The current study investigated the effects of active material, conductive additives, and binder in a composite electrode on battery performance. In addition, the parameters related to cell performance as well as side reactions were integrated in an electrochemical model. In order to predict the cell performance, key parameters including manganese dissolution, electronic conductivity, and resistance were first measured through experiments. Experimental results determined that a higher ratio of polymer binder to conductive additives increased the interfacial resistance, and a higher ratio of conductive additives to polymer binder in the electrode resulted in an increase in dissolved transition metal ions from the LiMn2O4 composite electrode. By performing a degradation simulation with these parameters, battery capacity was predicted with various fractions of constituents in the composite electrode. The present study shows that by using this integrated prediction method, the optimal ratio of constituents for a particular cathode composite electrode can be specified that will maximize battery performance.

A thorough investigation of both manganese (Mn) deposition onto graphite and its side reactions was conducted based on complementary techniques including CV, EIS, GCPL, ICP-OES, SEM and EDS. Each measurement revealed a specific aspect of the degradation phenomena, which taken together all pointed in a common direction. This study focused on 1) deposition mechanisms and effects of manganese ions on the SEI layer; 2) the effects of manganese deposition on electrochemical performance; and 3) direct observation of decomposed layers induced by manganese deposition. It was confirmed that adding Mn(PF 6 ) 2 salt in the electrolyte results in severe capacity decrease and impedance rise. It is found that manganese ions in the electrolyte participate to generate Mn-containing SEI layers when depositing onto the graphite surface accompanied by additional side reactions. Interestingly, before manganese ions deposit onto the graphite electrode, they enhance cell capacity due to additional oxidation reactions. It is found that the reaction of manganese ions changes with the voltage conditions during charge or discharge and the lithiation status of the graphite electrode.

This paper investigates the effects of surface orientation and doping on the dissolution of Mn ions from LiMn 2 O 4 structures using first principles calculations. Our aim is to understand why certain surface orientations and element dopings produce structures with lower Mn dissolution. By comparing the electronic properties and structures of systems with different surfaces and dopings, Mn dissolution mechanisms and their prevention can be better understood. Based on our calculations, Mn dissolution is strongly correlated with the electronic and bonding properties of the Mn-O bonds. Surface orientations with a larger number of Mn-O bonds and smaller bond length require more energy to break the Mn-O bonds. In addition, doping with certain elements changes the bonding state of Mn, which either prevents or aggravates Mn dissolution.

Dissolution is a critical challenge in metal oxide battery materials, which affects battery performance across multiple scales. At the particle level, the loss of active material as a result of dissolution directly results in capacity fade. At the electrode level, the re-deposition of dissolved metal ions onto the cathode increases cell polarization and hinders lithium transport. At the cell level, the dissolved ions further transport to and deposit on the anode, which consumes cycle-able lithium and leads to capacity fade. These processes lead to poor lithium reversibility, diffusivity, and conductivity. In this work, detailed experimental studies from the particle level up to the cell level are systematically conducted to provide parameters for model input and model validation. A multi-physics modeling framework is developed to reveal key mechanisms associated with metal-ion dissolution and their impact on battery performance. We simulate capacity degradation during cycling and compare the results to a series of experimental data such as cyclic voltammetry, electrochemical impedance spectroscopy, and battery cycling. The integrated study have revealed several key mechanisms related to dissolution, and quantitatively connected the particle level dissolution and deposition behaviors to the cell level performance. These can provide useful guidance for battery design and management.

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