高界面和电荷转移电...以钠金属为对电极的纽扣半电池通常被用来评价钠离子电池电极材料的电化学性能。本工作揭示了在低温环境下,钠金属半电池在商业化酯类电解液中用于评价电极材料电化学性能存在局限性,这是因为钠金属电极在低温下具有高界面和电荷转移电阻导致了大的Na+的沉积/剥离过电势,干扰了半电池对电极材料低温电化学性能的评价。Na||硬碳(HC)半电池在-20℃以0.2C (1C=300 m A/g)的倍率充放电时,钠金属电极的电位变化高达0.94 V,HC电极材料仅表现出21.1 m Ah/g比容量,存在对HC低温电化学性能不准确评价的可能性。针对此,本文提出了一种可以取代钠金属的Na15Sn4@Na复合电极用于钠离子电池电极材料的低温电化学性能评价。研究表明,Na15Sn4@Na电极有着与钠金属相同的电极电位。在-20℃的低温工况下,Na15Sn4@Na||Na15Sn4@Na对电池在0.1 m A/cm^(2)电流密度下的沉积/剥离过电势仅为0.09 V,远远小于钠金属电极0.96 V的沉积/剥离过电势。使用HC作为研究对象,所制备的Na15Sn4@Na||HC半电池在-20℃下,在HC析钠前,展现出高达100.8 m Ah/g的比容量,远高于以钠金属为对电极的半电池所展示的比容量(21.1 m Ah/g),说明基于Na15Sn4@Na对电极的半电池更能准确地表征材料本征的低温电化学性能。该工作为钠离子电池电极材料低温电化学性能的准确评价提供了实验依据。展开更多
The ether electrolytes usually outperform ester electrolytes by evaluating sodium-ion batteries(SIBs)rate performance,which is a near-unanimous conclusion of previous studies based on an essential configuration of the...The ether electrolytes usually outperform ester electrolytes by evaluating sodium-ion batteries(SIBs)rate performance,which is a near-unanimous conclusion of previous studies based on an essential configuration of the half-cell test.However,here we find that contrary to consensus,the ester electrolyte shows better Na storage capability than the ether electrolyte in full cells.An in-depth analysis of three-electrode,symmetric cell,and in situ XRD tests indicates that traditional half-cell test results are unreliable due to interference from Na electrodes.In particular,Na electrodes show a huge stability difference in ester and ether electrolytes,and ester electrolytes suffer more severe interference than ether electrolytes,resulting in the belief that esters are far inferior to ether electrolytes.More seriously,the more accurate three-electrode test would also suffer from Na electrode interference.Thus,a“corrected half-cell test”protocol is developed to shield the Na electrode interference,revealing the very close super rate capability of hard carbon in ester and ether electrolytes.This work breaks the inherent perception that the kinetic properties of ester electrolytes are inferior to ethers in sodium-ion batteries,reveals the pitfalls of half-cell tests,and proposes a new test protocol for reliable results,greatly accelerating the commercialization of sodium-ion batteries.展开更多
文摘以钠金属为对电极的纽扣半电池通常被用来评价钠离子电池电极材料的电化学性能。本工作揭示了在低温环境下,钠金属半电池在商业化酯类电解液中用于评价电极材料电化学性能存在局限性,这是因为钠金属电极在低温下具有高界面和电荷转移电阻导致了大的Na+的沉积/剥离过电势,干扰了半电池对电极材料低温电化学性能的评价。Na||硬碳(HC)半电池在-20℃以0.2C (1C=300 m A/g)的倍率充放电时,钠金属电极的电位变化高达0.94 V,HC电极材料仅表现出21.1 m Ah/g比容量,存在对HC低温电化学性能不准确评价的可能性。针对此,本文提出了一种可以取代钠金属的Na15Sn4@Na复合电极用于钠离子电池电极材料的低温电化学性能评价。研究表明,Na15Sn4@Na电极有着与钠金属相同的电极电位。在-20℃的低温工况下,Na15Sn4@Na||Na15Sn4@Na对电池在0.1 m A/cm^(2)电流密度下的沉积/剥离过电势仅为0.09 V,远远小于钠金属电极0.96 V的沉积/剥离过电势。使用HC作为研究对象,所制备的Na15Sn4@Na||HC半电池在-20℃下,在HC析钠前,展现出高达100.8 m Ah/g的比容量,远高于以钠金属为对电极的半电池所展示的比容量(21.1 m Ah/g),说明基于Na15Sn4@Na对电极的半电池更能准确地表征材料本征的低温电化学性能。该工作为钠离子电池电极材料低温电化学性能的准确评价提供了实验依据。
基金supported by the National Natural Science Foundation of China(22179094)the Tianjin Research Program of Application Foundation and Advanced Technology of China(15ZCZDGX00270)
文摘The ether electrolytes usually outperform ester electrolytes by evaluating sodium-ion batteries(SIBs)rate performance,which is a near-unanimous conclusion of previous studies based on an essential configuration of the half-cell test.However,here we find that contrary to consensus,the ester electrolyte shows better Na storage capability than the ether electrolyte in full cells.An in-depth analysis of three-electrode,symmetric cell,and in situ XRD tests indicates that traditional half-cell test results are unreliable due to interference from Na electrodes.In particular,Na electrodes show a huge stability difference in ester and ether electrolytes,and ester electrolytes suffer more severe interference than ether electrolytes,resulting in the belief that esters are far inferior to ether electrolytes.More seriously,the more accurate three-electrode test would also suffer from Na electrode interference.Thus,a“corrected half-cell test”protocol is developed to shield the Na electrode interference,revealing the very close super rate capability of hard carbon in ester and ether electrolytes.This work breaks the inherent perception that the kinetic properties of ester electrolytes are inferior to ethers in sodium-ion batteries,reveals the pitfalls of half-cell tests,and proposes a new test protocol for reliable results,greatly accelerating the commercialization of sodium-ion batteries.
