The present invention relates to a solid-state battery anode composition. More particularly, the present invention further relates to an anode composition comprising a graphitic material and solid electrolyte material.
The present invention still further relates to a method for producing a solid-state battery anode comprising an anode composition in accordance with the present invention.
Presently, Lithium-ion battery (LiB) technology has been successfully used in applications for electric devices including cell phones, laptops, tablets, and also for electric vehicles (PHEV, EV). However, LiBs suffer safety concerns due to their flammable liquid electrolyte. Solid-state batteries are an emerging form of rechargeable battery technology with the potential to combine high energy and high power with improved safety. In this sense, all solid-state batteries (SSBs) are of great interest due to their intrinsic safety and wide range of operating temperatures, largely due to the non-flammable solid electrolyte of choice. Moreover, SSBs provide benefits concerning high gravimetric and volumetric energy density [1,2]. Unlike LiBs that utilise a porous separator soaking within a liquid electrolyte, SSBs use a solid electrolyte which has a function as an electrical insulator and ionic conductor. The components of the electrolyte consist of solid materials with less, similar or higher ionic conductivity than liquid electrolyte [3,4].
The idea of a solid-state electrolyte for manufacturing solid-state batteries was initially proposed in the 1970s by Professor Wright who first reported fast ionic conduction in high molecular weight polyethylene oxide (CH2CH2O)n [5] and the work of Armand et al. [6] in the 1990s. Then Capiglia et al. proposed the utilization of SiO2 nano-composite polymer electrolyte for SSBs and their application in EV and HEV [7]. Since then, there have been many studies to improve ionic conductivity in solid electrolyte considering different types of polymers, ceramics and sulfide glass based solid electrolyte. One of the most promising solid electrolytes are the sulfide-based glasses, including Li2S—SiS2 [8,9,10,11], Li2S—P2S5 [12,13,14,15], and Li2S—B2S3 [16].
While solid-state batteries are theoretically capable of very high performance, in practice they can suffer a range of technical and commercial issues that have hindered their development, particularly for larger scale applications including electric vehicles (“EVs”). None of the solid-state batteries reported to date exceed all of the performance and economic requirements of today's best Li-ion batteries in EVs. A major bottleneck of SSBs development is the anode, where the use of metallic lithium can cause a range of issues leading to slower charge/discharge characteristics, safety issues both within the battery and in mass production, and higher cost. Takada et al. proposed a graphite-solid electrolyte construction by using Li2S—P2S5 electrolyte and Seino et al. investigated the graphite-Li2S—P2S5 based solid-state battery under pressure of 350 MPA. Those approaches showed a practicality of application of the graphite as anode material in the solid-state battery. However, the electrochemical characteristics of such a construction was still untested.
The solid-state battery anode composition and method of the present invention have as one object thereof to overcome substantially one or more of the above-mentioned problems associated with prior art processes, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. This discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
In accordance with the present invention there is provided a solid-state battery anode composition comprising a graphitic material and a solid electrolyte material, wherein the graphitic material is provided in the form of ground primary graphite particles.
The ground primary graphite particles preferably have a D50 of:
Preferably, the ground primary graphite particles have a surface area of about 2 to 9 m2/g, for example 7 to 9 m2/g.
Preferably, the ground primary graphite particles have XRD characteristics of one or more of a d002 of >3.35 Å, an Lc of >1000 Å and an La of >1000 Å. In a preferred form, the ground primary graphite particles have XRD characteristics of each of a d002 of >3.35 Å, an Lc of >1000 Å and an La of >1000 Å, and a purity of >99.9%.
Preferably, the solid electrolyte material comprises a sulphide-based glass. Still preferably, the sulphide-based glass is chosen from the group of Li2S—SiS2, Li2S—P2S5 and Li2S—B2S3. Still further preferably, the solid electrolyte material comprises Li2S—P2S5.
The solid-state battery anode composition of the present invention preferably comprises a graphitic material and a solid electrolyte material in the following proportions:
Preferably, the solid-state battery anode composition of the present invention provides, in half cell measurements using the Current Rest Method, an equilibrium component of less than about 60 Ohm, for example less than about 54 Ohm. The equilibrium component of the solid-state battery anode composition in half cell measurements using the Current Rest Method is preferably about half or less that of known commercial graphite materials.
