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In metal-air batteries, the size of the ionic radius determines the behavior of the differential electrochemical reactions.

The very high ionic conductivity of Li10GeP2S12(LGPS) solid electrolyte (SE) makes it a promising candidate SE for solid-state batteries in electrical vehicles. However, chemomechanical failure, whose mechanism remains unclear, has plagued its widespread applications. Here, we report in situimaging lithiation-induced failure of LGPS SE. We revealed a strong size effect in the chemomechanical failure of LGPS particles: namely, when the particle size is greater than 3 μm, fracture/pulverization occurred; when the particle size is between 1 and 3 μm, microcracks emerged; when the particle size is less than 1 μm, no chemomechanical failure was observed. This strong size effect is interpreted by the interplay between elastic energy storage and dissipation. Our finding has important implications for the design of high-performance LGPS SE, for example, by reducing the particle size to less than 1 μm the chemomechanical failure of LGPS SE can be mitigated.

The two biggest promises of solid-state lithium (Li) metal batteries (SSLMBs) are the suppression of Li dendrites by solid-state electrolyte (SSE) and the realization of a high-energy-density Li anode. However, LMBs have not met their expectations due to Li dendrite growth causing short-circuiting. In fact, Li dendrites grow even more easily in SSE than in liquid electrolyte, but the reason for this remains unclear. Here we report in situtransmission electron microscopy observations of Li dendrite penetration through SSE and “dead” Li formation dynamics in SSLMBs. We show direct evidence that large electrochemomechanical stress generates cracks in the SSE and drives Li through the SSE directly. We revealed that fresh Li nucleation sites emerged in every discharge cycle, creating new “dead” Li in the following charging cycle and becoming the dominant Coulombic efficiency decay mechanism in SSLMBs. These results indicate that engineering flaw size and reducing electronic conductivity in SSEs are essential to improve the performance of SSLMBs.

Solid-electrolyte interface (SEI) is “the most important but least understood (component) in rechargeable Li-ion batteries”. The ideal SEI requires high elastic strength and can resist the penetration of a Li dendrite mechanically, which is vital for inhibiting the dendrite growth in lithium batteries. Even though Li2CO3and Li2O are identified as the major components of SEI, their mechanical properties are not well understood. Herein, SEI-related materials such as Li2CO3and Li2O were electrochemically deposited using an environmental transmission electron microscopy (ETEM), and their mechanical properties were assessed by in situ atomic force microscopy (AFM) and inverse finite element simulations. Both Li2CO3and Li2O exhibit nanocrystalline structures and good plasticity. The ultimate strength of Li2CO3ranges from 192 to 330 MPa, while that of Li2O is less than 100 MPa. These results provide a new understanding of the SEI and its related dendritic problems in lithium batteries.

High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in solid-state Li-metal batteries (SSLMBs), as they lead to premature short-circuiting and failure of SSLMBs. Here, we report the synthesis of a composite anode comprising a three-dimensional LiCuxnanowire network host infiltrated with Li (Li* anode) with low interfacial impedance and superior electrochemical performance. The Li* anode is fabricated by dissolving Cu foil into molten Li followed by solidification. The Li* anode exhibits good wettability with Li6.4La3Zr1.4Ta0.6O12(LLZTO) and high mechanical strength, rendering low Li*/LLZTO interfacial impedance, homogeneous deposition of Li, and suppression of Li dendrites. Consequently, the Li* anode-based symmetric cells and full cells with LiNi0.88Co0.1Al0.02O2(NCA), LiFePO4(LFP), and FeF2cathodes deliver remarkable electrochemical performance. Specifically, the Li*/LLZTO/Li* symmetrical cell achieves a remarkably long cycle lifetime of 10 000 h with 0.1 mA·cm–2; the Li*/LLZTO/NCA full cell maintains capacity retention of 73.4% after 500 cycles at 0.5C; and all-solid-state Li*/LLZTO/FeF2full cell achieves a reversible capacity of 147 mAh·g–1after 500 cycles at 100 mA·g–1. This work demonstrates potential design tactics for an ultrastable Li*/garnet interface to enable high-performance SSLMBs.

All-solid Li–O2batteries have been constructed with Ag nanowire (AgNW) cathodes coated on Au-buffered garnet ceramic electrolytes and Li anodes on the other sides. Benefiting from the clean contacts of Li+, e–, and O2on the AgNWs, the surface pathway reactions are demonstrated. Upon discharge, two types of Li2O2morphologies appear. The film-like Li2O2forms around the smooth surfaces of AgNWs, and hollow disk-like Li2O2forms at the joints in between the AgNWs as well as at the garnet/AgNW interfaces. The formation of films and hollow disks is in accordance with the process of O2+ Li++ e–→ LiO2and 2LiO2→ Li2O2+ O2, indicating that the disproportionation of LiO2occurs at the solid interfaces. During the initial charge, decomposition occurs below the potential of 3.5 V, indicating the process of Li2O2→ LiO2+ Li++ e–and LiO2→ Li++ e–+ O2rather than Li2O2→ 2Li++ 2e–+ O2. The Li2O2decomposition starts at the AgNWs/Li2O2interfaces, causing the film-like Li2O2to shrink and the gas to release, followed by the collapse of hollow disk-like Li2O2. The results here clearly disclose the Li–O2reaction mechanism at the all-solid interfaces, facilitating a deep understanding of key factors influencing the electrochemical performance of the solid-state Li–O2batteries.

Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3–7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries.

The increasing demand for safe and dense energy storage has shifted research focus from liquid electrolyte-based Li-ion batteries toward solid-state batteries (SSBs). However, the application of SSBs is impeded by uncontrollable Li dendrite growth and short circuiting, the mechanism of which remains elusive. Herein, we conceptualize a scheme to visualize Li deposition in the confined space inside carbon nanotubes (CNTs) to mimic Li deposition dynamics inside solid electrolyte (SE) cracks, where the high-strength CNT walls mimic the mechanically strong SEs. We observed that the deposited Li propagates as a creeping solid in the CNTs, presenting an effective pathway for stress relaxation. When the stress-relaxation pathway is blocked, the Li deposition-induced stress reaches the gigapascal level and causes CNT fracture. Mechanics analysis suggests that interfacial lithiophilicity critically governs Li deposition dynamics and stress relaxation. Our study offers critical strategies for suppressing Li dendritic growth and constructing high-energy-density, electrochemically and mechanically robust SSBs.