• Energy Research

AbstractEfforts to enable fast charging and high energy density lithium‐ion batteries (LIBs) are hampered by the trade‐off nature of the traditional electrode design: increasing the areal capacity usually comes with sacrificing the fast charge transfer. Here a single‐layer chunky particle electrode design is reported, where red‐phosphorus active material is embedded in nanochannels of vertically aligned graphene (red‐P/VAG) assemblies. Such an electrode design addresses the sluggish charge transfer stemming from the high tortuosity and inner particle/electrode resistance of traditional electrode architectures consisting of randomly stacked active particles. The vertical ion‐transport nanochannels and electron‐transfer conductive nanowalls of graphene confine the direction of charge transfer to minimize the transfer distance, and the incomplete filling of nanochannels in the red‐P/VAG composite buffers volume change locally, thus avoiding the variation of electrodes thickness during cycling. The single‐layer chunky particle electrode displays a high areal capacity (5.6 mAh cm−2), which is the highest among the reported fast‐charging battery chemistries. Paired with a high‐loading LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, a pouch cell shows stable cycling with high energy and power densities. Such a single‐layer chunky particle electrode design can be extended to other advanced battery systems and boost the development of LIBs with fast‐charging capability and high energy density.

AbstractThe microstructure of an electrode plays a critical role in the electrochemical performance of lithium‐ion batteries, including the energy and power density. Using a micrometer‐scale Wadsley–Roth phase TiNb2O7 active material with Li intercalation chemistry as a model system, the relationship between electrochemical performance and microstructure of calendared electrodes with same mass loading but different electrode parameters is studied by both experimental investigation and theoretical modeling, providing a paradigm of calendaring‐driven electrode microstructure for balanced battery energy density and power density. Along with the reduction in porosity, ion and electron diffusion distance decreases, which is beneficial for charge transfer and rate capability. Nevertheless, the narrowed ion diffusion pathway increases the resistance for ion diffusion. The rate capability, volumetric capacity, and materials utilization are thus predominantly restricted by the microstructures of the electrode, providing fundamental insights into electrode microstructure design for different applications. As an example, an optimized TiNb2O7 electrode with compaction density of ≈2.5 g cm‐3 and mass loading of ≈8.5 mg cm‐2 provides the highest specific charge capacity of 271.3 mAh g‐1 at 0.2 C in half cell configuration and 70.4% capacity retention at 6 C in full configuration, enabling balanced energy density and power density of batteries.

AbstractConstructing silicon (Si)‐based composite electrodes that possess high energy density, long cycle life, and fast charging capability simultaneously is critical for the development of high performance lithium‐ion batteries for mitigating range anxiety and slow charging issues in new energy vehicles. Herein, a thick silicon/carbon composite electrode with vertically aligned channels in the thickness direction (VC‐SC) is constructed by employing a bubble formation method. Both experimental characterizations and theoretical simulations confirm that the obtained vertical channel structure can effectively address the problem of sluggish ion transport caused by high tortuosity in conventional thick electrodes, conspicuously enhance reaction kinetics, reduce polarization and side reactions, mitigate stress, increase the utilization of active materials, and promote cycling stability of the thick electrode. Consequently, when paired with LiNi0.6Co0.2Mn0.2O2 (NCM622), the VC‐SC||NCM622 pouch type full cell (~6.0 mAh cm−2) exhibits significantly improved rate performance and capacity retention compared with the SC||NCM622 full cell with the conventional silicon/carbon composite electrode without channels (SC) as the anode. The assembled VC‐SC||NCM622 pouch full cell with a high energy density of 490.3 Wh kg−1 also reveals a remarkable fast charging capability at a high current density of 2.0 mA cm−2, with a capacity retention of 72.0% after 500 cycles.

We demonstrated the interaction between electrolyte composition and P interphase of Si-based battery anode, and showed its exceptional stability and fast-charging capability by the formation of a robust Li3P/LiF solid electrolyte interphase.