Evolving Critical Metal Systems: Hype Cycles and Implications for Sustainable Innovation

Abstract

To achieve the transition to sustainable energy and mobility systems, we are relying heavily on critical metals. The sustainable extraction, use, and circulation of these materials is not straightforward as contestation over the social and ecological sustainability of these metals is characterised by so-called hype cycles of increased and decreased legitimacy. This impedes the energy and mobility transition. We propose and apply a novel approach using event graphs to assess critical metal systems as evolving socio-material systems, comparing three longitudinal cases (lithium, cobalt, tantalum). Our analysis leads to an ideal type hype cycle for critical metal systems. Our findings evidence the necessity for policymakers and industry practitioners to use approaches such as responsible innovation to ensure that the extraction, use, and circulation of critical metals does not undermine the transition to sustainable mobility and energy systems.

1. Introduction

Metals such as lithium, cobalt, rare earth elements (REEs), platinum group metals (PGMs), tungsten, tantalum, and many others are needed for technologies that are key in achieving sustainable energy and mobility provision [1,2]. Moreover, as we transition to cleaner technologies, it is anticipated that the balance of materials used for applications in our economy will change. For example, in the domain of transportation, the use of platinum group metals (PGMs) in auto catalysts will decrease. By contrast, the demand for PGMs in the hydrogen economy as well as battery materials like lithium and rare earth elements for use in electric vehicles is expected to increase significantly [3]. While they are also in use for other applications, a major reason for the current interest in these metals is their contribution to more sustainable energy and mobility systems. Moreover, a number of these metals are labelled as ‘critical’ due to their essentiality for the functioning of modern technologies, difficulty in substitution by any other material, and the risk of disrupted supply chains [4]. In addition, their potential contribution to a sustainable society requires them to be extracted, used, and circulated legitimately. Legitimacy is ultimately based on these activities to happen in a sustainable way: with minimal impact on (trans-) local ecosystems and with neutral or positive impact on the wellbeing of communities in which these activities take place.

Given the relevance of these materials, there must be a steady and growing supply of them either through primary extraction or the building up of routes of circulation, enabling their continued recovery, reuse, and recycling. Furthermore, a transition to sustainability and enhanced circularity, mindful of responsible innovation, necessitates the development of enhanced socio-technical systems for the recovery, reuse, recycling, and even upcycling [5] of these materials. However, by now we have several examples that indicate a pattern where these metals go through cycles of boom, bust, and contestation, posing a threat to their steady supply [6]. Such patterns have been observed through price fluctuations of critical metals, where a ‘hype’ develops, indicating either a potential or actual shortage [7]. However, a focus on price only is myopic given that extracting, refining, and using critical metals has significant social implications [8], they are crucial for vital technologies [5], and have policy, governance, and ethical implications [9]. We argue that it is important to incorporate a socio-technical lens that considers these different aspects while analysing the hype cycle-like patterns in the development of critical metals. Moreover, the socio-technical lens also allows us to frame critical metals as a complex socio-technical system with different elements and their connections [10]. We are thus focusing on the dynamics in a critical metal system (CMS). Understanding a CMS is vital for developing metals in a sustainable way.

To this end, we aim to uncover patterns in the socio-technical development of CMSs to provide generalisable insights related to the evolution of a CMS over time. We theorise this development based on hype cycle theory because our system of interest displays phenomena like hype cycles: distinct periods where articulations of expectations about a critical metal and its application drives the hype or the disappointment. Although hype cycle theory has traditionally been applied to specific technologies and their associated expectations, we extend its application to a different context—namely, CMS—in response to calls for using hype cycle theory across diverse applications and environments to explore variations in hype cycle structures [11]. In uncovering these patterns, we aim to deduce an ‘ideal-type’ hype cycle for CMS wherein an ideal type is a generalisation or mental representation of a social phenomenon that, while not necessarily an exact reflection of reality, serves as a useful framework for understanding it [12]. This will enable us to identify path dependencies that lead to unwanted consequences or contestations. To this end, the two-tiered research question that we address is as follows:

What generalisable patterns can be observed in the development of a CMS with a particular focus on legitimacy? How do these patterns relate to the transition to sustainable energy and mobility systems?

Answering this question will produce novel insight into the way in which CMSs evolve over time in terms of the societal legitimacy of their extraction, use, and disposal. To achieve this, we study three critical metal case studies, lithium, tantalum, and cobalt, through a qualitative reconstruction of event sequences [13,14] pertaining to these critical metals and analyse the patterns in their socio-technical development. By addressing the research question, we uncover patterns in the socio-technical development of CMSs using hype cycle theory and present the application of hype cycle theory in diverse contexts and environments as suggested by Van Lente [11]. The remainder of the paper is organised as follows. In Section 2, we present our conceptual framework. In Section 3, the data and methods used in this study are introduced. In Section 4, we present the results of our analysis followed by a discussion in Section 5. Section 6 concludes our study through providing reflections and suggestions for future research.

