Graphite based electrochemical cell

Abstract

The present invention relates to an electrochemical cell comprising a graphite working electrode and a counter electrode, as well as a method of charging and / or discharging the electrochemical cell. Also described is a method of preparing the electrochemical cell and an electrochemical cell obtained or obtainable by the method. In the present invention, the working electrode active material comprises graphite particles having a D50 particle length by volume of D50w and the counter electrode active material, such as LCO or NCM, comprises particles having a D50 particle length by volume of D50c, wherein D50w and D50c satisfy Formula (Ia): D50c = C50 × D50w, wherein C50 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less.

Description

[0001] GRAPHITE BASED ELECTROCHEMICAL CELL

[0002] Related Application

[0003] The present case claims the benefit of, and priority to, GB 2315718.3 filed on 13 October 2023 (13.10.2023), the contents of which are hereby incorporated by reference in their entirety.

[0004] Field of the Invention

[0005] The present invention relates to an electrochemical cell comprising a graphite working electrode and a counter electrode, as well as a method of charging and / or discharging the electrochemical cell. Also described is a method of preparing the electrochemical cell and an electrochemical cell obtained or obtainable by the method.

[0006] Background

[0007] High-rate lithium ion battery electrode materials are able to receive large quantities of energy in only a few minute of charging. Such batteries are of increasing importance in electric vehicles, grid-scale batteries, and power-intensive devices.

[0008] Particulate electrodes are commonly used for both working electrodes and counter electrodes. Although particulate electrodes are straightforward to manufacture and offer good physical properties, the particles have limitations in terms of lithium ion diffusion. This can lead to poor capacity at high rates, as the lithium ions are unable to get through the whole of the electrode layers. These limitations are exacerbated at high charge rates, where lithium ion diffusion is at its fastest.

[0009] For example, graphite is widely used as an anode working electrode material due to its relative abundance, low cost and relatively high energy density. However, developments around graphite particles in electrodes have typically focused on improving packing efficiency and electrode density, in order to improve volumetric capacity and volumetric energy density.

[0010] Despite good lithium ion mobility within graphite particles, graphite has traditionally not been used in high-rate applications due to the risk of particle fracturing and lithium dendrite formation during fast charging. This limits the use of graphite anodes in high-rate applications, as lithium plating at the surface may occur if the charging rate exceeds the lithium ion intercalation rate. Such plating leads to rapid capacity fade and potential safety events if lithium dendrites develop. Similarly for cathode counter electrode materials, the use of particulate electrodes leads to limitations in fast charging capability of the cells. Accordingly, there is a need to provide new working electrode and counter electrode materials for electrochemical cells that are capable of operating at high rates with good capacity retention and good lifetime capacity retention.

[0011] Summary of the Invention

[0012] Generally, the present inventors have provided a graphite based electrochemical cell optimised for fast charging performance.

[0013] The electrochemical cell is a graphite-containing electrochemical cell. The electrochemical cell utilises graphite as an electrode active material.

[0014] The inventors have established that when a working electrode and a counter electrode contain active particles of complementary size the electrochemical cell has an improved high- rate capacity. In particular, for a working electrode (e.g., anode) having a particular particle size, then the use of a counter electrode having a particle size the same as, or slightly larger than the working electrode particle size has been shown to provide improved high-rate capacity. In particular, providing a working electrode and counter electrode having particles having a similar particle size distribution (e.g., similar D10, D50 and D90) values has been found to result in excellent high-rate performance.

[0015] The inventors have also found that a working electrode active material of graphite particles having a particular size distribution, such as a high spread of the D10, D50 and D90 values, provides excellent electrochemical performance. Using graphite particles having a bi-modal particle size distribution was found to particularly improve the properties of the cell.

[0016] Without wishing to be bound by theory, it is thought that having a larger range of particle sizes at the working electrode reduces the tortuosity for the lithium ions in the electrolyte. They have identified that this can be quantitatively identified by the tap density of the graphite particles, wherein the tap density is 0.8 g / cm3or less, preferably 0.7 g / cm3or less, and more preferably 0.65 g / cm3or less. It may also be quantified by the BET surface area of the graphite particles, such as a BET surface area of 4 m2 / g or more, preferably 5 m2 / g or more, more preferably 6 m2 / g or more.

[0017] Relatedly, the inventors have found that a counter electrode active material composed of particles (e.g., LCO, NCM, NCA particles) having a similar particle size distribution provides excellent complementarity to the graphite working electrode. A low distribution in the counter electrode active material particles can, with a complimentary graphite working electrode, also improve the cell cycling properties.

