The recycling of lithium-ion batteries

About: The article was published on 2018-01-01 and is currently open access. It has received 4 citations till now. The article focuses on the topics: Lithium.

Summary

LIST OF TABLES

• Many of the issues plaguing lithium-ion systems can be attributed to the lack of reusable components once the batteries have been completely exhausted.
• Over the last decade the recycling problem has been under question, sparking comprehensive research with an emphasis on the precious metals within the battery's cathode.
• With an effective and efficient method still not prominent and the market expanding at such a large rate further investigation must be provided.
• From the limited investigations conducted into the recycling of the cathode metal, the main concentration has been given to methods such as leaching, bioleaching and solvent extraction.
• Many companies have been able to develop various pyro and hydrometallurgical process, however none have successfully been able to solve the recycling problem.

1.3. Aim and Objectives

• The objective of this thesis is to successfully determine a safe and efficient solution to the recycling of spent lithium-ion batteries.
• Investigating the following will complete this: Finding the most suitable leaching reagent possible to successfully remove the maximum percentage of the precious metals; Analyse and determine the most appropriate (effective and efficient) method of solidliquid extraction for precipitation possible; and Produce a new operational battery cell with the recycled precious metals from the spent lithium-ion battery.

2.1. Lithium-ion Batteries

• Lithium batteries are a collection of galvanic cells designed to be proficient sources of electrical power (Oldham, Myland and Bond 2012) .
• Due to their high discharge voltage, high energy density and the increasingly efficient cycle life, lithium-ion batteries are fast becoming the most important member of the rechargeable family (Heelan, et al. 2016) .
• It also requires an inflow of electrons hence changing the oxidation state of the host (Oldham, Myland and Bond 2012) .
• Equations 1 and 2 describe the reactions of each electrode; charging taking place in the forward direction with discharge being in the reverse.
• Therefore, lithium-ion batteries must maintain a specified voltage range of 2.8 -4.2V, warranting that temperatures exceeding 30℃ are avoided and pressure relief is given when necessary (Battery University 2017).

2.1.1. Cathode

• Lithium-ion batteries refer to a large group of the secondary battery family, all with varying cathode compositions delivering varying battery properties.
• These properties, dependent on the cathode material include the specific energy, specific power, safety, durability, charging ability and cost.
• A compound transition metal -typically LiCoO2 for mobile phones -is pasted onto an aluminum foil providing the active cathode material.
• This cathode deintercalates lithium-ions during charging from their crystalline structure (Heelan, et al. 2016) .
• Fig. 2 displays the various compounds used in lithium-ion batteries and the best application for each.

2.1.2. Battery Chemistries

• As seen in Fig. 2 , the most common types of lithium-ion batteries are as follows: Lithium cobalt oxide (LCO); Lithium manganese oxide (LMO); Lithium nickel manganese cobalt oxide (NMC); and Lithium nickel cobalt aluminium oxide (NCA).
• Each composition provides the battery with a unique set of properties, allowing for a range of opportunities, from mobile phones to electric vehicles.
• Table 2 provides a more in-depth analysis to the suitable applications for each composition.
• Blake Dykes - Table 3 provides an analysis of each composition further outlining the specific properties they hold due to the layered oxide material.

2.1.3. Anode

• The anode, typically carbon, is referred to as the negative electrode during dischargingwhilst the battery is being used.
• A graphite paste is often bonded to a copper foil to produce the active anode material (Elwert, Romer and Sutter 2015) .
• Graphite is selected for its low interaction potential and the high specific energy (Heelan, et al. 2016) .
• Equation 1shows the reactions undertaken by the anode with a reduction in the forward direction and oxidation in the reverse.

2.1.4. Separator

• The separator in a lithium-ion battery is a porous polyolefin membrane, which allows lithiumions to transmit through the pores, preventing a short circuit via contact between electrodes (Chagnes and Pospiech 2013) .
• It also provides an ionic conduction path for the liquid electrolyte.
• This membrane is used due to its increased performance and safety over other alternatives, not to mention the reduced costs.

