Solid-state battery

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A solid-state battery is an

Solid-state battery

All-solid-state battery with a solid electrolyte between two electrodes
Specific energy	Thin film type300–900 Wh/kg (490–1,470 kJ/lb) bulk type 250–500 Wh/kg (410–820 kJ/lb)
Self-discharge rate	6%ｰ85 °C (month) cycles V, [3] Thin film type 4.6 V [4]
Operating temperature interval	-50 °C 〜 125 °C
Charge temperature interval	-20 °C 〜 105 °C

While solid electrolytes were first discovered in the 19th century, several issues prevented widespread application. Developments in the late 20th and early 21st century generated renewed interest in the technology, especially in the context of electric vehicles.

Solid-state batteries can use metallic lithium for the anode and oxides or sulfides for the cathode, increasing energy density. The solid electrolyte acts as an ideal separator that allows only lithium ions to pass through. For that reason, solid-state batteries can potentially solve many problems of currently used liquid electrolyte Li-ion batteries, such as flammability, limited voltage, unstable solid-electrolyte interface formation, poor cycling performance, and strength.^[5]

Materials proposed for use as electrolytes include

In 2011, Kamaya et al. demonstrated the first solid-electrolyte, Li₁₀GeP₂S₁₂ (LGPS), capable of achieving a bulk ionic conductivity in excess of liquid electrolyte counterparts at room temperature.[17] With this, bulk solid-ion conductors could finally compete technologically with Li-ion counterparts.

Researchers and companies in the transportation industry revitalized interest in solid-state battery technologies. In 2011,

In 2012, Toyota began conducting research into automotive applications.^[18] At the same time, Volkswagen began partnering with small technology companies specializing in the technology.

In 2013, researchers at the University of Colorado Boulder announced the development of a solid-state lithium battery, with a solid iron–sulfur composite cathode that promised higher energy.^[19]

In 2017,

Qing Tao started the first Chinese production line of solid-state batteries in 2018, with the intention of supplying SSBs for "special equipment and high-end digital products".[30]

2020-

QuantumScape is a solid-state battery startup that spun out of Stanford University. It went public on the NYSE on November 29, 2020, as part of a SPAC merger with Kensington Capital.^[31][32] In 2022 the company introduced its 24-layer A0 prototype cells. In Q1 2023, it introduced QSE-5, a 5 amp-hour lithium metal cell. Volkswagen's PowerCo stated that the A0 prototype had met the announced performance metrics. QuantumScape's FlexFrame design combines prismatic and pouch cell designs to accommodate the expansion and contraction of its cells during cycling.^[33][34]

In July 2021, Murata Manufacturing announced that it would begin mass production, targeting manufacturers of earphones and other wearables.^[35] Cell capacity is up to 25mAh at 3.8V,^[36] making it suitable for small mobile devices such as earbuds, but not for electric vehicles. Lithium-ion cells used in electric vehicles typically offer 2,000 to 5,000 mAh at a similar voltage:^[37] an EV would need at least 100 times as many of the Murata cells to provide equivalent power.

Ford Motor Company and BMW funded the startup Solid Power with $130 million, and as of 2022 the company had raised $540 million.^[38]

In September 2021, Toyota announced their plan to use a solid-state battery, starting with hybrid models in 2025.^[39]

In February 2021, Hitachi Zosen announced demonstration experiments on the International Space Station. The Cygnus No. 17, launched on February 19, 2022, confirmed that all-solid-state batteries would be tested on the ISS.^[40]

In January 2022, ProLogium signed a technical cooperation agreement with Mercedes-Benz. The investment will be used for solid-state battery development and production preparation.^[41]

In early 2022, Swiss Clean Battery (SCB) announced plans to open the world's first factory for sustainable solid-state batteries in Frauenfeld by 2024 with an initial annual production of 1.2 GWh.^[42]

In July 2022, Svolt announced the production of a 20 Ah electric battery with an energy density of 350-400 Wh/kg.^[43]

