Three-dimensionally multiple protected silicon anode toward ultrahigh areal capacity and stability

Preparing Carbon-Coated Copper Foil with a Low-Cost and Environmentally Friendly Carbon Slurry to Stabilize Silicon Anode for Lithium-Ion Battery

Introducing a conductive carbon layer between the copper foil current collector and silicon active material effectively mitigates electrode damage and battery capacity loss caused by uneven silicon expansion. In this study, a low-cost, environmentally friendly carbon-coated copper foil (CCF) is designed using zeolitic imidazolate framework 8-derived carbon (ZPC) as the carbon source, polyethylenepyrrolidone (PVP) as the binder, and deionized water as the solvent. The large surface area and porosity of ZPC effectively accommodate the volume expansion of silicon, thereby enhancing the overall performance of the battery. The bare copper foil electrode experiences rapid decay, with a failure occurring after just 75 cycles at 0.5 C. In contrast, the CCF electrode maintains a reversible capacity of 576.8 mAh/g even after 200 cycles. The CCF electrode demonstrates superior specific capacity and cycle stability in both the rate and cycling test. According to the relaxation time distribution (DRT) analysis, the porous carbon layer on the CCF surface ensures excellent electrical contact between silicon and the Cu foil during cycling, facilitates uniform lithium insertion into silicon, prevents uncontrolled growth of the SEI layer, and guarantees stable battery operation. This CCF preparation process provides a promising solution to mitigate the degradation of battery performance caused by silicon expansion.

Li-Si alloy pre-lithiated silicon suboxide anode constructing a stable multiphase lithium silicate layer promoting Ion-transfer kinetics

Enhancing the initial Coulombic efficiency (ICE) and cycling stability of silicon suboxide (SiOx) anode is crucial for promoting its commercialization and practical implementation. Herein, we propose an economical and effective method for constructing pre-lithiated core-shell SiOx anodes with high ICE and stable interface during cycling. The lithium silicon alloy (Li13Si4) is used to react with SiOx in advance, allowing for improved ICE of SiOx without compromising its reversible specific capacity. The pre-lithiated surface layer contains uniform multiphase lithium silicates (L2SiO3, Li4SiO4, and Li2Si2O5) in the nanoscale. This multiphase lithium silicate layer exhibits mechanical robustness against variation of micro-stress, which can act as a buffer layer to relieve volume variation. In addition, analysis of dynamic electrochemical impedance spectroscopy (dEIS) and distribution of relaxation time (DRT) confirm that the multiphase lithium silicate layer enhances Li-ion diffusion kinetics and contributed to constructing stable SEI. As a result, the optimal L10-850 anode shows a high ICE of 85.3 %, together with a high specific capacity of 1771.5mAh mg-1. This work gives a perspective strategy to modify SiOx anodes by constructing a pre-lithiated surface layer with practical application potentials.

Interfacial self-healing polymer electrolytes for Long-Cycle silicon anodes in High-Performance solid-state lithium batteries

For all-solid-state lithium-ion batteries (ASSLIBs), silicon (Si) stands out as an appealing anodes material due to its high energy density and improved safety compared to lithium metal. However, the substantial volume changes during cycling result in poor solid-state physical contact and electrolyte-electrode interface issues, leading to unsatisfactory electrochemical performance. In this study, we employed in-situ polymerization to construct an integrated Si anodes/self-healing polymer electrolyte for ASSLIBs. The polymer chain reorganization stems from numerous dynamic bonds in the constructed self-healing dynamic supermolecular elastomer electrolyte (SHDSE) molecular structure. Notably, SHDSE also serves as a Si anodes binder with enhanced adhesive capability. As a result, the well-structured Li|SHDSE|Si-SHDSE cell generates subtle electrolyte-electrode interface contacts at the molecular level, which can offer a continuous and stable Li+ transport pathway, reduce Si particle displacement, and mitigate electrode volume expansion. This further enhances cyclic stability (>500 cycles with 68.1 % capacity retention and >99.8 % Coulombic efficiency). More practically, the 2.0 Ah wave-shaped Si||LiCoO2 soft-pack battery with in-situ cured SHDSE exhibits strongly stabilized electrochemical performance (1.68 Ah after 700 cycles, 86.2 % capacity retention) in spite of a high operating temperatures up to 100 °C and in various bending tests. This represents a groundbreaking report in flexible solid-state soft-pack batteries containing Si anodes.

Boron-doped three-dimensional porous carbon framework/carbon shell encapsulated silicon composites for high-performance lithium-ion battery anodes

Deleterious volumetric expansion and poor electrical conductivity seriously hinder the application of Si-based anode materials in lithium-ion batteries (LIBs). Herein, boron-doped three-dimensional (3D) porous carbon framework/carbon shell encapsulated silicon (B-3DCF/Si@C) hybrid composites are successfully prepared by two coating and thermal treatment processes. The presence of 3D porous carbon skeleton and carbon shell effectively improves the mechanical properties of the B-3DCF/Si@C electrode during the cycling process, ensures the stability of the electrical contacts of the silicon particles and stabilizes the solid electrolyte interface (SEI) layer, thus enhancing the electronic conductivity and ion migration efficiency of the anode. The developed B-3DCF/Si@C anode has a high reversible capacity, excellent cycling stability and outstanding rate performance. A reversible capacity of 1288.5 mAh/g is maintained after 600 cycles at a current density of 400 mA g-1. The improved electrochemical performance is demonstrated in a full cell using a LiFePO4-based cathode. This study presents a novel approach that not only mitigates the large volume expansion effects in LIB anode materials, but also provides a reference model for the preparation of porous composites with various functionalities.

Dynamic hydrogen bond cross-linking binder with self-healing chemistry enables high-performance silicon anode in lithium-ion batteries

The structure instability and cycling decay of silicon (Si) anode triggered by stress buildup hinder its practical application to next-generation high-energy-density lithium-ion batteries (LIBs). Herein, a cross-linking polymeric network as a self-healing binder for Si anode is developed by in situ polymerization of tannic acid (TA) and polyacrylic acid (PAA) binder labelled as TA-c-PAA. The branched TA as a physical cross-linker complexes with PAA main chains through abundant dynamic hydrogen bonds, endowing the cross-linking TA-c-PAA binder with unique self-healing property and strong adhesion for Si anode. Benefiting from the mechanical robust and hard adhesion, the Si@TA-c-PAA electrode exhibits high reversible specific capacities (3250 mAh/g at 0.05C (1C = 4000 mA g-1)), excellent rate capability (1599 mAh/g at 2C), and impressive cycling stability (1742 mAh/g at 0.25C after 450 cycles). After Ex situ morphology characterization, in situ swelling analysis, and finite element simulation, it is found that the TA-c-PAA binder allows the Si anode to dissipate stress and prevent pulverization during lithiation and delithiation, thus the hydrogen bonds among interpenetrating network may be adaptable to the stress intensity. Our work paves a new avenue for the design of efficient and cost-effective binders for next-generation Si anode in LIBs.