2.1.5. Electrolyte

• Commercially, the majority of lithium-ion systems incorporate high-grade lithium salts, such as lithium hexafluorophosphate (LiPF6) or lithium tetrafluoroborate (LiBF4), which are dissolved into dipolar aprotic organic solvents forming the electrolyte (Chagnes and Pospiech 2013) .
• These solvents, characteristically with low reactivity and high polarity, are often carbonates or lactones.
• Typically, modern lithium-ion batteries use a mixture of alkyl carbonates, such as ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DC) (Heelan, et al. 2016 ).
• Today's lithium-ion batteries almost exclusively use LiPF6 due to its high conductivity and non-corrosive relationship with the current collectors, however sometimes it can be thermally and hydrolytically unstable.

2.2. Need for Recycling

• The attraction of recycling spent lithium-ion batteries provides some interesting economic, environmental and geopolitical stances.
• The DRC is politically unstable; hence the supply of cobalt is considered to be a major risk due to its economic importance.
• These projections are based off handheld Blake Dykesdevices as well as electric vehicles and electricity grid storage, as seen in Adelaide by Tesla Group.
• Australia have very limited government regulations pertaining to recycling, whilst European nations have developed more stringent protocols for the disposal of rechargeable batteries.
• Hence, for the sake of sustainability and safety, governments may impose an obligation to recycle lithium-ion batteries, even if recycling does not prove adequately attractive economically.

2.3. Current Recycling Methods

• Currently there are only a few solely hydrometallurgical recycling processes available for lithium-ion batteries due to the extensiveness of pretreatment.
• As such, pyrometallurgical processes were preferred in the past.
• Some of the largest pyro and hydrometallurgical process include the Umicore, Toxco and Recupyl methods.
• Each process is described in extensive detail with the intension to provide a sufficient estimation for the experimental procedure outlined in section 3.

2.3.1. Umicore Method

• The Umicore process is a combined pyro and hydrometallurgical recycling process dedicated to Li-ion and Nickel-metal hydride (NiMH) batteries.
• The top of the furnace is the pre-heating zone where the temperature is maintained below 300 °C (Saloojee and Lloyd 2015) .
• Here the plastic is removed from the batteries.
• As a result of this exothermic reaction the energy released upwards heats the pre-heating zone as mentioned previously.
• In this zone the remaining material is separated into an alloy phase and a slag.

2.3.2. Toxco Method

• Originally, Toxco's hydrometallurgical process was established to safely recycle spent primary lithium batteries (Georgi-Maschler, et al. 2012) .
• The method the company has produced requires the batteries to be treated through a patented cryogenic process, whereby batteries are cooled to temperatures of -175 ℃ to -195 ℃ (Saloojee and Lloyd 2015) .
• These low temperatures also cause the plastic casing to become brittle, rendering them easily broken.
• These fluff by-products produce plastics and stainless steels, along with copper-cobalt by-products, of which are packaged and sold.
• The lithium solution then enters a holding tank, before being filtered through a carbon filter press producing a cake of metal oxides.

2.3.3. Recupyl Method

• Initially developed in France by Recupyl SA this process is able to successfully recycle both primary and secondary lithium batteries through a combination of physical and chemical procedures.
• The two-step crushing process commences in a rotary shredder operating in atmospheric conditions of carbon dioxide and 10-35 % argon gas (Tedjar and Foudraz 2010) .
• The separation process is carried out via screening, magnetic separation and densimetric separation.
• With the lithium dissolved the remaining solids are vacuum filtered pushing the lithium solution into the precipitation step.
• The residual cobalt is either recovered by electrolysis or by precipitation with sodium hypochlorite to form cobaltic hydroxide (Co(OH)3).

2.4. Current Leaching Techniques

• Currently, the most efficient recycling methods use a combination of pyro and hydrometallurgical processes.
• Typically, hydrometallurgical techniques are preferred and involve the use of aqueous solutions to leach metals from the respective ores.
• Pyrometallurgical processes, on the other hand, require a rather large input of energy to maintain high temperatures whereby chemical reactions are undertaken in gaseous and solid states.

Spectroscopy (SEM-EDS)

• Put simply, the Scanning Electron Microscopy -Energy Dispersive X-Ray Spectroscopy (SEM-EDS) is a high-energy electron microscope that allows samples to be examined at high magnifications and analyses specific elements within the sample.
• The electron source, located directly above the specimen, shoots electrons down striking the sample.
• As such these images captured for EDS analysis and appear only in grayscale due to the electrons detected being beyond the light spectrum (NTS 2018).
• The EDS operates using an X-ray detector to qualitatively and at times "semi-quantitatively" determine the elemental composition of a specimen, initially identified and observed using the secondary electron and backscatter detectors (NTS 2018) .
• The difference in energy between the higher-energy shell and lower-energy shell emits a characteristic x-ray.

