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Lithium metal anodes are ideal for realizing high-energy-density batteries owing to their advantages, namely high capacity and low reduction potentials. However, the utilization of lithium anodes is restricted by the detrimental lithium dendrite formation, repeated formation and fracturing of the solid electrolyte interphase (SEI), and large volume expansion, resulting in severe "dead lithium" and subsequent short circuiting. Currently, the researches are principally focused on inhibition of dendrite formation toward extending and maintaining battery lifespans. Herein, we summarize the strategies employed in interfacial engineering and current-collector host designs as well as the emerging electrochemical catalytic methods for evolving-accelerating-ameliorating lithium ion/atom diffusion processes. First, strategies based on the fabrication of robust SEIs are reviewed from the aspects of compositional constituents including inorganic, organic, and hybrid SEI layers derived from electrolyte additives or artificial pretreatments. Second, the summary and discussion are presented for metallic and carbon-based three-dimensional current collectors serving as lithium hosts, including their functionality in decreasing local deposition current density and the effect of introducing lithiophilic sites. Third, we assess the recent advances in exploring alloy compounds and atomic metal catalysts to accelerate the lateral lithium ion/atom diffusion kinetics to average the spatial lithium distribution for smooth plating. Finally, the opportunities and challenges of metallic lithium anodes are presented, providing insights into the modulation of diffusion kinetics toward achieving dendrite-free lithium metal batteries.

Lithium metal anode possesses overwhelming capacity and low potential but suffers from dendrite growth and pulverization, causing short lifespan and low utilization. Here, a fundamental novel insight of using single-atomic catalyst (SAC) activators to boost lithium atom diffusion is proposed to realize delocalized deposition. By combining electronic microscopies, time-of-flight secondary ion mass spectrometry, theoretical simulations, and electrochemical analyses, we have unambiguously depicted that the SACs serve as kinetic activators in propelling the surface spreading and lateral redistribution of the lithium atoms for achieving dendrite-free plating morphology. Under the impressive capacity of 20 mA h cm

It is widely accepted that catalysts in batteries can decrease the energy barriers of conversion reactions. However, little attention has been paid to their influence on ionic diffusion in the electrode or across the interface. Herein, we report that lithium ion diffusivity can be significantly accelerated in an intrinsically electrode by atomically-distributed metal catalyst. Electrochemical measurements have found single atomic cobalt catalyst embedded in a nanocarbon network is capable of increasing the kinetics of lithium ion, providing rapid conversion reaction rate in an ultrahigh-rate Li2S battery. Meanwhile, density functional theory simulations have revealed that the lithium ion diffusion barrier on a nanocarbon surface is highly sensitive to the dopant atoms and can be decreased by introduction of cobalt atoms. The synergetic effects of the well-known Li2S decomposition catalysis and the lithium ion diffusion acceleration allow us to achieve a high Li2S mass loading cathode with superior rate performance and reversibility. The as-prepared Li2S electrode converted from cheap Li2SO4 precursors can deliver a high rate capacity (441 ​mA ​h ​g-1 based on Li2S at 10 ​C) and long lifespan for 1500 cycles at 2 ​C with average capacity fading of 0.04% per cycle. Impressively, the high areal mass loading cells display a specific capacity of 340 ​mA ​h ​g-1 based on Li2S mass at 23.4 ​mA ​cm-2 (5 ​C) and a long cycle life (2.26 ​mA ​h ​cm-2 at 6.77 ​mA ​cm-2 after 200 cycles), which have not been reported for Li2S cathodes.

Oxygen defect-rich iron oxide (ODFO) nanoparticle catalyst on nanocarbon is in situ synthesized with the assistance of multi-ion modulation in one pot. The nanoparticle catalyst is employed to propel electrochemical kinetics in lithium/sulfur batteries. Electrochemical analysis and theoretical simulation evidently verify the critical role of defect sites on catalyzing conversion reactions of sulfur species and reducing energy barriers. As a consequence, the ODFO-enhanced sulfur cathode exhibits a high specific capacity of 1489 mA h g-1 at 0.1 C, an excellent rate performance of 644 mA h g-1 at 10 C, and a superior cycling stability with an average capacity fading rate of as low as 0.055% per cycle under an ultrahigh rate of 10 C. More importantly, even with a high sulfur loading of 11.02 mg cm-2, the Li/S cell can still deliver an areal capacity of 8.7 mA h cm-2 at 0.5 C (9.23 mA cm-2). Such performance is the highest among reported metal oxide-catalyzed sulfur cathodes. This work opens a new route to boosting conversion reaction kinetics by introduction of active oxygen defect sites in electrodes of various emerging ultrafast batteries.

