New-Generation Batteries Technologies

New-Generation Batteries Technologies: History

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Subjects: Engineering, Electrical & Electronic

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Battery technologies have recently undergone significant advancements in design and manufacturing to meet the performance requirements of a wide range of applications, including electromobility and stationary domains. For e-mobility, batteries are essential components in various types of electric vehicles (EVs), including battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and fuel cell electric vehicles (FCEVs). These EVs rely on diverse charging systems, including conventional charging, fast-charging, and vehicle-to-everything (V2X) systems. In stationary applications, batteries are increasingly being employed for the electrical management of micro/smart grids as transient buffer energy storage. Batteries are commonly used in conjunction with power electronic interfaces to adapt to the specific requirements of various applications. Furthermore, power electronic interfaces to batteries themselves have evolved technologically, resulting in more efficient, thermally efficient, compact, and robust power converter architectures.

battery roadmap
e-mobility
energy storage
lithium batteries

1. Introduction

There is no doubt that the next ten or twenty years will experience a transformation concerning energy storage system technology, especially for batteries and power electronics converters. It concerns not only the manufacturing and commercialization of batteries but also encompasses a supply chain driven by a strong decision of countries or continents to be part of this solid transformation. The electrification of transportation is an undeniable reality. Automotive manufacturers, battery OEMs (Original Equipment Manufacturers), research laboratories, and governmental institutions must adapt according to the new obligations powered by a fast-changing climate, energy and raw materials independence strategies, environmental and health considerations, a substantial presence in the expanding electromobility market, and applied research.

The Paris Agreement [1] seeks to reduce greenhouse gas emissions by encouraging the transition of energy systems within the industrial and transportation sectors. Meanwhile, the European Green Deal [2] is working towards achieving a reduction in net greenhouse gas emissions by at least 55% by 2030, compared to 1990 levels. In its pursuit of decarbonizing the transportation sector, the European Union (EU) has set the ambitious goal of achieving full decarbonization of its economy and attaining climate neutrality by 2050. To accelerate progress in the battery sector, the European Commission established the European Battery Alliance (EBA) in 2017 and adopted the Strategic Action Plan on Batteries in 2018 [3]. The EU funding programs Horizon Europe and Important Projects of Common European Interest (IPCEI) represent key instruments in this regard. Operating under the umbrella of the European Battery Alliance, their aims are to promote research and innovation, stimulate investment, and foster partnerships among industrial, governmental, and educational institutions. The ultimate objective is to establish cost-effective and environmentally friendly gigafactories on European soil. Similarly, the United Kingdom plans to stop the sale of internal combustion engine vehicles by the end of 2030 [4]. The United States addressed the climate crisis by building a clean and equitable energy economy. Their strategy aims to achieve carbon-pollution-free electricity by 2035 and to reach net-zero emissions no later than 2050 [5]. The investments in energy transition spiked to attain 297 billion dollars in China in 2021, compared to 120 billion dollars spent by the United States [6].

In order to have a share in this important market, stakeholders should secure access to raw and refined materials, discover alternatives for critical materials, and integrate recycled material as part of the circular economy [7].

2. New Generation Batteries

2.1. Components of a Lithium Battery

2.1.1. Positive Electrode (Cathode)

The ionic conductivity of cathode material is determined by the mobility of the lithium ions, which is in turn defined by the material’s structure. Cobalt enhances the chemical and thermal stability of lithium-ion batteries (LIBs). Nickel improves the energy density of the battery and has the advantages of low cost and good conductivity. Manganese is a more affordable alternative to cobalt and nickel for use in LIBs.

The first commercially available electrodes were LiMn₂O₄ (LMO) and LiCoO₂ (LCO). The LiMn₂O₄ material, which has a lattice structure known as a spinel, allows for three-dimensional conductivity for lithium cations. While it offers a good capacity and an affordable cost, it still needs improvement in terms of stability in common electrolyte solutions. LiCoO₂ is a layered trigonal crystalline oxide offering two-dimensional mobility. It is known for its high specific capacity, thermal instability, and cost.

A cathode made from a combination of nickel, LMO, and LCO, called LiNiMnCoO₂ (NMC), has a longer lifespan and higher energy density. The specific ratio of Ni, Mn, and Co in the mixture determines the properties of the cathode.

