The current prominent battery chemistries and emerging chemistries

Last updated: Feb 2021 by Narasimhan Santhanam

This post is a part of EV Next’s EV Perspectives.

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Introduction

The chemistry of Li-ion battery is a topic of significant interest and importance in the energy storage domain today, as the right chemistry can provide both the performance that the market desires at a cost the market can bear.

This blog post provides an overview of the prominent Li-ion battery chemistries and also provides inputs on the possible trends in these chemistries for the 2020-2030 timeline.

The common types of lithium-ion chemistries are

1. Lithium-Cobalt Oxide Battery
2. Lithium-Titanate Battery
3. Lithium-Iron Phosphate Battery
4. Lithium-Nickel Manganese Cobalt Oxide Battery
5. Lithium-Manganese Oxide Battery

• The five types of lithium batteries listed above are established commercially. There are many other chemistries that are under the research phase in lithium batteries. 
• The main thing to be noted is that each chemistry has different energy density, power density, reliability and safety. One can choose battery chemistry that best suits based on the application. 
• There are also other lithium battery chemistries that do not fall in the category of Lithium-Ion. These include Lithium Sulphur, Lithium Air and Lithium Silicone. These technologies are still emerging but hold tremendous potential.

• Lithium cobalt oxide batteries (LCO) are popular because they are widely used previously in electronics like cell phones, Laptops, cameras, etc. 
• Even though they have high energy density and low discharge rates, the main problem is that it is highly unstable when damaged. 
• The lack of cobalt leads to the high pricing of this chemistry and difficult to be a viable option for use in EVs.
•  Nevertheless, this high energy-dense battery powers the Tesla Roadster and Smart Fortwo electric drive (ED).
• LiFePO4 (LFP) offers good electrochemical performance with low resistance, besides high current rating and long cycle life. The phosphate helps to stabilize the electrode against overcharging and provides a higher tolerance to heat which limits the breakdown of the material.
•  These batteries have a wide temperature range and can operate between +60o C to −30o C and are much less likely to suffer from thermal runaway.
• LiFePO4 has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging. This is one of the widely used chemistries in India for Electric Vehicles.
• Lithium- Titanate can operate at very low temperatures. They have moderate energy density and rapid charge and discharge cycle. They are one of the safest batteries with good cycle life in Lithium-ion chemistry. The cost of the Lithium titanate batteries are still on the higher side which makes it difficult to be adopted for Ev usage.

• Different battery chemistries could be ranked higher based on the priority of the required function. LFP and LTO might serve cases where a large number of charge cycles are required. While NMC and Li-CO are prioritized when higher battery capacity is needed.
• NMC (as valid from the above picture) is a good balance of all important factors and hence makes up most of the Li-ion batteries.
• Specific energy – This defines the battery capacity in weight (Wh/kg). More output from a lesser quantity of lithium would be desirable. This factor determines the amount of power it can supply over an hour. Specific energy also means the capacity because it gives a figure on how much time the battery can run the load for.
• Specific power – It is the ability to deliver high current and indicates loading capability. This factor determines how much power can the battery give out at any specific point of time. 
• Performance – This measures how well the battery works over a wide range of temperature. Most batteries are sensitive to heat and cold and require climate control. Heat reduces the life, and cold lowers the performance temporarily.
• Lifespan – This reflects cycle life and longevity and is related to factors such as temperature, depth of discharge and load. Hot climates accelerate capacity loss. 
• Safety – This relates to factors such as the thermal stability of the materials used in the batteries. The materials should have the ability to sustain high temperatures before becoming unstable. Instability can lead to thermal runaway in which flaming gases are released. 
• Cost – Batteries have complex chemistries and use rare metals in heavier quantities. This makes cost a very valuable factor in deciding the type of battery used.

Which are the LiB chemistries that have just started getting used?