2. Conceptual Framework

Our conceptual framework is based on a process perspective that enables us to articulate a critical metal system to undergo a hype cycle-like trajectory over time. There are three building blocks to our conceptual framework: (1) critical metal systems, (2) hype cycle, and (3) process perspective. We explain each of these building blocks in the following sections.

2.1. Critical Metal System

To conceptualise a CMS, we draw on the sociology of scientific knowledge: actor-network theory (ANT) or the sociology of translation [15,16]. Following these approaches, we view a CMS as an assemblage of socio-technical heterogeneous actants such as a critical metal, its associated regulations, individuals, and organisations that engage with the critical metal, and the technologies that use the critical metal. These heterogeneous actants interact to form a network that emerges, evolves, and dissolves over time through the interplay between the actants and events that unfold [17]. Drawing from this understanding, we define a CMS as an assemblage of different human and non-human actants around a particular critical metal. The actants could be anything ranging from mining companies (covering a spectrum of enterprises from established to new entrant junior miners through artisanal and small-scale mines), policies around critical metals, an NGO contesting the mining of the critical metal, the artefacts used to explore and mine the ore, or even a research paper about the critical metal. It is also important to note that elements of the supply chain may occur in radically different geo-institutional contexts—often extractive industries are located in poorer countries in the global south that may have less developed governance structures, whilst the consumption side of CMS’s is located in more affluent countries where more restricted governance structures may act as a barrier to the development of extractive industries. Both human and non-human actants can be a part of the system, the only qualifying criteria being that they must have some agency. In the context of ANT, it is crucial to note that non-human actants can also have agency equivalent to human actants [18]. For example, mining equipment ‘acts’ in the sense that it requires persons to act in a certain way, and through its potential danger, organisations concerned with safety draw up regulations. Moreover, as these different heterogenous components of the system interact with one another through translation [16], they establish the ‘legitimacy’ of the system wherein certain combinations of artefacts, regulations, actions, and actors become ‘taken for granted’ as the way to produce and use the critical metal. ANT does not theorise extensively about general patterns in the evolution of an actor network, and for this reason we turn to hype cycles to provide a framework for the generalised patterns in a CMS.

2.2. Hype Cycle

The notion of a ‘hype’ is often used to characterise developments in technology, and models of technological hype cycles determine the state of the technology along its diffusion curve [19]. Theorising hype cycles in relation to innovations relates types and levels of expectations about the innovation (as the independent variable) to concrete steps in its development (the dependent variable). Shi and Herniman [20] distinguish between emotional and logical expectations, hypothesising that the former is dominant in the early stages of emerging technology, while later on, expectations based on increased understanding and analysis take over. A major mechanism explaining how expectations relate to the further development of technology is the establishment and maintenance of legitimacy [11]. Positive expectations provide an underpinning for actors investing resources into further development; negative expectations undermine such actions. This mechanism is especially relevant in situations where uncertainty exists in the absence of reliable information about the prospects of a technology and (positive and negative) consequences of its application; then, processes of legitimation provide the basis for action [21].

Our systems of interest (CMSs) display phenomena like hype cycles: distinct periods where (changing) expectations about a material and its applications are articulated. Such expectations relate not only to their potential economic profitability, but also to these materials being ‘solutions’ to existing problems. Expectations can also focus on potential negative consequences of the widespread application of a material. These expectations affect two types of innovations relevant for sustainable innovations: (1) the use of material in a new application that replaces an unsustainable technology, and (2) innovations required to establish complete pathways for recycling. The former is interesting as emerging technologies generate expectations about the future demand for the material. The latter is interesting as the innovation process for the recycling of a material unfolds within an already mature material system. Additionally, whilst some recycling pathways exist, there is scope for innovation as these systems mature and agents and actors go through learning processes as the system develops, both in the technical sphere with enhanced toolboxes of techniques for recycling technology metals [22], but also innovation of the social configuration of those new industries—with, e.g., the location of these industries having a crucial bearing on the sustainability of the system [23]. In addition, in mature systems, we find phenomena that resemble hype cycles related to the contestation of existing uses of the material or its extraction and production (based on emerging and evolving normative considerations about the social cost of mining). We thus seek to build on theorising on hype cycles to better understand these phenomena in critical material systems. In our view, theorising on hype cycles can be usefully extended to better understand dynamics in CMS, and for this we make explicit adjustments in terms of (1) application context, (2) axes, and (3) time duration of the hype cycle.

