Promising Anode For Next-generation Batteries Research Articles

Guiding lithium growth direction by Au coated separator for improving lithium metal anode

Lithium metal is the most promising anode for next-generation batteries due to its highest theoretical capacity and lowest electrochemical potential. However, its dendritic growth hinders its practical use due to the consequent poor reversibility, potential short-circuit, and safety concerns. Suppressing lithium dendrite is difficult since dendritic growth is thermodynamically and kinetically favorable. Herein, we guide lithium to uniformly deposit along the opposite direction to normal by a nanolayer Au coating on a commercial polypropylene separator. It prevents lithium dendrites from piercing the separator, instead of inhibiting dendrites growth only. Au is lithiophilic, and lithium is calculated to be more attracted to Au and is confirmed to uniformly deposit on Au at the separator side rather than on the current collector side. Furthermore, Au also regulates the morphology of deposited lithium from a mossy state to a bulky state. In this work, the symmetric cell with the designed structure achieves excellent electrochemical performances of a long-life cycle over 2,000 h at 1 C for 1 mA h cm-2. Pairing with LiFePO4 cathode as a full cell, lithium metal anode with Au-modified polypropylene separator exhibits extraordinary performance with a high Coulombic efficiency of 99.23% over 800 cycles at 1 C.

(Invited) Development of Interfacial Materials for High-Performance Battery Materials

Metal and alloy anode materials are the most promising anode for next-generation batteries. The interfacial instability in the electrochemical energy storage devices has been the primary issue hindering their practical application. In this talk, I will present approaches on de novo designing and architecting stable interphases on electrode materials using chemically and electrochemically active materials. The strategy works by introducing multiple functional components into the polymer composite which can bond to the Li-based material surface to participate in the formation of the SEI. The reinforced SEI shows much better stability than the SEI generated by the electrolyte additive strategy. The functional-material-derived interfaces/interphases present desirable ionic conductivity, density, homogeneity, and mechanical strength. The interfaces/interphases reinforced by the interfacial materials show much better stability than that reinforced by conventional strategies such as using electrolyte additive-commercially used solution to interface stability issues. Our findings open a new way to design stable electrochemically stable interfaces in electrode materials for next-generation electrochemical energy storage.

Towards high performance Li metal batteries: Surface functionalized graphene separator with improved electrochemical kinetics and stability

Lithium (Li) metal is a promising anode for next-generation batteries owing to its ultrahigh theoretical capacity (3,860 mAh g−1) and the lowest reduction potential (−3.04 vs SHE at RT). However, the development of Li-metal batteries (LMBs) is still in the research stage due to the inherent problems related to the growth of Li dendrites and unlimited volume change in Li metal. Among diverse approaches, the introduction of functional separators is regarded as an effective strategy for improving the safety and electrochemical performance of LMBs. Herein, we deposited two different graphene layers onto the separators to explore the influence of surface functionalized graphene layer on the electrochemical performance and cycle stability of LMBs. When a surface functionalized graphene separator (SFGS) was used in the LMBs, it exhibited superior electrolyte wettability than a graphene separator (GS), contributing to the improved ionic conductivity and homogeneous Li-ion flux. Due to the improved electrochemical kinetics and reversible electrochemical reactions, Li/Cu cells with the SFGS exhibited the most stable cycle performance with a high Coulombic efficiency of 98 % over 200 cycles compared with other Li/Cu cells. Our strategy would resolve many issues related to the poor electrochemical reversibility of Li-metal anodes and advance the development of practical surface-modified separators for high-performance LMBs.

Double Perovskite La2 MnNiO6 as a High-Performance Anode for Lithium-Ion Batteries.

Traditional lithium-ion batteries cannot meet the ever-increasing energy demands due to the unsatisfied graphite anode with sluggish electrochemical kinetics. Recently, the perovskite material family as anode attracts growing attention due to their advantages on specific capacity, rate capability, lifetime, and safety. Herein, a double perovskite La2 MnNiO6 synthesized by solid-state reaction method as a high-performance anode material for LIBs is reported. La2 MnNiO6 with an average operating potential of <0.8V versus Li+ /Li exhibits a good rate capability. Besides, the Li|La2 MnNiO6 cells perform long cycle life without decay after 1000 cycles at 1C and a high cycling retention of 93% is observed after 3000 cycles at 6C. It reveals that this material maintains stable perovskite structure with cycling. Theoretical calculations further demonstrate the high electronic conductivity, low diffusion energy barrier, and structural stability of the lithiated La2 MnNiO6 . This study highlights the double perovskite type material as a promising anode for next-generation batteries.

Graphene membrane hosted compact lithium metal anode enabled by capillary force-tuned lithium infiltration

Lithium metal anodes, the promising anodes for next-generation batteries, are troubled by the instability and safety issues induced by the dendrite growth. Three-dimensional hosts are widely used to accommodate lithium metal to solve the above problems. However, they are constantly challenged by large thickness and excess space in the host, lowering the volumetric energy density of batteries. Here, we used the reduced graphene oxide membrane (rGOM) assembled with small graphene oxide sheets as the host and obtained a compact, ultrathin (<20 μm) and free-standing lithium metal-rGO composite anode with good flexibility and high volumetric capacity. The overlap sites derived from the stacking of small size of GO act as abundant diffusion channels for the gas release during the spark reduction process, producing narrow interlamellar space in the rGOM and thus enhancing the capillary molten Li infusion to form a compact composite anode. These sites also guide the uniform deposition of Li metal on the surface and interior of the membrane, effectively suppressing the dendrite growth. This compact composite anode delivers a high volumetric capacity (1223 mAh cm−3) and stable cycling performance in the symmetrical cells and the full cells coupled with high mass loading LiFePO4 cathode under a low N/P ratio.