Preferably, the solid-state battery anode composition of the present invention provides a conductivity of 10˜2×10 S/cm over a compression density range of 0.5˜2 g/cm3. The conductivity of the solid-state battery anode composition is preferably about one order of magnitude higher than that of known commercial graphite materials.
Preferably, the graphitic material has a graphitisation degree of greater than 96%.
Still preferably, the graphitic material has a bulk resistance of:
Preferably, the solid-state battery anode composition of the present invention provides, in half cell measurements, a capacity of greater than 90% at 3 C, for example about 91.6% at 3 C.
Preferably, the solid-state battery anode composition of the present invention provides, in half cell measurements, a discharge profile substantially free of polarisation effects.
In accordance with the present invention there is further provided a method for producing a solid-state battery anode comprising an anode composition that in turn comprises a graphitic material and a solid electrolyte material, as described hereinabove.
The present invention will now be described, by way of example only, with reference to two embodiments thereof and the accompanying drawings, in which:—
The present invention provides a solid-state battery anode composition comprising a graphitic material and a solid electrolyte material. The graphitic material comprises ground primary graphite particles.
The ground primary graphite particles may have a D50 of:
The ground primary graphite particles have a surface area of about 2 to 9 m2/g, for example 7 to 9 m2/g. The ground primary graphite particles have XRD characteristics of one or more of a d002 of >3.35 Å, an Lc of >1000 Å and an La of >1000 Å. In a preferred form, the ground primary graphite particles have XRD characteristics of each of a d002 of >3.35 Å, an Lc of >1000 Å and an La of >1000 Å, and a purity of >99.9%.
The solid electrolyte material comprises a sulphide-based glass. The sulphide-based glass is chosen from the group of Li2S—SiS2, Li2S—P2S5 and Li2S—B2S3. For example, the solid electrolyte material comprises Li2S—P2S5.
In one preferred form, the solid-state battery anode composition of the present invention comprises a graphitic material and a solid electrolyte material in the following proportions:
The solid-state battery anode composition of the present invention provides in one form, in half cell measurements using the Current Rest Method, an equilibrium component of less than about 60 Ohm, for example less than about 54 Ohm. The equilibrium component of the solid-state battery anode composition in half cell measurements using the Current Rest Method is in one form about half or less that of known commercial graphite materials.
The solid-state battery anode composition of the present invention provides a conductivity of 10˜2×10 S/cm over a compression density range of 0.5˜2 g/cm3. The conductivity of the solid-state battery anode composition is about one order of magnitude higher than that of known commercial graphite materials.
The solid-state battery anode composition of the present invention provides, in half cell measurements, a capacity of greater than 90% at 3 C, for example about 91.6% at 3 C.
The solid-state battery anode composition of the present invention provides, in half cell measurements, a discharge profile substantially free of polarisation effects.
The present invention further provides a method for producing a solid-state battery anode comprising an anode composition that in turn comprises a graphitic material and a solid electrolyte material, as described hereinabove and exemplified hereinafter.
Table A below provides an example of an appropriate ground primary graphite particle for use in/as used in the composition and method of the present invention, whilst Table B provides the elemental analysis of that ground primary graphite particle.
The composition and method of the present invention may be better understood with reference to the following non-limiting example.
The anode graphite anode precursor used for the present investigation was extracted from the Vittangi graphite mine in the County of Norrbotten in northern Sweden. This natural graphite source is characterised by hard particles having a very narrow distribution, with microcrystalline flake. The graphite was then chemical purified at the Applicant's pilot plant in Rudolstadt and process engineered to be applied in the solid-state system. This process is as described hereinabove for the production of ground primary graphite particles and in turn secondary graphite particles (variously also referred to herein as ‘Talnode-E’, ‘Talnode-E powder’ or ‘Talnode-C’ throughout).