In terms of application context, the hype cycle is mostly used to map developments in specific technologies. However, it has been argued that it can also be used to investigate higher-level trends and ideas, such as strategies, standards, management concepts, competencies, and capabilities [24]. Specifically focussing on mining, it has been used to describe perceived opportunities for profit that lead to price spikes and subsequent investment in research and prospecting, particularly where mining is related to new technologies that lead to over-optimistic demand forecasts [7,25]. However, this application in the mining context was restricted to demand–supply mismatches and price spikes due to over-optimistic forecast demand. There are also attempts to map specific technologies related to critical metals: lithium-ion batteries (LiBs) in cars and tantalum capacitors in mobile phones wherein the LiBs are placed in the technology trigger stage and tantalum capacitors are placed in the mature stage of development. However, our focus here is not only on the specific technologies but rather the CMS of which a particular technology is part. This allows us to explore socio-technical dynamics and the notion of hype cycles beyond conventional technology case studies and contexts in line with the research agenda outlined by Van Lente et al. [11].

In terms of axes, the conventional Gartner Hype Cycle has been subjected to criticism surrounding its articulation of the y-axis, originally defined as ‘visibility’ and later as ‘expectations’. Despite the definitions provided for these terms in the literature [24], scholars argue that it lacks operational clarity. For our study, we consider legitimacy as the y-axis. As argued by Van Lente et al. [11], the notion of legitimacy is closely linked to the notion of expectations in a hype cycle because expectations guide the activities of innovation by setting agendas, thereby providing ‘legitimacy’ and thus helping to attract financing and enrol actors. We use the widely accepted definition from Suchman [26]: “legitimacy is a generalised perception or assumption that the actions of an entity are desirable, proper, or appropriate within some socially constructed system of norms, values, beliefs, and definitions”. This definition resonates with the notion of responsible mining where mining activities are considered responsible and legitimate when they consider environmental, human rights, and social issues associated with mining and mined products [27]. Thus, it operationalises a key dimension of the sustainable extraction, use, and circulation of such materials.

Lastly, we measure time on the X axis like the classic hype cycle. According to Gartner, a technology passes through the hype cycle within five to eight years [19]. However, Dedehayir and Steinert [28] observe an average hype cycle duration of 21.76 years. In terms of the time duration represented by the hype cycle for CMS, we anticipate it to be much longer given that the time frame for geological exploration is quite long depending on the scale and complexity of the project [29].

2.3. Process Perspective

Drawing from ANT, we can analyse the CMS development through hype cycle stages from a process-oriented lens [30]. This perspective treats reality as a series of events [31], revealing how specific sequences contribute to the CMS hype cycle and its legitimacy. As an epistemological underpinning of our framework, a process perspective allows us to reveal the hype cycle as a series of events, a methodology that has been previously proposed in this context [28]. We build on prior research by Rodl et al. [14] which identifies six event types (see

Table 1. Observable implications of legitimacy based on event types.

Event Types	Observable Implications
Contestation—events where a proposed or realised practice of one actor is challenged by other actors.	Events related to contestation are likely to decrease legitimacy.
Market dynamic—the interplay of demand and supply for finished products and the materials necessary to produce them.	Events related to market dynamics are likely to increase or decrease legitimacy. If supply—demand imbalances are managed responsibly taking ESG into account, then legitimacy increases. If supply—demand imbalances are managed without taking RI and ESG into account, it leads to contestation and reduced legitimacy.
Mass production economics—the process of upscaling the production of products to exploit the cost advantages of large-scale production, leading to a supply push of the materials and products involved.	Events related to mass production are likely to increase or decrease legitimacy. If mass production is undertaken responsibly taking ESG into account, then legitimacy increases. If mass production is undertaken without taking RI and ESG into account, then it leads to contestation and reduced legitimacy.
Rules and standards—defining regulations, rules, and standards, by governments, credentialing associations, and professional bodies.	Events related to rules and standards are likely to increase legitimacy.
Lead time to market—the process necessary between the invention and the actual making available of a product/service to the user.	Events related to lead time to market are likely to increase or decrease legitimacy. Legitimacy increases if the product is successfully made available to the users. Legitimacy decreases if there is failure in making it available to the users.
Guided research and innovation—the process of steering research and innovation in a particular direction.	Events related to guided research and innovation are likely to increase or decrease legitimacy. Legitimacy increases if the steering of research and innovation incorporates RRI practices. Legitimacy is threatened if the steering of research and innovation does not incorporate RRI practices due to contestation.

, first column) that fit with our conceptual framework. Together, these event types constitute the building blocks of hype cycles. These event types also act as a proxy to understand increasing or decreasing legitimacy. To this end, we draw observable implications for each event type through which legitimacy increases or decreases (Table 1, second column). Our framework builds on the assumption that certain events strengthen legitimacy while other events threaten it in the context of a CMS. For example, Warnaars [32] argues that adhering to regulations and securing licenses increases the legitimacy of mining activities undertaken by companies.

