High-voltage (5-V) lithium–ion batteries (LIBs) have garnered substantial interest due to their superior energy density. Nevertheless, the unstable interphase of high-voltage LIBs can cause electrolyte decomposition, electrode collapse, transition metal dissolution, and lithium dendrite growth during cycling, which impedes their widespread commercial use. To mitigate these challenges, various alkali-metal phosphates were incorporated into a carbonate-based electrolyte as film-forming additives, aiming to improve the electrochemical performance of LiNiMnO (LNMO)-based LIBs. Following a detailed comparison of the electrochemical performances of various alkali-metal phosphates, KHPO and NaHPO were selected for an in-depth investigation in this research. The highly protective passivation film generated by KHPO and NaHPO on the electrode surface provided significant protection by effectively inhibiting continuous electrolyte decomposition. This finding was supported by density functional theory calculations and a variety of electrochemical and characterization tests. The HPO primarily contributed to the formation of the cathode electrolyte interphase film on the cathode surface. KHPO (via the electrostatic shielding effect of ions) and NaHPO (through the co-precipitation of Na and Li ions) both effectively inhibited the growth of lithium dendrites on the lithium metal anode. Additionally, the KHPO and NaHPO additives regulated the amount of HF in the electrolyte through acid–base equilibrium reactions. The electrolytes containing additives significantly enhanced the electrochemical performances of Li||Li, LNMO/Li, LNMO/graphite, and LNMO/LiTiO cells. LNMO/Li half-cells with standard electrolyte (STD) supplemented with KHPO and NaHPO additives demonstrated capacity retentions of 92.9 % and 90.0 % after 500 cycles at 5 C, respectively, in contrast to only 79.4 % for the STD electrolyte alone. Furthermore, the LNMO/graphite full cell exhibited an increased capacity retention, reaching 81.1 % (STD+KHPO) and 78.29 % (STD+NaHPO), up from 70.8 % with the STD, after 100 cycles at 0.5 C. Given their ease of use, affordability, and widespread availability, KHPO and NaHPO additives show significant potential to enhance the electrochemical properties of high-voltage LIBs.

中文翻译：

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碱金属磷酸盐添加剂对5-V LiNi0.5Mn1.5O4基锂离子电池界面结构的影响


高压 (5V) 锂离子电池 (LIB) 因其卓越的能量密度而引起了广泛关注。然而，高压锂离子电池不稳定的界面会导致循环过程中电解质分解、电极塌陷、过渡金属溶解和锂枝晶生长，从而阻碍其广泛的商业应用。为了缓解这些挑战，将各种碱金属磷酸盐作为成膜添加剂添加到碳酸盐基电解质中，旨在提高 LiNiMnO (LNMO) 基锂离子电池的电化学性能。在详细比较了各种碱金属磷酸盐的电化学性能后，本研究选择了 KH2PO 和 Na2HPO 进行深入研究。 KHPO和NaHPO在电极表面生成的高保护性钝化膜通过有效抑制电解液的持续分解提供了显着的保护。这一发现得到了密度泛函理论计算以及各种电化学和表征测试的支持。 HPO主要有助于阴极表面上阴极电解质界面膜的形成。 KH2PO（通过离子的静电屏蔽作用）和Na2HPO（通过Na离子和Li离子的共沉淀）都有效抑制了锂金属负极上锂枝晶的生长。此外，KHPO 和 NaHPO 添加剂通过酸碱平衡反应调节电解液中 HF 的含量。含有添加剂的电解质显着增强了Li||Li、LNMO/Li、LNMO/石墨和LNMO/LiTiO电池的电化学性能。 采用标准电解质 (STD) 并补充 KH2PO 和 NaHPO 添加剂的 LNMO/Li 半电池在 5 C 下循环 500 次后，容量保持率分别为 92.9% 和 90.0%，而单独 STD 电解质的容量保持率仅为 79.4%。此外，LNMO/石墨全电池表现出更高的容量保持率，在 0.5 C 下循环 100 次后，容量保持率达到 81.1% (STD+KH2PO) 和 78.29% (STD+Na2HPO)，而 STD 为 70.8%。由于使用、经济性和广泛可用性，KHPO 和 NaHPO 添加剂显示出增强高压锂离子电池电化学性能的巨大潜力。