The Growth Mechanism of Lithium Dendrites and its Coupling to Mechanical Stress

Operando high-resolution light microscopy with extended depth of field is used to observe large regions of an electrode during electrodeposition of lithium. The analysis of the morphology of the evolving deposit reveals that besides electrochemistry, mechanics and crystalline defects play a major role in the growth mechanism. Based on the findings, a growth mechanism is proposed that involves the diffusion of lithium atoms from the lithium surface into grain boundaries and the insertion into crystalline defects in the metal. Crystalline defects are a result of plastic deformation and hence mechanical stimulation augments the insertion of lithium

Similarities in Lithium Growth at Vastly Different Rates

Lithium electrodeposition is important for lithium metal batteries and is presently a safety and reliability concern for the lithium-ion technology. In the literature, many models for the growth of dendrites can be found and a strong dependence on deposition rate is expected. To elucidate the process of the lithium deposition, operando light microscopy at the physical resolution limit of light was performed at rates varying by more than three orders of magnitude. The results show different growth regimes depending on the rate, and where needles, bushes, or accelerated bushes dominate the deposition. All these deposits are based on small crystalline needles and flakes. Little evidence for concentration gradient driven deposition was found. At the highest rate, the electrolyte ionically depletes, but the deposition continues by non-directional bush growth mainly from their insides. An important step at all rates is the insertion into defects in the crystalline lithium

Switching from Lithium to Sodium—an Operando Investigation of an FePO4_{4} Electrode by Mechanical Measurements and Electron Microscopy

Many physical and chemical properties of Na$^{+}$ are very similar to those of Li$^{+}$, and therefore, some electrode materials for lithium-ion batteries can also work with sodium ions. As the Na$^{+}$ ion is larger than Li$^{+}$, the strains in the host lattice are larger, which can cause deviations in the electrochemical reactions. Herein, mechanical stresses are compared, which are measured by the in situ substrate curvature method during (de)lithiation/(de)sodiation of an FePO$_{4}$ electrode. The (de)lithiation and (de)sodiation experiments are performed on the same electrode. According to the change of the lattice parameters, during electrode operation, NaxFePO$_{4}$ particles experience a volume change that is 2.6 times larger than that of LixFePO$_{4}$. In the measurements, the composite electrode exhibits a change of the stress amplitude between operation with Li and Na by roughly one order of magnitude for 0 < x < 1. Compared with Li$^{+}$, the mechanical stress evolution during extraction and insertion of Na$^{+}$ is highly asymmetric. The observed asymmetry in the electrochemical and the mechanical data may be explained by the different energies that are required to move an intermediary amorphous phase away from or toward the crystalline sodium-rich regions during the (de)sodiation of NaFePO$_{4}$

The growth mechanism of lithium dendrites and its coupling to mechanical stress

Operando high-resolution light microscopy with extended depth of field is used to observe large regions of an electrode during electrodeposition of lithium. The analysis of the morphology of the evolving deposit reveals that besides electrochemistry, mechanics and crystalline defects play a major role in the growth mechanism. Based on the findings, a growth mechanism is proposed that involves the diffusion of lithium atoms from the lithium surface into grain boundaries and the insertion into crystalline defects in the metal. Crystalline defects are a result of plastic deformation and hence mechanical stimulation augments the insertion of lithium

Aluminum Foil Anodes for Li-Ion Rechargeable Batteries: the Role of Li Solubility within β-LiAl

Lithium-ion battery electrodes contain a substantial amount of electrochemically inactive materials, including binders, conductive agents, and current collectors. These extra components significantly dilute the specific capacity of whole electrodes and thus have led to efforts to utilize foils, for example, Al, as the sole anode material. Interestingly, the literature has many reports of fast degradation of Al electrodes, where less than a dozen cycles can be achieved. However, in some studies, Al anodes demonstrate stable cycling life with several hundred cycles. In this work, we present a successful pathway for enabling long-term cycling of simple Al foil anodes: the β-LiAl phase grown from Al foil (α-Al) exhibits a cycling life of 500 cycles with a ∼96% capacity retention when paired with a commercial cathode. The excellent performance stems from strategic utilization of the Li solubility range of β-LiAl that can be (de-)lithiated without altering its crystal structure. This solubility range at room temperature is determined to be ∼6 at %. Consequently, this design circumvents the critical issues associated with the α/β/α phase transformations, such as volume change, mechanical strain, and formation of nanopores. Application-wise, the maturity of the aluminum industry, combined with excellent sustainability prospects, makes this anode an important option for future devices

