Multi-Scale Characterization Studies of Aged Li-Ion Large Format Cells for Improved Performance: An Overview

Abstract

Among various electrical energy storage devices the recent advances in Li-ion battery technology has made this technology very promising for the electric vehicles. The advantage of these batteries is high energy and power density. Understanding the aging mechanisms of these batteries to improve the cycle life is critical for electrification of vehicles. Aging of the cells at the system level is quantified by the increase in internal resistance and drop in capacity. It is imperative to understand the degradation of the electrode materials of the battery related to these system level parameters. The degradation of the material is caused by several simultaneous physiochemical processes that occur within the batteries, which makes material characterization of the electrodes challenging. This review provides results of a systematic multi-scale characterization study to understand the degradation mechanisms in LiFePO 4 cathode material. The study includes various techniques to understand the physical, morphological, electrical, chemical and structural changes in the cathode material. The review also presents an overview of the various modeling techniques used for Li-ion batteries. Simulation results of one of the models are presented using results of multi-scale characterization studies of the cathode material.

Nanoscale Measurements of Lithium‐Ion‐Battery Materials using Scanning Probe Techniques

“…Early AFM ex situ studies on LiFePO 4 showed an increase in nanoparticle agglomeration with aging of the battery, and subsequent in situ studies at various degrees of charging found significant particle shape and size changes, which were linked to unit‐cell volume differences for Li + release and uptake . Importantly, when analyzing four particles, surface changes were found to be inhomogeneous, thus suggesting non‐uniform utilization of the electrode …”

Three‐Component Functional Additive in a LiPF6‐Based Carbonate Electrolyte for a High‐Voltage LiCoO2/Graphite Battery System

“…As ar esult of their intrinsic high energyd ensity and long lifespan, rechargeable lithium-ion batteries (LIBs) have been used widelya st he main power source in portable electronic devices and are expected to play ap rominent role in the field of stationary energy storage systems and electric transportationt ools. [1][2][3][4][5] Currently, to meet the highere nergy density requirements of future LIBs,g reat efforts are being made toward the developmento fcathodes with higher working voltages and larger specific capacity. [6][7][8][9][10][11][12][13] Lithium cobalt oxide (LCO), which has ar eversible specific capacity of only approximately 140 mAh g À1 (half of its theoretical specific capacity,2 74 mAh g À1 )a ta nu pper cut-off voltage of 4.2 V, is the most successfulc athode material for commercialized LIBs.…”

“…Therefore,L CO-based LIBs are anticipated to operate at higher voltages than 4.2 Vt oo btain an increased capacity.U nfortunately,a ni ncrease of the upper cut-offv oltage to exceed 4.2 Valways leads to ac lear deterioration of battery performances (especially cyclability and safety)b ecause of the accelerated interfacial parasitic reactions between the charged LCO electrode and nonaqueous electrolytes.C onsequently,u nwanted crystal-structure damage/phase transition, Co dissolution-migration-deposition, and electrolyte decomposition occur. [14,15] At present,t here are two main approaches to improve the interfacial stability between the LCO electrode and nonaqueous electrolytes at elevated cut-off charge voltages.F irst, the LCO surface can be coatedw ith various materials,s uch as metal oxides (e.g.,A l 2 O 3 ,M gO,Z nO,Z rO 2 ), [16][17][18][19][20][21][22][23] metal phosphates (e.g.,A lPO 4 ), [24][25][26] metal fluorides/oxyfluorides (e.g.,A lF 3 ,Z rO x F y ), [27,28] Li ionc onductors (e.g.,L i 2 CO 3 , lithium phosphorus oxynitride,L i 3 PO 4 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ), [15,[29][30][31] and polymers (e.g.,p olyimide). [32] However, it is generally accepted that functional electrolyte additives are of considerable importance in modifying and stabilizing the solid-electrolyte interface( SEI) layer, which determines the cycle life and safety of LIBs significantly.…”

Lithium Battery Technologies

“…66,67 There is also the high solubility of the manganese especially in the discharged state because of a disproportionation of the Mn 3þ ion (2Mn 3þ /Mn 2þ þMn 4þ ) that leads to the more soluble Mn 2þ . It is mostly important at high temperature (above 50 C).…”