In June 2023, Maxell Corporation began mass production of large-capacity solid-state batteries. This battery has long life and heat resistance. Production of 200mmAh cylindrical solid-state batteries was to begin in January 2024. Size: diameter 23mm/height 27mm.^[44]

In September 2023, Panasonic unveiled a solid-state battery for drones. It can be charged from 10% to 80% in 3 minutes, and lasts for 10,000 to 100,000 cycles (at 25 °C). The battery was expected to be available in the late 2020s.^[45]

In October 2023, Toyota announced a partnership with Idemitsu Kosan to produce solid-state batteries for their electric vehicles starting in 2028.^[46]

In November 2023, Guangzhou Automobile Group announced that it would adopt solid-state batteries in 2026. The company also revealed that its battery has achieved 400Wh/kg. Mass production was scheduled to begin in 2025.^[47]

On December 28, 2023, Hyundai published its patent for an “all-solid-state battery system provided with pressurizing device”. The cell is a solid-state battery that maintains constant pressure regardless of charging and discharging rates. The system includes an iso-temperature element.^[48]

In January 2024, Volkswagen announced that test results of a prototype solid-state battery retained 95% of its capacity after driving 500,000 km. It also passed other performance tests.^[49]

Materials

Solid-state electrolytes (SSEs) candidate materials include ceramics such as lithium orthosilicate,^[50] glass,^[20] sulfides^[51] and RbAg₄I₅.^[52][53] Mainstream oxide solid electrolytes include Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP), Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP), perovskite-type Li_3xLa_2/3-xTiO₃ (LLTO), and garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZO) with metallic Li.^[54] The thermal stability versus Li of the four SSEs was in order of LAGP < LATP < LLTO < LLZO. Chloride superionic conductors have been proposed as another promising solid electrolyte. They are ionic conductive as well as deformable sulfides, but at the same time not troubled by the poor oxidation stability of sulfides. Other than that, their cost is considered lower than oxide and sulfide SSEs.^[55] The present chloride solid electrolyte systems can be divided into two types: Li₃MCl₆ ^[56][57] and Li₂M_2/3Cl₄.^[58] M Elements include Y, Tb-Lu, Sc, and In. The cathodes are lithium-based. Variants include LiCoO₂, LiNi_1/3Co_1/3Mn_1/3O₂, LiMn₂O₄, and LiNi_0.8Co_0.15Al_0.05O₂. The anodes vary more and are affected by the type of electrolyte. Examples include In, Si, Ge_xSi_1−x, SnO–B₂O₃, SnS –P₂S₅, Li₂FeS₂, FeS, NiP₂, and Li₂SiS₃.^[59]

One promising cathode material is Li–S, which (as part of a solid lithium anode/Li₂S cell) has a theoretical specific capacity of 1670 mAh g⁻¹, "ten times larger than the effective value of LiCoO₂". Sulfur makes an unsuitable cathode in liquid electrolyte applications because it is soluble in most liquid electrolytes, dramatically decreasing the battery's lifetime. Sulfur is studied in solid-state applications.^[59] Recently, a ceramic textile was developed that showed promise in a Li–S solid-state battery. This textile facilitated ion transmission while also handling sulfur loading, although it did not reach the projected energy density. The result "with a 500-μm-thick electrolyte support and 63% utilization of electrolyte area" was "71 Wh/kg." while the projected energy density was 500 Wh/kg.^[60]

Li-O₂ also have high theoretical capacity. The main issue with these devices is that the anode must be sealed from ambient atmosphere, while the cathode must be in contact with it.^[59]

A Li/

A cell with a pure silicon μSi||SSE||NCM811 anode was assembled by Darren H.S Tan et al. using μSi anode (purity of 99.9 wt %), solid-state electrolyte (SSE) and lithium–nickel–cobalt–manganese oxide (NCM811) cathode. This kind of solid-state battery demonstrated a high current density up to 5 mA cm⁻², a wide range of working temperature (-20 °C and 80 °C), and areal capacity (for the anode) of up to 11 mAh cm⁻² (2890 mAh/g). At the same time, after 500 cycles under 5 mA cm⁻², the batteries still provide 80% of capacity retention, which is the best performance of μSi all solid-state battery reported so far.[62]

