Explore the vast range of titles available.

Commercial lithium ion cells are now optimised for either high energy density or high power density. There is a trade off in cell design between the power and energy requirements. A tear down protocol has been developed, to investigate the internal components and cell engineering of nine cylindrical cells, with different power–energy ratios. The cells designed for high power applications used smaller particles of the active material in both the anodes and the cathodes. The cathodes for high power cells had higher porosities, but a similar trend was not observed for the anodes. In terms of cell design, the coat weights and areal capacities were lower for high power cells. The tag arrangements were the same in eight out of nine cells, with tags at each end of the anode, and one tag on the cathode. The thicknesses of the current collectors and separators were based on the best (thinnest) materials available when the cells were designed, rather than materials optimised for power or energy. To obtain high power, the resistance of each component is reduced as low as possible, and the lithium ion diffusion path lengths are minimised. This information illustrates the significant evolution of materials and components in lithium ion cells in recent years, and gives insight into designing higher power cells in the future.

Silicon-Few Layer Graphene (Si-FLG) composite electrodes are investigated using a scalable electrode manufacturing method. A comprehensive study on the electrochemical performance and the impedance response is measured using electrochemical impedance spectroscopy. The study demonstrates that the incorporation of few-layer graphene (FLG) results in significant improvement in terms of cyclability, electrode resistance and diffusion properties. Additionally, the diffusion impedance responses that occur during the phase changes in silicon is elucidated through Staircase Potentio Electrochemical Impedance Spectroscopy (SPEIS): a more comprehensive and straightforward approach than previous state-of-charge based diffusion studies.

To investigate the influence of cell formats during a cell development programme, lithium-ion cells have been prepared in three different formats. Coin cells, single layer pouch cells, and stacked pouch cells gave a range of scales of almost three orders of magnitude. The cells used the same electrode coatings, electrolyte and separator. The performance of the different formats was compared in long term cycling tests and in measurements of resistance and discharge capacities at different rates. Some test results were common to all three formats. However, the stacked pouch cells had higher discharge capacities at higher rates. During cycling tests, there were indications of differences in the predominant degradation mechanism between the stacked cells and the other two cell formats. The stacked cells showed faster resistance increases, whereas the coin cells showed faster capacity loss. The difference in degradation mechanism can be linked to the different thermal and mechanical environments in the three cell formats. The correlation in the electrochemical performance between coin cells, single layer pouch cells, and stacked pouch cells shows that developments within a single cell format are likely to lead to improvements across all cell formats.

This work introduces a new method for inserting a Lithium reference electrode into commercially available 18650-type cells in order to obtain electrode potentials during cell operation. The proposed method is simple and requires limited equipment. Furthermore, electrical performance is significantly better and the cell capacity and resistance can be recorded for longer durations when compared to some of the previously used methods. Electrical performance of this new third electrode method is characterized and compared to 18650 cells with no reference electrode inserted. The capacity retention of the modified cell is more than 98% in the first 20 cycles. Harvested electrodes from a disassembled cell were also used to make coin cells that was proven to be a rather critical approach to get electrode potentials and capacities. This is an initial study that shows three-electrode performances of a commercial 18650-type cell, which suggests it could be used for understanding electrode behavior throughout a cell lifetime and for manufacturing instrumented cells.

The electrode formulation has a significant effect on the performance of lithium ion cells. The active material, binder, and conductive carbon all have different roles, and finding the optimum composition can be difficult using an iterative approach. In this study, a design of experiment (DoE) methodology is applied to the optimisation of a cathode based on lithium iron phosphate (LFP). The minimum LFP content in the electrodes is 94 wt%. Seventeen mixes are used to evaluate adhesion, resistivity, and electrochemical performance. The coating adhesion increases with binder content, and the coating conductivity increases with carbon nano-tube content. The best coatings achieve 5C:0.2C capacity ratios above 50%, despite the relatively high coat weight. Models based on just the component mixture do not replicate the discharge capacities at high rates. However, a combined mixture + process model can fit the data, and is used to predict an optimum formulation.

