One thousandth of quaternity slurry additive enables one thousand cycle of 5V LNMO cathode

Abstract

5 V high voltage LiNi0.5Mn1.5O4 (LNMO) is one of the most promising cathode candidates for high energy density lithium-ion batteries. However, the electrochemical performance of high voltage LNMO is significantly affected by the interfacial compatibility between cathode and electrolyte. High voltage leads to decomposition of electrolyte at the cathode-electrolyte interface (CEI), consuming electrolyte and forming an uneven, unstable, and unprotected CEI, and hindering Li+ diffusion and reducing electrochemical efficiency. At the same time, along with the dissolution of transition metals and irreversible crystal structure damage over cycles, its electrochemical performance is seriously impaired. To solve these problems, it is proposed to pre-form a stable passivation layer on the LNMO surface using tiny amount of quaternity slurry additive of potassium-nonafluoro-1-butanesulfonate (KPBS). The K+ in KPBS assists construction of uniform and stable electric field at the cathode particle surface together with the Li+, which induces uniform deposition of the CEI. The lithium-ion diffusion at the interface is accelerated due to existence of rich phase boundaries between KF and LiF species within the CEI. The sulfonic acid group of KPBS is capable of inhibiting transition metal dissolution via coordination boding with Ni/Mn cations. The nona fluoro butyl structure improves the interface compatibility with the poly(vinylidene difluoride) (PVDF) binder to enhance the structure robustness of the electrode. The quadruple effects exercised by the KPBS enable the LNMO almost no capacity decay after 1000 cycles at 1C and 5 V. This work has a great potential to boost significant advance of the high energy density lithium-ion battery technology.