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Vanadium Flow Batteries

Introduction

Lithium-ion batteries have dominated the ESS market to date. However, they have inherent limitations when used for long-duration energy storage, including low recyclability and a reliance on “conflict minerals” such as cobalt.


Vanadium flow batteries (VFBs) are a promising alternative to lithium-ion batteries for stationary energy storage projects. Also known as the vanadium redux battery (VRB) or vanadium redox flow battery (VRFB), VFBs are a type of long duration energy storage (LDES) capable of providing from two to more than 10 hours of energy on demand. They are gaining significant attention for their unparalleled ability to store and deliver power on an industrial scale.


VFBs may not be as well-known as their lithium-ion counterparts, but they offer a promising alternative for stationary energy storage projects. Developed in the 1980s at the University of New South Wales, VFB technology has quietly evolved into a reliable and sustainable energy storage solution. Several countries around the world including the United States, Canada, Australia and the European Commission have classified vanadium as a critical raw material.

 VoltStorage 50 kWh Vanadium Redox Flow Battery. Source: VoltStorage
VoltStorage 50 kWh Vanadium Redox Flow Battery. Source: VoltStorage

The Chemistry

VFBs use vanadium, a metal produced around the world and used primarily to harden steel. Unlike lithium-ion batteries, VFBs are highly recyclable and do not degrade with use, lasting 25 years or more even with heavy daily use. Vanadium is readily available and can be either mined or recovered from industrial waste. VFBs are also a safe choice as they are fundamentally non-flammable.


Advantages of Vanadium Flow Batteries
High energy density:

VFBs have a high energy density, meaning they can store a lot of energy in a small space. This makes them ideal for stationary energy storage applications, where space is often limited.


Long cycle life

VFBs have a very long cycle life, meaning they can be charged and discharged many times without losing performance. This makes them ideal for applications where frequent cycling is required, such as renewable energy integration.


Wide operating temperature range

VFBs can operate in a wide range of temperatures, from -20°C to 50°C. This makes them suitable for use in a variety of climates.


Safety

Safety is a top priority for energy storage systems. VFBs are inherently non-flammable, offering peace of mind in terms of fire risk. This characteristic allows VFBs to be positioned safely, even inside buildings.


Recyclable

Unlike lithium-ion batteries, VFBs use a vanadium-based electrolyte that remains unchanged over time. When a VFB reaches the end of its life cycle, the electrolyte can be recycled and repurposed for use in other batteries or applications.


Exceptional Durability

One of the standout features of VFBs is their remarkable durability. These batteries can be charged and discharged hundreds of thousands of times without suffering from significant degradation. This longevity makes them ideal for long-term energy storage solutions.


Highly Scalable

VFBs are scalable to meet various energy storage needs. Whether it's a small residential installation or a large industrial project, VFBs can be tailored to the required capacity.

Invinity’s VFB at the Energy Superhub Oxford, UK. Source: Invinity
Invinity’s VFB at the Energy Superhub Oxford, UK. Source: Invinity

Comparing VFBs to Lithium-Ion Batteries

While VFBs offer several compelling advantages, they also have some limitations when compared to lithium-ion batteries:


Lower Energy Density

VFBs have lower energy densities compared to lithium-ion batteries. This means they may not be suitable for high-power applications that require rapid energy delivery.


Limited Charge Cycles

Lithium-ion batteries can often endure more charge cycles before degradation sets in, some reaching up to 10,000 cycles. VFBs, while durable, have a lower energy density and may not be as well-suited for certain applications.


Cost

VFBs are currently more expensive than lithium-ion batteries. However, the cost of VFBs is expected to come down as the technology becomes more widely adopted.


Size

VFBs are way more larger and bulkier than lithium-ion batteries. They often come in common containers. For this reason, they are typically used for largescale and heavy-duty grid energy storage or attached to power plants/electrical grids and are not suitable for non-stationary purposes like consumer electronics and electric vehicles.

While lithium-ion batteries have dominated the energy storage market, vanadium redox flow batteries have emerged as a compelling alternative. Their exceptional durability, recyclability, and safety features make them an attractive choice for stationary energy storage. As the march toward a more sustainable future continues, VFBs are proving to be a valuable asset in our quest for cleaner, more efficient energy solutions. With ongoing research and development support, vanadium flow batteries are set to play a pivotal role in shaping the energy landscape of tomorrow. The cost of VFBs is expected to come down as the technology becomes more widely adopted. In the mean time, Lithium remains king and for good reasons too.


Vanadium is not as abundant as lithium and is less available, which contributes to the higher cost of VFBs. Additionally, VRFBs require a bidirectional DC/AC inverter to interface with the grid, which adds to the cost. However, recent progress has been made in improving the cost and performance of VFBs. For example, researchers have developed new electrolyte compositions that can reduce the amount of vanadium required, and they have also developed new membrane and electrode materials that can improve the efficiency and power and current densities of VRFBs. New membrane materials have been developed that can improve the efficiency and power and current densities of VFBs, such as anion exchange membranes (AEMs) and composite membranes.


Also, new electrode materials have been developed that can improve the efficiency and power and current densities of VRFBs, such as carbon-based electrodes and metal-organic framework (MOF) electrodes. In addition to these technological advances, there are also a number of commercial developments that are helping to reduce the cost of VRFBs. For example, several companies are now mass-producing VRFB components, such as electrolytes, membranes, and electrodes. This is helping to drive down the cost of VRFBs and making them more competitive with lithium.



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