How far are solid-state batteries?

In 2025, solid-state batteries are becoming the focus of the global new energy industry with unprecedented enthusiasm.

On one hand, mainstream liquid lithium battery technology is gradually approaching the theoretical ceiling in terms of energy density and safety, with more breakthroughs concentrated in engineering fields such as material compaction density and cell grouping efficiency; on the other hand, from laboratories to the industry, news about technological breakthroughs, sample releases, and mass production timelines for solid-state batteries has been continuous recently, raising expectations in the capital markets and among the public amidst a myriad of concepts and terminologies.

All-Solid-State Battery is recognized as the next-generation battery technology with disruptive advantages, seen by the industry as the "ultimate solution" to address range anxiety and safety concerns in electric vehicles.

Its energy density is expected to exceed 600Wh/kg (watt-hours per kilogram), which is more than twice that of the current mainstream battery technology—liquid lithium battery single-cell energy density (200Wh/kg-300Wh/kg); its safety is also higher, eliminating the thermal runaway risk of liquid lithium battery electrolytes.

However, the road from scientific theory to commercial mass production is far more difficult than imagined. The selection and stability of solid electrolytes, along with high development costs and challenging manufacturing processes, constitute the "valley of death" that lies before industrialization.

In the current global race for solid-state batteries, Chinese companies are almost on the same starting line as competitors from Europe, America, Japan, and South Korea, all at a critical stage of climbing from scientific validation to engineering validation, with no company yet having reached the threshold for large-scale commercial use. Among Chinese companies, traditional battery manufacturers such as Guoxuan High-Tech and SUNWODA, as well as companies focusing on solid-state battery technology like QingTao Energy and WeiLan Technology, and even automotive companies like Chery and SAIC, are actively exploring in the field of solid-state batteries, laying out multiple technological paths in sulfides, oxides, and polymers.

All-solid-state batteries have already demonstrated disruptive potential at the laboratory sample stage. For example, the sample released by SUNWODA has an energy density of 400Wh/kg, and the "Rhino S" battery module showcased by Chery has a cell energy density of up to 600Wh/kg. There are also various materials still in the experimental stage that have energy densities exceeding 700Wh/kg.

Currently, products that have been applied on a small scale mostly belong to the category of "semi-solid batteries" (also known in the industry as "solid-liquid batteries"), with single-cell energy densities around 350Wh/kg. For instance, the battery equipped in the SAIC IM L6 model comes from QingTao Energy, with an energy density of 368Wh/kg, and the 150KWh ultra-long-range battery pack of Nio has cells sourced from WeiLan Technology, with an energy density of 360Wh/kg.

There is an essential technical difference between "all-solid" and "semi-solid." All-solid-state batteries represent a disruptive innovation in materials, processes, and performance compared to existing technologies. In contrast, solid-liquid batteries are improvements based on the existing liquid lithium-ion battery system, inheriting the material system, manufacturing processes, and equipment from the liquid lithium battery supply chain, and essentially remain within the realm of liquid lithium batteries, with relatively limited performance enhancements The technological gap between the two is enormous, but some market participants often blur definitions or mix terms in their promotions. Industry associations, technical experts, and relevant departments are keen to clarify the distinction between "solid-state" and "semi-solid" batteries, with the most mainstream voice advocating for the standardized naming of "semi-solid batteries" as "solid-liquid hybrid electrolyte lithium-ion batteries," abbreviated as "solid-liquid batteries." This move aims to clearly differentiate this type of battery from true solid-state batteries, avoiding excessive hype around the concept of solid-state batteries.

Standardized naming is also intended to cool down the current heated market sentiment. Since the beginning of this year, there have been continuous technological breakthroughs, sample releases, and new developments in the solid-state battery field, pushing market enthusiasm to new heights. In October 2025, significant news regarding solid-state batteries frequently appeared in the media.

The intensive progress has heightened market attention towards solid-state batteries. The solid-state battery index (BK0968) released by the internet financial service institution Dongfang Caifu rose from a low of 1288 points on April 9, 2025, to a high of 2426 points on October 9, nearly doubling in six months. However, amidst the market frenzy, there is a general underestimation of the significant gap between experimental results and commercialization.

