Capacity fade in lithium-ion battery electrodes can result from a degradation mechanism in which the carbon black-binder network detaches from the active material. Here we present two approaches to visualize and quantify this detachment and use the experimental results to develop and validate a model that considers how the active particle size, the viscoelastic parameters of the composite electrode, the adhesion between the active particle and the carbon black-binder domain, and the solid electrolyte interphase growth rate impact detachment and capacity fade. Using carbon-silicon composite electrodes as a model system, we demonstrate X-ray nano-tomography and backscatter scanning electron microscopy with sufficient resolution and contrast to segment the pore space, active particles, and carbon black-binder domain and quantify delamination as a function of cycle number. The validated model is further used to discuss how detachment and capacity fade in high-capacity materials can be minimized through materials engineering.
Phase-change
memory materials refer to a class of materials that
can exist in amorphous and crystalline phases with distinctly different
electrical or optical properties, as well as exhibit outstanding crystallization
kinetics and optimal phase transition temperatures. This paper focuses
on the potential of colloids as phase-change memory materials. We
report a novel synthesis for amorphous GeTe nanoparticles based on
an amide-promoted approach that enables accurate size control of GeTe
nanoparticles between 4 and 9 nm, narrow size distributions down to
9–10%, and synthesis upscaling to reach multigram chemical
yields per batch. We then quantify the crystallization phase transition
for GeTe nanoparticles, employing high-temperature X-ray diffraction,
differential scanning calorimetry, and transmission electron microscopy.
We show that GeTe nanoparticles crystallize at higher temperatures
than the bulk GeTe material and that crystallization temperature increases
with decreasing size. We can explain this size-dependence using the
entropy of crystallization model and classical nucleation theory.
The size-dependences quantified here highlight possible benefits of
nanoparticles for phase-change memory applications.
Summary
The transition from liquid organic electrolytes to solid-state electrolytes promises safer and more energy-dense lithium ion batteries. Although this technology has been demonstrated, the question of how to manufacture solid-state batteries at the cost and scales needed to be competitive remains. Here we propose and demonstrate curtain coating as a method for manufacturing composite solid-state electrolytes in roll-to-roll processes at web-speeds of over 80 m/min. The method is compatible with existing lithium-ion battery electrode manufacturing lines and is able to produce uniform electrolyte films with thicknesses below 15 micrometers.
Water has now become the standard process solvent for graphite-based anodes, eliminating the use of toxic and costly N-Methyl-pyrrolidone (NMP) in anode manufacturing. Ideally, water could also become the standard for cathodes; however, water-based processing of NMC cathode materials induces lithium leaching, which reduces their specific capacity and leads to capacity fade. Here, we demonstrate that leached lithium ions can be exploited during aqueous slurry preparation to create a Li-containing polymer binder that enables cathode performance comparable to those fabricated using NMP. Specifically, we show that leached lithium ions from LiNi0.8Mn0.1Co0.1O2 (NMC 811) particles react with polyacrylic acid (PAA) to form a lithium polyacrylate (LPA) surface coating and binder. Because the resulting LPA binder is water soluble, aqueous-based recycling of the cathode particles is feasible and over 90% capacity retention is shown in recycled material after 100 cycles.
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