3. Data and Methods

Our approach was developed as a part of the UKRI circular economy centre for technology metals: Met4Tech. We draw from three critical metal cases, i.e., lithium, tantalum, and cobalt to answer the research questions, using a qualitative process approach which builds on the systematic exploration of sequences of events and draws inspiration from similar exercises of developing qualitative timelines [13,14]. The choice of lithium, cobalt, and tantalum was driven by its critical importance in sustainable technologies, particularly in electric vehicle batteries, renewable energy storage, and advanced electronics. These metals also present significant ethical, environmental, and geopolitical challenges including resource depletion, human rights concerns, and supply chain vulnerabilities. Furthermore, their market volatility, limited substitutability, and potential for circulation make them highly relevant for our analysis. Our analysis produces a systematic narrative, showing how a sequence of events unfolds to produce a particular outcome [31,33,34]. In this case, the outcome is the legitimacy of a CMS. The initial step in conducting an event sequence analysis involves identifying the central subject [35]. In this study, the central subject is a specific critical metal.

Firstly, the authors conducted formal and informal interviews with experts who were part of the Met4Tech project. The expertise of the interviewed project members in metallurgy and geology spans over two decades and they also had been extensively involved in some key initiatives related to critical metals research in the UK, such as the Faraday Institute, ReLiB, and the Responsible Cobalt Initiative. In addition to tapping into the insights and expertise of the experts through interviews, participating in this project gave us access to expertise gained through longitudinal immersion [36]. Based on this, we generated a first version of an event sequence map which very crudely represented relevant aspects of the historical development for each of the critical metals. This map consisted of events (nodes) and arrows linking these events. Each of these events is represented through a number. These nodes were then laid out in chronological order, and we added annotations to each of these nodes to describe the event in some detail. We also colour-coded the events following the event types outlined earlier in Table 1. This version of the event sequence map was then presented and discussed at an internal Met4Tech project workshop. We received comments and feedback on the event sequence map from the workshop participants which helped us develop the next iteration of the event sequence map.

Following this, we started to develop the next version of event sequence map by filling in with additional events from archival sources, including news archives, academic publications, and website information. We used the database Factiva to uncover such events. The choice of Factiva is driven by our previous experience of working on event sequence analysis [13,14] and the database provides a detailed repository of news items over the years. This exercise also served as a triangulation exercise to counteract potential bias in the information provided by the experts and helped to add more depth to our event sequence maps. The construction of an event sequence thus follows a progressive contextualisation approach [37]. Furthermore, while qualitatively analysing the events, we aggregate events to ensure that we cover most of the important developments; this process is called colligation [31]. For instance, in the case of lithium, the period in the early 1990s has most events that indicate the commercialisation of the lithium-ion battery by different companies such as Sony, Philips, Apple. There are over 250 news items on Factiva that indicate these developments. Given that the final aim is to unpack stages in development of the CMS, these events can be coded together as mass commercialisation of LiBs. Subsequently, a period of massive product recalls followed where such events from multiple players were reported and are then represented as aggregated events.

Lastly, once events are aggregated and linkages between events have been established by qualitatively reviewing all events, an event graph is generated. In this generated event graph, we also qualitatively evaluate events to understand how legitimacy is increasing or decreasing through the different event types. The event graph is a timeline of events pertaining to each critical metal that is also annotated with the major developments and event types so that it provides the researcher a visualisation of how the development of the CMS unfolded over time.

The second stage involves conducting an ideal-type analysis (ITA), a qualitative research method based on Max Weber’s concept of the ideal type [38,39]. ITA involves systematically comparing cases within a qualitative dataset to form ideal types or groupings of similar cases. These ideal types serve as generalisations or mental representations of a social phenomenon, helping us understand and make sense of reality [36]. We use the event graphs generated for three critical metal cases to develop ideal-type stages in the hype cycle of a CMS. This process includes familiarising with the dataset, writing case reconstructions, qualitatively analysing the cases, identifying similarities and differences, and constructing ideal-type descriptions for each stage of the hype cycle [40]. It is acknowledged that researchers do bring their own perspectives and interpretations to the data and different researchers may construct different ideal types [41,42]. The credibility and validity of ideal types are established by grounding them in the data and framework and reflecting on the researchers’ role in shaping the analysis (ibid). The ideal types developed in this study serve a heuristic purpose [43,44,45], providing a framework to understand the socio-technical development of CMSs over time.

4. Results

In this section, we present the results of our study: the event graphs along with brief case reconstructions (Section 4.1) and the ideal-type hype cycle (Section 4.2).

4.1. Event Graphs

We present event graphs to show the socio-technical development of each of the CMSs and provide short case reconstructions to contextualise the event graphs. Along with the historical timeline, we also annotate the event graphs with four phases that we discuss later in Section 4.2.

