Yiwen Xie,Haiyan Zhang,Jiale Yu,Zhenjiang Liu,Shangshang Zhang,Huaiyu Shao,Yuliang Cao,Xifeng Huang,Shengkai Li
Lithium (Li) metal is an excellent anode of Li ion batteries because of its high theoretical capacity and the low redox potential compared to other anodes. However, the uncontrollable growth of Li dendrites still incurs serious safety issues and poor electrochemical performances, leading to its limited practical application. An oxygen and boron codoped honeycomb carbon skeleton (OBHcCs) is reported and a stable Li metal-based anode is realized. It can be coated on a copper foil substrate to be used as a current collector for a dendrite-free Li metal anode. OBHcCs effectively reduces the local current density owing to the high surface area and inhibits Li dendrite growth, which is explored by scanning electron microscopy and an X-ray photoelectron spectra depth profile. The abundant lithiophilic oxygen and boron-containing functional groups reduce the potential barrier of nucleation and lead to the homogeneous Li ions flux as confirmed by the density functional theories. Therefore, the Li metal anode based on OBHcCs (OBHcCs@Li) stably runs for 700 h in a symmetric cell with a Li stripping capacity of 1 mAh cm −2 at 1 mA cm −2 . Furthermore, the OBHcCs@Li|LiFePO 4 full cell shows a good capacity retention of 84.6% with a high coulombic efficiency of 99.6% at 0.5 C for 500 cycles.
To solve the serious safety issues such as highly flammable organic electrolyte, this work developed a novel lithium metal battery containing quasi-solid-state electrolyte (QSSE) with ionic liquid (ILs)/Li salt as electrolyte and covalent organic frameworks (COFs) as hosts. The micro-scale structure and dynamics properties of several ILs confined in COFs were investigated in detail using molecular dynamics (MD) simulations. It is found that the distinctly alternate layering structure of cations and anions of ILs from the pore surface to pore center are formed inside COFs due to the strong interaction between cations/anions and pore wall of COFs. The orientational preferences of confined ILs are observed depending on the size of anions. Inside the larger pores of COFs, the bulk-like structure of confined ILs is found, which tends to enlarge the leakage risk of electrolytes, while the smaller pore size of COFs can reduce the diffusion of ILs and further limit the ionic conductivity of electrolytes. The prepared QSSE with the appropriate-size ILs confined in medium pore-size COFs shows a higher ionic conductivity (0.87 mS cm −1 at 30 °C), more efficient inhibition of lithium dendrite (above 2000 h stability) and better battery performance (150.4 mAh g −1 at 0.1C). These findings from both simulations and experiments confirm the potential of COFs for achieving nondendritic lithium growth in lithium metal batteries.
Cai Zuo,Hongping Li,Gong Chen,Jun Yang,Zhixin Xu,Zhigang Xue
Lithium metal batteries with liquid electrolytes usually suffer from the growth of lithium dendrites and safety issues such as leaking and volatilization. Solid polymer electrolytes (SPEs) can relieve these problems due to their chemical and electrochemistry stability. However, PEO-based SPEs are still too brittle to endure bending, stretching, and shearing. Herein, highly elastic cyclodextrin-based triblock polymer electrolytes (CDTPEs) were fabricated via the ring-opening polymerization and initiator-free thiol–ene reaction. The rubbery PTMC segment endows the CDTPEs excellent elasticity to suffer from bending, stretching, and complicated conditions. This CDTPE integrates an excellent elongation (580%) and favorable ionic conductivity (1.5 × 10–3 S cm–1 at 100 °C). More importantly, the stable lithium stripping/plating process for over 2200 h was achieved due to the uniform lithium electrodeposition. The cyclodextrin component is verified to be beneficial for the uniform lithium electrodeposition. The LiFePO4/CDTPE/Li cells exhibit stable cycling performance and reversible specific discharge capacity. Our work may provide a method for stabilizing lithium metal batteries.
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