capacity now achievable in the anode are not accessible. Consequently, substantial efforts are being expended to develop higher capacity cathode materials that might displace current commercial technologies with ones that are both robust in use and more environmentally benign over their service lifetime.Organic cathodes are a promising class of materials as they hold the possibility of replacing metal oxides with less environmentally impactful materials, while also improving performance metrics. [1,8] Many different organic cathode chemistries have been explored and are the subject of recent reviews. [9,10] Organic carbonyl compounds have emerged as the most promising class of organic cathode material due to their high energy density and electrochemical stability. [11] Small molecule carbonyl based cathodes such as pyrene-4,5,9,10-tetraone [12] and lithium rhodizoate [13] can provide capacities of up to 580 mA h g −1 , yet frequently suffer from dissolution in common electrolytes leading to capacity fade. Recent reports have successfully addressed dissolution of monomers by chemical interactions with either the binder [14] or current collector phase, [15] but these methods are not yet sufficiently developed to allow adoption in commercially relevant contexts.Polymerization is a more general technique for preventing active material dissolution. Recent advances made in the synthesis of polymeric quinone cathodes as well as an exhaustive list of studied materials can be found in literature reviews. [9][10][11]16] While the problem of quinone cathode dissolution has largely been solved by polymerization, polymer quinone cathodes have yet to achieve capacities similar to high performance monomers. The disconnect in performance between monomeric and polymeric quinones stems mainly from the incorporation of only two Li + per monomeric unit in the polymers reported to date. The only reports of a quinone polymer cathode incorporating more than two Li + per monomer is the four-electron redox of polymer bound pyrene-4,5,9,10-tetraone [17] and the four-electron redox of poly(anthraquinone norbornene). [18] In both examples of a four-electron redox quinone polymer, the large molecular framework of the monomer results in only modest capacities of the polymer (≈230 mA h g −1 for pyrene-4,5,9,10-tetraone [17] and 205 mA h g −1 for poly (anthraquinone norbornene)). [18] To our knowledge, the current record for highest capacity in a stable quinone polymer cathode is 275 mA h g −1 obtained using poly (benzoquinonyl sulfide) as the active material. [19] Despite recent advances, current polymeric organic cathode materials have failed to incorporate a high degree of lithium storage in a small molecular framework, resulting in low capacities relative to monomers. This report discloses the development of a lithium salt polymer of dihydroxyanthraquinone (LiDHAQS) capable of storing four Li + per monomer. The combination of storing four Li + per monomer and a low molecular weight monomer results in a capacity of 330 mA h g −1 , a record f...

In situ strain and stress measurements are performed on composite electrodes to monitor potentialdependent stiffness changes in lithium manganese oxide (LiMn 2 O 4 ). Lithium insertion and removal results in asynchronous strain and stress generation in the electrode. Electrochemical stiffness changes are calculated by combining coordinated stress and strain measurements. The electrode experiences dramatic changes in electrochemical stiffness due to potential-dependent Li + ion intercalation mechanisms. The development of stress in the early stages of delithiation (at ca. 3.95 V) due to a kinetic barrier at the electrode surface gives rise to stiffness changes in the electrode. Strain generation due to phase transformations reduces stiffness in the electrode at 4.17 V during delithiation and at 4.11 V during lithiation. During lithiation, stress generation due to Coulombic repulsions between occupied and incoming Li + ions leads to stiffening of the electrode at 3.96 V. The electrode also experiences greater changes in stiffness during delithiation compared to lithiation. These changes in electrochemical stiffness provide insight into the interplay between mechanical and electrochemical properties which control electrode response to lithiation and delithiation.

All-solid-state Li-ion batteries afford possibilities to enhance battery safety while improving their energy and power densities. Current challenges for achieving high-performance all-solid-state batteries with long cycle life include shorting resulting predominantly from Li dendrite formation and infiltration through the solid electrolyte (SE) and increases in cell impedance induced by SE decomposition at the SE/electrode interface. In this work, we evaluate the electrochemical properties of two interlayer materials, Si and Li x Al (2−x/3) O 3 (LiAlO), at the Li 7 P 3 S 11 (LPS)/Li interface. Compared to the Li/LPS/Li symmetric cells in absence of interlayers, the presence of Si and LiAlO both significantly enhance the cycle number and total charge passing through the interface before failures resulting from cell shorting. In both cases, the noted improvements were accompanied by cell impedances that had increased substantially. The data reveal that both interlayers prevent the direct exposure of LPS to the metallic Li and therefore eliminate the intrinsic LPS decomposition that occurs at Li surfaces before electrochemical cycling. After cycling, a reduction of LPS to Li 2 S occurs at the interface when a Si interlayer is present; LiAlO, which functions to drop the potential between Li and LPS, suppresses LPS decomposition processes. The relative propensities toward SE decomposition follows from the electrochemical potentials at the interface, which are dictated by the identities of the interlayer materials. This work provides new insights into the phase dynamics associated with specific choices for SE/electrode interlayer materials and the requirements they impose for realizing high efficiency, long lasting all-solid-state batteries.

We used in situ X-ray diffraction, XPS, SEM, and electrochemical methods to interrogate the mechanism of Mg electrodeposition from PhMgCl/AlCl3 (APC) and EtMgCl electrolytes. An open circuit potential (OCP) pause following Mg deposition led to retained enhancement of Mg deposition and stripping kinetics along with lowered overpotentials for both. In situ X-ray diffraction demonstrated that the OCP pause led to a more polycrystalline deposit relative to that without the pause, while SEM presented micrographs that showed smaller deposits with an OCP hold. The improvement is attributed to an “enhancement layer” that formed on the electrode during the OCP hold. Analysis of XPS data suggests that the “enhancement layer” consists of Mg and Cl retained on the electrode surface, possibly following electrode depassivation.

The insertion and removal of Li + ions into Li-ion battery electrodes can lead to severe mechanical fatigue because of the repeated expansion and compression of the host lattice during electrochemical cycling. In particular, the lithium manganese oxide spinel (LiMn 2 O 4 , LMO) experiences a significant surface stress contribution to electrode chemomechanics upon delithiation that is asynchronous with the potentials where bulk phase transitions occur. In this work, we probe the stress evolution and resulting mechanical fracture from LMO delithation using an integrated approach consisting of cyclic voltammetry, electron microscopy, and density functional theory (DFT) calculations. High-rate electrochemical cycling is used to exacerbate the mechanical deficiencies of the LMO electrode and demonstrates that mechanical degradation leads to slowing of delithiation and lithiation kinetics. These observations are further supported through the identification of significant fracturing in LMO using scanning electron microscopy. DFT calculations are used to model the mechanical response of LMO surfaces to electrochemical delithiation and suggest that particle fracture is unlikely in the [001] direction because of tensile stresses from delithiation near the (001) surface. Transmission electron microscopy and electron backscatter diffraction of the as-cycled LMO particles further support the computational analyses, indicating that particle fracture instead tends to preferentially occur along the {111} planes. This joint computational and experimental analysis provides molecularlevel details of the chemomechanical response of the LMO electrode to electrochemical delithiation and how surface stresses may lead to particle fracture in Li-ion battery electrodes.