The size of a lithium iron phosphate (LFP) cathode mix was increased by a factor of thirty, and the capacity of the cells produced with it by a factor of three-hundred. As well as rate and cycling tests, the coatings were also characterised for adhesion and resistivity. The adhesion and total through-plane resistance were both dependent on the drying conditions during coating. The discharge capacities at high rates and the pulse resistances showed much less influence from the drying temperature. The mix formulation contained 97 wt% LFP, and was based on an earlier design of experiments (DoE) study, using relatively high active material contents. Overall, the mix exceeded the performance predicted by the modelling study.

The impacts on battery cell ageing from high current operation are investigated using commercial cells. This study utilised two tests–(i) to establish the maximum current limits before cell failure and (ii) applying this maximum current until cell failure. Testing was performed to determine how far cycling parameters could progress beyond the manufacturer’s recommendations. Current fluxes were increased up to 100 C cycling conditions without the cell undergoing catastrophic failure. Charge and discharge current capabilities were possible at magnitudes of 1.38 and 4.4 times, respectively, more than that specified by the manufacturer’s claims. The increased current was used for longer term cycling tests to 500 cycles and the resulting capacity loss and resistance increase was dominated by thermal fatigue of the electrodes. This work shows that there is a discrepancy between manufacturer-stated current limits and actual current limits of the cell, before the cell undergoes catastrophic failure. This presumably is based on manufacturer-defined performance and lifetime criteria, as well as prioritised safety factors. For certain applications, e.g., where high performance is needed, this gap may not be suitable; this paper shows how this gap could be narrowed for these applications using the testing described herein.

Solid-state lithium metal batteries show substantial promise for overcoming theoretical limitations of Li-ion batteries to enable gravimetric and volumetric energy densities upwards of 500 Wh kg −1 and 1,000 Wh l −1 , respectively. While zero-lithium-excess configurations are particularly attractive, inhomogeneous lithium plating on charge results in active lithium loss and a subsequent coulombic efficiency penalty. Excess lithium is therefore currently needed; however, this negatively impacts energy density and thus limiting its thickness is essential. Here we discuss the viability of various technologies for realizing thin lithium films that can be scaled up to the volumes required for gigafactory production. We identify thermal evaporation as a potentially cost-effective route to address these challenges and provide a techno-economic assessment of the projected costs associated with the fabrication of thin, dense lithium metal foils using this process. Finally, we estimate solid-state pack costs made using thermally evaporated lithium foils. Preparing suitable lithium anodes is crucial for high-performance solid-state batteries. This study evaluates methods for producing thin lithium films, emphasizing thermal evaporation as a cost-effective approach while estimating associated pack costs.

Clinicians and staff of the Department of Veterans Affairs Health Care System (VA), who provide services to veterans, have invented many devices and methods for improving veterans' lives. However, translating those inventions to the market has been a challenge due to limited collaboration between the clinical inventors and the scientists, researchers, and engineers who can produce the prototypes necessary for licensing the technology. The VA Technology Transfer Program office and the Human Engineering Research Laboratories, a research laboratory with experience with developing prototypes and licensing technology, jointly developed a program called the Technology Transfer Assistance Project (TTAP) to bridge the gap between clinical inventors and prototypes ready for licensing. This paper describes TTAP and provides examples of the first inventions that were developed or enhanced through TTAP.

The COVID-19 pandemic stressed healthcare systems all over the world. Two primary challenges that healthcare systems faced were a shortage of personal protective equipment and the need for new technologies to handle infection prevention for staff and patients. The Department of Veteran's Affairs (VA) Technology Transfer Program responded by prioritizing the development of innovations in the Technology Transfer Assistance Project which addressed the pandemic. This paper describes several innovations that addressed the needs of the VA healthcare system during the pandemic and how they were rapidly developed.