4.1.1. Lithium

The initial use of lithium was limited to pharmaceuticals such as the treatment of mental health disorders [46,47], as well as in the production of ceramics, glass, and lubricants [47,48,49]. Motivated by the energy crisis, researchers at Exxon produced the first lithium-ion battery (LiB) prototype in the 1970s which had high energy density and rechargeability [50]. However, there was no commercialisation of the LiB until the early 1990s when Sony and Asahi Kasei made progress to commercialise the LiB [51]. LiBs were then used in portable electronic devices such as laptops and mobile phones. In the last two decades, the demand for lithium has skyrocketed with the rise of electric vehicles (EVs) and the need for renewable energy storage. Even though lithium had been discovered and used for a longer period, LiBs were the trigger that led to a ‘hype’ around lithium.

With the rising commercialisation of LiBs, there was a surge in demand which led to a notable increase in global lithium production with countries like Australia, Chile, Argentina, and the USA. A widely distributed lithium trade network was also established with USA, China, European Union, Chile, and Australia playing essential roles [52]. New lithium mines and extraction projects were developed to meet the growing market demand [53]. It is worthwhile to note that along with the widespread use of LiBs, there was contestation due to the massive product recalls by companies due to the explosion of batteries raising safety concerns pertaining to LiBs. This led to some groups looking for alternatives for LiBs [54,55]. However, the increased hype around LiBs continued and further strengthened with their use in EVs. This increased demand leads to an expected demand–supply shortage in the foreseeable future [56]. This in turn feeds additional efforts to explore alternatives to LiBs and alternative lithium sources such as geothermal brines and lithium-rich clay deposits [57,58,59]. The increased usage also led to an emerging problem with spent LiBs. Reusing the lithium in spent LiBs has been considered a key alternative source for lithium to match the supply–demand mismatch [60].

The intensified demand for lithium despite the search for alternatives raises tensions and contestation due to several factors in terms of the impact of primary extraction [61,62], the environmental and social tensions arising in the lithium triangle (Bolivia, Chile, and Argentina) [8,63,64], (NB: Since this research was conducted more contemporaneously, we see an emerging challenge around Ukraine’s lithium reserves, and the Trump administration’s efforts to strong-arm a minerals deal, showing that the issue of contestation continues to be relevant [65]), the rising issue of spent LiBs without adequate governance and infrastructure to manage them, and the likelihood of supply disruption globally. Such contestations and tensions have driven extensive guided innovation to drive efforts focusing on enhancing battery performance, increasing energy density, reducing costs, exploring alternatives, enabling the circular economy, and innovation to develop and evolve recycling techniques and enhance metal recovery [66,67,68,69]. These efforts aim to establish a just supply chain and address safety concerns.

In the recent years, there are stronger efforts in devising rules and regulations around the use of lithium in the form of critical metal strategies and digital passports [70,71,72]. Global initiatives such as the United Nations Framework Classification for Resources (UNFC) provide a standardised framework for classifying and reporting mineral resources and reserves [73]. The WEF’s Global Battery Alliance aims to promote sustainable battery value chains. Such rules and standards increase the legitimacy of the system. Figure 1 visualises the above sequence of events.

4.1.2. Tantalum

Initially, tantalum was primarily used for filaments in incandescent light bulbs and electronic vacuum tubes due to its high melting point and resistance to corrosion [74]. The demand for tantalum increased with the growth of the electronics industry. During World War II and the subsequent Cold War period, tantalum gained strategic importance due to its use in the manufacture of electronic capacitors which were essential for radar and communications equipment [75]. This use in capacitors led to the ‘hype’ of tantalum. Furthermore, tantalum was used extensively in electronics equipment such as Hp calculators [76].

This led to increased demand for coltan, a mineral containing both tantalum and niobium. The demand for coltan surged with the rising use of capacitors in consumer electronics. However, the tin crash impacted the tantalum industry because tin smelters produce significant tantalum bearing slag [77]. This led to exploration of alternative sources of tantalum and substitutes for tantalum. The dotcom bubble also led to further price spikes related to tantalum [25]. By this time, there was a significant portion of tantalum that was secured from Africa, in particular from the Democratic Republic of Congo (DRC) and neighbouring countries. These materials were increasingly associated with conflict minerals, as armed groups in the region exploited mineral resources such as tantalum to finance their activities, leading to human rights abuses and environmental degradation. This led to increased contestation pertaining to tantalum. A report by Amnesty International highlighting the concerns around armed conflict and unethical mineral value chains in DRC further strengthened the contestations [78]. There were other reports and inquiries during this period of contestation such as the UK House of Commons inquiry and a report by UN on MNC looting [79]. These tensions raised awareness about the need for responsible sourcing and ethical supply chains. In response to the conflict minerals issue, various certification programs and regulations were established to promote responsible sourcing and ensure that tantalum and other minerals are extracted and traded ethically.