• Conventional graphite anodes suffer from poor rate capability and lithium dendrite problems upon overcharging, leading to internal short circuits and safety concerns, including fire or explosion owing to its flammable nature. Lithium titanate (LTO) is a promising candidate for replacing graphite in lithium-ion battery anodes because of its unique advantages for EV applications.
• Silicon is a typical alloying anode and has long been regarded as one of the most promising anode materials for replacing graphite. Si has the highest known theoretical specific capacity for lithium of about 4200 mAh/g, which is more than ten times that of graphite anodes. For the past few years, battery manufacturers have been introducing silicon to their anode supplementing the graphite. Other research involves pure silicon that has achieved far greater charging potential which is yet to be commercialized, owing to safety concerns caused by structural inefficiency of silicon. (silicon tends to swell when subjected to electricity)

 Which LiB battery chemistries are expected to have good prospects starting 2025?

• Being technically sound doesn’t guarantee Lithium-ion batteries’ place as the most common electricity storage medium. Most if not all lithium-ion batteries contain rare metals. The commercialization and widespread use of batteries also depend on the ease of availability of these rare metals.
• Cobalt is extensively used in NMC and LCO chemistries. 60% of the world’s cobalt resources are located in the DRC region which is politically very unstable. Though however NMC is being preferred for its operational benefits, there is a limit on how many NMC batteries can be made. So battery manufacturers worldwide have tried to shift to better alternatives to NMC. As a result of such efforts, LFP(LiFePO4) has become the second most used Li-ion chemistry. It is only a matter of time before LFP replaces NMC. 
• For LCO, the lithium demand will be assumed to have a 0% CAGR in the future since it has gradually reached saturation in the market from 2011-2016 without an evident future growth. The market shares of NMC in the whole LIB market are 26% (2016) and 41% (prediction for 2025).
• Lithium–sulfur batteries may succeed lithium-ion cells because of their higher energy density and reduced cost due to the use of sulfur] Some Li–S batteries offer specific energies on the order of 500 Wh/kg, significantly better than most lithium-ion batteries. 

What are the key drawbacks of the current LiB battery chemistries and how are the emerging battery chem trying to overcome these?

• Requires protection circuit to maintain voltage and current within safe limits 
• Subject to aging, even if not in use – storage in a cool place at 40% charge reduces the aging effect. 
• Transportation restrictions – shipment of larger quantities may be subject to regulatory control. This restriction does not apply to personal carry-on batteries.
• Expensive to manufacture – about 40 percent higher in cost than nickel-cadmium.
• Not fully mature – metals and chemicals are changing on a continuing basis.
• It is estimated that there is a new development in battery chemistry almost every 6 months as more OEMs are particular about the technology they require for their vehicles and newer regulations coming into place from different geographies. 
• Innovation and performance characteristics in batteries aren’t limited to their electrode chemistries alone. Other factors such as coating materials, state of electrolyte, and their structural arrangement in a cell also contribute to the battery’s overall performance. Leclanché is working on a technology that uses lithium iron phosphate (LFP), which has an “olivine” structure, as the cathode, and lithium titanate oxide (LTO), which has a “spinel” structure, as the anode. These structures are better at handling the flow of lithium ions in and out of the material. These cells can be charged 100% in just 9 minutes.
• Regarding the silicon anode problem – Sila Nano’s approach is to encase silicon atoms inside a nano-sized shell with lots of empty room inside. That way, the SEI is formed on the outside of the shell and the expansion of silicon atoms happens inside it without shattering the SEI after each charge-discharge cycle.
• Regarding highly volatile electrolytes – Lithium batteries always use flammable liquids as the electrolyte.. One solution is to use solid electrolytes. But that means other compromises. A battery design can easily include a liquid electrolyte that’s in contact with every bit of the electrodes, making it able to efficiently transfer ions. It’s much harder with solids. Imagine dropping a pair of dice into a cup of water. Now imagine dropping those same dice into a cup of sand. Obviously, the water will touch far more surface area of the dice than the sand will. 
• Alternatives to lithium are quite far from batteries. It is difficult to find anodes for chemistries such as sodium-ion batteries. Employing nanosized or nanostructured forms of the active material has been demonstrated as an effective strategy to overcome this problem, yet it is questionable whether such methods are sufficiently cost-effective to be implemented on an industrial scale. Since the only advantages of SIBs are the low cost of sodium salts and the fact that low-cost Al current collectors can be used on the anode side (because Na, unlike Li, does not alloy with Al), many electrode materials developed to date for SIBs are unsuitable for the use in commercial cells considering the relatively high cost of their preparation.
• Estimations show that by 2025, 75% of the world’s lithium consumption will be for batteries which still puts it at half of the world’s available lithium resources, so there is a motive that the electric vehicle industry will not be severely affected by lithium scarcity. Moreover, almost every major EV OEM is looking towards battery recycling(which in itself is at an advanced stage where 98% of total constituents can be recovered) to ensure the value chain is not depreciating.

