The rapid development of flexible and wearable electronics proposes the persistent requirements of high-performance flexible batteries. Much progress has been achieved recently, but how to obtain remarkable flexibility and high energy density simultaneously remains a great challenge. Here, a facile and scalable approach to fabricate spine-like flexible lithium-ion batteries is reported. A thick, rigid segment to store energy through winding the electrodes corresponds to the vertebra of animals, while a thin, unwound, and flexible part acts as marrow to interconnect all vertebra-like stacks together, providing excellent flexibility for the whole battery. As the volume of the rigid electrode part is significantly larger than the flexible interconnection, the energy density of such a flexible battery can be over 85% of that in conventional packing. A nonoptimized flexible cell with an energy density of 242 Wh L is demonstrated with packaging considered, which is 86.1% of a standard prismatic cell using the same components. The cell also successfully survives a harsh dynamic mechanical load test due to this rational bioinspired design. Mechanical simulation results uncover the underlying mechanism: the maximum strain in the reported design (≈0.08%) is markedly smaller than traditional stacked cells (≈1.1%). This new approach offers great promise for applications in flexible devices.

Organic molecules with redox-active motifs are of great interest for next-generation electrodes for sustainable energy storage. While there has been significant progress in designing redox-active molecules, the practical requirements of...

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Silicon-based anodes are one of the promising candidates for the next generation high-power/energy density lithium ion batteries (LIBs). However, a major drawback limiting the practical application of the Si anode is that Si experiences a significant volume change during lithiation/delithiation, which induces high stresses causing degradation and pulverization of the anode. This study focuses on crack initiation within a Si anode during the delithiation process. A multi-physics-based finite element (FE) model is built to simulate the electrochemical process and crack generation during delithiation. On top of that, a Gaussian process (GP)-based surrogate model is developed to assist the exploration of the crack patterns within the anode design space. It is found that the thickness of the Si coating layer, TSi, the yield strength of the Si material, σFc, the cohesive strength between Si and the substrate, σFs, and the curvature of the substrate, ρ, have large impacts on the cracking behavior of Si. This coupled FE simulation-GP surrogate model framework is also applicable to other types of LIB electrodes and provides fundamental insights as building blocks to investigate more complex internal geometries.

Implementation of high Si-content anodes (> 10% v/v%) has been difficult to achieve at the loadings and manufacturing scale required for practical lithium-ion batteries (LIBs) applications. Three-dimensionally engineered electrically conductive porous scaffolds enable low silicon coating thicknesses (10-200 nm) and provide internal free volume to reduce the impact of Si volume changes upon cycling. Yet, scalable deposition of battery-grade silicon on these complex structures remains a challenge. Herein, we report a high energy-density Si-dominant electrodeposited material (EDEP-Si) onto 3D-structured Ni scaffolds and evaluate the impact of impurities inherent to the electrodeposition process on performance by comparing the behavior of the EDEP-Si with that of high-purity amorphous Si grown via static chemical vapor deposition (CVD). The long-term cycling stability and high reversible specific capacity of EDEP-Si and CVD-Si on a silicon basis are remarkably similar and near theoretical (~2400 mAh g-1 Si-1 after 100 cycles). However, the EDEP-Si exhibits a 13% lower first cycle efficiency and reduced round-trip efficiencies over the first 10-20 cycles relative to CVD-Si. Reactions between carbon (9-11 at%) and, more importantly, oxygen (42-44 at%) in the EDEP-Si with lithium are most likely responsible for the reduced early-cycle round trip efficiencies and low capacity relative to the mass of the total deposit. Based on our observations, we suggest directions for improving the composition and properties of EDEP-Si.