Scalable Synthesis of Nano-Sized Bi for Separator Modifying in 5V-Class Lithium Metal Batteries and Potassium Ion Batteries Anodes.

With the advantages of high theoretical-specific capacity and lowest working potential, lithium metal anode is considered as the most promising anode for next-generation batteries. Here, a scalable dealloying method is developed to prepare nano-sized bismuth (Bi). It is found that the Bi-modification can not only enhance the wettability of the commercial polyethylene separator but also suppresses the lithium dendrite growth. With the nano-sized Bi modified separator, 5V-class lithium metal batteries with commercial carbonate-based electrolyte show a 91% capacity retention ratio after 800 cycles. First-principle calculations prove that lithium atoms tend to deposit smoothly on the Bi surface. Moreover, for potassium ion batteries, nano-sized Bi shows a stable cycling performance and high capacity. The results may be useful for the development of high-energy and high-safety batteries.

Stabilization effect of solid-electrolyte interphase by electrolyte engineering for advanced Li-ion batteries

Sn-based materials have been highlighted as promising anodes for next-generation batteries; however, such alloying-based anodes suffer from gradual cell degradation caused by the associated large volume changes, leading to particle pulverization and an unstable solid electrolyte interphase (SEI). A key to constructing a stable SEI as well as effectively buffering the large volume expansion is to establish appropriate electrolyte conditions. In this work, to induce the formation of a favorable SEI layer, a Sn anode is paired with an electrolyte composed of eutectic succinonitrile (SN) combined with fluoroethylene carbonate (FEC) for the first time. Whereas conventional electrolytes are prone to form organic SEI components, which are vulnerable to large volume changes, the combination of SN and FEC enables the formation of a mechanically rigid SEI that is mainly composed of favorable inorganics such as LiF and Li3N. The synergistic effects of SN and FEC result in superior cycle performance of the Sn anode with improved efficiency compared with that achieved using conventional carbonate electrolytes. The modified SEI layer was closely investigated using various surface analysis techniques, with the individual effects of SN and FEC extracted. The rational design of the electrolyte provides a simple yet effective approach to enhance the electrochemical performance of Sn anodes and can be further extended to other alloying-based anode materials.

Pore-assisted lithium deposition in hierarchically porous and hollow carbon textile for highly stable lithium anode

Lithium (Li) metal is widely accepted as the most promising anode for next-generation batteries due to its highest theoretical capacity (3,860 mA h g−1) and lowest electrochemical potential (−3.04 V versus standard hydrogen electrode). However, Li-metal anodes suffer from low Coulombic efficiency and safety issues, due to the high activity and uncontrollable Li dendrite growth. Here, we demonstrate that a novel two-stage “outside-in” Li deposition behavior achieved through the use of bio-derived hollow carbon fiber textile with unique hierarchical porosity. We show that Li deposition first occurs on the external surface because of the abundant lithiophilic pores, followed by deposition both inside and on the wall of the hollow carbon fiber. This pore-induced mechanism is crucial for the carbon fiber textile serving as a stable and robust host for uniform Li deposition. This Li composite anode exhibits a high Coulombic efficiency for more than 500 cycles and high cycling stability of over 1,400 h at a current density of 1 mA cm−2. The scalable production and the novel understanding on the function of hierarchical porous structure provide critical insights into design and synthesis of carbon-based materials as hosts for Li anodes.

Ameliorating the interfacial issues of all-solid-state lithium metal batteries by constructing polymer/inorganic composite electrolyte

Lithium metal is one of the most promising anodes for next-generation batteries due to its high capacity and low reduction potential. However, the notorious Li dendrites can cause the short life span and safety issues, hindering the extensive application of lithium batteries. Herein, Li7La3Zr2O12 (LLZO) ceramics are integrated into polyethylene oxide (PEO) to construct a facile polymer/inorganic composite solid-state electrolyte (CSSE) to inhibit the growth of Li dendrites and widen the electrochemical stability window. Given the feasibility of our strategy, the designed PEO-LLZO-LiTFSI composite solid-state electrolyte (PLL-CSSE) exhibits an outstanding cycling property of 134.2 mAh g−1 after 500 cycles and the Coulombic efficiency of 99.1% after 1000 cycles at 1 C in LiFePO4-Li cell. When cooperated with LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, the PLL-CSSE renders a capacity retention of 82.4% after 200 cycles at 0.2 C. More importantly, the uniform dispersion of LLZO in PEO matrix is tentative tested via Raman and FT-IR spectra and should be responsible for the improved electrochemical performance. The same conclusion can be drawn from the interface investigation after cycling. This work presents an intriguing solid-state electrolyte with high electrochemical performance, which will boost the development of all-solid-state lithium batteries with high energy density.

Next-Generation Lithium Metal Anode Engineering via Atomic Layer Deposition.

Lithium metal is considered to be the most promising anode for next-generation batteries due to its high energy density of 3840 mAh g(-1). However, the extreme reactivity of the Li surface can induce parasitic reactions with solvents, contamination, and shuttled active species in the electrolyte, reducing the performance of batteries employing Li metal anodes. One promising solution to this issue is application of thin chemical protection layers to the Li metal surface. Using a custom-made ultrahigh vacuum integrated deposition and characterization system, we demonstrate atomic layer deposition (ALD) of protection layers directly on Li metal with exquisite thickness control. We demonstrate as a proof-of-concept that a 14 nm thick ALD Al2O3 layer can protect the Li surface from corrosion due to atmosphere, sulfur, and electrolyte exposure. Using Li-S battery cells as a test system, we demonstrate an improved capacity retention using ALD-protected anodes over cells assembled with bare Li metal anodes for up to 100 cycles.