New Delhi: In the ever-evolving and rapidly changing energy storage landscape, the advent of solid-state batteries (SSBs) is leading to a new era of possibilities making them a massive game changer. With the demand for enhanced performance and attempts to find safer energy storage solutions growing, SSBs have emerged as a frontrunner in the race for next-generation technology.
With new battery technologies being in continuous development, especially due to the rapid growth in vehicle electrification, which requires large battery packs, there is a growing demand for more efficient, reliable and environmentally friendly materials.
This points to Solid-state post-lithium-ion batteries as a possible next-generation energy storage technology.
One immediate advantage of this power source over commercial lithium-ion batteries is its potential to solve the resource issues of low-tension batteries as a cost-effective alternative. The second advantage is the removal of flammable liquid electrolytes. Solid electrolytes are more resistant to changes in temperature and physical damage and produce up to 80% less heat. They can withstand more charge/discharge cycles before their gradual degradation and ensure longer battery life.
Another immediate gain is that liquid electrolytes do not require membrane and casing. This may reduce the weight and volume of each cell, and increase the energy density of the battery.
This article describes the recent achievements in the development of sodium, potassium, and magnesium solid-state batteries. It is revealed that while the research community has progressed greatly towards solid–state alkali and alkaline-earth batteries, much more improvement is on the cards for the room-temperature ionic conductivity of solid electrolytes. To ensure the practical applications of these systems, the stability and interfacial reactions of solid electrolytes should be explored deeply.
In the 1990s, lithium-ion batteries seamlessly integrated into our lives, offering portability, longevity, and energy density thanks to their reliable performance, cost-effectiveness and widespread availability. These batteries consist of a graphite anode, a layered oxide cathode, and a separator soaked in an organic liquid electrolyte.
Solid-state batteries replace the flammable liquid electrolyte with a solid-state electrolyte-(SSE), and are inherently safer for all. SSEs also open the door to using different cathode and anode materials, expanding the possibilities of battery design. Although some SSBs are based on lithium-ion chemistry, not all follow this path.
Safety: SSBs are considered the ‘holy grail’ of battery technology due to their massively improved safety profile. The absence of flammable liquid electrolytes minimizes the risk of thermal runaway, making SSBs a safer and better option.
Higher energy density: SSBs offer the potential for higher energy density, a critical factor in applications like electric vehicles (EVs) and consumer electronics, where longer range and longer battery life are desired for effective use.
Longer cycle life: SSBs tend to have longer cycle lives, meaning they can withstand more charge and discharge cycles without significant degradation.
Wide temperature range: SSBs can operate effectively within a broader temperature range, making them suitable for extreme conditions.
Simple design: SSBs can simplify battery design due to their solid-state nature, potentially reducing the complexity of energy storage systems.
Flexibility: Some SSBs offer mechanical flexibility, allowing them to be integrated into various form factors.
Road to market realization
To define when SSBs will become a reality, it’s crucial to clarify and exemplify what constitutes an SSB. Currently, polymer-based SSBs are commercially available, while semi/hybrid/pseudo SSBs are undergoing trials. Ceramic-based all solid-state batteries (ASSBs) are being developed.
True SSBs should be devoid of any liquid or gel polymers. However, semi/hybrid/pseudo SSBs, which may contain liquid components, still offer advantages such as enhanced safety and higher energy density. They are often referred to as ‘Solid-state batteries’, in the public domain.
Several technological approaches are seen under the SSB umbrella, including oxide, sulphide and polymer systems, each with its specific variations. Sulphide electrolytes, for instance, offer high ionic conductivity but face challenges in manufacturing and safety issues. Polymer systems are easy to fabricate but have limitations in operating temperature and stability. Oxide systems offer stability but have higher manufacturing costs.
Commercialization may begin with polymer-based SSBs, followed by semi-solid oxide systems. Sulphide systems, while gaining attention, may take longer to reach the market.
The adoption of SSBs faces several challenges, including high capital expenditure (CAPEX), comparable operational costs (OPEX), and premium pricing. Clear value propositions must be presented in the main to gain public acceptance.
While discussions about the safety benefits of SSBs persist on a range of subjects, evidence suggests they offer higher abuse tolerance. Heightened energy density is another advantage, but it must align with cathode and anode material advancements, all of which are being presently done.
System-level efforts, such as cell-to-pack (CTP) design, thermal management systems, and mechanical innovations are gaining prominence and importance. CTP designs, driven by improved safety and bipolar stacking, enable flexible pack designs and higher energy density.
Initial generations of SSBs may have lower energy densities and higher costs than Li-ion batteries at the cell level. However, the benefits of flexible design and reduced material use may effectively make SSB packs competitive.
Thermal management systems for SSBs will be essential, featuring different operating temperature requirements than Li-ion batteries (LIB).
In addition to technology, considerations must address equipment utilization, factory footprint, supply chain establishment and manufacturing yield improvement.
SSB can be considered as a further evolutionary development of LIB. Mainly driven by the demand for higher energy and power density (specific energy and power) and improved safety — nevertheless at low costs — the “solidification” of cells is explored as one of the few options for continued optimization of the LIB cell concept. Thus, any solid-state concept should not be seen as a revolutionary step, but rather as a logical attempt for further improvement of an otherwise successful technology.
Reference for figures: Adv. Energy Mater. 2023, 13, 2301886
(Disclaimer: Yashodhan Gokhale is CTO of Battrixx, a lithium-ion battery manufacturing company in Maharashtra. Views are personal.)