Initiatives such as the fairphone movement, a social enterprise aiming to produce and promote ethically sourced smartphones with a focus on sustainability and fair labour practices, also started to gain traction from the year 2013, when the first fairphone model was launched. One of the key components in smartphones is tantalum, and fairphone’s approach was to ethically source and responsibly manufacture in the electronics industry, encouraging consumers to consider the social and environmental impacts of their technology purchases. Initiatives such as the Dodd Frank Act in the US and the Responsible Minerals Initiative (formerly the Conflict-Free Sourcing Initiative) have aimed to address the challenges associated with conflict minerals such as tantalum, thereby increasing the legitimacy of the system. These events are visualised in Figure 2.

4.1.3. Cobalt

Cobalt was already in use in the production of superalloys, heat-resistant materials used in aircraft engines and gas turbines [80,81]. However, cobalt gained significant importance only with the advent of LiBs. Cobalt-based cathodes, such as lithium cobalt oxide, played a crucial role in improving the energy density and performance of lithium-ion batteries [82]. These batteries revolutionised portable electronics, leading to the development of smaller and more powerful devices. The growing demand for electric vehicles (EVs) and renewable energy storage systems further propelled the importance of cobalt [83]. [We do not repeat the reconstruction related to LiBs as it was highlighted in the lithium case reconstruction].

The increasing demand for cobalt has raised concerns about ethical sourcing and sustainability. A significant portion of global cobalt production comes from the DRC, where concerns over labour rights, child labour, and human rights abuses have been raised which led to tensions and contestations related to cobalt. This led to regulations such as the responsible cobalt initiative to ensure responsible sourcing, traceability, and transparency in the cobalt supply chain [84,85]. Research is ongoing to reduce the cobalt content in lithium-ion batteries or develop alternative cathode chemistries that use less or no cobalt [86,87]. This research aims to address concerns about cobalt’s scarcity, cost, and potential environmental and social impacts. Scientists are exploring substitutes which may reduce cobalt dependency in the future [88,89]. Figure 3 summarizes the relevant sequence of events.

4.2. Ideal-Type Hype Cycle for a CMS

In this section, we present the ideal-type hype cycle which maps the socio-technical development of a CMS over time. We present four stages with different event types through these stages. Event types are a proxy to understand the evolving legitimacy in these stages (summarised earlier in Table 1). It is important to note that we see each of the critical metals undergoing similar stages and undergoing a complete hype cycle with similar time scales. The reason for this is that each of these metals is part of a bigger socio-technical development around the extraction, use, and circulation of critical metals which we discussed earlier in the introduction. In the following sub-sections, we describe each of the stages based on the case reconstructions.

4.2.1. Knowledge Development Followed by an Innovation Trigger and Commercial Availability

The initial phase is characterised by knowledge development followed by a trigger originating from a specific technology. When a metal is utilised in a technological breakthrough, it generates a growing fascination and attention towards that metal. If the technology is successfully made available to users, then a legitimate system is created and more actants such as technologies, companies, researchers, mines, reports and products start assembling around the metal. The legitimacy of the system strengthens if the new technology leads to new applications such that it offers superior performance that meets the needs of the market over the incumbent technology. However, there are also possibilities where there is high uncertainty regarding the commercial availability of the technology due to lack of infrastructure or support that is required [46], or the technology fails to perform in a way that it offers superior performance than the incumbent technology, and it does not become commercially available. This threatens the legitimacy of the system [90]. In the three case studies discussed earlier, the adoption of lithium and cobalt in rechargeable batteries and tantalum in capacitors sparked a surge in interest for these metals. With this trigger followed commercial availability and a legitimate system started to form.

Also important to acknowledge is that during this stage, the metal may not necessarily be considered critical as its criticality relates to conditions that are not yet present. Criticality is driven by three aspects: (1) the economic importance of the metals, (2) the potential supply risk of the metals, and (3) the technological importance of the metals wherein they are essential for specific technologies or products [91]; during this stage, these aspects are not yet present.

4.2.2. Mass Production and Managing Supply–Demand Imbalances

Once the technology becomes commercially available, it starts to establish a foothold in the market. It is then adopted by the majority, not just innovators and early adopters, so more actants start to assemble into the CMS. While mass production allows us to reap the benefits of economies of scale and establishes a legitimate system [92], it also reinforces supply–demand imbalances. This supply–demand mismatch is often due to the long lead time in mine development and mid-stream processing capacity for metals [93]. The foreseeable shortage of critical metals drives the exploration of alternative metals or technologies that can match the performance benefits offered by the technology, but with lesser reliance on the metal in focus. The increasing demand also spurs demand for increased mining of virgin metals and (experimentation with) the circulation of secondary metals. There is guided research and innovation in this stage when research, development, and funding is directed towards addressing the supply–demand imbalances through alternative metals or technologies. While this guided research and innovation legitimises the CMS further, it can also lead to contestation and unintended consequences if responsible research and innovation practices are not taken into consideration. As supply–demand imbalances also affect the price of the metal, the incentive to conserve the metal and use it more efficiently also increases at this stage. It is during this stage that the criticality of the metal is also established as the potential supply risk as well as the economic and technological importance of the metal comes to the forefront.

