碳涂层策略已成为改善聚阴离子阴极电导率的必不可少的方法。然而,由于碳的前体和阴极之间复杂的反应过程,建立碳质前体的统一筛选原则仍然是一个技术挑战。在这里,我们揭示了含碳前驱体热解化学不可否认地影响Na3V2(PO4)3(NVP)阴极的形成过程和性能。通过研究三种类型的碳质前体,发现含O/H的官能团可以为阴极前体提供更多的键合位点,并通过热解产生还原气氛,有利于形成聚阴离子材料和均匀的碳涂层。相反,官能团的过度热解导致大量的气体,这不利于碳层的致密性。此外,残余杂原子的大量存在减少了石墨化。在这种情况下,结果表明,具有合适官能团的碳点(CD)前体可以全面提高Na迁移速率,可逆性,和阴极材料的界面稳定性。因此,NVP/CD阴极显示出众的容量保持,在50℃的高速率下,10,000次循环后保持92%。这些发现为聚阴离子阴极的碳源选择提供了有价值的基准。
The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na3V2(PO4)3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na+ migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.