There are two main categories of LIBs based on the type of cathode used. The first category includes Lithium-Nickel-Cobalt-Aluminum oxide (LiNiCoAlO₂—NCA) and Nickel-Manganese-Cobalt (NMC) batteries, which are widely used in the electric vehicle (EV) industry due to their high voltage and high specific energy. Nickel offers high energy density, but it lowers battery stability. Additionally, while manganese can lower internal resistance and improve specific power, it has lower specific energy. Cobalt is a toxic material that is relatively expensive, and its supply chains pose a significant risk due to the political instability in the major region where it is sourced [41].

Three types of battery are commercially available in the NMC-class battery compositions: NMC111, NMC622, and NMC811. These designations are indicative of the proportion of Ni, Co, and Mn on a mole fraction basis. The NMC622 batteries, which are high in nickel content, are gradually replacing NMC111 batteries in EV applications. NMC811 batteries have already been produced and safety concerns are on the rise [47,48]. This does not prevent that LiNi_0.9Mn_0.05Co_0.05O₂ (NMC955 or NMC9 ½ ½) batteries, containing less cobalt, are currently in research process [49]. NMC9 ½ ½ is a Ni-rich cathode material having a higher energy density and a limiting cobalt content. However, Ni-rich metal oxides suffer from electrochemical cycling challenging, including substantial capacity fade, severe voltage decay, and higher safety concerns.

The second category is Lithium-Iron-Phosphate (LFP—LiFePO₄) batteries, which are popular in the Chinese market and are known for their cobalt-free composition, high cycle life, and low fire risk [50]. The olivine lattice structure of LFP permits linear ion movement in one dimension. However, they offer lower voltage and capacity compared to NCA and NMC batteries. In recent years, NMC batteries have gained more market share and research attention compared to LFP batteries. The prices of raw materials and the availability of mined reserves could also impact the choice of the next generation of battery chemistry.

2.1.2. Negative Electrode (Anode)

Graphite, having a capacity of 372 mAh/g, is a popular choice for anodes due to its abundance, good electrochemical stability, safety, and low expansion volume during charge and discharge. One way to increase the overall energy density is to include small amounts of metals with high theoretical energy densities, such as silicon (4200 mAh/g). Carbon-coated graphite and graphite-silicon anodes are often considered to be better alternatives because they experience less degradation and can hold more lithium ions. Silicon is considered a potential alternative to graphite as an anode material in lithium-ion batteries. It is considered a safe and reliable option with a sufficient energy density for use in electric vehicles. Despite this, silicon anodes have some downsides, including a volume expansion of up to 300 percent during charge and discharge, which can cause unstable solid electrolyte interphase (SEI) formation, low electrical conductivity, and mechanical grinding of graphite caused by the Si expansion/contraction. To address these issues, researchers are exploring the use of nano-silicon in a composite structure with graphite [53].

Lithium-Titanium oxide anodes (Li₄Ti₅O₁₂—175 mAh/g) have the longest cycle life and are used with lithium iron phosphate (LFP) cells [54] and NMC cells [55]. The anode material has an operating voltage of 1.55 V relative to lithium. The formation of lithium plating and a conventional solid electrolyte interphase are not considered problematic. Researchers are exploring alternatives to lithium titanate oxide (LTO), such as niobium titanium oxide (NTO) [56], as potential anode materials. It is expected that replacing anodes with thin lithium metal foils will significantly increase energy density, as long as they can be safely incorporated and stabilized in the system.

2.1.3. Electrolytes

The dissolution of a lithium salt, like lithium hexaflurophosphate (LiPF6) in an organic carbonate, such as ethylene carbonate (EC), dimethyl carbonate (DMC), or diethyl carbonate (DEC), constitutes the electrolyte liquid solution [57]. Fluororalkylphosphates promise advantages for 5 V batteries [58].

Additives could be used for liquid electrolytes to enhance safety, minimize the loss of capacity at the first charge-discharge, avoid oxidation, and prevent gases evolution by electrolysis. To achieve higher voltage cathodes, electrolyte additives will also play the role of stabilizing agents, retarding the thermal decomposition of LiPF6 salt.

