The battery technology landscape is witnessing a monumental shift as the nascent rigid battery technology aggressively vies for attention, challenging the established liquid battery systemsThis competitive surge is primarily fueled by the urgent need for higher energy density, increased safety, and longer life spans which solid-state batteries promiseAs leading automotive manufacturers and battery companies race to innovate, recent announcements have highlighted specific timelines for mass production, creating a buzz of anticipation amongst stakeholders.

In a notable statement during the second China All-Solid-State Battery Innovation Development Summit held on February 15, BYD Lithium Battery CoCTO, Sun Huajun, expressed that the company is poised to initiate bulk demonstration deployment of solid-state batteries by around 2027. Similarly, Wang Deping, chief scientist at China First Automobile Group, indicated that their solid-state battery project aims for small batch applications by the same yearBefore this, significant players such as Changan Automobile, SAIC Motor Corporation, and Chery Automobile have also voiced their intentions to reach mass production or vehicle integration of solid-state batteries between 2026 and 2027. This collective consensus marks 2027 as a pivotal year for the solid-state battery industry.

However, contrasting views emerge from industry giant CATL’s chairman, Zeng Yuqun, who at a performance interpretation conference last year, asserted that solid-state batteries remain far from commercialization, emphasizing that if a technical and manufacturing maturity scale from one to nine is applied—with one being nascent and nine being mature—then the entire industry is presently hovering around a level four maturityFurther discontent was expressed by CATL's chief scientist, Wu Kai, who bluntly stated that the industry does not yet possess the capability for mass production of solid-state batteries.

A quest for the ideal technological approach

What sets solid-state batteries apart from their liquid counterparts is their solid electrolyte

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This fundamental difference facilitates distinct advantages in energy density and safetyYet, the challenge lies in the manufacturing processes of these batteries, which face several critical hurdles, particularly in selecting the right electrolyte technology.

Among the various options, sulfide electrolytes boast high ionic conductivity but are plagued by poor chemical stability, reacting adversely with moisture and oxygenCertain sulfides also exhibit instability at elevated temperatures, posing safety risksOxide electrolytes, while stable, present challenges due to their brittleness, difficult process handling, and high interfacial resistance leading to subpar contact with electrodesPolymer electrolytes are easier to process but sacrifice ionic conductivity, detrimentally affecting battery performanceHalides emerge as a newer option, offering decent ionic conductivity and stability but display brittleness complicating assembly and higher costs—factors that make their adoption hesitant.

In the spectrum of these imperfect electrolytes, the focus seems centered around sulfide and oxide electrolytes which dominate current research and patent strategies in the industryToyota’s pathway employs sulfide electrolytes, and Professor Ai Xinping from the School of Chemistry and Molecular Sciences at Wuhan University asserts, "while sulfides represent a promising angle, further investigation is required to ascertain their viability for practical applications and inherent safety."

Beyond electrolytes, both the anodes and cathodes in solid-state batteries present a range of choicesCathode materials vary from ternary materials, lithium-rich manganese-based, lithium iron phosphate to spinel compositions, while anode materials range from carbon-based to alloy materials, titanium dioxide, and innovative choices like silicon and lithium metal

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Each material carries its own strengths and weaknesses regarding performance, stability, and cost, contributing to an ongoing debate within R&D circles.

Another pressing difficulty encompasses interface issues—an intricate technical hurdleZeng Yuqun has highlighted that thorough research into materials and chemical systems is critical for developing all-solid-state batteries, with the "solid-solid interface" problem being the most challengingThe physical contact between the solid electrolyte and electrode materials is less than optimal, which elevates contact resistance and adversely affects charging and discharging efficiencyMoreover, during operation, the inherent volume expansion and contraction of electrode materials further deteriorate this contact, compounding the challengeInterface reactions could lead to structural breakdown, fostering the growth of lithium dendrites, which can penetrate the electrolyte, resulting in short-circuits and dangerous heat escalation.