Iron disulfide-based cathodes have been regarded as promising for use in high-energy-density lithium batteries owing to their low cost. However, low utilization, sluggish lithium ion insertion kinetics and rapid capacity fading prevent their practical application. Herein, defect-rich iron disulfide nanoflowers are synthesized by self-assembly on a hierarchical porous catalytic heteroatom-doped carbon matrix. Both electrochemical experiments and density functional theory simulations reveal that the iron defects in the cathode help to decrease the diffusion barrier so that lithium ions can freely and easily insert into the crystal and improve the transport kinetics. Meanwhile, the hierarchical porous structure also accommodates volumetric changes and facilitates electrolyte immersion. As a consequence, the as-prepared cathode delivers an initial specific capacity of 841 mA h g−1 at 0.1C and retains an energy density of ∼500 W h kg−1 at a high power density of 26.7 kW kg−1 (20C). Even working for 3000 cycles at 4C, the cell can still preserve an energy efficiency of above 95% and display a high energy density of 220 W h kg−1 with an average capacity fading as low as 0.020% per cycle, showing its superior electrochemical stability and lifetime.

Lithium-ion batteries based on tin (Sn) anode have the advantage of high energy density at a reasonable cost. However, their commercialization suffers from rapid capacity fading caused by active material aggregation, huge volumetric change, and continuous formation/deformation of solid-electrolyte interphase (SEI). Herein, we report an anode made of nanosized metallic Sn particles embedded in a hierarchically porous sulfur-doped graphene foam (Sn@3DSG). In this design, the sulfur-doped graphene foam provides abundant active defect sites to facilitate the rapid lithium-ion diffusion from outside to inside the Sn nanoparticles. Meanwhile, the hierarchical pores resulting from the self-assembly of graphene and evaporation of nanosized metallic Zn provide sufficient space to hold the volumetric changes of Sn. Owing to these merits, the as-prepared Sn electrode exhibits an excellent lithiated capacity (1272 mA h g–1 at 200 mA g–1) and high-rate performance (345 mA h g–1 at 2000 mA g–1) in the LiFSI-based elect...

The Mg/S battery is attractive because of its high theoretical energy density and the abundance of Mg and S on the earth. However, its development is hindered by the lack of understanding to the underlying electrochemical reaction mechanism of its charge-discharge processes. Here, using a unique in situ X-ray absorption spectroscopic tool, we systematically study the reaction pathways of the Mg/S cells in Mg(HMDS)

Lithium-sulfur batteries are among the most promising candidates for next-generation energy-storage systems due to its high theoretical energy density. However, the shuttle effect of polysulfides and sluggish reaction kinetics severely hinder the development of practical Li-S batteries. Merely depending on an adsorption strategy to resist the shuttle effect is insufficient to boost the overall electrochemical conversion reaction. Recently, single atom catalysts (SACs) have been used to solve this problem by decreasing the energy barriers of sulfur-species interconversion and Li2 S decomposition. Herein, the research progress made in using SACs in Li-S batteries is discussed, focusing on their functions and catalytic mechanism. The challenges and prospects for future application of SACs in electrochemical energy-storage systems are also discussed.

Lithium sulfur batteries have exhibited unparalleled advantages in energy density. However, the sulfide oxidation reactions (SORs) in sulfur cathode are much more sluggish, which is mainly restricted by high conversion barriers. Herein, the catalytic “Li-N” bond sites are designed to activate SORs in high areal loading cathode with the multi-functions of bridging the active materials and carbon matrix tightly. The presence of catalytic “Li-N” bonds is co-revealed by X-ray photoelectronic spectroscopy and electronic energy loss spectroscope. As unraveled by theoretical physical van der Waals interaction analysis and various electrochemical tests, the improved kinetics and mechanism of SORs are achieved by motivating polysulfide interconversions and propelling lithium ion diffusion. Consequently, the so-fabricated electrode with abundant Li-N bond catalytic sites deliveries 900 mA h g−1 at 0.05 C and a stable retention of 74.3% at 1 C after 300 cycles. More impressively, high-loading with high-weight-content cathodes remain rapid SORs kinetics, high capacity utilization and retention from 3.0 to 6.9 mg cm−2. At 6.5 mg cm−2, the cathode displays 550 mA h g−1 at 0.76 mA cm−2 corresponded to 3.58 mA h cm−2, which is better than many reports. These results shed light on using intrinsic catalytic sites to realize application of batteries.

