Atomic‐Scale Laminated Structure of O‐Doped WS₂ and Carbon Layers with Highly Enhanced Ion Transfer for Fast‐Charging Lithium‐Ion Batteries

Abstract

improving the fast-charging performances of LIBs, in which the enhancements of anode materials are undisputedly important. [4] Graphite, the most commonly used anode material in LIBs, mainly faces the following problems: 1) The small interlayer distance of graphite (0.33 nm) is far from sufficient to perform rapid Li + transport; 2) During the fast charging, high current densities result in Li dendrite growth on graphite anode and thereby raising serious safety concerns; [5,6] 3) With the specific capacity of graphite anode approaching its ceiling (372 mAh g −1 ), further increase in capacity is expected to encounter huge challenges and thus limited energy density. Various anode materials, such as metal oxides (SnO 2 ), [7] metal sulfides (WS 2 , SnS 2 , Sb 2 S 3 ), [8] SiO x (0 < x < 2), [9] metals (Sn, Sb, Ge, Li), etc., [10,11] have been extensively explored as anode materials for fastcharging LIBs.Among them, tungsten disulfide (WS 2 ) with tunable interlayer distance, high theoretical capacity (432 mAh g −1 ), and large density (7.6 g cm −3 , about three-times larger than graphite) has drawn significant attention as fast-charging anode material for LIBs. [12][13][14] However, several critical challenges, such as sluggish ion diffusion kinetics, poor intrinsic electrical conductivity, and large volume fluctuations upon cycling, should be addressed for the successful utilization of WS 2 in fast-charging LIBs. Defect engineering in terms of heteroatom doping with the strong capabilities of regulating the electronic structure and increasing ion storage sites shows huge advantages to offer the fast-charging capability. [15,16] Besides, the fabrication of nano structured WS 2 and conducted coatings is also a feasible strategy, [17] which shortens ion and electron diffusion path and increases electrical conductivity. However, the unimproved electron and ion transport inside WS 2 brings limited improvement of fast-charging capability. Constructing the few-layer WS 2 /carbon layer-by-layer stacked structure has been confirmed as an available strategy towards the above issues, [18] which increases the contact area between WS 2 and carbon, thus accelerating ionic and electronic transport. Nevertheless, maximizing the molecular layer contact area of WS 2 and C by constructing a stacked structure of single-layer WS 2 and C to further improve ionic and electronic transport is still a huge challenge and has not been realized so far.

Monolayer MoS2 Fabricated by In Situ Construction of Interlayer Electrostatic Repulsion Enables Ultrafast Ion Transport in Lithium-Ion Batteries

“…5 below, the space charge zone is constructed on the surface of formed superparamagnetic Mo and Co particles after the electrodes discharged to 0.01 V. Due to the formation of space charge zone, rectangular CV curves representing capacitive or pseudocapacitive behavior appear in voltage range of 0.01–1.0 V. The b value for peak 5 at 0.01 V is calculated to be approximately equal to 1, which signals that a strong capacitive response occurs in the CoMoS 2 /C-II electrode. The equation can be used to calculate the lithium-ion diffusion coefficient ( D Li + ) [ 7 ] to further reveal Li + diffusion kinetics, in which i p , v , A , n , and C Li+ represent peak current, scan rate, contact area of materials/electrolyte, electrons number involved in reaction, and Li + bulk concentration, respectively. According to linear relationship of and (Figs.…”

“…Considering the above results, the capacity of CoMoS 2 /C-II is about 2.5 times theoretical capacity of MoS 2 for the following reasons: i) enormous Co doping sites to enhance surface energy of MoS 2 to store extra Li + [ 7 , 19 ]; ii) extremely high capacity of monolayer MoS 2 [ 30 , 32 ]; iii) vast contact interfaces of monolayer MoS 2 and C to increase Li + active sites [ 7 , 9 , 46 , 51 ]; iv) formed ultrasmall Co particles to create strong space charge region as excess Li + active sites [ 49 , 52 ]. Among them, creating space charge regions during conversion reaction due to the formation of ultrasmall Co has changed Li + storage mechanism of traditional MoS 2 materials.…”

“…MoS 2 with interlayer spacing of 0.62 nm and lithium-ion storage capacity of 670 mAh g −1 looks very attractive [ 6 , 7 ]. But the anisotropic ion transport channels caused by the layered nanostructure and poor electrical conductivity (EC) due to its inherent semiconducting properties cause unacceptable ion transport performance in fast-charging LIBs [ 9 ].…”

“…But the anisotropic ion transport channels caused by the layered nanostructure and poor electrical conductivity (EC) due to its inherent semiconducting properties cause unacceptable ion transport performance in fast-charging LIBs [ 9 ]. Based on these limitations, strategies such as designing MoS 2 nanostructure [ 16 , 17 ], enlarging MoS 2 interlayer spacing [ 18 ], doping MoS 2 [ 19 ], reducing MoS 2 layers number [ 20 ], and fabricating composites of MoS 2 /carbon [ 6 , 7 , 9 ] have been proposed. Although these routes have greatly improved the lithium-ion transport capability of MoS 2 , the anisotropic ion transport features due to the native layered structure of MoS 2 are not fundamentally changed, which inevitably leads to the same ion transport capability.…”

Carbon Confined Mesoporous Catkin-like SnPS3 Nanostructure for Lithium Storage with Great Superiority

“…Figure c presents the initial charge and discharge capacities of the full cells are 155 and 131 mAh g –1 (based on the total mass of SnPS 3 @C and LFP), respectively. The average discharge voltage is about 2.9 V. Therefore, the energy density of the SnPS 3 @C||LFP full cell reaches to 380 Wh kg –1 , which is a lot higher compared to that of commercial lithium ion batteries (230 Wh kg –1 ). − Besides, the SnPS 3 @C||LFP full cell also shows good cycling stability, maintaining a discharge capacity of 113 mA h g –1 after 50 cycles at 100 mA g –1 with the capacity retention of 86% (Figure d). The above results indicate that the catkin-like SnPS 3 @C anode has enormous potential for the practical application in high-energy-density lithium ion batteries.…”