01 Solid-State Battery Technology "Progress Bar"

To evaluate the current development level of solid-state batteries, the industry has introduced the "Technology Readiness Level" (TRL) developed by NASA in the 1970s, which is a universal tool used by various global technology and industrial organizations to assess the maturity of different technologies. It categorizes the maturity of a technology from laboratory to mass production into 1 to 9 levels, belonging to three major stages: scientific validation, engineering validation, and commercial validation.

According to this classification standard, solid-state battery technology still has a considerable distance to reach mature mass production. Recent advancements in the research community and the market can also be positioned according to this development stage.

Two research achievements (TRL2-TRL3) published by a research team from the Chinese Academy of Sciences are significant breakthroughs at the fundamental science level, with results published in top academic journals, proving their scientific principles. However, these breakthroughs are currently limited to verified scientific concepts and have not yet been integrated into battery cell product design.

The latest QSE-5 battery cell sample from American company QuantumScape (TRL5-TRL6) began delivery to its partners for vehicle testing in the third quarter of 2025. At the Munich Motor Show held in September, this battery cell sample was demonstrated on a motorcycle. Completing prototype battery cells, testing in relevant environments (motorcycles and cars), designing manufacturing processes, and building pilot production lines are all major tasks at the TRL5-TRL6 stage. However, these remain at the sample stage and are not yet mass-produced goods.

SUNWODA released a solid-state battery (TRL5-TRL6) with an energy density of 400Wh/kg and plans to establish a pilot production line of 200MWh (megawatt-hours) by the end of 2025. Similar to QuantumScape, it is currently in the prototype testing and pilot line validation stage.

Chery Automobile's solid-state battery module prototype "Rhino S" (TRL4-TRL5) claims an energy density of up to 600Wh/kg and has passed multiple extreme safety tests, including drilling, steel needle puncture, 50% compression deformation, and even immersion in water, without experiencing thermal runaway. Sample validation conducted in a controlled laboratory environment is a typical stage of TRL4-TRL5. Chery plans to conduct vehicle testing in 2027, marking its entry into the TRL6 stage.

Guoxuan High-Tech's "Jinshi" solid-state battery (TRL7) has a pilot line of 200MWh that is already operational, with a stable yield of 90%. Test vehicles equipped with "Jinshi" solid-state battery samples have completed over 10,000 kilometers of driving distance. The operational pilot line and long-distance real vehicle road testing signify entry into the TRL7 stage, indicating successful testing and data collection in a real operating environment, rather than just remaining at the pilot line sample stage.

However, it should be noted that this battery did not choose the metallic lithium anode, which has the highest energy density but also presents greater challenges. Instead, it adopted the combination of "sulfide electrolyte + high nickel cathode + silicon anode," which currently has lower mass production challenges. The final cell energy density is 350Wh/kg, which, although significantly improved compared to ternary and lithium iron phosphate batteries, does not have an advantage over solid-liquid batteries.

Currently, no company's all-solid-state battery has entered the commercial validation stage globally. The timelines proposed by various companies, such as Toyota's 2027-2028 and Chery's 2027, refer to entering the TRL7/TRL8 stage, which is the point of conducting prototype testing and system validation in real environments, rather than completing TRL9, which means achieving full commercial deployment. Therefore, industry leaders like CATL and BYD remain cautious about the high enthusiasm for solid-state batteries, continuously increasing investment in technological research and development. For instance, CATL's solid-state battery R&D team has exceeded a thousand people, but they expect that the timeline for large-scale mass production and sales will not be earlier than 2030.

02 The "Long March" of Liquid Lithium Batteries

When assessing the prospects of solid-state batteries, people often compare them to the previous milestone technology, lacking a real perception of the "invention to commercialization" process. Looking back at the development history of liquid lithium batteries, it is often simplified as: Nobel Prize-level scientific breakthroughs in the 1970s and 1980s, Sony's successful mass production in 1991, and the electric vehicle wave that began in 2010.

This narrative overlooks the efforts made by scientists and engineers for engineering optimization and manufacturing process innovation over the decades from laboratory discovery to mass production, and from mass production to today, as well as the costs incurred by the entire battery industry chain to reduce costs Early lithium batteries were expensive due to complex manufacturing processes and costly raw materials, with prices reaching as high as $7,500 per kWh when mass production began in 1991. Today, over 30 years later, prices have dropped to less than $100 per kWh. This process was not instantaneous but resulted from sustained large investments, expansion of production scale, continuous optimization of process control, and ongoing improvements in material utilization and production yield.

