SIMT Technology Observation Nayuan new materials
SIMT Technology Observation is a cutting-edge technology and industry transformation in-depth dialogue column launched by Sodium Yuan New Materials (SIMT). As an important component of the Na Yuan new material technology ecosystem, this column will regularly invite experts from fields such as new energy, artificial intelligence, materials science, and intelligent manufacturing Frontline PhDs and Researchers In the form of dialogue, break down the technical challenges they have overcome, the latest developments in the laboratory, and the real path from theory to industrialization.
👤 Interview guests for this issue
Professor Jun Wang obtained his doctorate degree in material physics and chemical engineering from Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences in 2012, served as a researcher in MEET Battery Research Center (European Top Battery Research Center), University of Munster, Germany from 2012 to 2018, and has served as a researcher/professor and doctoral supervisor in South University of Science and Technology since 2018. Its main research direction isResearch on high-energy density and high safety lithium batteries, as well as other new types of batteriesHosted sub projects of the National Natural Science Foundation of China, Guangdong Provincial Key R&D Program, and Shenzhen Major Technology Research Project, served as a young editorial board member of eScience, Sci. China Mater., Energy Storage Science and Technology Journal, and vice chairman of the New Materials Professional Technical Committee of Guangdong Provincial Youth Science and Technology Innovation Research Association.
already in Nat. Rev. Chem., Chem. Soc. Rev., Nat. Commun., Joule，Energy Environ. Sci.，Adv. Mater.，Angew. Chem. Published over 200 academic papers in top international journals, with more than 9500 citations and an H-index of 53; Applied for over 50 invention patents.
If we only look at the capital market and public opinion field, solid-state batteries seem to be a technology that is about to emerge: they are safer, have higher energy density, and can also be compatible with lithium metal negative electrodes. It seems that only the last step is needed to replace today's liquid lithium-ion batteries and become the standard answer for the next generation of power batteries.
In the past two years, judgments such as mass production in 2027 and large-scale application in 2030 have frequently appeared, coupled with the continuous increase of car companies, material companies, and battery companies. Solid state batteries have almost become one of the most concerned technological directions in the entire new energy industry.
But if we pull the perspective back from the capital narrative to the laboratory, material system, and battery manufacturing site, we will find a judgment that is closer to reality:The technology of solid-state batteries has been successfully implementedHowever, there is still a long way to go before the comprehensive industrialization of large capacity, long lifespan, mass production, and delivery can be achieved.
To understand solid-state batteries, the first step is to answer a more fundamental question:What is the liquid electrolyte doing in today's lithium-ion batteries?
Only by understanding why liquid electrolytes have long dominated can we understand why solidification is a much more complex system reconstruction than imagined.
01 Electrolyte, in battery systems; Blood ";
In public perception, the core of a battery is often the positive and negative electrodes. The positive electrode material determines the energy density, while the negative electrode material is related to the rate, lifespan, and safety boundary. Therefore, the most discussed upgrade paths in the industry are visible materials such as high nickel ternary, lithium iron phosphate, silicon-based negative electrodes, and lithium metal negative electrodes.In contrast, electrolyte is often seen as a relatively complementary component, as if it were just a "liquid filler" used to conduct ions in batteries。
Professor Wang:;The electrolyte is actually the blood of the battery.The thermal runaway of batteries often begins with the decomposition of the electrolyte. The reason why we choose to use semi-solid and all solid electrolytes is because liquid electrolytes are prone to leakage, combustion, and explosion. If we compare a battery to a house, the positive pole determines the ceiling, the negative pole determines the floor, and the electrolyte determines whether it can fit in. "
In a true electrochemical system, the electrolyte is much more than just a passive medium. It is not only a channel for lithium ion migration between positive and negative electrodes, but also a participant in the formation of electrode surface facial mask. It is also a key variable that affects high pressure stability, low temperature performance, fast charging ability and safety.As Professor Wang said, electrolyte is more like the "blood" in the whole battery system: it not only needs to flow and reach every electrode pore, but also needs to maintain stability under complex working conditions. At the same time, it can form an appropriate interface facial mask when necessary to protect the active materials so that the whole system can work continuously.In actual research and development, one“Good electrolyte”The following standards need to be met:1. There is enough widthElectrochemical stability windowOtherwise, it will preferentially oxidize and decompose in front of the high-voltage positive electrode;
2. Yes, there isAppropriate viscosity and good wettabilityOnly then can it truly penetrate into the interior of the porous electrode and establish a continuous ion transport network;
3、Ionic conductivity should be high enoughTo ensure magnification performance and transmission efficiency under low temperature conditions;
4. Must be formed on the positive and negative electrode surfacesStable, uniform and sustainable facial maskTo prevent the battery from continuously experiencing side reactions, impedance rise, gas evolution, and structural instability during cycling.
5. We cannot ignore the limitations at the industrial level and must establish a foundation inMass production, storage and transportation, controllable cost, acceptable environment and regulationsOn the basis of.
This means that the reason why liquid electrolytes can support the large-scale industrialization of lithium-ion batteries today is not only because they can conduct electricity, but also because they provide a comprehensive balance optimized over many years between transmission, infiltration, interface, and manufacturing adaptability.