During this stage, the legitimacy of the CMS strengthens if mass production and supply–demand imbalances are addressed responsibly with thorough Environment, Social, and Governance (ESG) scrutiny [94]. However, there are also instances where the need to manage supply–demand imbalances leads to overlooking ESG issues, in turn triggering contestation within the CMS. Thus, mass production and managing supply–demand imbalances when carried out responsibly can increase the legitimacy of the system; overlooking ESG issues and not considering RI can threaten legitimacy in the CMS. However, it is also important to acknowledge that certain unintended consequences transpire only after mass production and are almost inevitable which leads to contestation and threats to legitimacy.

In our case studies, mass production of LiBs and capacitors and its increasing importance led to increasing the legitimacy of the CMSs. However, we also observed instances of contestation, for instance in the case of LiBs where safety issues associated with LiBs led to numerous product recalls. However, overall actants constituting the lithium CMS continued to produce a win-win narrative [95]. Thus, contestation only emerged in silos while the overall CMS continued to gain legitimacy.

4.2.3. Increasing Contestation

In this stage, there is increasing contestation that follows from the activities of the previous stages that can threaten the legitimacy of the system. While there could be an instance where contestation starts to emerge in the previous stage, it is mostly in silos without receiving much traction within the CMS. From our analysis of the event database, we find various causes that lead to unintended consequences and contestation related to critical metals and their uses.

First, there is the environmental and social impact of primary extraction of a metal. Due to the events in the previous stages, the use of the metals and its impacts become more visible and there is a need to reduce shortages. This increases the chance that extraction and processing will take place without ESG scrutiny. For instance, there have been reports of unethical practices, including child labour, unsafe working conditions, and human rights abuses in DRC [79] and the lithium triangle [8] to match the increasing demand from primary mining. Secondly, there is inadequate responsibility and traceability given; there have been concerns about the presence of conflict minerals sourced from regions associated with armed conflict and human rights abuses [78]. Thirdly, resource inequality and geopolitical issues also lead to further unintended consequences and contestation. The geographical concentration of these resources in a few countries can create resource inequality and geopolitical tensions. This concentration of resources can lead to economic disparities, power struggles, and geopolitical instability. Lastly, an emerging area of contestation is the proper disposal and circulation of lithium, cobalt, and tantalum products, which poses significant challenges. Such factors also emerge from a mature system rather than in the earlier stages because mass production and consumption of the technology has been achieved, leading to further contestation.

4.2.4. Reconfiguration of Rules and Standards

As market failures to deliver solutions become clearer, at least in part due to contestation, this attracts the attention of law and standards makers who seek to address perceived flaws in the operation of the CMS. If successful, these restore legitimacy. It is important to note that the landscape for rules and standards could vary by jurisdiction and geographies wherein some countries could have their own national laws or initiatives. The emergence of these laws is driven by concerns such as environmental impact, labour rights, human rights abuses, transparency in supply chains, and the responsible extraction and use of these metals. The aim is to address the challenges associated with their production, promote sustainable practices, and prevent negative social, environmental, and economic impacts. Figure 4 visualises the ideal-type hype cycle.

5. Discussion

In this paper, we argue that it is important to understand the way in which legitimate CMSs evolve, to underpin efforts to develop more sustainable energy and mobility provision that requires such materials. In addition to providing insight into the legitimacy of a CMS, the approach taken here shows how the criticality of the metal is established over time, the factors that influence contestation within the system, how this contestation is addressed, and legitimacy is reinstated. The ideal-type hype cycle for CMSs we presented can be considered as a heuristic device to understand the generic development of a CMS. The ideal-type hype cycle maps the evolving legitimacy of a CMS and how events in the different stages either establish, threaten, or reinstate legitimacy.

Addressing the research question posed earlier, i.e., what generalisable patterns are observed in the development of a CMS with a particular focus on legitimacy, we outline four stages in the hype cycle for CMS, i.e., new knowledge development followed by an innovation trigger, mass production, and managing supply–demand imbalances, increasing contestation, and reconfiguration through rules and standards discussed in detail in Section 4.2. The hype cycle stages are divergent from the classic hype cycle stages that only map technologies. Also, as argued by van Lente et al. [11], this difference can be explained by the difference in the context of the hype cycle. Specifically, when examining the hype cycle for the CMS, we identify a crucial stage of mass production wherein demand–supply imbalances occur. During this phase, the economics of mass production significantly impact the availability, pricing, and accessibility of critical metals. Our argument advocates for a broader focus beyond individual technologies (such as lithium-ion batteries) to encompass the CMS for lithium, necessitating the inclusion of mass production economics in our analysis. It is evident that the three metals have followed similar stages in their socio-technical development. This similarity can be attributed to the larger dynamics related to extraction, use, and circulation of critical metals which was discussed earlier in the introduction.

