Wang Wei, Zhang Jiaolong, Yang Qin, Wang Shuwei, Wang Wenhui, Li Baohua
Shenzhen Key Laboratory on Power Battery Safety Research and Shenzhen Geim Graphene Center, Tsinghua Shenzhen International Graduate School, Shenzhen 518055, China.
School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
ACS Appl Mater Interfaces. 2020 May 20;12(20):22901-22909. doi: 10.1021/acsami.0c03952. Epub 2020 May 10.
Functional electrolytes that are stable toward both Li-metal anode and high-voltage (>4 V vs Li/Li) cathodes play a critical role in the development of high-energy density Li-metal batteries. Traditional carbonate-based electrolytes can hardly be used in high-voltage Li-metal batteries due to the dendritic Li deposits, low Coulombic efficiency, and anodic instability in the presence of aggressive cathodes. Herein, we design a concentrated dual-salt electrolyte that achieves high stability for both Li anodes and high-voltage cathodes of LiNiMnO (LNMO) and LiNiCoMnO (NCM). A Li||Cu cell in the designed electrolyte shows a high Coulombic efficiency of >98% in long-term plating/stripping for 900 cycles. Li||LNMO and Li||NCM cells achieve a capacity retention of 88.5% over 500 cycles and 86.2% over 200 cycles with a cutoff voltage of 4.9 and 4.3 V, respectively. The Li||LNMO full cell with a cathode areal capacity of 1.8 mAh/cm and only 3× excess Li was fabricated, and it delivered a high capacity retention of 87.8% after 100 cycles. The reasons for the good cycling stability of the cells in a concentrated dual-salt electrolyte can be attributed to the reversible dendrite-free plating/stripping of a Li-metal anode and stable interfacial layers on both anode and cathode.
对锂金属负极和高压（相对于Li/Li为>4V）正极均稳定的功能性电解质在高能量密度锂金属电池的发展中起着关键作用。传统的碳酸盐基电解质由于锂枝晶沉积、库仑效率低以及在存在活性正极时的阳极不稳定性，几乎无法用于高压锂金属电池。在此，我们设计了一种浓双盐电解质，该电解质对LiNiMnO（LNMO）和LiNiCoMnO（NCM）的锂负极和高压正极均具有高稳定性。在设计的电解质中的Li||Cu电池在900次循环的长期电镀/剥离过程中显示出>98%的高库仑效率。Li||LNMO和Li||NCM电池在截止电压分别为4.9V和4.3V时，在500次循环中容量保持率达到88.5%，在200次循环中达到86.2%。制备了阴极面积容量为1.8mAh/cm且仅过量3倍Li的Li||LNMO全电池，在100次循环后其容量保持率高达87.8%。在浓双盐电解质中电池具有良好循环稳定性的原因可归因于锂金属负极的可逆无枝晶电镀/剥离以及阳极和阴极上稳定的界面层。