Therefore, solid-state batteries need to replace liquid systems, and the actual discussion is how to replace the composite functions that liquid electrolytes undertake in the entire system.
02 Difficulties in solid-state batteries, interface engineering issues
In recent years, with the rapid development of sulfides, oxides, polymers, and composite solid electrolytes, sulfide technology is the most mature. The ionic conductivity of some sulfide systems at room temperature has reached 10 ⁻³~10 ⁻ 2 S/cm, surpassing the level of liquid electrolytes.But the problem is that the battery is not a standalone electrolyte material, but a complex system that includes a positive electrode, negative electrode, electrolyte, conductive phase, current collector, and packaging structure.
What determines the performance of a system is not just the indicators of a certain material itself, but how they come into contact with each other, how they react, and how they maintain compatibility in long-term cycles.
Therefore, in the eyes of more and more frontline researchers, the most difficult part of solid-state batteries is no longer finding an electrolyte with sufficiently high ionic conductivity, but how to deal with the ubiquitous interface problems inside the battery.Professor Wang:; Liquid electrolyte is liquid-phase conduction, from solvation to desolvation; Solid electrolytes are defect conductive and grain boundary conductive. The migration rate, activation energy, and path length of these two conduction modes are different. "
⚡ Interface Problems of Solid State Batteries: Four Dimensional Analysis |
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| Solid solid contact | When two solids come into contact, it is impossible to naturally eliminate the gap like a liquid. There will always be gaps in the real interfaceHollow, rough, and mismatched contact areasIn addition, different material hardness, elastic modulus, and thermal expansion behavior can introduce additional stress. |
| Chemical Compatibility | High voltage positive electrode may interact with certain solid electrolytesside effectEspecially in the combination of high nickel ternary and sulfide electrolytes, such problems are very prominent. The accumulation of interface side reaction products leads to a continuous increase in impedance. |
| Mechanical stability | During the charging and discharging process, the positive electrode active particlesLattice changeAnd the lithium metal negative electrodeSedimentation/stripping behaviorBoth will cause local stress changes, leading to further debonding, cracking, or failure of the already imperfect interface. |
| Scaling up | A laboratory button battery can be usedHigh reactor pressure barely maintainedWhen the contact relationship is amplified to ampere hour level, and then to larger capacity soft packs or square cells, it is likely to completely fail. The problem of uneven pressure distribution and interface instability has been rapidly amplified. |
Because the research and development of solid-state batteries is full of challenges, the current discussion of solid-state batteries cannot simply stay at the level of "material breakthroughs", but must enter intoInterface EngineeringAt the level of.The so-called interface engineering is to break through the limitations of a single surface coating, and work together from multiple dimensions such as chemical stability, space charge layer regulation, mechanical compatibility, particle size and morphology design, and stack pressure condition optimization to achieve overall performance upgrades through collaborative optimization.For the positive electrode,Surface coatingCan alleviate side reactions with sulfide electrolytes;Throughelement dopingandComponent regulationIt can reduce the anisotropic strain during the charging and discharging process, reduce particle cracking, and enhance the continuous contact ability with solid electrolytes;
Meanwhile,Single crystal or quasi single crystal structureIt has been proven that the risk of crack propagation and interface instability in cycling is often lower than that of polycrystalline secondary particles.03 Reconstruction of structural engineering and manufacturing systems beyond interfaces
If interface issues explain why many solid-state batteries can be made but cannot run quickly, then structural engineering and manufacturing issues explain why many solutions, even if they can run in the laboratory, may not necessarily be industrialized.Although they are both "batteries", the structures of solid-state batteries and liquid batteries are completely different.Taking the positive electrode as an example:In a liquid battery system, the electrolyte can fully infiltrate the interior of the electrodes. The positive electrode particles only need to build a connected electronic transmission path, while reserving suitable pores for electrolyte penetration. The work of ion transmission is basically undertaken by the liquid electrolyte, and the design of the electrode structure is relatively simple.However, in the solid-state battery system, the working conditions undergo fundamental changes, and the positive electrode must balance the triple functions of electronic conduction, ion conduction, and mechanical structural stability.Professor Wang:; The positive electrode of solid-state batteries does not use new materials, but its engineering structure is different. "
Therefore, the positive electrode of solid-state batteries is no longer just a simple combination of active materials, conductive agents, and binders, but requires the introduction of solid-state electrolyte particles and the redesign of particle distribution, porosity, densification degree, molding pressure, and interlayer contact relationships.
This also means that the iterative upgrade of solid-state batteries is not just about replacing the existing liquid production line with a different electrolyte, but also about restructuring the electrode processing logic, lamination method, pressure management method, and even packaging ideas.
