Solid electrolytes (SEs) with superionic conductivity and interfacial stability are highly desirable for stable all-solid-state Li-metal batteries (ASSLMBs). Here, we employ neural network potential to simulate materials composed of Li, Zr/Hf, and Cl using stochastic surface walking method and identify two potential unique layered halide SEs, named Li 2 ZrCl 6 and Li 2 HfCl 6 , for stable ASSLMBs. The predicted halide SEs possess high Li + conductivity and outstanding compatibility with Li metal anodes. We synthesize these SEs and demonstrate their superior stability against Li metal anodes with a record performance of 4000 h of steady lithium plating/stripping. We further fabricate the prototype stable ASSLMBs using these halide SEs without any interfacial modifications, showing small internal cathode/SE resistance (19.48 Ω cm 2 ), high average Coulombic efficiency (∼99.48%), good rate capability (63 mAh g −1 at 1.5 C), and unprecedented cycling stability (87% capacity retention for 70 cycles at 0.5 C).
As typical 2D materials, VSe2 and MoSe2 both
play a complementary role in Li/Na/K storage. Therefore, we designed
and optimized the VSe2/MoSe2 heterostructure
to gain highly efficient Li/Na/K-ion batteries. Most importantly,
achieving fast Li/Na/K-ion diffusion kinetics in the interlayer of
VSe2/MoSe2 is a key point. First of all, first-principles
calculations were carried out to systematically investigate the packing
structure, mechanical properties, band structure, and Li/Na/K storage
mechanism. Our calculated results suggest that a large interlayer
spacing (3.80 Å), robust structure, and metallic character pave
the way for achieving excellent charge–discharge performance
for the VSe2/MoSe2 heterostructure. Moreover,
V and Mo ions both suffer a very mild redox reaction even if Li/Na/K
ions fill the interlayer space. These structures were all further
verified to show thermal stability (300 K) by means of the AIMD method.
By analyzing the Li/Na/K diffusion behavior and the effect of vacancy
defect on the structural stability and energy barrier for Li interlayer
diffusion, it is found that the VSe2/MoSe2 heterostructure
exhibits very low-energy barriers for Na/K interlayer diffusion (0.21
eV for Na and 0.11 eV for K). Compared with the VSe2/MoSe2 heterostructure, the V0.92Se1.84/MoSe2 heterostructure not only can still maintain a stable structure
and metallic character but also has much lower energy barrier for
Li interlayer diffusion (0.07 vs 0.48 eV). These
discoveries also break new ground to eliminate the obstacles preventing
Li+ diffusion in the interlayer of other heterostructure
materials. Besides, both VSe2/MoSe2 and V0.92Se1.84/MoSe2 heterostructures have
low average open-circuit voltage (OCV) values during Li/Na/K interlayer
diffusion (1.07 V for V0.92Se1.84/MoSe2
vs Li+, 0.86 V for VSe2/MoSe2
vs Na+, and 0.54 V for VSe2/MoSe2
vs K+), such
low OCV values are beneficial for anode materials with excellent electrochemical
properties. The above findings offer a new route to design anode materials
for Li/Na/K-ion batteries.
Lead halide perovskite nanocrystals (LHP NCs) are regarded
as promising
emitters for next-generation ultrahigh-definition displays due to
their high color purity and wide color gamut. Recently, the external
quantum efficiency (EQE) of LHP NC based light-emitting diodes (PNC
LEDs) has been rapidly improved to a level required by practical applications.
However, the poor operational stability of the device, caused by halide
ion migration at the grain boundary of LHP NC thin films, remains
a great challenge. Herein, we report a resurfacing strategy via pseudohalogen
ions to mitigate detrimental halide ion migration, aiming to stabilize
PNC LEDs. We employ a thiocyanate solution processed post-treatment
method to efficiently resurface CsPbBr3 NCs and demonstrate
that the thiocyanate ions can effectively inhibit bromide ion migration
in LHP NC thin films. Owing to thiocyanate resurfacing, we fabricated
LEDs with a high EQE of 17.3%, a maximum brightness of 48000 cd m–2, and an excellent operation half-life time.
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