2.5.2. ICP Testing

• Inductive Coupled Plasma (ICP) is a widely recognized technique for providing bulk elemental composition in a sample through the use of plasma and a spectrometer (Krosse and van der Ven 2018).
• A wide variety of samples can be analysed including powders, solids, liquid and suspensions.
• An ICP-OES (Inductively coupled plasma -Optical emission spectrometry), much like the one present at the University of Queensland, is composed of two major parts: the ICP and the optical emission spectrometer.
• This quartz torch, typically fed with argon gas, produces plasma through a cooled conduction coil resulting in an intense electromagnetic field, accelerating electrons in a circular trajectory (Krosse and van der Ven 2018).
• The collision of these electrons and the argon atoms produce plasma through a process known as ionization.

2.6. Conclusion

• With a large variety of lithium-ion batteries flooding the market it is important to develop a flexible and effective recycling technique.
• Lithium-ion batteries have vastly dominated the portable electronic market for decades, however large expansion into electric vehicles is imminent, if not already present.
• Due to inexpensive costs as well as accessibility, sulphuric and hydrochloric acid are the most suitable solutions.
• This testing format allows for exact quantitative compositions to be determine for accurate efficiency results.

Figures

Table 12 Cobalt Extraction Efficiencies

Table 18 Full SEM of Leached solids

Figure 30 Oxidizing and Reducing Agent reactions

Table 6 Initial sample weights issued to the ICP-OES

Figure 20 EDS analysis of the topside of the Copper foil

Figure 27 EDS Spectra analysis of panel sample 2

Table 11 Acid leaching ICP results

Table 9 provides the observations recorded throughout the vacuum filtration process regarding each sample’s final solution colour as well as its filtering ability. Vacuum filtration is an efficient and effective process used to ensure that any remaining solid samples are removed from the acidic solution. These acidic solutions are then used for ICP testing, determining elemental composition, as well as for the precipitation of the leached cobalt.

Figure 33 Impendance Plot

Figure 28 Cobalt extracted from each of the leaching samples

Figure 19 Images of the SEM analysis of the Copper Foil at a magnification of 500x: (A) Top Side - Graphite; (B) Underside - Graphite

Table 9 provides the observations recorded throughout the vacuum filtration process regarding each sample’s final solution colour as well as its filtering ability. Vacuum filtration is an efficient and effective process used to ensure that any remaining solid samples are removed from the acidic solution. These acidic solutions are then used for ICP testing, determining elemental composition, as well as for the precipitation of the leached cobalt.

Table 3. Negative electrode materials and the respective properties

Figure 24 EDS analysis of panel sample 2)

Figure 5. Umicore recycling process (Yazicioglu and Tytgat 2011)

Table 8 Initial acid-sample reactions

Table 15 Relevant comparison reagents from Table 15

Table 1 Scope requirements

Table 13 Cathode and Active Material Mass

Figure 23 EDS analysis of panel sample 2

Figure 17 Images of the SEM analysis of the Aluminum Foil at a magnification of 500x: (A) Top Side- LCO; (B) Underside - LCO

Full text

THE UNIVERSITY OF QUEENSLAND
The Recycling of Lithium-ion Batteries
Student Name: Blake Dykes
C
ourse Code: MECH4501
Supervisor: Dr. Ruth Knibbe
S
ubmission date: 1
st
June 2018

