Composite Anodes for Lithium Metal Batteries

Abstract

The applications of lithium-ion batteries have been limited because their energy density can no longer meet the requirements of an emerging energy society. Lithium metal batteries (LMBs) are being considered as potential candidate for nextgeneration energy storage systems owing to the high theoretical specific capacity and low electrochemical potential of lithium metal. However, the commercialization of LMB is limited due to several challenges, such as uncontrollable formation of dendrites, unstable solid electrolyte interface, and infinite anode volume change, which can lead to grievous catastrophe. In this study, several typical mechanisms of lithium dendrite formation and growth are summarized. The results suggest that a smaller current density, greater Li + transference number, higher mechanical strength of the electrolyte, and a more homogeneous distribution of Li + on the substrate are conducive to the uniform deposition morphology of lithium metal. In view of these results, combined with the researches on LMBs conducted in recent years, composite anodes can be summarized into three level from internal to external. (i) Internal composite of lithium metal anode: the scaffolds composited with lithium metal are classified as non-conductive (NC), electron-conductive (EC), ion-conductive (IC), and mixed ion and electron-conductive (MIEC) scaffolds. Composited with NC scaffolds, the tip effect can be weakened through the interaction between polar functional groups and Li + . The composite of lithium metal and EC scaffolds can effectively reduce the local current density, while IC scaffolds can increase the ion flux. However, the performance of LMBs may be hindered by the insulation of electrons or Li + at high rates. In comparison, MIEC scaffolds can provide fast ion/electron transfer channels for the deposition or dissolution of lithium metal, which is beneficial for the electrochemical performance of LMBs even at high rates. (ii) Internal composite of LMB: Compared with liquid electrolytes, solid-state electrolytes (SSEs) and quasi-solid-state electrolytes are much safer. However, their interfacial contact with lithium metal anodes has been seriously criticized. Lithium metal anodes can be composited with SSEs or quasi-solid-state electrolytes to optimize the interface contact performance and reduce the interface resistance, thereby promoting the development of solid-state batteries. (iii) Composite of internal environment and external operating conditions: Composited with external physical fields, such as electric fields, magnetic fields, and temperature fields, the distribution of Li + can be homogeneous and the initial nucleation process can be regulated. Overall, this review summarizes several composite anodes that have greatly optimized the performance of LMBs and highlights the potential of multi-level composites for applications in lithium metal anodes.

Self-Healing Nucleation Seeds Induced Long-Term Dendrite-Free Lithium Metal Anode

“…Up to now, various strategies have been proposed to address these hazardous issues involved in Li metal anodes, including adjusting electrolyte compositions, , constructing artificial SEI layers, − utilizing solid-state electrolytes (SSEs), − and designing 3D micro/nanostructure of Li hosts. − Great progress on technical aspects has been achieved in prolonging the lifespan of Li metal anodes. However, the lithiophobic nature of the electrode materials (typically carbon and copper) and large volume change during Li plating/stripping still pose a huge challenge for effectively avoiding lithium dendrites growth. − Considering that the final Li deposition morphology critically depends on the nucleation process, numerous lithiophilic seeds, such as doped carbon, − metal, − and metal oxide nanoparticles, , were utilized to direct smooth Li nucleation and deposition. Although the nucleation barrier can be largely reduced during initial cycles, the deformation and pulverization of these lithiophilic sites or nanoparticles will undoubtedly cause the loss of seeding function, leading to the dendritic Li deposition with cycling.…”

Commercially Viable Hybrid Li-Ion/Metal Batteries with High Energy Density Realized by Symbiotic Anode and Prelithiated Cathode

“…However, the volume fluctuation derived from continuous Li plating/stripping on planar current collector should be also took into account, especially in the practical pouch cells [ 19 ]. Therefore, it can be concluded that designing porous structures as both hosts and current collectors for accommodating Li deposits and buffering its volumetric change is essential for anode-free Li metal batteries [ 20 , 21 ]. Diverse metallic scaffolds with different porosity have been introduced to reduce the local current density [ 22 – 26 ].…”

Growing Nanostructured CuO on Copper Foil via Chemical Etching to Upgrade Metallic Lithium Anode

“…9−11 Unfortunately, the 3D frameworks, especially copper foil and carbon-based materials, have poor affinity with lithium metal, resulting in uneven Li deposition. 12,13 One effective approach is to introduce lithiophilic materials, such as Ag, NiO, ZnO, or Cu 2 O, to the surface of current collectors to guide uniform Li nucleation and deposition by reducing nucleation overpotential. 14−17 Besides, optimization of the interfaces between Li and electrolyte via employing electrolyte additives, building an artificial SEI, or using solid-state electrolytes can enhance the mechanical properties and stability of SEI layers to suppress Li dendrite growth.…”

“…In recent years, diverse strategies have been proposed to address the challenges facing Li metal batteries. Among them, the use of a stable three-dimensional (3D) framework such as GN@Cu foam, 3D Cu mesh, and MXene is found to effectively decrease local current density and regulate the surface energy. − Unfortunately, the 3D frameworks, especially copper foil and carbon-based materials, have poor affinity with lithium metal, resulting in uneven Li deposition. , One effective approach is to introduce lithiophilic materials, such as Ag, NiO, ZnO, or Cu 2 O, to the surface of current collectors to guide uniform Li nucleation and deposition by reducing nucleation overpotential. − Besides, optimization of the interfaces between Li and electrolyte via employing electrolyte additives, building an artificial SEI, or using solid-state electrolytes can enhance the mechanical properties and stability of SEI layers to suppress Li dendrite growth. − However, the construction of a 3D framework and artificial synthesis of SEI generally require complicated procedures such as dealloying, templating, and coating, which unfavor scalable processing of a lithium metal anode.…”