Search

Background Anode-free lithium metal batteries (AFLMBs) are promising power sources. However, Li dendrite and dead Li formation hindered it from practical applications. These challenges mainly result from inhomogeneous Li plating and fragile SEI due to the rough bare copper (bare Cu) surface and commonly used carbonate electrolytes. Methods Herein, we designed a two-step modification on the copper surface with synthesized Ag nanoparticles wrapped with polydopamine (Ag@P) and an artificial protection film (APF) to introduce an interface functional double layers. The first layer serves as Li-seeds for uniform Li nucleation and deposition. The latter (PVDF-HFP/LiTFSI) encapsulates the deposited Li to promote the formation of an anion-derived compact SEI film and minimize the inevitable electrolyte decomposition with Li. Significant findings It is found that the double-layer coating on copper enables homogenous and Li dendrite-free morphology. The anode-free cell with double layer-coated copper and NMC cathode maintains a superior coulombic efficiency (CE) of 98.15% and over 70 cycles at 40% capacity retention (CR) compared to the CE of 96.18% after 25 cycles at 40% CR on the bare Cu under 0.2 mA cm−2. These prominent achievements stem from the synergetic role of the lithiophilic Ag nanoparticles and the generation of an anion-derived robust LiF-rich SEI film. This study offers an alternative approach for current collector surface modification for the feasibility of AFLMBs.

Anode-free lithium metal batteries (AFLMBs) have been extensively studied due to their intrinsic high energy and safety without a metallic Li anode in cell design. Yet, the dendrite and dead-Li buildup continuously consumes the active Li upon cycling, leading to the poor lifespan of AFLMBs. Here, we introduce lithium oxalate into the cathode as an electrode additive providing a Li reservoir to extend the lifespan of AFLMBs. The AFLMB using 20% lithium oxalate and a LiNi

LiGe2(PO4)3 (LGP), a NASICON-type solid electrolyte, has many advantages such as its superior electrochemical and thermal stability for use in all solid-state lithium batteries. However, its low ionic conductivity is one of the challenges that can hinder its practical application commercially. In this work, the influence of adding different amounts of scandium and aluminum on the Li+ conductivity of LGP was investigated computationally and experimentally. Substituting 25% of Ge4+ ions in the LGP structure with Al3+ and/or Sc3+ ions to obtain doped LGP in the form of Li1+x+yAlxScyGe2−x−y(PO4)3, where x + y = 0.5, led to more Li+ ions in the 36f vacant sites (M2) and resulted in enhanced ionic conductivity of the material. In both approaches, the highest bulk Li+ conductivity of 5.826 mS cm−1 was obtained for Li1.5Al0.33Sc0.17Ge1.5(PO4)3 from the experimental measurement. The activation energy was also investigated theoretically using the nudged elastic band method, and the lowest value (0.279 eV) was obtained for this composition. Furthermore, the Li1+x+yAlxScyGe2−x−y(PO4)3 electrolytes were synthesized using a melt-quenching method and subsequently transformed into a glass–ceramic material through heat treatment. X-ray diffraction, electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the structure, measure the Li+ conductivity and determine the electrochemical window of the synthesized glass–ceramic material, respectively. There was a remarkable agreement between the computationally calculated and experimentally measured values of ionic conductivity, activation energy and electrochemical window. Finally, its applicability in a solid-state battery was tested, and it showed good electrochemical performance.

Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is a promising solid electrolyte for use in next-generation lithium batteries. Nevertheless, its lower bulk and grain-boundary ionic conductivities are major restrictions preventing its practical utilization. Mg was introduced into LAGP to form Li1.6Al0.4Mg0.1Ge1.5(PO4)3 (LAMGP) based on computational analysis. The doping of LAGP with Mg results in advantages such as increasing the Li+ concentration and expanding the material dimensions due to the larger ionic radius of Mg, leading to enhanced ionic conductivity. Mg had a two-birds-with-one-stone effect in the LAMGP electrolyte, not only generating super high bulk ionic conductivity of 7.435 mS cm−1, compared to 2.896 mS cm−1 in LAGP, but also generating low grain-boundary resistance due to improved densification. The lowering of the grain-boundary resistance and the increased densification are related to choosing the right precursor for the dopant. Using LAMGP as a hybrid solid electrolyte, a solid battery delivered great electrochemical performance in comparison to when LAGP was used. Interfacial analysis was also conducted, which revealed that the formation of an interface prevented the reduction of components in LAMGP by Li metal, therefore ensuring the long-term durability of LAMGP in liquid electrolyte. These results suggest that LAMGP is an auspicious solid electrolyte for achieving practical solid-state lithium batteries.

The uncontrolled lithium dendrite growth during cycling causes safety issues that impede lithium metal batteries from practical applications. In anode-free lithium metal batteries (AFLMBs), the unregulated plating of lithium on bare copper enforces a more severe growth of lithium dendrite. Herein, we guide the direction of lithium (Li) depositions towards the backside of gold sputter perforated polyimide film (PI@Au), which serves as an anode current collector. Thus, Li can deposit on the surface of PI@Au, and subsequently, Li growth takes place in the direction away from the separator face (ASF). This backside deposition and growth tactic allow the battery to operate safely, even when lithium dendrite exists. Remarkably, the dendrite free separator facing (SF) of PI@Au anode demonstrates highly improve cycling stability. Hence, PI@Au//LFP cell is capable of maintaining capacity retention (CR) of 20% for 340 cycles with an average Coulombic efficiency (Av. CE) of 98.7% (0.5 mA/cm2). In contrast, the control cell (Cu//LFP) runs only for 165 cycles under the same value of CR. This work not only proposes an innovative approach in developing ultra-safe AFLMBs but also validates the feasibility of electrically nonconductive substrates as anode current collectors by modifying their lithiophilicity.