5 research outputs found
Long-Life Nickel-Rich Layered Oxide Cathodes with a Uniform Li<sub>2</sub>ZrO<sub>3</sub> Surface Coating for Lithium-Ion Batteries
As
nickel-rich layered oxide cathodes start to attract worldwide interest
for the next-generation lithium-ion batteries, their long-term cyclability
in full cells remains a challenge for electric vehicles. Here we report
a long-life Ni-rich layered oxide cathode (LiNi<sub>0.7</sub>Co<sub>0.15</sub>Mn<sub>0.15</sub>O<sub>2</sub>) with a uniform surface
coating of the cathode particles with Li<sub>2</sub>ZrO<sub>3</sub>. A pouch-type full cell fabricated with the Li<sub>2</sub>ZrO<sub>3</sub>-coated cathode and a graphite anode displays 73.3% capacity
retention after 1500 cycles at a C/3 rate. The Li<sub>2</sub>ZrO<sub>3</sub> coating has been optimized by a systematic study with different
synthesis approaches, annealing temperatures, and coating amounts.
The complex relationship among the coating conditions, uniformity,
and morphology of the coating layer and their impacts on the electrochemical
properties are discussed in detail
Interfacial Chemistry in Solid-State Batteries: Formation of Interphase and Its Consequences
Benefiting
from extremely high shear modulus and high ionic transference
number, solid electrolytes are promising candidates to address both
the dendrite-growth and electrolyte-consumption problems inherent
to the widely adopted liquid-phase electrolyte batteries. However,
solid electrolyte/electrode interfaces present high resistance and
complicated morphology, hampering the development of solid-state battery
systems, while requiring advanced analysis for rational improvement.
Here, we employ an ultrasensitive three-dimensional (3D) chemical
analysis to uncover the dynamic formation of interphases at the solid
electrolyte/electrode interface. While the formation of interphases
widens the electrochemical window, their electronic and ionic conductivities
determine the electrochemical performance and have a large influence
on dendrite growth. Our results suggest that, contrary to the general
understanding, highly stable solid electrolytes with metal anodes
in fact promote fast dendritic formation, as a result of less Li consumption
and much larger curvature of dendrite tips that leads to an enhanced
electric driving force. Detailed thermodynamic analysis shows an interphase
with low electronic conductivity, high ionic conductivity, and chemical
stability, yet having a dynamic thickness and uniform coverage is
needed to prevent dendrite growth. This work provides a paradigm for
interphase design to address the dendrite challenge, paving the way
for the development of robust, fully operational solid-state batteries
Interfacial Chemistry in Solid-State Batteries: Formation of Interphase and Its Consequences
Benefiting
from extremely high shear modulus and high ionic transference
number, solid electrolytes are promising candidates to address both
the dendrite-growth and electrolyte-consumption problems inherent
to the widely adopted liquid-phase electrolyte batteries. However,
solid electrolyte/electrode interfaces present high resistance and
complicated morphology, hampering the development of solid-state battery
systems, while requiring advanced analysis for rational improvement.
Here, we employ an ultrasensitive three-dimensional (3D) chemical
analysis to uncover the dynamic formation of interphases at the solid
electrolyte/electrode interface. While the formation of interphases
widens the electrochemical window, their electronic and ionic conductivities
determine the electrochemical performance and have a large influence
on dendrite growth. Our results suggest that, contrary to the general
understanding, highly stable solid electrolytes with metal anodes
in fact promote fast dendritic formation, as a result of less Li consumption
and much larger curvature of dendrite tips that leads to an enhanced
electric driving force. Detailed thermodynamic analysis shows an interphase
with low electronic conductivity, high ionic conductivity, and chemical
stability, yet having a dynamic thickness and uniform coverage is
needed to prevent dendrite growth. This work provides a paradigm for
interphase design to address the dendrite challenge, paving the way
for the development of robust, fully operational solid-state batteries
Facilitating the Operation of Lithium-Ion Cells with High-Nickel Layered Oxide Cathodes with a Small Dose of Aluminum
Layered
oxide cathodes with a high Ni content of >0.6 are promising
for high-energy-density lithium-ion batteries. However, parasitic
electrolyte oxidation of the charged cathode and mechanical degradation
arising from phase transitions significantly deteriorate the cell
performance and cycle life as the Ni content increases. We demonstrate
here a significantly prolonged cycle life with superior cell performance
by substituting a small-dose of Al (2 mol %) for Ni in LiNi<sub>0.92</sub>Co<sub>0.06</sub>Al<sub>0.02</sub>O<sub>2</sub>; the capacity retention
after operating a full cell fabricated with graphite anode for 1000
cycles increases from 47% to 83% on going from the Al-free LiNi<sub>0.94</sub>Co<sub>0.06</sub>O<sub>2</sub> to the Al-doped LiNi<sub>0.92</sub>Co<sub>0.06</sub>Al<sub>0.02</sub>O<sub>2</sub> cathode.
Through in situ X-ray diffraction, we provide the operando evidence
that the Al-doping tunes the H2–H3 phase transition process
from a two-phase reaction to a quasi-monophase reaction, minimizing
the mechanical degradation. Furthermore, secondary-ion mass spectrometry
reveals considerably suppressed transition-metal dissolution with
Al-doping, effectively preventing sustained parasitic reactions and
active Li trapping due to chemical crossover on graphite anodes. This
work offers a viable approach for adopting high-Ni cathodes in lithium-ion
batteries
Formation and Inhibition of Metallic Lithium Microstructures in Lithium Batteries Driven by Chemical Crossover
The
formation of metallic lithium microstructures in the form of
dendrites or mosses at the surface of anode electrodes (<i>e</i>.<i>g</i>., lithium metal, graphite, and silicon) leads
to rapid capacity fade and poses grave safety risks in rechargeable
lithium batteries. We present here a direct, relative quantitative
analysis of lithium deposition on graphite anodes in pouch cells under
normal operating conditions, paired with a model cathode material,
the layered nickel-rich oxide LiNi<sub>0.61</sub>Co<sub>0.12</sub>Mn<sub>0.27</sub>O<sub>2</sub>, over the course of 3000 charge–discharge
cycles. Secondary-ion mass spectrometry chemically dissects the solid–electrolyte
interphase (SEI) on extensively cycled graphite with virtually atomic
depth resolution and reveals substantial growth of Li-metal deposits.
With the absence of apparent kinetic (<i>e</i>.<i>g</i>., fast charging) or stoichiometric restraints (<i>e</i>.<i>g</i>., overcharge) during cycling, we show lithium
deposition on graphite is triggered by certain transition-metal ions
(manganese in particular) dissolved from the cathode in a disrupted
SEI. This insidious effect is found to initiate at a very early stage
of cell operation (<200 cycles) and can be effectively inhibited
by substituting a small amount of aluminum (∼1 mol %) in the
cathode, resulting in much reduced transition-metal dissolution and
drastically improved cyclability. Our results may also be applicable
to studying the unstable electrodeposition of lithium on other substrates,
including Li metal