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Last updated: Feb 2020 by Narasimhan Santhanam



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Introduction

Graphite currently is the dominant anode material for Li-ion batteries. 

The global anode material market could be worth $10 billion by 2025.

What are the expected trends for anode material for the 2020-2030 period? Will the domination of graphite continue?

This post reviews the possible trends in anode materials for Li-ion batteries for the 2020-2030 timeline.

Graphite is the primary anode material

  • Graphite is the most commonly used material for EV battery anodes. 25kg of high purity graphite is needed for an average-sized battery, and up to 54kg for large batteries such as those used in the Tesla Model S.
  • Producing anode-grade graphite with 99.99 percent purity is expensive and the process creates waste. The end-cost is not so much the material but the purification process. Recycling old Li-ion to retrieve graphite will not solve this because of the tedious purification process
  • Graphite comes in two forms: natural graphite from mines and synthetic graphite from petroleum coke. Both types are used for Li-ion anode material with 55 percent gravitating towards synthetic and the balance to natural graphite. Synthetic graphite for Li-ion sells for around US $10,000 per ton whereas spherical graphite made from natural flake sells for US $7,000 (2015 prices)
  • Artificial graphite in battery anodes is expected to nearly double by 2025, to 320,000 tonnes from 165,000 tonnes in 2020

Silicon Replacing Graphite in various proportions

  • Silicon has a number of advantages over graphite as an anode material, including the lower cost of the material and manufacturing. Also, it can absorb and contain a much higher number of lithium ions upon charging than graphite. This increases the efficiency of the battery, meaning EVs can reach higher distances on a single charge. Silicon anodes are still in development, but it’s likely that they will be in commercial use by 2020.
  • Sila Nanotechnologies in 2011 to develop a commercial silicon anode. The conventional wisdom is to replace, say, 10% of the graphite in a battery anode with silicon metal or oxide, improving density without introducing too much swelling. The company has created a nanocomposite of covalently bonded nanostructures of which 50% are silicon and the rest undisclosed non graphite materials. The composite is porous but encapsulated with a sealed outer layer that prevents electrolyte penetration into the composite, protecting it from damage during charge and discharge. The composite is contained in a porous scaffold structure so it is able to expand and contract without puncturing the coating. Sila’s material has an energy storage capacity four or five times that of graphite, enabling the energy density of a lithium-ion battery to increase by 20–40%.
  • Amprius has a 100% silicon anode that Airbus successfully tested in lithium-ion batteries for its Zephyr S pseudo satellite. The batteries have an energy density of over 435 (W h)/kg—substantially higher than that of commercial lithium-ion batteries in use today.

Lithium metal Anode

  • A lithium-metal anode has the highest specific capacity of any anode material, at 3,862 (mA h)/g, says Oxis’s chief technical officer, David A. Ainsworth. When paired with an optimized sulfur-based cathode, it will allow Oxis’s Li-S battery to achieve an energy density of more than 425 (W h)/kg, he says, compared with about 200 (W h)/kg for a lithium-ion battery.
  • Lithium-sulfur batteries are known to suffer from fading performance after a number of recharge cycles.
  • Equipping the battery with a lithium sulfide electrolyte protects the lithium-sulfide anode from degradation because the electrolyte instantly forms a film on the anode With a melting point of more than 900 °C, this coating protects the lithium even at extreme temperatures.( information from Oxis Company)
  • Volta Energy’s Chamberlain says. The most likely scenario will be the gradual adoption of silicon blended with graphite in anodes, rather than a jump to 100% silicon or lithium, he says. Overshadowing these marketplace developments is uncertainty about intellectual property rights relating to silicon anode technology because so many patents have been filed. About 1,100 patents relating to silicon anodes were filed in 2016 alone, and filings are increasing annually, according to the technology market research firm IDTechEx. Samsung was the most prolific in 2016 with almost 250 patents filed, followed by LG Chem, Panasonic, Sony, and Nexeon.

Anode

Lithium Titanate Oxide (lithium titanium oxide) Battery Technology

  • Lithium titanate (LTO) replaces the graphite in the anode of a standard lithium-ion battery and the material forms into a spinel structure. It can be used in combination with LMO or NMC cathode
  • In essence, the LTO is a rechargeable battery based on the, or modified from, the Lithium-Ion (li-ion) battery technology. Li-titanate oxide (LTO) replaces the graphite in the anode of the typical Li-Ion battery and forms the materials into a spinel 3D crystal structure. Having a nominal a cell voltage of 2.40V, it releases a high current discharge current that is 10 times the capacity of the other types of lithium batteries. Instead of using carbon particles on its surface as other lithium batteries do, Lithium Titanate utilizes lithium-titanate nanocrystals.
  • The effect and benefit of this alteration and inclusion of lithium-titanate nanocrystals is that the surface area of the anode of the Lithium-Titanate battery is about 100 square meters per gram in contrast to the only 3 square meters per gram that Li-Ion batteries hold. The result of the lithium-titanate nanocrystals with their enlarged surface area is that electrons are able to enter and leave the anode much more rapidly, leading to fast recharging and enhanced lifetimes of the battery.

 

Read more on the EV Battery ecosystem from: EV battery Innovations | Components of BMS | FCEV Trends | FCEV Indian Efforts | Anode/Cathode R&D | Li-ion Battery Trends | BMS Innovations | Indian Battery Manufacturers | Cost of Li-ion Batteries | Anode Materials in 2020-2030 | Key Drivers shaping Battery Chemistry |


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