Solid-state batteries (SSBs) can
offer a paradigm shift in battery
safety and energy density. Yet, the promise hinges on the ability
to integrate high-performance electrodes with state-of-the-art solid
electrolytes. For example, lithium (Li) metal, the most energy-dense
anode candidate suffers from severe interfacial chemomechanical issues
that lead to cell failure. Li alloys of In/Sn are attractive alternatives,
but their exploration has mostly been limited to the low capacity
(low Li content) and In-rich Li
x
In (x ≤ 0.5) systems. Here, the fundamental electro-chemo-mechanical
behavior of Li–In and Li–Sn alloys of varied Li stoichiometries
is unraveled in sulfide electrolyte-based SSBs. The intermetallic
electrodes developed through a controlled synthesis and fabrication
technique display impressive (electro)chemical stability with Li6PS5Cl as the solid electrolyte and maintain nearly
perfect interfacial contact during the electrochemical Li insertion/deinsertion
under an optimal stack pressure. Their intriguing variation in the
Li migration barrier with composition and its influence on the observed
Li cycling overpotential is revealed through combined computational
and electrochemical studies. Stable interfacial chemomechanics of
the alloys allow long-term dendrite free Li cycling (>1000 h) at
relatively
high current densities (1 mA cm–2) and capacities
(1 mAh cm–2), as demonstrated for Li13In3 and Li17Sn4, which are more
desirable from a capacity and cost consideration compared to the low-Li-content
analogues. The presented understanding can guide the development of
high-capacity Li–In/Sn alloy anodes for SSBs.
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