Energy Storage Division

Vehicle Technologies

Our research includes study and preparation of novel materials and electrodes for high energy, high power, and safe batteries including those capable of fast charge and function in extreme environments.

Improved Capacity Retention of Lithium Ion Batteries under Fast Charge via Metal-Coated Graphite Electrodes

A primary barrier preventing repetitive fast charging of Li-ion batteries is lithium metal plating at the graphite anode. One approach toward mitigating Li metal deposition is the deliberate modification of the graphite anode surface with materials demonstrating high overpotentials unfavorable for Li metal nucleation, such as Ni or Cu nanoscale films. Batteries incorporating graphite electrodes with high metal film loadings exhibited an improvement in capacity retention after 500 fast (10-minute) charge cycles of 9% compared to uncoated anodes. The work highlights the use of nanoscale functional surface coatings for prevention of Li plating during battery fast charging.

Low-Oxidized Siloxene Nanosheets with High Capacity, Capacity Retention, and Rate Capability in Lithium-Based Batteries

The mechanical degradation experienced by Si electrodes during Li (de)alloying reactions can potentially be mitigated by using Si-based materials with layered 2D geometries. Such materials are expected to exhibit favorable mechanical properties and be capable of buffering the volume change associated with (de)lithitation. In this work, 2D siloxene nanosheets are synthesized using a facile topotactic reaction followed by ultrasonication as an exfoliation step. The Li/siloxene cell exhibits high rate capability with a capacity of 935 mAh g–1 at 3200 mA g–1 and ≈99.5% coulombic efficiency.

Multimodal electrochemistry coupled microcalorimetric and X-ray probing of the capacity fade mechanisms of Nickel rich NMC – progress and outlook

Lithium nickel manganese cobalt oxide (NMC) is a commercially successful Li-ion battery cathode due to its high energy density; however, its delivered capacity must be intentionally limited to achieve capacity retention over extended cycling. This perspective outlines recent developments in the elucidation of capacity fade mechanisms in NMC through hard X-ray probes, surface sensitive soft X-ray characterization, and isothermal microcalorimetry. A case study on the effect of charging potential on NMC811 over extended cycling is presented to illustrate the benefits of these approaches.

Progress Towards Extended Cycle Life Si-based Anodes: Investigation of Fluorinated Local High Concentration Electrolytes

Silicon (Si) anodes are promising candidates for Li-ion batteries due to their high specific capacity and low operating potential. Implementation has been challenged by the significant Si volume changes during (de)lithiation and associated growth/regrowth of the solid electrolyte interphase (SEI). In this report, fluorinated local high concentration electrolytes (FLHCEs) were designed such that each component of the electrolyte (solvent, salt, diluent) is fluorinated to modify the chemistry and stabilize the SEI of high (30%) silicon content anodes. Si-graphite/NMC622 pouch cell batteries utilizing the FLHCEs enabled enhanced capacity retention compared to batteries incorporating conventional carbonate based electrolytes.