To improve sustainability, we connect our analysis to responsible innovation (RI). This academic discourse and field of praxis is explicitly geared to transform innovation practices to be more anticipatory, reflexive, inclusive, and responsive [96]. When looking at the different types of events that constitute our ideal-type hype cycle, we note that only a few seem to have an unambiguous impact on legitimacy. Events related to rules and standards are likely to always establish the legitimacy of a system [97] while events related to contestation threaten legitimacy [21]. In critical metals and similar systems like chemicals that are highly scrutinised, rules and standards are crucial in ensuring that a legitimate system is created [98,99], and contestation is minimised.

However, other event types can either enhance or reduce legitimacy. For the events’ lead time to market and mass production economics, our cases display a lack of consideration of environmental assessments. Materials and products that we now associate with environmental problems were initially often introduced as solutions to other problems [14]. For example, LiBs emerged as a solution to the energy crisis in the 1970s and now we are tackling the issue of spent LiBs after the mass commercialisation. During the mass production stage, the safety issues were overlooked which led to the product recalls. Moreover, the increasing amount of lithium and cobalt waste safety challenges and concerns about materials availability and the impacts of extraction were not taken into consideration before the mass commercialisation. Identifying such potential negative effects of widespread diffusion of an innovation is a key objective of RI. This enables a systems-based approach that considers the impact of the solution on other parts of the system. This will not completely prevent negative impacts from occurring, as CRMs link into other complex systems in ways that can generate long-term consequences [100]. But as Remme and Jackson [95] argue, unintended consequences often go unnoticed and unanticipated in the win-win discourse that is produced by actors. The authors build on the EV case and argue that vested interests of actors lead to strategically filtering and forgetting crucial information which is a result of a cognitive defence mechanism rather than conspiracy. The crucial aspect to consider here is that even though unintended consequences may be inevitable, it is important to anticipate them and develop mitigation strategies because unanticipated unintended consequences pose even higher risks [101].

A further consideration stresses the relevance of responsible innovation for CRMs. The criticality of materials is a reason why, when their extraction, use, or circulation is contested, a succession of hype cycles may emerge (see Figure 5). For instance, if tantalum capacitors are replaced by ceramic capacitors, then potentially palladium, silver, nickel, copper, or platinum are required, increasing their criticality. Likewise, when cobalt is to be substituted from battery chemistry formulations, this will require nickel, another critical metal. If we move to battery technologies using cheaper, less critical (and thus fewer valuable materials), there is a diminishing economic incentive to recycle them at the end of life. Thus, there are unintended consequences that could emerge due to the domino effects from substituting critical metals. We argue that this phenomenon is still poorly understood and requires further attention.

6. Conclusions: Sustainable Evolution of CRMs: The Potential of Responsible Innovation

In this section, we present our conclusion specifically reflecting on the second part of our research question, specifying what our comparative analysis of three evolving CRMs, specifically lithium, tantalum, and cobalt, teaches us about the transition to more sustainable systems of energy and mobility. As CRMs are essential material feedstocks for such systems, the sustainable extraction, use, and circulation of such materials is required to make energy and mobility provision more sustainable.

We argue that criticality is not an inherent property but instead a temporally established condition that emerges as a result of the scale-up of production of materials; as the socio-technical system evolves to find applications, so follows the manifestation of economic, supply, and technological dependencies. Contestation is driven by environmental and social externalities, ethical concerns, and global geopolitical movements which act on the established system as a potentially destabilising force which challenges the legitimacy of the existing configuration.

By contrast, regulatory interventions and attempts at standardisation and codification of norms serve to restore legitimacy by addressing systemic and market failures. Responsible innovation (RI) principles are posited as being central to anticipatory mitigation of potentially unintended consequences in order to promote sustainability in CMS development.

Furthermore, a heuristic tool is proposed in the form of the “ideal-type hype cycle” for anticipating and steering the development of emerging critical technology metals. It is anticipated that this can be used to facilitate proactive governance to minimise the many potential negative externalities that can arise through CMS development. In terms of future research, it will be useful to consider this ideal-type hype cycle as a heuristic device and check its conformance in the case metals on the ‘watch list’ or nearing criticality. An early assessment of patterns which these metals could exhibit can enable the avoidance of unintended consequences and provide the possibility of anticipatory governance.