Outside of LiB, which are the top 3 or 5 battery types that have the potential for EVs? What is their current status of development/ commercialization?

• Magnesium-ion batteries could serve as an alternative to lithium-ion batteries in electric cars and grid storage. Such batteries would use a cathode and an electrolyte similar to that of lithium-ion. However, the anode would be critically different. A typical Mg-ion battery would not make use of graphite, or any sort of intercalation anode, and would directly use magnesium metal.
  • On paper, magnesium-ion offers a tremendous potential energy boost over lithium-ion, possibly as much as two-to-one. In theory, such capabilities would enable automakers to use batteries that are half the size, while offering the same power. However, such advancements face several technical challenges and are still far from the prototype stage.
• .Lithium–Sulphur – Magnesium-ion batteries could serve as an alternative to lithium-ion batteries in electric cars and grid storage. Such batteries would use a cathode and an electrolyte similar to that of lithium-ion. However, the anode would be critically different. A typical Mg-ion battery would not make use of graphite, or any sort of intercalation anode, and would directly use magnesium metal.
  • On paper, magnesium-ion offers a tremendous potential energy boost over lithium-ion—possibly as much as two-to-one. In theory, such capabilities would enable automakers to use batteries that are half the size, while offering the same power. However, such advancements face several technical challenges and are still far from the prototype stage.
• Nickel-zinc batteries are cost-effective, safe, non-toxic, eco-friendly batteries that could compete with Li-ion batteries for energy storage. However, the main barrier for commercialization has been the low cycle life of nickel-zinc batteries.
  • Chinese researchers from the Dalian University of Technology have developed a breakthrough technique to improve the performance of Ni-Zn batteries by solving the issue of Zn electrode dissolution, dendrite formation, and performance.
• Sodium-Metal – Stanford researchers released a paper claiming that their sodium batteries could compete with lithium-ion batteries. The Stanford battery uses sodium, a cheaper, more abundant material than lithium, and is still in the development stage.
  • The cathode of this battery is made up of sodium, and the anode is made from phosphorus, with the addition of a compound derived from rice bran or corn. According to researchers, this chemical combination yields efficiency rates comparable to that of lithium-ion batteries at a lower cost. The main advantage of the sodium battery lies in the fact that sodium is much more abundant than lithium, and it costs $150 per ton versus $15,000 for lithium. 
• Aluminum-ion and Lithium-ion batteries are very similar, except that the former has an aluminum anode. Aluminum-ion batteries provide increased safety and faster charging time at a lower cost than lithium-ion batteries; however, there are still issues with cyclability and life span. Stanford University is a leading developer of aluminum-ion batteries that incorporate a graphite cathode. The research holds the potential for making cheap, ultra-fast charging, and flexible batteries, with thousands of charge cycles, in addition to being a safe, non-flammable option with a high charge storage capacity.
  • Aluminum-air flow batteries for EVs outperform the existing lithium-ion batteries in terms of higher energy density, lower cost, longer cycle life, and higher safety. Aluminum-air flow batteries are primary cells, which means that they cannot be recharged via conventional means. In EVs, they produce electricity by replacing the aluminum plate and electrolyte. Considering the actual energy density of gasoline and aluminum of the same weight, aluminum is superior.

Major global Manufacturers of battery chemistries are

• Panasonic
• CATL
• LG Chem
• BYD
• Samsung

• Among these chemistries, Lithium-Nickel Manganese Cobalt Oxide Battery is one of the most popular chemistries that’s been manufactured by the world’s leading manufacturers like CATL, LG, Samsung, etc. 
• The second most popular chemistry among the top manufacturers in the Lithium iron phosphate and are manufactured by CATL and BYD.
• LG makes LFP chemistry particularly for the Indian EV industry based on the alliance with Mahindra. 
• Panasonic, which is one of the top manufacturers of lithium batteries, makes Lithium cobalt oxide cells.

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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