Safety has also undergone a long evolution. Early lithium batteries had serious safety hazards, particularly thermal runaway issues. The entire industry spent decades gradually establishing a complete safety system, stringent testing protocols, and industry standards, enabling large-scale applications in consumer electronics, automotive, and energy storage sectors. This was a passive evolution process, often driven by significant safety incidents, involving both the efforts of researchers and painful costs.

At the same time, the global supply chain needed to start from scratch to build key materials such as battery-grade lithium, cobalt, nickel, graphite, and separators, and it continues to face multiple challenges related to resource extraction and geopolitical environments.

The development history of the liquid lithium battery industry indicates that the most profound impacts on cost reduction and reliability improvement often occur after the first commercialization. The true cost and performance of solid-state batteries will only become apparent after overcoming the challenges of scaling up mass production.

Current cost predictions for solid-state batteries are mostly based on laboratory-scale processes and idealized assumptions. However, based on the experience of liquid lithium batteries, real-world manufacturing costs primarily depend on yield, production efficiency, and equipment depreciation—factors that remain unknown for the current stage of solid-state batteries.

03 Known and Unknown Challenges

Whether solid-state batteries can pass engineering and commercial validation largely depends on breakthroughs in the technology route of their core material—the solid electrolyte. Currently, the industry is generally focused on three mainstream technology routes: sulfides, oxides, and polymers, each facing severe challenges in different directions.

The advantage of the sulfide route lies in its highest room temperature ionic conductivity, comparable to that of liquid electrolytes. However, the challenges are equally significant: it is extremely sensitive to air and moisture, reacting with humidity to produce toxic hydrogen sulfide gas. Therefore, a very low-humidity dry environment must be provided for the manufacturing process, and the sealing and waterproofing requirements for the finished batteries are also more stringent, leading to high costs. The interface reactions with electrode materials are active, necessitating the development of complex interface technology to control the reaction process. Additionally, the key raw material lithium sulfide (Li2S) is expensive, and the supply chain is not yet established.

The advantage of the oxide route is its excellent thermal and chemical stability. The main challenge is that the material itself is hard and brittle, making it difficult to process into the ultra-thin, defect-free electrolyte membranes required for large-scale production Typically requires sintering at nearly 1000 degrees Celsius, which is a high-energy, high-cost process and difficult to be compatible with cathode materials. The rigid physical properties make it difficult to form close contact with the electrodes, resulting in significant interfacial resistance and poor battery charge and discharge performance.

The most notable advantage of the polymer route is its ease of manufacturing, which can be compatible with some existing production processes. The challenge lies in the low performance ceiling, specifically the low ionic conductivity at room temperature, which usually requires the battery to be heated above 60 degrees Celsius to function properly. Additionally, polymers currently have poor compatibility with high-voltage cathodes, thus limiting the potential for energy density improvement.

Aside from these known challenges, the decades-long development of liquid lithium batteries has shown that many significant engineering challenges cannot be foreseen through prior analysis. Issues such as the rheological control of electrode slurries, coating uniformity, electrode cracking, particulate contamination control during production, and welding reliability only gradually emerge during high-speed, large-scale continuous production. Solving these problems requires substantial capital investment and top-notch engineering technology. Beyond the science, commercial validation is also fraught with uncertainty—good products can be hard to sell, which is not uncommon in the tech industry.

Currently, the enthusiasm for solid-state batteries is mainly focused on the scientific validation level (TRL1-TRL3), with a series of key breakthroughs gradually overcoming scientific issues related to the contact interface of anodes and cathodes, material routes, etc., achieving significant results.

Engineering validation (TRL4-TRL7) is just beginning, with a few leading companies having produced prototype samples and planned pilot lines, but this is also the most difficult and longest phase in the commercialization process of a technology, known as the "valley of death" in technology commercialization, filled with numerous engineering challenges and uncertainties.

As for commercial validation (TRL8-TRL9), currently no company's all-solid-state battery has reached this stage. The necessary conditions for commercialization, such as cost, yield, reliability, and supply chain, are still far from being met.

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