[0018] Accordingly, in a general aspect, the present invention provides an electrochemical cell comprising a working electrode having particles of a working electrode active material and a counter electrode having particles of a counter electrode active material, wherein the ratiobetween the particle size of the counter electrode active material and the working electrodeactive material is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably2 or less. In some embodiments, the ratio is 3 or less, preferably 2.5 or less and morepreferably 2 or less. In a first aspect of the invention there is provided an electrochemical cell comprising a working electrode, a counter electrode, and an electrolyte, wherein the working electrode comprises a working electrode active material, and the workingelectrode active material comprises graphite particles having a D50 particle length by volume of D50wthe counter electrode comprises a counter electrode active material, and the counter electrode active material comprises particles having a D50 particle length by volume of D50c, wherein D50w and D50c satisfy Formula (Ia): D50c = C50 × D50w (Ia)wherein C50 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less Preferably, C50 is 3 or less, preferably 2.5 or less, more preferably 2 or less. C50 is typically more than 0. In some embodiments, the graphite particles have particle length spread, Sw, of 1.6 or more, wherein the spread is defined by formula (IIa): Sw = (D90w – D10w) / (D50w) (IIa)wherein D90w and D10w are the D90 and D10 particle lengths by volume of thegraphite particles. In some embodiments the counter electrode active material comprises particles having a particle length spread, Sc, of 1.6 or less, wherein the spread is defined by formula (IIb): Sc = (D90w – D10w) / (D50w) (IIb)wherein D90w and D10w are the D90 and D10 particle lengths by volume of the counterelectrode active material particles. In a preferred embodiment, the electrode active material comprises graphite particles having a bimodal particle length distribution. In some preferred embodiments, a first population of the graphite particles have D50 particle length by volume of D50w1 and a second population of the graphite particles have a D50 particle length by volume of D50w2, wherein D50w1and D50w2satisfy Formula (IIIa): D50w1 = E50 × D50w2 (IIIa)wherein E50is 3 or less, preferably 2.5 or less, more preferably 2 or less. E50is typically more than 0. In second aspect of the present invention there is provided a method of charging and / ordischarging the electrochemical cell of the first aspect of the invention at a C-rate of 5C ormore, preferably 10C or more, more preferably 20C or more. In some embodiments, the method is a method of charging at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more.In some embodiments, the method comprises a cycle of charging and discharging theelectrochemical cell, and (i) the specific discharge capacity retention is 90% or more after 1000 cycles at a C-rate of 1C, and / or (ii) the specific discharge capacity retention is 80% or more after 2000 cycles at charge rate of 6C and a discharge rate of 1C.In another aspect there is provided a battery comprising two or more of the electrochemicalcells of the first aspect of the invention.In another aspect there is provided a use of the electrochemical cell of the first aspect of the invention charging and / or discharging at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more.Conventional developments to electrochemical cells have focused on increasing the particledensity, because this improves volumetric capacity and volumetric energy density and allows particles to be packed more efficiently. It is counterintuitive to use a material with a lower tap density. The inventors have identified a key parameter enabling fast charging with graphite working electrodes and complimentary counter electrodes.An inverse linear relationship has also been found between graphite tap density and therechargeability at very high rates. Tap density relates to powder particle size distribution and morphology, and the difference between tap density and true density represent the void volume that may contribute to ion transport when filled with electrolyte in the calendared electrodes. The particle sizes used in the working electrode and counter electrode are associated with those electrodes having a relatively low tap density and high number of voids, which increases lithium ion diffusion through the electrodes, as the electrolyte can flow into and through these voids.

[0019] The electrochemical cells described herein typically have a fast charging capability in the range 5C-20C, with excellent cycle-life, and the cells are capable of operating in this was whilst delivering energy densities of 200 Wh / kg or more.

[0020] These and other aspects and embodiments of the invention are described in more detail below.

[0021] Summary of the Figures

[0022] The present invention is described with reference to the figures listed below.

[0023] Figure 1 : Correlation between DCR after formation (bottom), 20C charge capacity (top) versus tap density of graphite in a 2025 half coin-cell with CMC:SBR binder.

[0024] Figure 2: Lithium intercalation voltage profiles of a high-energy, high tap density graphite, Sample A (top) and a low tap density fast charging graphite, Sample F (bottom) at 0.5, 1 , 2, 5, 10 and 20C charging rates.

[0025] Figure 3a: Lithiation rate capability in terms of specific capacity of half coin-cells having graphite anodes F, G or (1:1) blend by weight of F and G at 0.2, 0.5, 1 , 2, 5 and 10C charging rates. The error bars show standard deviation.

[0026] Figure 3b: Delithiation rate capability in terms of specific capacity of half coin-cells having graphite anodes F, G or (1:1) blend by weight of F and G at 0.1 , 0.2, 0.5, 1 , 2, 5 and 10C discharging rates. The error bars show standard deviation.

[0027] Figure 4: Correlation coefficient of capacity with tap density of graphite versus charging rate, for CMC:SBR or PVDF binder.

[0028] Figure 5: Charge and discharge capacity retention at 0.1 , 0.2, 0.5, 1 , 2, 5, 10 and 20C of half coin-cells using LCO Samples A or B as cathode active material with graphite Sample F as anode active material.

[0029] Figure 6: SEM images at 2k magnification of dry graphite powder Sample A (right) and Sample F (left).