The SEM images of
Solid electrolyte pellets were prepared in accordance with the method of the present invention, with reference to
The cell was prepared by sandwiching the solid electrolyte, the solid electrode pellets, the lithium-indium between SUS electrodes at a varying stack pressure of 100, 300, and 500 MPa. The indium and lithium foils pressed was used as reference electrode for the half cell. The steel holder (SUS) was used as current collectors. In order to allow control of the stack pressure during Electrochemical Impedance Spectroscopy (EIS) measurement and cycling, the cell was assembled in the cell holder described in
The half-cell obtained was cycled with cut-off voltages between 2.0V and −0.62 V versus Li—In at 0.05 C. The cell was kept at 70° C.±1° C. and had a 10 min pause for every 2 h during testing. Electric conductivities of the samples were measured at 70° C. by an A.C. impedance method. The impedance spectra were measured using an impedance analyzer (VeraSTAT4 Princeton Applied Research) in the frequency range from 0.1 Hz to 1 MHz, amplitude 50 mV, the results of which are set out in
With reference to
The Kyoto Research Institute used the same protocol for electrode, electrolyte preparation, as well as the impedance, and CRM characterisation for all other types of graphite in commerce and therefore Talnode-E was benchmarked versus typical commercial anode graphite. Such typical commercial anode graphite is, as noted elsewhere herein, based on about 200 types of graphite including both natural and artificial with a particle size ranging from 10 μm to 20 μm.
In
In
A simplified model, which is made by those elements, is called a Randles model, who presented the model at the Faraday society in 1947. A plot, which was imagined by the Randles model, is called the Nyquist plot. In the Nyquist plot, the characteristics of a cell are visibly illustrated. This model is indispensable for understanding an electrochemical system. However, real systems are very complicated and convoluted. The Nyquist plot of a simplified Randles cell is depicted in
Against this theoretical background, it is explained that the stack pressures impact on the semicircles (charge transfer resistance) and the diffusion part on EIS for Talnode-E. The emergence of a semicircle at the high-resistance region shifted to the low resistance (bulk resistance) region as the stack pressure increases. Additionally, the semicircle decreased when the stack pressure exceeds over 300 MPa. The grain boundaries of impedance can contribute to the emerging of a semicircle at the high-frequency region. Similar behaviour has been observed on oxide solid-state electrolytes. As the pellet's density increased by sintering, the grain boundary resistance reduced, and therefore, the conductivity increased [26,27]. It is interesting to see that the diffusion curve shows a steep slope of diffusivity at 100 MPa, while the slopes of the other two cases do not show such a steep slope at this pressure.
The high-rate test between 0.05 C and 3 C at 70° C. of Talnode-E was tested using a stack pressure of 100, 300, and 500 MPa, and the results thereof are shown in
As can be seen with reference to the above description, the Talnode-E electrochemical properties in sulfide-solid-state electrolyte were studied at different pressures and compared with typical commercial graphite. Talnode-E electrode shows a capacity of 324.1 mAh/g at 300 MPa. Furthermore, Talnode-E showed an increase in the electric conductivity of approximately one order of magnitude compared to the commercial graphite thanks to the high electrical conductivity of Talnode-E. High rate tests have shown that Talnode-E has high rate discharge capability associated with high capacity retention up to 3 C and low polarization discharge curve profiles. The behaviour was attributed to the high lithium diffusion of Talnode-E when compared with conventional graphite.
The Applicant has concluded that Talnode-E has high potential to be used as an alternative anode material with low resistance and high ionic diffusion in at least sulfide-based-solid-state batteries. Further, the solid-state battery anode composition of the present invention suggests significant improvements in energy density and cycle life while enabling faster charging with improved safety (for example no flammable solvents), all whilst maintaining broad compatibility with the most near-term forms of solid-state batteries.
The use of graphitic anodes in solid-state batteries also helps ensure suitable interaction at the electrolyte/active material interface to mitigate prior persistent issues such as high impedance and mechanical fatigue.
It is envisaged that by replacing current lithium metal anodes with a solid-state battery anode composition of the present invention, the cost of solid-state batteries can be reduced, as can the associated hurdle of manufacturing at scale.
It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 1 micrometer (μm) to about 2 μm should be interpreted to include not only the explicitly recited limits of from between from about 1 μm to about 2 μm, but also to include individual values, such as about 1.2 μm, about 1.5 μm, about 1.8 μm, etc., and sub-ranges, such as from about 1.1 μm to about 1.9 μm, from about 1.25 μm to about 1.75 μm, etc. Furthermore, when “about” and/or “substantially” are/is utilised to describe a value, they are intended to encompass minor variations (up to +/−10%) from the stated value.
The forgoing description is to be considered non-limiting. Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
2021900501 | Feb 2021 | AU | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/IB2022/051613 | 2/24/2022 | WO |
Number | Date | Country | |
---|---|---|---|
20240132360 A1 | Apr 2024 | US |