In order to decrease the amount of liquid electrolyte, gel/polymer electrolytes (such as LiN(CF₃SO₂)₂/LiTFSI) may be potential solutions while focusing on increasing ionic conductivity. In the long term, the goal is to use solid-state electrolytes once they have demonstrated sufficient ionic conductivity and a high level of manufacturability expertise.

There are two main types of solid electrolytes. Inorganic electrolytes are composed of ceramic crystalline materials such as LISICON, NASICON, perovskites, and polymer organic electrolytes [59]. Inorganic electrolytes have high ionic conductivity but present interfacial compatibility limitations. On the other hand, polymer electrolytes have good mechanical and thermal stability, but have lower ionic conductivity.

In terms of safety improvement, enhancing performance and thermal and electrochemical stability even for conventional organic solvent electrolytes is essential.

2.1.4. Separator

The separator, about 25 mm in thickness, consists of a porous membrane wetted with an organic electrolyte solution. Polymers such as polyethylene, polypropylene, or polyvinylidene fluoride (PVDF) are employed [60]. The properties include good permeability, high mechanical resistance, suitable porosity, electrolyte wettability, and good thermal and electrochemical stability. Ceramic coatings [61] are being used more frequently to provide robustness and mechanical strength, preventing short-circuits caused by mechanical damage or dendrite formation.

2.1.5. Current Collectors

Researchers are continuing to work on improving the thickness, hardness, and composition of current collectors to increase their mechanical strength, electrochemical stability, and adhesion with the electrode coating [62].

2.1.6. Anode and Cathode Coatings

In addition to the significant volume expansion during cycling, the observation of low electrical conductivity and the formation of a highly resistive solid electrolyte interphase (SEI) layer are common. In [63], the authors introduce silicon material design approaches and innovative synthesis methods aimed at enhancing the Si anodes properties through improved structural designs.

These volume changes lead to permanent cracking and the separation of the active material from the current collector. In [64], the authors focus on silicon anodes development, emphasizing surface chemistry and the structural integrity of the electrode. They have reported effective strategies for optimizing these anodes.

Combining silicon and silicon oxides offers a solution to tackle these challenges. Silicon monoxides (SiO) and silicon dioxides (SiO₂) can be used as coating material on the silicon-based anode electrodes. This helps stabilize the anode by reducing volume expansion during lithiation, and minimizing contraction that occurs during charge and discharge cycles, thus preventing structural degradation. This, in turn, can improve the overall performance, capacity, and cycle life of lithium-ion batteries [65]. Coating the anode with these materials helps also to prevent direct contact between the electrolyte and the silicon in the anode.

Chemical and physical characteristics of the cathode influence the performance of the battery. Interactions between cathodes and the electrolyte lead to surface modifications, resulting in degradation. These side-reactions contribute to a decline in battery performance, ultimately diminishing both battery lifespan and power capacity. In [68], the authors conduct an extensive review of advancements in the coating of NMC batteries, exploring multi-functionalities and mechanisms aimed at enhancing their electrochemical properties and overall performance.

Surface coating of the cathode active material with a thin layer of a protective material enhances the thermal and chemical stability of the cathode, reducing the risk of thermal runaway or detrimental surface reactions with the electrolyte.

2.2. Before the Lithium

Different classifications could exist for battery technologies such as the following:

lead-acid based: affordable, safe, and sustainable;
lithium-based: high energy density, low weight;
nickel-based: long life, reliable (NiMH, NiCd);
sodium-based: relative low cost; and
flow batteries [73].

Before lithium batteries, lead–acid batteries were the first to be invented in 1859. Lead-acid batteries still have their place in the starting, lighting, and ignition of vehicles. Gravimetric and volumetric energy are both relatively low and could attain 40 Wh/kg and 90 Wh/L.

The nickel–zinc battery (Ni-Zn) was the second invented, introduced in 1901. However, its relatively short cycle life paved the way for the nickel-metal hydride battery (Ni-MH) to emerge as a dominant choice, becoming the first battery to provide Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) with gravimetric and volumetric energy densities ranging from 80 to 120 Wh/kg and 140 to 200 Wh/L, respectively.

2.3. The Lithium-Ion Battery

Furthermore, the low maintenance, the lack of memory effect, the relatively long cycle life, and the low self-discharge paved the way for Li-ion to be used in electric powertrains [38]. On the other hand, the LIB suffers from cyclic and calendar aging, SEI layer formation, lithium plating, electrolyte degradation, side reaction products, and current collector corrosion. This is the main reason that Li-Ion batteries are always incorporated with a battery management system, ensuring a high degree of protection.