Chloride solid electrolytes also show promise over conventional oxide solid electrolytes owing to chloride solid electrolytes having theoretically higher ionic conductivity and better formability.^[63] In addition chloride solid electrolyte's exceptionally high oxidation stability and high ductility add to its performance. In particular a lithium mixed-metal chloride family of solid electrolytes, Li₂In_xSc_0.666-xCl₄ developed by Zhou et al., show high ionic conductivity (2.0 mS cm⁻¹) over a wide range of composition. This is owing to the chloride solid electrolyte being able to be used in conjunction with bare cathode active materials as opposed to coated cathode active materials and its low electronic conductivity.^[64] Alternative cheaper chloride solid electrolyte compositions with lower, but still impressive, ionic conductivity can be found with an Li₂ZrCl₆ solid electrolyte. This particular chloride solid electrolyte maintains a high room temperature ionic conductivity (0.81 mS cm⁻¹), deformability, and has a high humidity tolerance.^[65]

Uses

Solid-state batteries are potentially useful in pacemakers, RFIDs, wearable devices, and electric vehicles.^[66][67]

Electric vehicles

Honda stated in 2022 that it planned to start operation of a demonstration line for the production of all-solid-state batteries in early 2024,^[70] and Nissan announced that, by FY2028, it aims to launch an electric vehicle with all-solid-state batteries that are to be developed in-house.^[71]

In June 2023, Toyota updated its strategy for battery electric vehicles, announcing that it will not use commercial solid-state batteries until at least 2027.^[72][73]

Wearables

The characteristics of high energy density and keeping high performance even in harsh environments are expected in realization of new

In March 2021, industrial manufacturer Hitachi Zosen Corporation announced a solid-state battery they claimed has one of the highest capacities in the industry and has a wider operating temperature range, potentially suitable for harsh environments like space.^[75][76] A test mission was launched in February 2022, and in August, Japan Aerospace Exploration Agency (JAXA) announced ^[77] the solid-state batteries had properly operated in space, powering camera equipment in the Japanese Experiment Module Kibō on the International Space Station (ISS).

Drones

Being lighter weight and more powerful than traditional lithium-ion batteries it is reasonable that commercial drones would benefit from solid-state batteries. Vayu Aerospace, a drone manufacturer and designer, noted an increased flight time after they incorporated them into their G1 long flight drone.^[78] Another advantage of drones is that all solid battery can quickly charge. In September 2023, Panasonic announced a prototype all-solid-state battery that can charge from 10% to 80% in 3 minutes.^[45]

Industrial machinery

All-solid-state batteries have long lifespans and excellent heat resistance. Therefore, it is expected to be used in harsh environments. Production of Maxell's all-solid-state batteries for use in industrial machinery has already begun.

Portable solar generators

In 2023, Yoshino become the first producer of solid state portable solar generators, 2.5 times higher energy density, double rated and surge AC output wattage of non-solid state lithium (NMC, LFP) generators.^[79][80][81]

Challenges

Cost

Thin-film solid-state batteries are expensive to make

Low temperature operations may be challenging.[82] Solid-state batteries historically have had poor performance.^[19]

Solid-state batteries with ceramic electrolytes require high pressure to maintain contact with the electrodes.^[83] Solid-state batteries with ceramic separators may break from mechanical stress.^[14]

In November 2022, Japanese research group, consisting of Kyoto University, Tottori University and Sumitomo Chemical, announced that they have managed to operate solid-state batteries stably without applying pressure with 230Wh/kg capacity by using copolymerized new materials for electrolyte.^[84]

In June 2023, Japanese research group of the Graduate School of Engineering at Osaka Metropolitan University announced that they have succeeded in stabilizing the high-temperature phase of Li₃PS₄ (α-Li₃PS₄) at room temperature. This was accomplished via rapid heating to crystallize the Li₃PS₄ glass.^[85]

Interfacial resistance

High interfacial resistance between a cathode and solid electrolyte has been a long-standing problem for all-solid-state batteries.^[86]

Interfacial instability

The interfacial instability of the electrode-electrolyte has always been a serious problem in solid-state batteries.^[87] After solid-state electrolyte contacts with electrode, the chemical and/or electrochemical side reactions at the interface usually produce a passivated interface, which impedes the diffusion of Li⁺ across the electrode-SSE interface. Upon high-voltage cycling, some SSEs may undergo oxidative degradation.

