Solid-state batteries (SSBs) are a promising emerging technology for energy storage, offering high energy density, safety, and long cycle life. However, some challenges still persist in solid-state battery manufacturing. These include processing air-sensitive glass/ceramic materials and issues related to cost, materials availability, etc.
The global SSB market was valued at USD 126.7 million in 2022 and is expected to reach over USD 1,645.60 million by 2030.
Recent innovations in manufacturing techniques, better-suited materials, and techniques for stabilizing electrode-electrolyte interfaces aim to address these challenges. Researchers also aim to find ways to make solid electrolytes more flexible.
This article aims to report the progress and potential of SSBs in rеshaping the EV landscapе.
Solid-state Battery Manufacturing: Progressive Developments
The melting point of solid-state electrolytes typically ranges from 700°C to 1000°C, which poses a manufacturing challenge. However, new fabrication techniques allow manufacturing to be done at a much lower temperature range, roughly 200 to 300℃, making fabrication more efficient and easier.
Let’s review some other advancements below:
Improvements in Electrode Preparation And Cell Assembly
Some improvements in electrode preparation and cell assembly of solid-state battery manufacturing are:
- Thick Electrodes: A direct and efficient way to make lithium-ion batteries (LIBs) have more energy is to add thick electrodes that load more active material onto a smaller area. More cathode and anode active material added to each layer (greater electrode loading) and denser electrodes (lower porosity) increase cell energy density. Because of this, fewer layers per cell allow for greater energy storage per layer.
- Assembly Process: Researchers have noticed that cathode and anode dislocations frequently occur when assembling cells and proposed two improvement methods: “vacuum pen instead of tweezers” and “separator using BMF.” During the assembly of lithium-ion batteries, cathode and anode dislocations can frequently occur. These dislocations can lead to performance degradation and safety issues. To address this, researchers have proposed using a vacuum pen instead of tweezers for assembly. The vacuum pen can provide more precise control and reduce the risk of short circuits that can occur when using metal tweezers
Novel Coatings to Stabilize Interfaces
The thermodynamic instability of oxide cathode/sulfide solid electrolyte (SSE) interfaces leads to large resistances in all-solid-state lithium-ion batteries (ASSLIBs). To address this in solid-state batteries, researchers have proposed a flexible polyaniline (PANI) coating to stabilize the lithium cobalt oxide (LCO)/SSE interface.
A simple ball milling process followed by annealing creates the PANI coating. According to electrochemical studies, The PANI coating lowers and maintains the LCO/SSE interface resistance during cycling, leading to high capacity retention.
Optimized Binders and Composite Cathodes
Binders glue cathode active material particles and conducting carbons together and to current collectors. They also enhance cathode adhesion and cohesion, improve cycle life, provide mechanical stability at the cathode-electrolyte interface, and lower cell impedance by ensuring good contact between the electrode and current collector.
A lithium polyacrylate-sodium alginate composite binder series has been developed for these purposes.
Solid-state Battery: Current Number of Patents
Among actual battery manufacturers, LG Chem leads the pack with 5,539 solid-state battery patents. LG Chem has been granted more than 8,000 solid-state battery patents between October 2020 and October 2023. They purchased more than 40 patents relating to high-nickel cathode material from Hanyang University in March 2022.
Toyota Motor is another leading holder of solid-state battery patents, with 1,331 patents. Panasonic Holdings has 445 patents. One of their patents related to solid-state lithium batteries was filed in November 2016 and granted in October 2018.
Other automakers like Hyundai, Kia, and Honda also hold significant numbers of solid-state battery manufacturing patents.
Solid-state Battery Manufacturing: Evaluating Production Readiness
Evaluating the production readiness of solid-state batteries (SSBs) involves several key aspects:
1. Assessing Stability, Cycle Life, and Other Factors
In solid-state battery (SSB) manufacturing, assessing stability, cycle life, and interface integrity is crucial.
Stability encompasses the chemical durability of the solid electrolyte and the robustness of the electrode-electrolyte interfaces, which are essential for battery performance and longevity.