Mech4501 – Engineering Thesis Final Report
iii
Blake Dykes -
ABSTRACT
Currently in Australia, there remains no proven technology available for recycling of lithium
ion batteries. The purpose of the research undertaken in this thesis is to provide an outline of
the current lithium-ion battery-recycling problem whilst taking a closer look into alternative
hydrometallurgical solutions. Lithium ion batteries have been used in portable handheld
devices for several decades, but with companies like Tesla venturing into the electric vehicle
(EV) and grid energy storage market, recycling is becoming more of a necessity in this
technological evolution. As researched, the majority of consumer portable handheld devices –
mobile phones – are comprised of the lithium cobalt oxide formulation (LiCoO
2
) with a
combination of other metals introduced to enhance various aspects of performance.
To date many companies across the world have attempted to develop their own-patented
recycling techniques. Some are solely pyrometallurgical, whilst others, such as the Umicore
process rely on a combination of techniques. The methodology used was designed in
conjunction with the Toxco method whereby the battery would undertake a dismantling
phase, before acid leaching and precipitation and finally into the creation of a new lithium-ion
battery.
Optimizing the leaching process was the main aim of this investigation in order to achieve a
maximum leaching efficiency possible before precipitation. However, with laboratory issues
and large time delays from ICP-OES testing, the results required were not met. The most
efficient leaching reagent was that of sulphuric acid combined with sodium metabisulfite with
an efficiency of roughly 6.5%. The remaining three solutions sulphuric acid, sulphuric acid
with sodium persulfate and hydrochloric acid achieved efficiencies all under 2.5%.
These irregularly low efficiencies meant that precipitation was not possible due to the lack of
cobalt in the solution. As such, a new battery was created using the lithium cobalt oxide
recovered from the original iPhone battery. Using two ratios 8:1:1 (LCO:Carbon:PVDF) and
9:1 (LCO:PVDF) the new batteries was assembled and tested. The results suggested that the
addition of the carbon allowed a more stable electron flow from the cathode to the anode with
a 74.55 % difference in charge transfer resistance to that of the non-super P cell.

Mech4501 – Engineering Thesis Final Report
iv
Blake Dykes -
This area is one of significant importance for future development and despite technical
challenges there is a large scope within this field. Future recommendations would be avoid
using ICP as an analysis method due to the month-long delays making development very
difficult. Instead, it is recommended that the AAS system is used.
Furthermore, the acid concentrations must be increased for the experiments to provide an
indicative indication of acids ability to successfully leach cobalt from the exhausted batteries.
It is interesting to note that sulphuric acid, being the cheapest, is sufficient in providing the
best efficiency provided that a reducing agent is added. This reducing agent significantly aids
the reduction of cobalt oxide in the system enabling larger quantities of leaching.
Finally, if possible it is recommended that further works be carried out with a full battery
system, rather than the recovered material. This would resemble practices in closer to real
world applications.

Mech4501 – Engineering Thesis Final Report
v
Blake Dykes -
ACKNOWLEDGEMENTS
I would like to take this opportunity to thank Dr. Ruth Knibbe for her excellent guidance,
supervision and comprehensive knowledge of the thesis topic and similarly related topics. As
I knew nothing about this topic Dr. Knibbe’s enthusiasm was much appreciated and allowed
me to grow and learn the topic well. I greatly appreciate the organization she put into making
this thesis happen as well as the flexibility she gave me to provide my own thoughts and
direction during the thesis.
Further thanks must be given to William Hawker and Lingbing Ran for their tireless help in
supervising laboratory sessions and talking me through theory and concepts. Your help was
most appreciated.
Finally, I am very grateful for the support and assistance given by my parents, friends and
family during the process.

Blake Dykes -
Mech4501 – Engineering Thesis Final Report
vi
TABLE OF CONTENTS
ABSTRACT ............................................................................................................................. iii
ACKNOWLEDGEMENTS ...................................................................................................... v
TABLE OF CONTENTS ......................................................................................................... vi
LIST OF ABBREVIATIONS AND SYMBOLS ..................................................................... viii
TERM DEFINITION .......................................................................................................... viii
LIST OF FIGURES .................................................................................................................. x
LIST OF TABLES ................................................................................................................... xi
1. INTRODUCTION ........................................................................................................... 1
1.1. Background ........................................................................................................................................................... 1
1.2. Scope ....................................................................................................................................................................... 1
1.3. Aim and Objectives ............................................................................................................................................ 2
2. LITERATURE REVIEW ................................................................................................ 3
2.1. Lithium-ion Batteries ......................................................................................................................................... 3
2.1.1. Cathode .................................................................................................................................................................. 4
2.1.2. Battery Chemistries ............................................................................................................................................ 5
2.1.3. Anode ...................................................................................................................................................................... 7
2.1.4. Separator ................................................................................................................................................................ 7
2.1.5. Electrolyte ............................................................................................................................................................. 8
2.2. Need for Recycling ............................................................................................................................................. 8
2.3. Current Recycling Methods ........................................................................................................................... 11
2.3.1. Umicore Method ............................................................................................................................................... 11
2.3.2. Toxco Method .................................................................................................................................................... 13
2.3.3. Recupyl Method ................................................................................................................................................ 14
2.4. Current Leaching Techniques ....................................................................................................................... 15
2.5. Current Analysis Techniques ........................................................................................................................ 17
2.5.1. Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM-EDS) ........... 17
2.5.2. I
CP Testing ......................................................................................................................................................... 19
2.6. Conclusion ........................................................................................................................................................... 20
3. METHODOLOGY ........................................................................................................ 21
3.1. Battery Dismantling ......................................................................................................................................... 21