Dendrites

Solid

The exact mechanisms of dendrite growth remain a subject of research. Studies of metal dendrite growth in solid electrolytes began with research of molten sodium / sodium - β - alumina / sulfur cells at elevated temperature. In these systems, dendrites sometimes grow as a result of micro-crack extension due to the presence of plating-induced pressure at the sodium / solid electrolyte interface.[90] However, dendrite growth may also occur due to chemical degradation of the solid electrolyte.^[91]

In Li-ion solid electrolytes apparently stable to Li metal, dendrites propagate primarily due to pressure build up at the electrode / solid electrolyte interface, leading to crack extension.^[92] Meanwhile, for solid electrolytes which are chemically unstable against their respective metal, interphase growth and eventual cracking often prevents dendrites from forming.^[93]

Dendrite growth in solid-state Li-ion cells can be mitigated by operating the cells at elevated temperature,^[94] or by using residual stresses to fracture toughen electrolytes,^[92] thereby deflecting dendrites and delaying dendrite induced short-circuiting. Aluminum-containing electronic rectifying interphases between the solid-state electrolyte and the lithium metal anode have also been shown to be effective in preventing dendrite growth.^[95]

Mechanical failure

A common failure mechanism in solid-state batteries is

One proposed solution to this issue is to take advantage of the anisotropy of volume change in the cathode particles. As many cathode materials experience volume changes only along certain crystallographic directions, if the secondary cathode particles are grown along a crystallographic direction which does not expand greatly with charge/discharge, then the change in volume of the particles can be minimized.^[100][101] Another proposed solution is to mix different cathode materials which have opposite expansion trends in the proper ratio such that the net volume change of the cathode is zero.^[97] For instance, LiCoO₂ (LCO) and LiNi_0.9Mn_0.05Co_0.05O₂ (NMC) are two well-known cathode materials for Li-ion batteries. LCO has been shown to undergo volume expansion when discharged while NMC has been shown to undergo volume contraction when discharged. Thus, a composite cathode of LCO and NMC at the correct ratio could undergo minimal volume change under discharge as the contraction of NMC is compensated by the expansion of LCO.

Anode

Ideally a solid-state battery would use a pure

${\displaystyle \sigma _{creep}=\left({\frac {\dot {\varepsilon }}{A_{c}}}\right)^{1/m}\exp {\left({\frac {Q_{c}}{mRT}}\right)}}$

Where ${\displaystyle R}$ is the gas constant, ${\displaystyle T}$ is temperature, ${\displaystyle {\dot {\varepsilon }}}$ is the uniaxial strain rate, ${\displaystyle \sigma _{creep}}$ is the creep stress, and for lithium metal ${\displaystyle m=6.6}$, ${\displaystyle Q_{c}=37\,\mathrm {kJ} \cdot \mathrm {mol} ^{-1}}$, ${\displaystyle A_{c}^{-1/m}=3\times 10^{5}\,\mathrm {Pa} \cdot \mathrm {s} ^{-1}}$.^[103]

For lithium metal to be used as an anode, great care must be taken to minimize the cell pressure to relatively low values on the order of its

Solid-state battery technology is believed to deliver higher energy densities (2.5x).^[111]

Solid-state batteries have excellent theoretical energy density.

