Synergistic regulation of Li deposition on F-doped hollow carbon spheres toward dendrite-free lithium metal anodes.

The notorious issues of lithium (Li) dendrite growth and volume change hinder the practical applications of Li metal anodes. LiF as a key component of the solid electrolyte interface (SEI) governs Li+ transport and deposition, yet the formation of LiF consumes the anions (PF6-/TFSI-) in the electrolyte, preventing the stable cycling of Li anodes. Herein, fluorine (F)-doped hollow carbon (FHC) was synthesized and used to construct a composite current collector with FHC as an F-rich buffer layer for modifying the Cu foil. The F content provided by FHC not only mitigates the anion (PF6-/TFSI-) consumption but also enhances the stability of SEI. The hollow structure of FHC with abundant internal space can accommodate deposited Li to relieve the volume change during cycling. Besides, the significantly improved specific surface area of the electrode effectively reduces the local current density to achieve a homogeneous Li deposition. Due to the above cooperation, the symmetrical cell of Cu@FHC-Li||Cu@FHC-Li maintains stable cycling for more than 1800 h with a hysteresis voltage of 19 mV. In addition, full cell coupling with LiFePO4 cathode delivers excellent long-term cycling and rate performance. This work provides an effective route for developing stable Li metal anodes.

Locally regulating Li+ distribution on an electrode surface with Li-Sn alloying nanoparticles for stable lithium metal anodes.

Despite the fact that lithium metal batteries (LMBs) have the advantage of higher energy density than traditional lithium-ion batteries (LIBs), the development of Li anodes is hindered by the issues of dendritic Li growth and parasitic reactions during cycling, which can cause a coulombic efficiency decrease and capacity decay. Herein, a Li-Sn composite anode is developed by a facile rolling method. The in situ generated Li22Sn5 nanoparticles are uniformly distributed in the Li-Sn anode after the rolling process. The Li22Sn5 nanoparticles on the surface of the electrode exhibit excellent lithiophilicity, reducing the Li nucleation barrier. Multiphysics phase simulation discloses the distribution of local current density around the holes, guiding Li preferentially to deposit back onto the sites of previous Li stripping, and then realizing a controllable plating/stripping behavior of Li on the Li-Sn composite anode. Consequently, the symmetrical cell of Li-Sn||Li-Sn achieves a stable cycling lifetime of more than 1200 h at a current density of 1 mA cm-2 with a fixed capacity of 1 mA h cm-2. Besides, the full cell pairing with the LiFePO4 cathode delivers excellent rate performance and capacity retention after long cycles. This work provides new insight to modify the Li metal for preparing dendrite-free anodes.

A stable liquid-solid interface of a lithium metal anode enabled by micro-region meshing.

Although lithium metal is regarded as the most promising anode for high energy density lithium ion batteries, the unstable solid-liquid interface during cycling severely shortens the battery lifetime. The Li deposition behavior is greatly influenced by the current density distribution on the surface of the electrode, which is significantly associated with the electrode structure. A well-designed electrode structure plays a key role in stabilizing the solid-liquid interface of the Li metal anode. In this work, a lithiophilic honeycomb-like Ni3N nanosheet array modified Ni foam (Ni3N@NF) is prepared to stabilize the lithium metal anode. The honeycomb-like Ni3N nanosheet arrays divide the surface of Ni foam into numerous micro-regions, enabling Li to independently deposit in each mesh. Besides, Li3N is generated resulting from the in situ reaction between Li and Ni3N, improving the transportation of Li-ions. Consequently, a symmetrical cell of Ni3N@NF-Li||Ni3N@NF-Li achieves stable Li plating/stripping behavior for over 1500 h at a current density of 1 mA cm-2. Besides, a full cell of Ni3N@NF-Li||LiFePO4 exhibits enhanced cycling stability and outstanding rate performance.

Highly compacted TiO2/C micospheres via in-situ surface-confined intergrowth with ultra-long life for reversible Na-ion storage.

TiO2 as the promising anode material candidate of sodium-ion battery suffers from poor conductivity and slow ion diffusion rate, which severely hampers its development. Highly compacted TiO2/C microspheres without inner pores/tunnels are synthesized by a very facile one-pot rapid processing method based on novel in-situ surface-confined inter-growth mechanism. This highly compacted TiO2/C microspheres exhibit an excellent electrochemical performance of reversible Na+ storage despite with relatively large particle/aggregation size from submicrometer to micrometer. An outstanding cycling stability extending to 10,000 cycles is gained with a high retention capacity of 140.5 mAh g-1 at a current rate of 2 A g-1. An ultra-high reversible capacity of 362 mAh g-1 close to its theoretic specific capacity is obtained at a current rate of 0.05 A g-1. The successful combination of highly compacted structure with large particle size, excellent electrochemical performance as well as rapid cost-effective preparing process might provide a potential industrial approach for efficiently synthesizing electrode materials for Na ion batteries.

TiO2 quantum dots confined in 3D carbon framework for outstanding surface lithium storage with improved kinetics.

Pseudocapacitive lithium storage is an effective way to promote the improvement of electrochemical performance for lithium ion batteries. However, the intrinsically sluggish lithium ionic diffusion and the low electronic conductivity of TiO2 limit its capability of pseudocapacitive behavior with fast surface redox reaction. In this work, TiO2 quantum dots confined in 3-dimensional carbon framework have been synthesized by a facile process of reverse microemulsion method combined with heat treatment. The obtained composites effectively combine electrochemical redox with surface pseudocapacitive, showing excellent electrochemical properties. An ultra-high discharge capacity of 370.5 mAh/g can be retained after 200 cycles at a current density of 0.1 A/g. Ultra-long life extends to 10,000 cycles with an average capacity loss of as low as 0.00314% per cycle can be obtained at a high current density of 5.0 A/g, due to the high pesudocapacitance contribution of fast surface redox reaction. Furthermore, the practice application of the obtained electrode is also investigated in a full cell with LiCoO2 as the cathode and a high capacity retention of 93.5% is maintained after 100 cycles at the current density of 0.1 A/g.