Active formation of Li-ion batteries and its effect on cycle life

Tanveerkhan S Pathan,W D Widanage,Muhammad Rashid,Emma Kendrick,Marc Walker

doi:10.1088/2515-7655/ab2e92

Tanveerkhan S Pathan, W D Widanage + Show 3 more

Open Access

https://doi.org/10.1088/2515-7655/ab2e92

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Abstract

The formation of the solid electrolyte interphase during the formation and conditioning steps, is a very time consuming and expensive process. We present an active formation method in LiNi1/3Mn1/3Co1/3O2 (NMC-111) versus graphite lithium-ion batteries, which maintains the cycling performance of the cells. Ten different active formation protocols were evaluated, which consisted of cycling between an upper (Vu) and lower (Vl) voltages. The cells were evaluated using electrochemical impedance spectroscopy (EIS) and cycling. X-ray photoelectron spectroscopy was used to analyse the surface of the electrodes after cycling. Cycling performance and resistance measurements from the EIS results confirm the different effect of formation protocols in the lifetime and performance of the cells. We show that during the formation protocol the interface composition is optimised through the transport of lithium ions through the initial organic decomposition layer on the graphite at higher cell voltages (>3.65 V). These higher voltage cycling formation protocols giving an interface with greater stability and enhanced cycling are observed in the cells.

Highlights

Lithium-ion batteries (LIBs) are extensively used as a power source for portable electronic devices and the electrification of the modern transportation sector has driven the growth in demand for LIBs [1,2,3,4]
On the first charge/discharge of the cell, there is a loss in capacity known as the ‘irreversible capacity loss’, which is mainly needed to form the solid electrolyte interface (SEI) layer. (This can be seen in the dQ versus V plot in figure S.1, available online at stacks.iop.org/JPENERGY/1/ 044003/mmedia in the supplementary information.)
In order to probe the electrochemical formation of the SEI layer, several voltage windows were chosen for which the anodic voltage was near (0 V versus Li/Li+) and the cathodic cell voltage was low enough to reduce the high-voltage stress on the cathode

Summary

Introduction

Lithium-ion batteries (LIBs) are extensively used as a power source for portable electronic devices and the electrification of the modern transportation sector has driven the growth in demand for LIBs [1,2,3,4]. In addition to the materials development, significant research and development is required into current and future manufacturing methods for batteries, to improve and optimise the cell designs and lower the costs in manufacturing [6, 8,9,10,11,12,13]. Current manufacturing processes are based upon the methods developed by Sony in the 1990s [14]. Once the ink is deposited on the current collector, the electrode is dried and calendared. This process creates and optimises the porosity and the electronic conductive pathways. The cells are sealed and undergo a formation process

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