A multifunctional
coating with high ionic and electronic conductivity
is constructed on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) to boost the battery stability
upon cycling and during storage as well. Phosphoric acid reacts with
residual lithium species on the pristine NCM to form a Li3PO4 coating with extra carbon nanotubes (CNTs) penetrating
through, which shows high ionic and electronic conductivity. NCM,
Li3PO4, CNTs, and the electrolyte jointly form
a four-phase cathode electrolyte interface, which plays a key role
in the great enhancement of capacity retention, from 50.3% for pristine
NCM to 84.8% for the modified one after 500 cycles at 0.5C at room
temperature. The modified NCM also delivers superior electrochemical
performances at a high cut-off voltage (4.5 V), high temperature (55
°C), and high rate (10C). Furthermore, it can deliver 154.2 mA
h g–1 at the 500th cycle after exposed to air with
high humidity for 2 weeks. These results demonstrate that the well-constructed
multifunctional coating can remarkably enhance the chemical and electrochemical
performances of NCM. The improved cycling, storage, and rate performance
are attributed to the four-phase cathode electrolyte interface delivering
high electron and ionic conductivity and securing the cathode against
attack. This work broadens the horizon for constructing effective
electrode/electrolyte interfaces for electrochemical energy storage
and conversion.
Lithium metal anodes
(LMAs) are critical for high-energy-density batteries such as Li–S
and Li–O2 batteries. The spontaneously formed solid
electrolyte interface on LMAs is fragile, which may not accommodate
the cyclic Li plating/stripping. This usually will result in a low
coulombic efficiency (CE), short cycle life, and potential safety
hazards induced by the uncontrollable growth of lithium dendrites.
In this study, we fabricate a Li alginate-based artificial SEI (ASEI)
layer that is chemically stable and allows easy Li ion transport on
the surface of LMAs, thus enabling the stable operation of lithium
metal anodes. Compared to bare LMAs, the ASEI layer-protected LMAs
exhibit a more stable Li plating/stripping behavior and present effective
dendrite suppression. The symmetric Li∥Li cells with the ASEI
layer-protected LMAs can stably run for 850 and 350 h at current densities
of 0.5 and 1 mA cm–2, respectively. Additionally,
the LiFePO4∥Li full cell with the ASEI layer-protected
LMA exhibits a capacity retention of about 94.0% coupled with a CE
of 99.6% after 1000 cycles at 4 C. We believe that this study of engineering
an ASEI brings a new and promising approach to the stabilization of
LMAs for high-performance lithium metal batteries.
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