This study develops a tunable 3D nanostructured conductive gel framework as both binder and conductive framework for lithium ion batteries. A 3D nanostructured gel framework with continuous electron pathways can provide hierarchical pores for ion transport and form uniform coatings on each active particle against aggregation. The hybrid gel electrodes based on a polypyrrole gel framework and Fe O nanoparticles as a model system in this study demonstrate the best rate performance, the highest achieved mass ratio of active materials, and the highest achieved specific capacities when considering total electrode mass, compared to current literature. This 3D nanostructured gel-based framework represents a powerful platform for various electrochemically active materials to enable the next-generation high-energy batteries.

Controlling architecture of electrode composites is of particular importance to optimize both electronic and ionic conduction within the entire electrode and improve the dispersion of active particles, thus achieving the best energy delivery from a battery. Electrodes based on conventional binder systems that consist of carbon additives and nonconductive binder polymers suffer from aggregation of particles and poor physical connections, leading to decreased effective electronic and ionic conductivities. Here we developed a three-dimensional (3D) nanostructured hybrid inorganic-gel framework electrode by in situ polymerization of conductive polymer gel onto commercial lithium iron phosphate particles. This framework electrode exhibits greatly improved rate and cyclic performance because the highly conductive and hierarchically porous network of the hybrid gel framework promotes both electronic and ionic transport. In addition, both inorganic and organic components are uniformly distributed within the electrode because the polymer coating prevents active particles from aggregation, enabling full access to each particle. The robust framework further provides mechanical strength to support active electrode materials and improves the long-term electrochemical stability. The multifunctional conductive gel framework can be generalized for other high-capacity inorganic electrode materials to enable high-performance lithium ion batteries.

is a promising cathode material for Li-ion batteries, because of its high theoretical capacity (362 mAh g −1 ) and good rate performance. In this study, the structural evolution of Li 1.1 V 3 O 8 material during electrochemical dis(charge) processes was investigated using a combination of theoretical calculations and experimental data. Density functional theory (DFT) was used to predict the intermediate structures at various lithiation states, as well as the stability of major phases. In order to validate these predictions, in situ X-ray diffraction (XRD) data was collected operando, allowing for the phase transformations to be monitored under current load and eliminating the possibilities of structural relaxation processes and environmental oxidation. Rietveld refinement was performed to fit the diffraction data with the DFT-derived structures and to analyze the fractions of major phases as a function of dis(charge). The DFT calculations identified three stable states that were validated by the in situ XRD result: a Li-poor αphase (Li 1 ), a Li-rich α-phase (Li 2.5 ), and a β-phase (Li 4 ). The DFT-predicted particle shape based on the surface energy of the (100), (001), and (010) planes rationalized the preferential orientation of Li 1.1 V 3 O 8 particles along the [010] direction in the electrode. Furthermore, the onset and offset of the α → β transition, as well as the phase fractions of α and β determined via in situ XRD, related well with the DFT-derived relative stability of each phase. Thus, by integrating DFT calculations with experimental work, this work provides a thorough understanding of the structural transformations in Li 1.1 V 3 O 8 during electrochemical dis(charge).

The whole versus the sum of its parts; contributions of nanoscale iron-containing materials to the bulk electrochemistry of composite electrodes.