Active Material Interfacial Chemistry and Its Impact on Composite Magnetite Electrodes

Abstract

Rational design of battery systems with specific performance characteristics are needed to meet the growing, diverse needs of energy storage as batteries penetrate a range of sectors from automobiles to consumer electronics, among others. Here, we surface modified magnetite particles with distinct molecular entities containing different electronic and ionic conductivities and investigated how the local surface environment affected key battery characteristics such as capacity retention, rate capability, and electrode impedance. Herein, direct covalent attachment of poly [3-(4-carboxypropyl)­thiophene] onto magnetite nanoparticles via a Fischer esterification scheme was shown to create robust anodes with low charge transfer resistances, excellent charge capacity retention at 0.3 C, and robust charge capabilities/specific capacities. The functionalization strategies used here rely on manipulating the native hydroxide layer of the active material, and thus can be applied to various conversion-type electrode materials. This work contributes to the growing toolset of chemical techniques to modify active materials to create battery systems with specific performance characteristics.

Understanding the Role of Polymer Interactions within Binders in Composite Lithium-Ion Anodes

“…The ever-increasing global demand for energy storage solutions is driven by the thirst for low carbon footprint, scalable, and power-dense technologies. The biggest component of the global battery market share is being propelled by the electrification of the vehicle fleet, which is expected to account for 85+% of total battery storage deployments by 2030. , This anticipated demand has burgeoned a push toward the use of conversion-type transition metals (Fe 3 O 4 : 926 mAh g –1 ; MnO: 756 mAh g –1 ; CuO: 670 mAh g –1 ) and alloying-type silicon (3579 mAh g –1 ) as high-capacity anodes in lithium-ion batteries − because these materials can provide for attractive technologies capable of delivering high gravimetric capacity. While conversion-type electrode-based technologies offer as much as 10 times the gravimetric capacity as commercially available graphite electrodes (372 mAh g –1 ), it comes at the expense of significant volume expansions (300+% for silicon; ∼200% for Fe 3 O 4 − ) which results in catastrophic capacity fade and low cyclability.…”

Understanding Interfacial Chemistry Interactions in Energy-Dense Lithium-Ion Electrodes

“…It appears that it is within high current densities that the added benefit of having an electronically conductive environment is observed. Direct comparison of PEG-coated magnetite and PPBT-coated magnetite show that at increasing C rates, the specific capacity difference between the PEG- and PPBT-coated magnetite widens: at 2C and 0.3C, respectively, the specific capacity of the PEG-coated alternative was ∼20% (500 mAh g –1 ) and ∼5% lower than that of the PPBT-coated active particles . This effect may be attributed to lower polarization resistances and enhanced transport/kinetic properties as a result of the added high electronic conductivity.…”

“…Copyright 2019 American Chemical Society. Part (e) reproduced with permission from ref . Copyright 2021 American Chemical Society.…”

“…Direct comparison of PEG-coated magnetite and PPBT-coated magnetite show that at increasing C rates, the specific capacity difference between the PEG-and PPBT-coated magnetite widens: at 2C and 0.3C, respectively, the specific capacity of the PEG-coated alternative was ∼20% (500 mAh g −1 ) and ∼5% lower than that of the PPBT-coated active particles. 28 This effect may be attributed to lower polarization resistances and enhanced transport/ kinetic properties as a result of the added high electronic conductivity. Studies where PPBT was attached to the active material surface with various chemical entity spacers between the PPBT core−shell structure support the hypothesis that the local environment directly on the particle surface plays an important role in electrochemical performance.…”

“…Further enhanced tuning of electrochemical performance can be achieved through incorporation of electronically conductive entities onto the particle surface. For instance, Na et al and Gonzalez et al attached PPBT directly onto the surface of silicon and magnetite nanoparticles, respectively, to create long-ranged mixed conducting networks that extend throughout the electrode and serve to interconnect the active material particles (Figure f). With its thiophene backbone, PPBT undergoes electrochemical doping within a battery environment, thereby providing for enhanced electronic conductivity .…”