The fabrication of high-performance cathodes with high sulfur content is essential for the practical realization of lithium–sulfur (Li–S) systems. The preparation of high-sulfur-content electrodes is currently hindered by poor dispersion of the conductive agents; nonuniformly distributed conductive agents cannot provide sufficient sulfur-loading sites, thereby resulting in aggregation of sulfur/Li2S and severe polarization. To deal with this issue, we prepare CO2 modified carbon nanotube (CNT)-based cathodes for Li–S batteries. CNTs are exposed to CO2 at 900 °C, resulting in uniformly distributed negative charges on the external surface of the tubes; the electrostatic repulsion facilitated the dispersion of CNTs. Compared with the previous work on CNTs prepared by air oxidation (denoted as air-CNTs), the dispersions of the CO2-treated CNTs (denoted as CO2-CNTs) are more stable, which allows higher sulfur loading and improves sulfur utilization. A free-standing CO2-CNT&S electrode with a sulfur content of 80 wt% is fabricated through a sonication-assisted method. The excellent dispersion of the CO2-CNT&S network results in little kinetic barriers, low polarization, and fast charge transport at the interface of the electrode and electrolyte. The CO2-CNT&S electrode delivers a lower capacity fading rate and superior rate performance compared with the air-CNT&S electrode.

High performance cathode with sufficiently high areal sulfur loading is still a major challenge for practical Li/S batteries. Herein, we propose a 3D nanocarbon architecture with robust electrical “highway” network for high sulfur mass loading and efficient sulfur utilization. The structure is constructed by “welding” highly conductive nitrogen-doped graphene (NG) and nitrogen-doped carbon nanotubes (NCNT) together through in-situ polymeric crosslinking and nitrogen-doped carbon shell (NCS) formation. The highly sulfur-absorptive NCS provides strong physical and chemical confinements to sulfur and polysulfides, which is confirmed by in-situ Raman and electrochemical analysis. At a moderate sulfur loading, the NG-NCNT@NCS@S cathode exhibits a high initial discharge capacity of 1421 mA h g−1, excellent rate performance of 750 mA h g−1 at 2 C and 465 mA h g−1 at 5 C, and a capacity fading rate as low as 0.037% per cycle at 2 C for 1400 cycles. At high areal sulfur loading up to 10.2 mg cm−2, the cathode retains a high areal capacity of 5.43 mA h cm−2 after 150 cycles at a high current rate (1 C). A large areal cathode (77 × 50 mm2) with sulfur loading of 8.5 mg cm−2 delivers a record-high capacity of 9.04 mA h cm−2 at 0.1 C, demonstrating its great potential for practical application in Li/S batteries.

Reducing the fast recombination of photogenerated electron-hole pairs of semiconductor photocatalyst is very important to improve its photocatalysis. In this paper we fabricate Cu2O nanocube-decorated BiVO4 nanocrystal (denoted as BiVO4@Cu2O nanocrystal@nanocube) heterostructure photocatalyst by coupling n-type BiVO4 with p-type Cu2O. The BiVO4@Cu2O nanocrystal@nanocube photocatalysts show superior photocatalytic activities in photoelectrochemical (PEC) activity and photocatalytic water oxidation to BiVO4 photocatalysts under visible light illumination. The BiVO4@Cu2O nanocrystal@nanocube heterostructure electrode achieves the highest photocurrent density of ∼ 10 μA cm−2 at 0 V versus Ag/AgCl, 5 times higher than that of BiVO4 nanocrystal electrode (∼ 2 μA cm−2). The light induced evolution rate of O2 generation for BiVO4@Cu2O nanocrystal@nanocube heterostructures is as high as 150 μmol h−1100 mg cat−1, more than 3 times higher than that (48 μmol h−1100 mg cat−1) of BiVO4 nanocrystals. The enhanced photocatalysis activities of the BiVO4@Cu2O nanocrystal@nanocube photocatalysts are attributed to the efficient separation of the photoexcited electron-hole pairs caused by inner electronic field (IEF) of p-n junction. This study opens up new opportunities in designing photoactive materials with highly enhanced performance for solar energy conversion.