Longhao Qi

Cycling of a Lithium‐Ion Battery with a Silicon Anode Drives Large Mechanical Actuation

Lithium-ion batteries with a Si anode can drive large mechanical actuation by utilizing the dramatic volume changes of the electrode during the charge/discharge cycles. A large loading of more than 10 MPa can be actuated by a LiFePO4 ||Si full battery with a rapid response while the driving voltage is lower than 4 V.

Uniform Lithium Deposition Induced by Polyacrylonitrile Submicron Fiber Array for Stable Lithium Metal Anode

The lithium dendrite growth and low Coulombic efficiency (CE) during lithium plating/striping cycles are the main obstacles for practical applications of lithium metal anode. Herein, we demonstrate that polyacrylonitrile (PAN) submicron fiber array could guide the lithium ions to uniformly disperse and deposit onto current collector. The PAN submicron fiber array nearly does not increase the volume of electrode with ultralow mass. By this simple design, we achieved stable cycling of lithium metal anode with an average CE of ∼97.4% for 250 cycles at a current density of 1 mA cm-2 with total Li capacity of 1 mAh cm-2.

Surface graphited carbon scaffold enables simple and scalable fabrication of 3D composite lithium metal anode

Lithium metal is the most promising anode material due to its high specific capacity (∼3860 mA h g−1) and low electrochemical potential (−3.04 V vs. standard hydrogen electrode). However, lithium dendrite growth, low coulombic efficiency (CE) and the infinite relative volume change during lithium plating/striping cycles have severely limited its practical applications. Using a composite lithium metal anode fabricated by melt infusion of lithium is employed as an effective method to solve the aforementioned issues, but the fabrication process is always complicated and it is difficult to realize large-scale production. Herein, we demonstrate a simple and scalable method to fabricate a composite Li structure. By heat treatment at 1200 °C, a common carbon matrix turns into a surface graphited carbon scaffold, which possesses good Li affinity and can be used to fabricate a three-dimensional (3D) composite Li anode by Li melt infusion. The one-step method makes it easy to realize scalable and cheap production of a lithium affinity scaffold. We achieved stable cycling of the lithium metal anode for 100 cycles at a high current density of 3 mA cm−2 in a carbonate electrolyte. The full-cell batteries with the 3D composite Li anode also delivered better rate and cycling performance than those with a bare Li anode.

Scalable Synthesis of 2D Si Nanosheets

2D Si nanomaterials have attracted tremendous attention due to their novel properties and a wide range of potential applications from electronic devices to energy storage and conversion. However, high-quality and large-scale fabrication of 2D Si remains challenging. This study reports a room-temperature and one-step synthesis technique that leads to large-scale and low-cost production of Si nanosheets (SiNSs) with thickness ≈4 nm and lateral size of several micrometers, based on the intrinsic delithiation process of chemically leaching lithium from the Li13 Si4 alloy. Together with experimental results, a combination of theoretical modeling and atomistic simulations indicates that the formation of single SiNS arises from spontaneous delamination of nanosheets from their substrate due to delithiation-induced mismatch. Subsequently, the synthesized Si nanosheets evolve from amorphous to nanocrystalline to crystalline structures during annealing at different temperatures. It is demonstrated that these SiNSs possess unique mechanical properties, in particular ultralow friction, in contrast to their bulk counterparts.