In manufacturing, a debate continues around the choice of dry versus wet processing techniques for fabricationThe dry method is lauded for its simplicity and high efficiency, yet struggles to ensure adequate contact between the electrolyte and electrode materialsConversely, the wet method offers improved interface contact, albeit at the cost of increased complexity and higher expensesFurthermore, the meticulous production demands for solid-state batteries involving heightened temperatures and pressures necessitate advanced equipment and add to production challenges—factors that collectively render the mass production journey tumultuous and unpredictable.

Ambiguity on the road to mass production

While the most suitable technological route for solid-state batteries remains elusive, various domestic automakers and battery manufacturers are vigorously pursuing their distinct research paths to stake their claim in the competitive landscape as market players

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Each company has unveiled unique approaches to solid-state battery mass production, signifying a diverse array of technological routes.

BYD leverages a composite sulfide electrolyte along with high nickel ternary cathodes and silicon-based anodes, whereas Chery Automobile is exploring the oxide solid electrolyte route, employing high nickel ternary or lithium-rich manganese-based materials for cathodes and examining lithium metal anodesMeanwhile, Changan Automobile opts for a composite oxide solid electrolyte, utilizing lithium-rich manganese for cathodes and composite lithium metal-based materials for anodesGAC Group diversifies its approach, pursuing both sulfide-based and polymer-based multi-component systemsNot to be outdone, CATL is navigating both sulfide and oxide electrolyte technologies.

The diverse selections among car companies and battery manufacturers on solid-state battery technological routes paint a picture of vibrant competition, reflecting the underlying uncertainty surrounding the path to large-scale productionA pivotal question remains: which technological route will emerge as the prevailing choice for future development? Ouyang Minggao, an academician of the Chinese Academy of Sciences and a professor at Tsinghua University, stated at the solid-state battery forum that this is a critical moment for solid-state batteries, stressing the need to establish a definitive technological pathway which is central to the sustainable and healthy growth of the Chinese new energy vehicle sector.

According to Ouyang, the current focus for the solid-state battery technology roadmap should zero in on sulfide electrolytes paired with high nickel ternary cathodes and silicon-carbon anodesHe believes that numerous companies have established small-scale supply capacities for sulfide solid electrolytes that must be further developed with scalable manufacturing processes

Several global and local automakers, including Toyota, Honda, BYD, and Geely, seem to be converging on the sulfide technology route, affirming a collective shift in focus.

Looking toward the medium- to long-term development trajectory for solid-state batteries, Ouyang advocates that between 2025 and 2027, the goal should be to achieve a development target of 200–300 Wh/kg with graphite/low silicon anode sulfide solid-state batteries, facilitating breakthroughs in the technological chainFrom 2027 to 2030, targets should elevate to 400 Wh/kg and 800 Wh/L, emphasizing high-capacity silicon-carbon anodes for the next-generation passenger vehicle batteries; while from 2030 to 2035, objectives will scale to 500 Wh/kg and 1000 Wh/L, concentrating on lithium anodes and gradually evolving toward higher voltage high specific capacity cathodes compatible with suitable electrolytes.

As for mass production timelines, while most automakers have set their sights on 2027, some aim even earlier in 2026. Wuxi XianDao Intelligent Equipment CoMarketing General Manager Ye Zhengping opined that the target to achieve solid-state battery mass production by 2027 is rather ambitious, highlighting the significant challenges related to the large-scale production of sulfide electrolytes, as demonstrated by BYD’s experience.

The challenges escalate with high-cost rare metals potentially being utilized in solid-state electrolyte, compounded by elevated production demands and equipment investments which ultimately raises the total cost of solid-state batteriesThis cost barrier remains a considerable hurdle for mass application of solid-state batteriesHowever, experts remain hopeful that technological advancements and economies of scale will render solid-state batteries competitively pricedAccording to Sun Huajun, large-scale applications of solid-state batteries are expected to achieve parity with liquid batteries post-2030.

In summary, solid-state batteries represent the focal point within the new energy vehicle sector, yet their path to mass production is fraught with controversies and challenges

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