Current trends in battery technology involve the utilization of electrodes with higher capacities, such as sulfur (1675 mAh/g [79]), silicon (4200 mAh/g [80]), and lithium metal (3863 mA/g [81]), as well as the increase in single-cell voltage. These developments collectively enhance the overall energy density of the battery, consequently extending the vehicle’s range.

Li-ion battery manufacturing will, by far, dominate the market through 2030 and could potentially achieve a production capacity of 6 500 GWh [82]. For an LIB, the work on positive electrodes (NMC, NCA, LFP) is focused on increasing energy density and the batteries’ safety while reducing the cobalt content. Higher-capacity cathodes lead to higher-capacity anode utilization (graphite/silicon). From the negative electrodes’ point of view, work is much related to safety (fast charging at lower temperature preventing dendrites formation). In order to increase the performance and safety of the battery, flammable electrolytes are replaced by gel/polymer, or solid-state electrolytes.

As mentioned, the LIB has an average density of 300 Wh·kg⁻¹ [83]; a fully operational 500 Wh·kg⁻¹ battery should be ready by 2025 [84]. Thus, it will have major consequences for reducing the car weight, the raw materials quantities during manufacturing, and expanding drive range. A recent issue has emerged in the UK, as highlighted by the British Parking Association, regarding the weight of electric vehicles parked in multi-story and underground car parks.

2.4. Current and Future Promising Technologies

2.4.1. Generation 3

A roadmap for 2030 primarily focuses on lithium-based technologies that use modified nickel cobalt manganese oxide (NMC) materials. The optimized NMC811 has a higher nickel content and a lower cobalt content, in combination with carbon/silicon composite materials that have a high capacitive anode.

To enhance energy density, the primary approach is to elevate the cell’s voltage to 5 V by incorporating high-voltage electrode materials (as current materials typically reach 4.2 V), such as the 3D oxide-structured 5 V spinel. However, achieving a stable electrolyte for sustained cycling poses a significant challenge. An alternative is to increase the storage capacity of the battery in terms of weight or volume, which can be achieved by increasing the faradic capacity of the electrodes (mAh/g).

Despite ongoing research into lithium-metal batteries (particularly solid-state batteries) and post-lithium technologies, it is evident that lithium-metal batteries (LMBs), particularly solid-state batteries (SSBs), represent a highly promising technology capable of significantly enhancing energy density.

Lithium-sulfur batteries (lower environmental impact, better depth of discharge) and sodium-ion batteries are serious alternatives to lithium-ion batteries. Metal-air batteries (such as lithium-air batteries) promise theoretically specific energy comparable to gasoline. Thus, some technological challenges are yet to be overcome, such as insufficient cycle life.

2.4.2. Generation 4

Liquid electrolytes of LIBs consist of a lithium salt dissolved in a combination of several organic solvents. This configuration may induce serious safety hazards due to the electrolyte’s toxicity, leakage, and flammability [90]. The advantages of solid-state batteries in comparison to liquid electrolyte cells are quite numerous. We could enumerate higher energy density, enhanced safety, absence of liquid electrolyte, lower manufacturing cost, and excellent shelf life. The passage from a Si/C anode (Gen. 4a) to a lithium metal anode (Gen. 4b and 4c) could improve the specific energy from 400+ Wh/kg, 800+ Wh/L to 500+ Wh/kg, 1000+ Wh/L [91]. Perpetual efforts to replace these types of electrolytes with solid-state batteries are facing challenges such as power limitation due to poor ionic conductivity, high interfacial resistance, poor interface contacts, chemical instabilities at interfaces, and surely the need to update manufacturing processes.

Li-metal technology combines lithium metal with the negative electrode, insertion materials with the positive electrode, and a solid electrolyte (such as extruded polyethylene oxide, PEO, [92]). The primary advantage of lithium metal lies in its higher energy density compared to the graphite used in lithium-ion batteries, with 3860 mAh/g vs. 372 mAh/g, respectively.

