All smart electronics devices today are working on Lithium-ion batteries. Be it a smartphone, laptop, ear pods, smart watch or electric vehicles. Lithium-ion batteries are the most favourite energy storage device as it can hold the energy for the longer duration. However, there are serious challenges present with Lithium-ion batteries. Lithium based batteries are toxic when discarded. Extraction of the Lithium mining needs lot of fresh water and toxic material damages the soil too. Moreover, recycling and recovering of the Lithium from the used cells for reuse is also a difficult and costly affair. It is also true that Lithium recycling is not well established and research in this area seems stagnant.

In the given scenario, the global EV industry need is to find alternatives of Lithium-ion batteries. There is also a need to understand the alternatives of the Lithium should not own ecological challenges. These should also include better energy density, least hazardous, better sustainability and long lasting batteries which can be recycled easily.

First let us understand that the Lithium-ion battery is an energy storage unit and not a source of renewable energy. Function of any energy storage unit is to store the energy and release it when required as per demand and the storage unit can be recharged with the suitable charging method. For electric vehicles to get the longer range batteries need to be recharge quickly or need to find bigger energy storage system. Lithium-ion battery meets the requirement of the higher energy density, lesser space requirement in the vehicle and long lasting cleaner electric power on board.

Looking at the EV production demand and volume, there are clear possibilities of Lithium crises as well as Production Vs Demand issues. For future requirements there is a need of better RESS.

What is RESS?

It means Rechargeable Energy Storage System. RESS provides electric energy to electric vehicles. The battery which is primarily used for auxiliary loads, lighting and engine start-stop function do not considered as a RESS.

Desired Characteristics of RESS

1. Safe in operation and storage
2. Quick recharge
3. High energy density
4. Minimum weight
5. More drive cycles (Charge/Discharge cycle)
6. Hazard proof
7. Scalable
8. Cleaner and greener energy
9. Non-toxic chemical compositions
10. Easy Recycle

Alternatives to Lithium-ion Batteries

There are few technologies, such as Fuel-Cell, Sodium-ion, Zinc-air, Solid-state, and Flow batteries are already in various stages of deployment and development. However, cost parity should not be the only metric and other parameters must also be evaluated before choosing a technology for any use case. Some of the key parameters are mentioned below: 

1. Power density and energy on-board (predominantly for mobility applications)
2. Shelf life 
3. Average net cost for the use case 
4. Technology readiness level (TRL) or maturity
5. Safety in various use conditions 
6. Existing manufacturing capacity 
7. Recyclability 

Additionally, we need to be very mindful of these technologies in terms of environmental impact. Which includes Green House Gas (GHG) emissions formed during manufacturing and installation, as well as the waste generated at the end-of-life stage. Keeping these deliberations in mind, this article throws the light on the key battery storage technologies.

Fuel-Cell

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. A fuel cell uses the chemical energy of hydrogen or other fuels to cleanly and efficiently produce electricity. If hydrogen is the fuel, the only products are electricity, water, and heat. Fuel cells are unique in terms of the variety of their potential applications; they can use a wide range of fuels and feed stocks and can provide power for systems as large as a utility power station and as small as a laptop computer.

Advantages of Fuel-Cell

• Higher energy density
• Lighter in weight
• Longer range
• Quick recharge
• Easily handle temperature changes
• Less downtime
• Longer lifespan

Disadvantages of Fuel-Cell

• Hydrogen production
• Expensive catalyst materials
• Infrastructure for storage and transportation of Hydrogen
• Availability and distribution

Sodium-Ion

The Sodium-ion battery uses Sodium ions (Na+) as the charge carriers. The working principle and cell construction of Sodium-ion battery are identical to Lithium-ion battery types, but Sodium compounds are used instead of Lithium compounds. Sodium-ion batteries are strong in performance and reliability as compared to Lithium-ion batteries. Sodium is thousand times more abundant than lithium and there is practically an infinite source available as a sea water. Also the extraction and purification cost is overall lower than Lithium.

Advantages of Sodium-Ion Battery

• Cost per kWh of capacity is less
• Better safety
• Earth-abundant
• Negligible self-discharge

Disadvantages of Sodium-Ion Battery

• Volumetric energy density is less
• Less charging cycle at 80% DoD
• Slightly higher in cost being a new technology

Zinc-Air

Zinc-air batteries are promising in terms of higher energy density, low cost and inherent safety. A typical Zn-air battery consists of a porous air cathode and a Zn metal anode, separated using a membrane separator and filled with a concentrated alkaline electrolyte. Zinc-air batteries have some properties of fuel cells as well as batteries: the zinc is the fuel, the reaction rate can be controlled by varying the air flow, and oxidized zinc/electrolyte paste can be replaced with fresh paste. Possible future applications of this battery include its deployment as an electric vehicle battery and as a utility-scale energy storage system.

Advantages of Zinc-Air Battery

• Same power and performance as lithium chemistry
• Longer shelf-life
• Lower risk of catching fire
• Earth reserves are more than lithium
• Economical compared to Lithium-ion batteries

Disadvantages of Zinc-Air Battery

• Recycling of Zinc could be costlier
• Stability
• Low energy density

Solid-State

Unlike Lithium-ion or Lithium-polymer batteries, a Solid-state battery uses solid electrodes and solid electrolyte instead of liquid or polymer gel electrolytes. Solid-state batteries are potentially useful in pacemakers, RFIDs, wearable devices, and electric vehicles. Materials recommended for use as solid electrolytes in solid-state batteries include ceramics (e.g., oxides, sulphides, phosphates), and solid polymers. Ideally, solid-state batteries can replace Lithium-ion batteries in electric vehicles. In fact many well-known automakers like BMW, Volkswagen, Ford and Toyota have already started investing in the technology.

Advantages of Solid-State Battery

• Higher energy density
• High performance in harsh environment
• Toxic materials can be avoided
• Lower risk of catching fire
• Fast charging and longer cycle life possible

Disadvantages of Solid-State Battery

• Costly manufacturing
• Low temperature functions are challenging
• High interfacial resistance
• Mechanical failure

Flow Batteries

In flow battery, two liquids are separated by a membrane and circulated in order to enable ion exchange between them. It is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system or separate side of the membrane. The energy capacity is a function of the electrolyte volume and the power is a function of the surface area of the electrodes. Flow batteries are capable of storing large amount of electricity and scalability makes them right fit for the electric vehicle application. For large electric vehicles Flow batteries can be an ideal option. However, Flow batteries include very costly fluids which are corrosive and toxic.

Advantages of Flow Battery

• Flexible layout
• Longer cycle life
• No harmful emissions
• Do not contain any flammable electrolytes
• Absence of degrading material and hence longer life-span
• Ideal for consistent energy delivery

Disadvantages of Flow Battery

• Lower energy density
• Low charge-discharge rate
• Lower energy efficiency
• Technology cost and industry immaturity
• Heavier and consumes more space due to storage tanks

Conclusion

The future is surely electric and need of batteries will be raising exponentially high. EV performance is also dependent on the right size and type of the battery. Looking at environmental and safety challenges Lithium-ion batteries are going to be replaced by better rechargeable energy storage systems. Although there are challenges with all types of chemistry and technologies of RESS, the promising technology for RESS will be dependent on its type of application. Weather it is for mobile application for passenger vehicles or grid-side storage system for renewable energy sources, there will be many type of batteries and chemistry which will be replaced by Lithium-ion batteries and certainly there will be alternative of Lithium battery in the coming future.