Aluminum Foil Anodes for Li-ion Rechargeable Batteries: The Role of Li Solubility within β-LiAl

Li-ion battery (LIB) electrodes contain a substantial amount of electrochemically inactive materials, including binder, conductive agent, and current collectors. These extra components significantly dilute the specific capacity of whole electrodes, and thus have led to efforts to utilize foils, e.g., Al, as the sole anode material. Interestingly, the literature has many reports of fast degradation of Al electrodes, where less than a dozen cycles can be achieved. However, in some studies, Al anodes demonstrate stable cycling life with several hundred cycles. In this work, we present a successful pathway for enabling long-term cycling of simple Al foil anodes: β-LiAl phase grown from Al foil (α-Al) exhibits a cycling life of 500 cycles with a ~96% capacity retention when paired with a commercial cathode. The excellent performance stems from strategic utilization of the Li solubility range of β-LiAl that can be (de-)lithiated without altering its crystal structure. This solubility range at room temperature is determined to be ~6 at%. Consequently, this design circumvents the critical issues associated with the α/β/α phase transformations, such as volume change, mechanical strain, and nanopore formation. Application-wise, the maturity of aluminum industry, combined with excellent sustainability prospects, makes this anode an important option for future devices

Pattern Formation of Ion Channels with State Dependent Electrophoretic Charges and Diffusion Constants in Fluid Membranes

A model of mobile, charged ion channels in a fluid membrane is studied. The channels may switch between an open and a closed state according to a simple two-state kinetics with constant rates. The effective electrophoretic charge and the diffusion constant of the channels may be different in the closed and in the open state. The system is modeled by densities of channel species, obeying simple equations of electro-diffusion. The lateral transmembrane voltage profile is determined from a cable-type equation. Bifurcations from the homogeneous, stationary state appear as hard-mode, soft-mode or hard-mode oscillatory transitions within physiologically reasonable ranges of model parameters. We study the dynamics beyond linear stability analysis and derive non-linear evolution equations near the transitions to stationary patterns.Comment: 10 pages, 7 figures, will be submitted to Phys. Rev.

Insulin resistance and glycemic abnormalities are associated with deterioration of left ventricular diastolic function: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Left ventricular diastolic dysfunction (LVDD) is considered a precursor of diabetic cardiomyopathy, while insulin resistance (IR) is a precursor of type 2 diabetes mellitus (T2DM) and independently predicts heart failure (HF). We assessed whether IR and abnormalities of the glucose metabolism are related to LVDD.</p> <p>Methods</p> <p>We included 208 patients with normal ejection fraction, 57 (27%) of whom had T2DM before inclusion. In subjects without T2DM, an oral glucose tolerance test (oGTT) was performed. IR was assessed using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The lower limit of the top quartile of the HOMA-IR distribution (3.217) was chosen as threshold for IR. LVDD was verified according to current guidelines.</p> <p>Results</p> <p>IR was diagnosed in 38 (18%) patients without a history of diabetes. The prevalence of LVDD was 92% in subjects with IR vs. 72% in patients without IR (n = 113), respectively (p = 0.013). In the IR group, the early diastolic mitral inflow velocity (E) in relation to the early diastolic tissue Doppler velocity (averaged from the septal and lateral mitral annulus, E'av) ratio (E/E'av) was significantly higher compared to those without IR (9.8 [8.3-11.5] vs. 8.1 [6.6-11.0], p = 0.011). This finding remains significant when patients with IR and concomitant T2DM based on oGTT results were excluded (E/E'av ratio 9.8 [8.2-11.1)] in IR vs. 7.9 [6.5-10.5] in those without both IR and T2DM, p = 0.014). There were significant differences among patients with and without LVDD regarding the HOMA-IR (1.71 [1.04-3.88] vs. 1.09 [0.43-2.2], p = 0.003). The HOMA-IR was independently associated with LVDD on multivariate logistic regression analysis, a 1-unit increase in HOMA-IR value was associated with an odds ratio for prevalent LVDD of 2.1 (95% CI 1.3-3.1, p = 0.001). Furthermore, the E/E'av ratio increases along the glucose metabolism status from normal glucose metabolism (7.6 [6.2-10.1]) to impaired glucose tolerance (8.8 [7.4-11.0]) and T2DM (10.5 [8.1-13.2]), respectively (p < 0.001).</p> <p>Conclusions</p> <p>Insulin resistance is independently associated with LVDD in subjects without overt T2DM. Patients with IR and glucose metabolism disorders might represent a target population to prevent the development of HF. Screening programs for glucose metabolism disturbances should address the assessment of diastolic function and probably IR.</p