[Lithium ion secondary battery]

Cathode: Lithium cobaltate ⇄ Anode: Graphite→Energy density 370Wh/kg (Cobalt type: theoretical limit value)

[Solid-state battery]

Cathode: Oxide/Sulfide ⇄ Anode: Metallic lithium→Energy density 1440Wh/kg (sulfide type: theoretical limit value)

They may avoid the use of dangerous or toxic materials found in commercial batteries, such as organic electrolytes.^[112]

Because most liquid electrolytes are flammable and solid electrolytes are nonflammable, solid-state batteries are believed to have lower risk of catching fire. Fewer safety systems are needed, further increasing energy density at the module or cell pack level.^[2][112] Recent studies show that heat generation inside is only ~20-30% of conventional batteries with liquid electrolyte under thermal runaway.^[113]

Solid-state battery technology is believed to allow for faster charging.^[114][115] Higher voltage and longer cycle life are also possible.^[112][82]

Thin-film solid-state batteries

Background

The earliest thin-film solid-state batteries is found by Keiichi Kanehori in 1986,^[116] which is based on the Li electrolyte. However, at that time, the technology was insufficient to power larger electronic devices so it was not fully developed. During recent years, there has been much research in the field. Garbayo demonstrated that "polyamorphism" exists besides crystalline states for thin-film Li-garnet solid-state batteries in 2018,^[117] Moran demonstrated that ample can manufacture ceramic films with the desired size range of 1–20 μm in 2021.^[118]

Structure

Anode materials: Li is favored because of its storage properties, alloys of Al, Si and Sn are also suitable as anodes.

Cathode materials: require having light weight, good cyclical capacity and high energy density. Usually include LiCoO2, LiFePO4, TiS2, V2O5and LiMnO2.^[119]

Preparation techniques

Some methods are listed below.^[120]

• Physical methods:
  1. Magnetron sputtering (MS) is one of the most widely used processes for thin-film manufacturing, which is based on physical vapor deposition.^[121]
  2. Ion-beam deposition (IBD) is similar to the first method, however, bias is not applied and plasma doesn't occur between the target and the substrate in this process.^{[citation needed]}
  3. Pulsed laser deposition (PLD), laser used in this method has a high power pulses up to about 10⁸ W cm⁻².^{[citation needed]}
  4. Vacuum evaporation (VE) is a method to prepare alpha-Si thin films. During this process, Si evaporates and deposits on a metallic substrate.^[122]
• Chemical methods:
  1. Electrodeposition (ED) is for manufacturing Si films, which is convenient and economically viable technique.^[123]
  2. Chemical vapor deposition (CVD) is a deposition technique allowing to make thin films with a high quality and purity.^[124]
  3. Glow discharge plasma deposition (GDPD) is a mixed physicochemical process. In this process, synthesis temperature has been increased to decrease the extra hydrogen content in the films.^[125]

Development of thin-film system

• Lithium–oxygen and nitrogen-based polymer thin-film electrolytes has got fully used in solid-state batteries.
• Non-Li based thin-film solid-state batteries have been studied, such as Ag-doped germanium chalcogenide thin-film solid-state electrolyte system.^[126] Barium-doped thin-film system has also been studied, which thickness can be 2μm at least.^[127] In addition, Ni can also be a component in thin film.^[128]
• There are also other methods to fabricate the electrolytes for thin-film solid-state batteries, which are 1.electrostatic-spray deposition technique, 2. DSM-Soulfill process and 3. Using MoO3 nanobelts to improve the performance of lithium-based thin-film solid-state batteries.^[129]

Advantages

• Compared with other batteries, the thin-film batteries have both high gravimetric as well as volumetric energy densities. These are important indicators to measure battery performance of energy stored.^[130]
• In addition to high energy density, thin-film solid-state batteries have long lifetime, outstanding flexibility and low weight. These properties make thin-film solid-state batteries suitable for use in various fields such as electric vehicles, military facilities and medical devices.

Challenges

• Its performance and efficiency are constrained by the nature of its geometry. The current drawn from a thin-film battery largely depends on the geometry and interface contacts of the electrolyte/cathode and the electrolyte/anode interfaces
• Low thickness of the electrolyte and the interfacial resistance at the electrode and electrolyte interface affect the output and integration of thin-film systems.
• During the charging-discharging process, considerable change of volumetric makes the loss of material.^[130]

See also

References