Frequently asked questions

Q1. What are the contributions in this paper?

The purpose of the research undertaken in this thesis is to provide an outline of the current lithium-ion battery-recycling problem whilst taking a closer look into alternative hydrometallurgical solutions. As researched, the majority of consumer portable handheld devices – mobile phones – are comprised of the lithium cobalt oxide formulation ( LiCoO2 ) with a combination of other metals introduced to enhance various aspects of performance. Optimizing the leaching process was the main aim of this investigation in order to achieve a maximum leaching efficiency possible before precipitation. The results suggested that the addition of the carbon allowed a more stable electron flow from the cathode to the anode with a 74. 

Q2. What is the key to the formation of grain boundaries in the Fig. 17 (A)?

This degradation, along with the battery being completely exhausted are key to the formation of grain boundaries present in Fig. 17 (A) and (B). 

Q3. Why are the Toxco and Recupyl preferred to that created by Umicore?

Due to the extreme temperatures involved in pyrometallurgy, methods such as the Toxco and Recupyl are preferred to that created by Umicore. 

Q4. What is the process used to recycle lithium batteries?

The batteries are milled in lithium brine, in which the lithium dissolves with several salts forming lithium chloride (LiCl) (Saloojee and Lloyd 2015). 

Q5. What was the effect of the leaching agents on the panel samples?

It was noted that the powdered samples, in which had not been ground into a fine powder prior to leaching, were slowly being disintegrated as the solution colour seemingly darkened in colour. 

Q6. What is the importance of determining an efficient and effective leachant?

With acid leaching pivotal to the hydrometallurgical process, it highlights the importance of determining an efficient and effective leachant. 

Q7. Why do the powdered samples appear darker than the panel samples?

the powdered samples appear marginally darker than the panel samples, in part due to the acid covering a larger surface area of the lithium cobalt oxide solid. 

Q8. What are the common uses of lithium-ion batteries?

In the current era, lithium-ion batteries are typically used in portable handheld electronic devices such as mobile phones and laptop PC’s. 

Q9. What was the initial ICP analysis of the aluminium and copper foils?

Initial ICP AnalysisSamples of lithium cobalt oxide and graphite were carefully removed from the aluminium and copper foils respectively. 

Q10. What is the typical discharge range of a lithium battery?

As each battery originated from an iPhone, initially a 3.7 V LiCoO2 battery, the typical end-of-discharge range is from 2.8-3.0 V (Cadex 2018). 

Q11. What is the efficiencies of the two cathode pastes?

Using the recovered lithium cobalt oxide, from the original iPhone battery, two cathode pastes were produced one ratio with additional carbon (Super P) and one without. 

Q12. Why is it difficult to determine what component of the lithium?

Due to the tested battery voltages being below the acceptable discharge range it is difficult to determine exactly what component the lithium resides in. 

Q13. How many vials were used to prepare the recovered LCO material?

The remaining material, after ICP testing, was used to prepare 4 vials each containing 500 mg of the recovered LCO material along with 4 vials containing a single panel of the top separator. 

Q14. What does the efficiencies of the non-super P batteries show?

This shows that the non-super P batteries do not contain enough carbon, which acts as a conductor for the electric energy in the cell. 

Q15. What is the sulphuric acid in the map?

The mapping confirms the large remaining grains to be the cobalt oxide compounds with the majority of the dark wash between them as the sulphuric acid.