A facile physics-based model for non-destructive diagnosis of battery degradation

The identification of battery degradation is of significant importance for estimating the state of health. Loss of lithium inventory (LLI), loss of active materials of the negative electrodes (LAMNE), and loss of active materials of the positive electrodes (LAMPE) are three main degradation modes. This paper proposes an advanced model based on open circuit voltage and differential voltage (DV) fitting to diagnose and quantify the degradation modes of batteries at different stages, showing high fidelity. This physics-based model avoids solving many partial differential equations and is not computationally demanding. Using commercial batteries with NCA/SiC electrodes as a case study, the LLI, LAMPE, and LAMNE induced by battery cycling and storage at various temperatures, State-of-Charge, and charging/discharging rates are systematically identified and analyzed.</p

Dual Additives for Stabilizing Li Deposition and SEI Formation in Anode-Free Li-Metal Batteries

Anode-free Li-metal batteries are of significant interest to energy storage industries due to their intrinsically high energy. However, the accumulative Li dendrites and dead Li continuously consume active Li during cycling. That results in a short lifetime and low Coulombic efficiency of anode-free Li-metal batteries. Introducing effective electrolyte additives can improve the Li deposition homogeneity and solid electrolyte interphase (SEI) stability for anode-free Li-metal batteries. Herein, we reveal that introducing dual additives, composed of LiAsF6 and fluoroethylene carbonate, into a low-cost commercial carbonate electrolyte will boost the cycle life and average Coulombic efficiency of NMC||Cu anode-free Li-metal batteries. The NMC||Cu anode-free Li-metal batteries with the dual additives exhibit a capacity retention of about 75% after 50 cycles, much higher than those with bare electrolytes (35%). The average Coulombic efficiency of the NMC||Cu anode-free Li-metal batteries with additives can maintain 98.3% over 100 cycles. In contrast, the average Coulombic efficiency without additives rapidly decline to 97% after only 50 cycles. In situ Raman measurements reveal that the prepared dual additives facilitate denser and smoother Li morphology during Li deposition. The dual additives significantly suppress the Li dendrite growth, enabling stable SEI formation on anode and cathode surfaces. Our results provide a broad view of developing low-cost and high-effective functional electrolytes for high-energy and long-life anode-free Li-metal batteries.</p