However, these batteries have a limited operating temperature in order to assure sufficient ionic conductivity. The PEO electrolyte may be unstable at voltages higher than 4 V, which restricts its use to lithium iron phosphate (LFP) cathodes. When combined with a graphite anode, the LFMP (lithium-iron-manganese-phosphate) battery cell can be charged up to 4.25 V. This allows for high power capability while also enhancing thermal stability and safety. Additionally, the LFMP battery exhibits excellent cyclability and storage performance [93,94].

The French manufacturer Blue Solutions, a subsidiary of the Bolloré Group, utilizes lithium-metal-polymer (LMP) technology, which employs a dry polymer electrolyte and a negative lithium electrode. This battery functions effectively at temperatures exceeding 60 °C, requiring battery heating during extended stops. Due to these characteristics, Blue Solutions promotes this technology for buses and stationary storage applications, which are better suited to managing thermal considerations.

Several solutions were proposed by using additives to improve the solid electrolyte interphase (e.g., vinylene carbonate, and methyl cinnamate) [96], or some flame-retardant additives (e.g., trifluoropropylene carbonate, hexamethoxycyclotriphosphazene, trimethyl phosphate, triethyl phosphate) [97].

2.4.3. Generation 5

a. Metal-Air Battery

The metal-air battery utilizes the electrochemical principle that involves a metal negative electrode (Zn, Al, Li, Mg, Ca, etc.) and an oxygen-reducing cathode made of mesoporous carbon. Metal-air batteries have a high amount of energy stored in relation to their weight. Besides the lithium-air type, with a nominal voltage of 2.91 V, the metal-air batteries could include zinc-air, aluminum-air, magnesium-air, and calcium-air. While lithium-air batteries have a specific energy of 13.2 kW/kg (similar to gasoline), aluminum-air batteries tend to have a more stable performance.

b.: Lithium Sulfur Battery

Lithium-sulfur batteries (LiSBs) use lithium metal as an anode, sulfur composite as a cathode, and organic liquid as an electrolyte. They exhibit high theoretical gravimetric capacity (1675 mAh·g⁻¹) and high theoretical specific energy (2600 Wh·kg⁻¹) [102,103]. Furthermore, the low cost, high abundance of sulfur, and absence of critical materials make LiS batteries a promising option for future energy storage applications. This type of battery has less environmental impact, as well as sulfur may be sourced from recycled materials. The nominal voltage of an LiSB cell is 2.1 V. The battery has the potential to have a deeper depth of discharge than the LIB, with the LiSB reaching 100% compared to LIB’s 80%.

c.: Batteries beyond Lithium

The goal is to eventually replace lithium battery technologies with more affordable and sustainable light metals such as sodium. However, the significant challenge is developing durable and stable electrodes with high energy density and fast charge/discharge rates.

Among various chemistries (sodium, magnesium, zinc based), the sodium-ion battery (SIB) [110] has gained attention due to its low cost, the abundance of sodium on earth, and its similar chemistry to LIBs. However, it has a lower energy density of 90 Wh·kg⁻¹ [111]. The Chinese manufacturer CATL aims to reach 200 Wh·kg⁻¹ [112].

The operating principle of sodium-ion batteries (NIBs) is similar to that of Li-ion batteries. Sodium resources are inexpensive and widespread; it is considered the 4th most prevalent element on the planet. NIBs suffer from a fast decrease in capacity and a lower cycle life (relatively to LiBs) due to the difficult insertion of sodium ions into the anode and cathode [113].

d.: Solid-State Li-Ion Micro-Batteries

While the market for micro-batteries [115] may be comparatively smaller than that dedicated to electromobility and stationary power-grid applications, the importance of lithium-ion micro-battery technology span a vast array of applications. Anticipated growth forecasts indicate an ascent from a 2023 valuation of 0.5 billion USD to reach 1.3 billion USD by the year 2028 [116].

Multiple sectors are engaged, encompassing healthcare devices, environmental monitoring, wearable personal electronics, IoT (Internet of Things) with smart and connected miniaturized sensors [117], as well as microelectronics (in smart packaging, smart cards, etc.), and radiofrequency identification systems, thus requiring high flexibility and ultra-thin design. Another sector also emerges, which falls within the domain of micro-drones and/or micro-robots known as insectoids [118].

This entry is adapted from the peer-reviewed paper 10.3390/en16227530

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