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What is a semi-solid-state battery? A Detailed Introduction  

The rapid development of the new energy industry has placed power battery technology in the spotlight. While liquid lithium-ion batteries continue to dominate, the semi-solid-state battery has emerged as a transitional technology, seeking to bridge the gap between liquid and all-solid-state batteries.

However, this pathway is fraught with challenges, as the technology faces competition from both ends of the spectrum. This article explores the technical features, advantages, disadvantages, market applications, and future prospects of the semi-solid-state battery.

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What is a semi-solid-state battery?

In the evolution of energy storage technologies, the semi-solid-state battery is gaining traction as a promising solution between liquid lithium-ion and all-solid-state designs. It is defined as a battery in which either one electrode does not contain liquid electrolyte while the other does, or where the solid electrolyte accounts for more than half of the total electrolyte mass or volume.

Working principle of semi-solid batteries

Positive and negative electrode materials: The positive and negative electrode materials of semi-solid batteries follow the common materials in lithium-ion batteries (such as NCM, LFP, etc.), and can also be combined with new materials of solid-state batteries.

Semi-solid electrolyte: It is mainly composed of solid particles and a small amount of liquid electrolyte, which can not only maintain ionic conductivity, but also improve the stability and safety of the battery. It can be a gel-state or polymer-based electrolyte, which has a lower risk of leakage and better high temperature resistance than traditional liquid electrolytes.

Charging and discharging process:

  • During charging: lithium ions are released from the positive electrode, migrate to the negative electrode through the semi-solid electrolyte, and are embedded in it (such as embedded in graphite or silicon negative electrode).
  • During discharging: lithium ions are released from the negative electrode, pass through the semi-solid electrolyte, return to the positive electrode, and release energy for the device to use.

Advantages of the semi-solid-state batteries

Alta densidad energética

While conventional lithium-ion batteries are typically capped at 300Wh/kg, the semi-solid-state battery can exceed this limit, achieving 300-400Wh/kg and potentially higher. Some laboratory studies suggest a theoretical energy density of up to 700Wh/kg, nearly twice that of high-performance liquid lithium-ion batteries.

Compact size and lightweight design

Traditional lithium batteries allocate around 40% of their volume and 25% of their weight to the electrolyte (explore the electrolito de batería de iones de litio) and separator. By incorporating solid electrolytes, the semi-solid-state battery minimizes these materials, allowing for a more compact design. This makes it ideal for applications requiring strict weight and size constraints, such as drones and electric vehicles.

The feature of flexibility

The use of flexible ceramic-based solid electrolytes enables them to exhibit a certain degree of bending when reduced to millimeter thicknesses. This property is particularly beneficial for wearable devices and flexible electronics.

Enhanced safety

Liquid lithium batteries pose risks of fire or explosion due to external impacts, punctures, or short circuits. The semi-solid-state battery, by utilizing solid electrolytes, eliminates the risk of liquid leakage and significantly reduces the likelihood of battery thermal runaway. For instance, a 314Ah semi-solid-state battery has demonstrated a 40% increase in thermal runaway resistance compared to conventional cells, greatly improving safety.

Challenges and barriers faced by semi-solid-state batteries

High production costs

Despite its advantages, the semi-solid-state battery is still expensive to manufacture. Current production costs reach approximately 1800 yuan/kWh, compared to 710 yuan/kWh for liquid ternary lithium batteries. This high cost stems from the expensive solid-state electrolyte materials and an underdeveloped production process.

Difficulty in electrolyte content control

For optimal safety, the electrolyte content in the semi-solid-state battery should be below 5%. However, current technology limits this to 10%-15%, comparable to high-nickel liquid lithium batteries, diminishing its competitive edge.

Limited industrialization

Although some degree of industrial application has been achieved, the widespread adoption of the semi-solid-state battery still faces technical and market hurdles. The electric vehicle industry, for example, prioritizes cost reduction and efficiency, making it difficult for high-cost technologies to integrate into the supply chain in the short term.

Application scenarios of semi-solid-state batteries

  • Vehículos eléctricos: Premium electric vehicles and motorcycles are adopting this technology. Such as the TYCORUN semi-solid battery for electric motorcycles, ebike, and scooters,  improving their safety, enabling longer driving ranges.
  • Almacenamiento de energía: Urban energy storage systems, 5G base stations, and data centers require highly stable batteries. The semi-solid-state battery, with its improved thermal stability, is well-suited for these applications.
  • Drones and aerospace: Drones demand lightweight, high-energy-density power solutions. The semi-solid-state battery provides a significant advantage in this sector. 

All-Solid-State vs semi-solid-state vs liquid: which is more advantageous?

Artículo Liquid Lithium-Ion Battery Semi-Solid State Battery Solid-State Battery
Electrolyte Type Liquid electrolyte Partially solid + liquid electrolyte Fully solid electrolyte
Energy Density 150-300 Wh/kg 300-400 Wh/kg 400-500 Wh/kg
Seguridad Flammable, risk of leakage and thermal runaway Improved safety, reduced risk of thermal runaway but still contains liquid Extremely safe, non-flammable, no leakage, minimal thermal runaway risk
Ciclo de vida 800-2000 cycles 1500-3000 cycles 3000-5000 cycles
Manufacturing Cost Low, mature technology, large-scale production Higher than liquid batteries, complex process, high cost Very high, still in early development, not yet mass-produced
Technology Maturity Most mature, widely used in the market Transitional technology, some commercial applications Still in R&D, expected commercialization after 2030

Future development and breakthroughs

  • Enhancing solid electrolyte performance

Most current designs use hybrid solid-liquid electrolytes, but their ionic conductivity remains inferior to liquid counterparts. Future innovations must optimize materials like sulfides and oxides to improve battery cycle stability and efficiency.

  • Cost reduction

With increasing production scale, costs are expected to decline. The newly established 6GWh semi-solid-state battery production facility, launched by Guangdong Energy Group and Beijing Weilan New Energy in March 2025, has begun mass production of 314Ah high-capacity cells, setting a precedent for cost reduction.

  • Integration with all-solid-state battery technology

In the long run, the semi-solid-state battery serves as a stepping stone toward fully solid-state designs. Some companies are actively developing hybrid technologies, such as in-situ solidification methods, to gradually phase out liquid electrolytes.

Conclusión

Although the semi-solid-state battery currently faces challenges related to cost and industrialization, its advantages in safety and energy density make it an attractive choice for electric vehicles, high-end energy storage, drones, and more.

As technology progresses and production scales up, the costs of the semi-solid-state battery are expected to decrease, paving the way for wider adoption. This will contribute to a safer and more efficient energy storage landscape, driving the future of the global new energy industry.

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Chase Wu
Hola, soy Chase. Estoy especializado en ofrecer información detallada y las últimas actualizaciones sobre sistemas de intercambio de baterías eléctricas de dos y tres ruedas, desde la tecnología de las baterías de litio hasta las soluciones de intercambio inteligente. Mi objetivo es desglosar conceptos técnicos complejos en contenidos claros y accesibles, ayudando a empresas y particulares a navegar por el cambiante panorama de la movilidad eléctrica y la energía sostenible.
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