Cycle life in SSBs, indicative of their ability to withstand repeated charge-discharge cycles, is increasingly surpassing traditional lithium-ion batteries, enhancing their suitability for EVs.
Environmentally, producing a CR2032 All-solid-state lithium-ion battery (ASSLIB) requires about 2.6 MJ of primary energy and generates roughly 0.1 kg CO2-eq. in global-warming potential (GWP), underscoring the ongoing need for eco-friendlier manufacturing methods in this evolving field.
2. Scale-Up Demonstration Projects
Several projects are underway to demonstrate the scalability of SSB production. These projects aim to transition the technology from the lab to the pilot scale and eventually to commercial production.
3. Comparison to Lithium-Ion Battery Manufacturing
Compared to traditional lithium-ion batteries, in the long run solid-state battery manufacturing promises significantly shorter manufacturing times, reduced overall costs, and improved production efficiency.
Here are some examples of recent breakthroughs in the manufacturing of solid-state batteries with lithium-ion technology:
- Yoshino Power has released some of the first solid-state lithium products: portable power stations in various sizes for home backup, running power tools, and camping.
- Researchers at Harvard University have designed a stable, lithium-metal, solid-state battery that can be charged and discharged at least 10,000 times at a high current density.
- Panasonic is developing Solid-State Lithium-Ion Batteries (SS-LIBs) using oxidic and sulfidic electrolytes with a lithium metal anode.
- Samsung is also working on SS-LIBs, using a sulfidic glass electrolyte with an Ag–C coated lithium anode.
Solid-state Battery Manufacturing: Flexibility and Cost Analysis
Flexibility and cost analysis are critical in the strategic decision-making process for businesses. This includes the following components:
1. Ability of New Processes to Prismatic Cell Formats
The manufacturing of solid-state batteries (SSBs) will likely adopt processes from both conventional lithium-ion batteries (LIBs) and solid oxide fuel cell communities. The battery laboratory at Fraunhofer IFAM has suitable technologies like glovebox is equipped for physical vapor deposition (PVD) for each step of battery development.
Current advancements in optimizing the cell finishing process involve including a secondary filling process for bigger prismatic cells and Electrochemical Impedance Spectroscopy (EIS) as potential techniques for quality assessment. The secondary filling process in the context of solid-state batteries involves filling the remaining gaps or void spaces within the solid-state battery cell after the primary manufacturing steps.
Also, concerted efforts are underway to decrease the duration of pre-treatment and enhance the degassing procedure in order to guarantee optimal cell performance, quality, and safety.
2. Estimated Costs Compared to Lithium-Ion Cells
Advancements in the development of materials and electrode engineering have reduced lithium-ion battery costs by 90% per unit. It is predicted that the cost of lithium-ion batteries will keep going down and that by 2030, the average price per 1 kWh will dip below $60. Solid-state battery prices are estimated to range from $800/kWh to $400/kWh by 2026.
According to a review of battery cost forecasting methods and results, the cost of advanced lithium-ion batteries could potentially go below $90/kWh, while lithium-metal based batteries, which include SSBs, could potentially go below $70/kWh by 2050. However, these are long-term projections and the costs in the near future could be higher.
3. How Innovations Address Cost Barriers
A new fabrication technique known as melt-infiltration technology uses electrolyte materials that can be infiltrated into porous yet densely packed, thermally stable electrodes.
The melt-infiltration technology developed is adaptable to various material chemistries, including conversion-type electrodes. These materials have been shown to enhance the energy density of automotive cells by over 20% currently and potentially more than 100% in the future.
This patent-pending manufacturing technology mimics the low-cost fabrication of commercial Li-ion cells with liquid electrolytes. Instead, it uses solid-state electrolytes with low melting points that are melted and infiltrated into dense electrodes.
Conclusion
The promising manufacturing advances in solid-state batteries (SSBs), including nonflammable ceramic electrolytes, improved electrode preparation, and novel coatings, are transforming the electric vehicle (EV) market. The outlook for SSBs in EVs is optimistic, with industry experts foreseeing mainstream adoption around 2030.