The complex three-phase composition of lithium-ion battery electrodes-containing an ion-conducting pore phase, a nanoporous electron-conducting carbon binder domain (CBD) phase, and an active material (AM) phase-provides several avenues of mesostructural engineering to enhance battery performance. We demonstrate a promising strategy for engineering electrode mesostructures by controlling the strength of adhesion between the AM and CBD phases. Using high-fidelity, physics-based colloidal and granular dynamics simulations, we predict that this strategy can provide significant control over electrochemical transport-relevant properties such as ionic conductivity, electronic conductivity, and available AM surface area. Importantly, the proposed strategy could be experimentally realized through surface functionalization of the AM and CBD phases and would be compatible with traditional electrode manufacturing methods.

The transition between shear-flowing and shear-arrested states of frictional granular matter is studied using constant-stress discrete element simulations. By subjecting a dilute system of frictional grains to a constant external shear stress and pressure, friction-dependent critical shear stress and density are clearly identified with both exhibiting a crossover between low and high friction.The critical shear stress bifurcates two nonequilibrium steady states: (i) steady state shear flow characterized by a constant deformation rate, and (ii) shear arrest characterized by temporally decaying creep to a statically stable state. The onset of arrest below critical shear stress occurs at a time tc that exhibits a heavy-tailed distribution, whose mean and variance diverge as a power law at the critical shear stress with a friction-dependent exponent that also exhibits a crossover between low and high friction. These observations indicate that granular arrest near critical shear stress is highly unpredictable and is strongly influenced by interparticle friction.Granular materials exhibit complex deformation and rheological phenomena due to the discrete character of their constituent particles and dissipative frictional interactions between them. It exists-or can co-existin fluidlike and solidlike states, and transitions between these states (i.e., yielding or arrest) are often induced by applying normal and deviatoric stresses at the boundary. Historically, the yielding of granular matter has been modeled using failure criteria such as the Mohr-Coulomb theory, which predicts yield when the ratio of deviatoric to normal stress exceeds a material-dependent threshold. Later, plasticity theories such as critical state soil mechanics [1] were developed that define a critical state at which granular matter yields at a constant critical shear stress, pressure and volume fraction. However, these theories are restricted to quasistatic rate-independent yielding of granular matter. Recent advances have addressed rate dependence of steady granular flows by extending such plasticity theories to viscoplastic rheology [2]. These rheological models have been successful in describing yielding and steady dense granular flows in various geometries [3].However, transient granular dynamics during the initiation [4][5][6] or arrest of a steady flow [7-9] exhibit remarkable features that are unexplained by current models, such as anomalous velocity profiles [4,7], hysteresis between flow initiation and flow arrest [7], transient dilatancy [6], and a breakdown of isostaticity [10]. In addition, granular matter often exhibits slow unsteady creep flows below a critical stress [11][12][13]. These phenomena are not captured by existing theories.The mechanics of granular matter near the staticdynamic transition (i.e., quasistatic flows) are also highly intermittent and stochastic, and remain unexplained by deterministic theories described previously. Growing avalanches [14,15], localized plastic rearrangements [12], and fluctuations in stresses [...

The packing and flow of aspherical frictional particles are studied using discrete element simulations. Particles are superballs with shape |x| s + |y| s + |z| s = 1 that varies from sphere (s = 2) to cube (s = ∞), constructed with an overlapping-sphere model. Both packing fraction, φ, and coordination number, z, decrease monotonically with microscopic friction µ, for all shapes. However, this decrease is more dramatic for larger s due to a reduction in the fraction of face-face contacts with increasing friction. For flowing grains, the dynamic frictionμ -the ratio of shear to normal stresses -depends on shape, microscopic friction and inertial number I. For all shapes,μ grows from its quasi-static valueμ0 as (μ −μ0) = dI α , with different universal behavior for frictional and frictionless shapes. For frictionless shapes the exponent α ≈ 0.5 and prefactor d ≈ 5μ0 while for frictional shapes α ≈ 1 and d varies only slightly. The results highlight that the flow exponents are universal and are consistent for all the shapes simulated here. arXiv:1810.13262v1 [cond-mat.soft]

Abstract

A new method is introduced to simulate jamming of polyhedral grains under controlled stress that incorporates global degrees of freedom through the metric tensor of a periodic cell containing grains. Jamming under hydrostatic/isotropic stress and athermal conditions leads to a precise definition of the ideal jamming point at zero shear stress. The structures of tetrahedra jammed hydrostatically exhibit less translational order and lower jamming-point density than previously described 'maximally random jammed' hard tetrahedra. Under the same conditions, cubes jam with negligible nematic order. Grains with octahedral symmetry jam in the large-system limit with an abundance of face-face contacts in the absence of nematic order. For sufficiently large faceface contact number, percolating clusters form that span the entire simulation box. The response of hydrostatically jammed tetrahedra and cubes to shear-stress perturbation is also demonstrated with the variable-cell method.