When the industry wishes to further introduce lithium metal anodes to achieve higher energy density, the problem becomes even more complex:The deposition/stripping of lithium metal itself is accompanied by significant volume changes and interface instability, and may also grow along electrolyte defects in solid-state systems, posing a risk of dendrite penetration.At the same time, solid-state batteries often rely on external stack pressure to maintain interface contact, and once they enter the large-scale application scenarios of automotive grade batteries, how to maintain reasonable and uniform pressure in long-term use will become a new system engineering problem.So, the industrialization of solid-state batteries has never been a task that can be completed with a single breakthrough. More and more professionals in the industry are defining solid-state batteries as a system level reconstruction.04 Industrial reality, when will solid-state batteries become popular
Professor Wang believes that the most concerning issue regarding the launch of solid-state batteries is:"2027 Annual mass production can achieve small-scale applications, but there may be limitations in certain application scenarios, and it may be the first to land in high-end cars and low altitude fields. Although there are many uncertain factors that affect the mass production and application of solid-state batteries, it can be confirmed that, 2027 Year to Year 2030 Year is a crucial time point. "
From the perspective of industry laws, any new battery technology that truly enters the mainstream must meet at least several conditions simultaneously:
● Key material and interface issues have been resolved with sufficient stability;
● The design and manufacturing process of battery cells can achieve replicability, scalability, and controllable yield;● Reduce costs to an acceptable range for downstream customers;● Being able to prove through long-term verification that its lifespan, safety, and consistency are not accidental laboratory results;● The upstream and downstream supply chains have formed relatively mature synergies.For solid-state batteries, these conditions are still in the process of being gradually integrated, so solid-state batteries are highly likely to be developed in the next few yearsWill not fully replace liquid batteries”And it will be applied in high-end car models and special scenarios that are more sensitive to volume density or brand technology image, and can withstand higher costs.
In other words, currently solid-state batteries are more likely to experience“From demonstration application to gradual scaling up”The process still has a long way to go before it can be fully popularized and enter thousands of households.
05 Looking at sodium electricity again, innovative development in different dimensions
When discussing next-generation battery technology, sodium ion batteries often appear together with solid-state batteries, but the two are not actually in the same dimension.Solid state emphasizes the system reconstruction brought about by changes in electrolyte morphology, while sodium electrolysis is primarily an electrochemical system route based on resource endowment, cost expectations, and scenario adaptability.⚖️ Sodium ion batteries: advantages and challenges |
| ✅ The core advantage is abundant resources and cost friendly. The crustal reserves of sodium are much higher than lithium, evenly distributed, not constrained by geopolitics, and have a resource foundation for large-scale popularization. The selection of positive electrode materials is more flexible and easier to use relatively inexpensive transition metal element systems such as iron, manganese, and copper, thereby reducing dependence on scarce resources such as nickel, cobalt, and lithium, and significantly improving supply chain security. |
| ⚠️ The structural challenge of ion radius leads to structural instability. Sodium ions have a significantly larger radius than lithium ions, making them more prone to interlayer slip, structural distortion, and complex phase transitions during insertion and extraction of positive electrode structures. They can maintain stable structures in lithium battery systems, but often exhibit stronger instability in sodium batteries. |
This is also why sodium batteries have an overall energy density that is difficult to compete head-on with mainstream lithium-ion power batteries in some systems.This determines that sodium batteries are more suitable for applications that are cost sensitive, require high low temperatures, and have relatively less extreme energy density requirements, such as some energy storage scenarios, two wheelers, A00 level vehicles, etc.Professor Wang believes that polyanions are the short-term optimal solution for energy storage scenarios.Professor Wang:; Polyanions have good capacity, stable structure, excellent recyclability, and good safety. “
In the first half of 2026, the overall shipment proportion of polyanion materials in the sodium positive electrode market remained stable at 70% -75%.(Data source: SMM Shanghai Nonferrous Network)Its open framework structure provides excellent ion transport channels and structural stability, with a cycle life of up to 10000-15000 cycles. It has significant advantages in long-term energy storage scenarios, which also matches the current demand for multi-dimensional collaborative optimization in the energy storage market.Meanwhile, Professor Wang is also very optimistic about the long-term potential of layered oxides.Professor Wang:" The energy density of layered oxides can already reach nearly 160Wh/kg, which is close to 180Wh/kg of lithium iron phosphate on the market. With the development of new materials, there is great hope for breakthroughs even greater than lithium iron phosphate. "
Professor Wang believes that for a long time in the future,Lithium batteries will occupy the high-end market with high energy density, sodium batteries will occupy the cost and safety oriented market, and lead-acid batteries will be squeezed out by both.Looking back, in the past decade, the battery industry has been at its strongestThere is no better technological narrative than the increase in energy density.In order to achieve higher battery life, the industry has shifted from lithium iron phosphate to ternary, from medium nickel to high nickel, and then turned its attention to silicon-based negative electrodes, lithium metal negative electrodes, and solid-state batteries, forming a very distinct energy density upgrade route.But as the industry develops to this day, a new reality has become increasingly clear:The lead of a single indicator is no longer enough to determine whether a technology can truly win.In the coming years, whether it is the continuous optimization of liquid electrolytes or the advancement of semi-solid and all solid state batteries, the real competition will shift from a simple energy density competition to a systematic collaborative competition in material design, interface control, electrode structure, and manufacturing processes.The future development of the battery industry is still full of imagination.
