Ultrathin Si Nanosheets Dispersed in Graphene Matrix Enable Stable Interface and High Rate Capability of Anode for Lithium‐ion Batteries

Abstract

Owing to the thinness and large lateral size, 2D Si materials exhibit very promising prospects as the high-performance anodes of lithium-ion batteries (LIBs). However, the facile synthesis of ultrathin 2D Si nanosheets (Si-NSs) and their efficient application still remain a great challenge. Herein, the fabrication of ultrathin Si-NSs with the average thickness of <2 nm is demonstrated using a unique etching-reduction protocol. After hybridizing with graphene, the as-prepared Si-NSs@rGO material delivers ultrahigh rate capability (2395.8 mAh g −1 at 0.05 A g −1 and 1727.3 mAh g −1 at 10 A g −1 ), long cycling lifespan (1000 cycles at 2 A g −1 with a capacity decay rate of 0.05% per cycle) and high average Coulombic efficiency (99.85% during 1000 cycles). The superior performance is attributed to the ultrathinness of Si-NSs that greatly improves the diffusivity and reversibility of Li + ions. This work provides a strategy for fabricating a high-rate-capability anode material to meet the growing demand for high power density LIBs.

Facile Synthesis of Hybrid Anodes with Enhanced Lithium-Storage Performance Realized by a “Synergistic Effect”

“…The b value reflects the dominant process during Li + insertion. A b value of 0.5 represents diffusion-controlled behavior, while 1.0 indicates surface-mediated capacitive behavior. − As shown in Figure d, the b value can be obtained by the linear fitting of the log­( v )–log­( i ) plot. For SnO 2 /Si@G, the b values of cathodic and anodic peaks are 0.86 and 0.84, respectively, implying that the Li + storage mechanism is a mixed process.…”

“…Nevertheless, the BET specific surface areas are 16.5, 62.2, and 48.8 m 2 g –1 for nano-SnO 2 , nano-Si, and SnO 2 /Si@G, respectively (Figure S17), indicating that the high capacitive contribution ratio of SnO 2 /Si@G is mainly attributed to the kinetics enhancement rather than the increase of specific surface area. This high capacitive-controlled contribution ratio of SnO 2 /Si@G is supposed to benefit from the reasonable compositing and novel structural properties. , …”

“…This high capacitive-controlled contribution ratio of SnO 2 /Si@G is supposed to benefit from the reasonable compositing and novel structural properties. 50,55 To further elaborate the impact of the synergistic effect between the components on the electrochemical performance of composites, we systematically investigated the cycled electrodes. As seen in Raman spectra shown in Figure 5a, a peak at around 590.3 cm −1 emerges after the initial lithiation/ delithiation processes, which can be attributed to Li 2 SiO 3 (PDF #29-0828), suggesting the in situ formation of lithium silicates.…”

Design of a hydrolysis‐supported coating layer on the surface of Ni‐rich cathodes in secondary batteries

“…When the TEOS solution is poured over the NCM(OH) 2 precursor containing NH 4 OH on the surface, only the TEOS that meets the NH 4 OH on the NCM(OH) 2 surface is selectively hydrolyzed to form a SiO 2 film on the cover of the NCM(OH) 2 particles. The hydrolysis and condensation reactions of TEOS, which are known to occur favorably in an environment with high pH, 51 proceed according to Equation (1).…”

“…High‐Ni Li(Ni x Co y Mn z )O 2 (LNCM, x ≥ 0.8) exhibits a high reversible capacity because of the larger number of Li ions that can intercalate in the Li layer by the oxidation‐reduction couples (Ni 2+/3+/4+ ) of Ni. As this material also has the characteristics of low cost and environmental friendliness, it is considered the most promising material for Li‐ion batteries (LIBs) 1‐6 . However, for actual use, it is essential to secure cycling safety and thermal stability by solving the problems caused by the increased Ni contents.…”