[0030] Figure 7: A graph showing the coat weight, layer thickness, and coating density (calendar density) for graphite anode Samples A-G and F+G.Figure 8: A graph of capacity retention at 12 C charge and 1 C discharge of a pouch cellusing NCM811 as cathode active material with graphite Sample F as anode active material. Detailed Description of the Invention In a general aspect, the present invention provides an electrochemical cell comprising a working electrode having particles of a working electrode active material and a counter electrode having particles of a counter electrode active material, wherein the ratio between the particle size of the counter electrode active material and the working electrode active material is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less. In some embodiments the ratio is 3 or less, preferably 2.5 or less and more preferably 2 or less. In a first aspect of the invention there is provided an electrochemical cell comprising a working electrode, a counter electrode, and an electrolyte, wherein the working electrode comprises a working electrode active material, and the workingelectrode active material comprises graphite particles having a D50 particle length by volume of D50w the counter electrode comprises a counter electrode active material, and the counter electrode active material comprises particles having a D50 particle length by volume of D50c, wherein D50w and D50c satisfy Formula (Ia): D50c = C50 × D50w (Ia)wherein C50 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less. In some embodiments, C50 is 3 or less, preferably 2.5 or less, more preferably 2 or less. Some particulate graphite working electrodes are known.CN 113140697 describes cells including a LCO coating on a cathode with the particles havinga D50 of 10 to 12 µm, along with a graphite anode comprising particles having a D50 of10 µm. However, the particle sizes described are much larger those of the present invention.The tap density of the particles is also not described.US 2023 / 0016746 relates to multi-layer silicon or silicon oxide anodes. The examplesdescribe silicon and graphite composite anodes. One specific example includes graphiteparticles having a particle size of 16.7 µm and a tap density of 0.91 g / cm3, and aLiNi0.6Co0.2Mn0.5O2cathode with particles having a D50 of 15 µm. This gives a C50value of 0.9, which is outside of the preferred ranges of the present invention. The document also does not describe the particle sizes or tap density of the graphite used in the present invention. The anodes described also include substantial amounts of silicon, so graphite is not the main active material.

[0031] CN 107910483 describes LCO-graphite cells, where the D50 of the LCO particles is 5 to 10 pm and the D50 of the graphite particles is 4 to 10 pm. The examples use LCO with particles having a D50 of 6 pm and graphite particles with a D50 of 8 pm. The examples give a C50 value of 0.75, which is outside of the preferred ranges of the present invention. The preferred particle distributions (e.g., D10 and D90 values), bimodal particle size distribution and tap densities of the graphite are also not described.

[0032] KR 1020230131294 describes examples of graphite anode materials with particles having a D50 ranging from 5 to 16 pm in Table 1 . No information on the particle size of the cathode is provided.

[0033] US 7749659 relates to a lithium-ion battery with spherical graphite particles as the anode, and defines a logarithmic relationship between the graphite D10, D50 and D90 values. The preferred embodiments refer to mixtures of large and small graphite particles. The examples use LCO cathodes. However, there is no information about the particle sizes of the cathode material.

[0034] WO 2021 / 125755 describes an anode active material which is a multilayer particle including a core of graphite and pitch coke, and a shell coating of hard carbon. The particles are said to have a D50 of 14 to 19 pm, but the examples refer to a D50 of 6 to 9 pm. The document does not describe the particle size of the cathode and so is not relevant to the present invention.

[0035] CN110649256B describes single-particle and secondary-particle mixed high-energy-density graphite negative electrode materials and their preparation. The particles are intended to increase the tap density of the electrode and thereby increase the energy density of the cell. CN111725485B and CN112397691A also describe increasing energy density of graphite electrodes by increasing the compression density of graphite particles.

[0036] On the contrary, the present inventors have found that providing graphite particles with a low tap density is surprisingly advantageous for fast charging and discharging properties of the electrode. The low tap density may be achieved by providing graphite particles having a particle length spread, A, of 1.6 or more. The relatively large spread decreases the packing efficiency of the electrode, hence reducing the tap density. Moreover, matching the graphite particles with complimentary cathode particles provides excellent fast-charging performance.

[0037] Graphite has a theoretical density of 2.26 g / cm3and so a tap density of 0.8 g / cm3or less represents a packing efficiency of less than 0.35. A calendar density of 1.5 g / cm3or less represents a packing efficiency of less than 0.66. The C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. The C-rate may be defined as the inverse of the number of hours to reach a defined theoretical capacity e.g., 10C corresponds to a 6 min discharge or charge time. In this work, C-rate is defined relative to one electron transfer per each C6 formula unit, e.g., forgraphite, 1C = 372 mA·h·g–1, 20C = 7,440 mA·h·g–1. The theoretical capacity is calculatedby: Where n is the number of electrons transferred per formula unit (1 electron per C6 unitin graphite), F is Faraday’s constant, 3.6 is a conversion factor between Coulombs and theconventional mA·h·g–1, and m is the mass per formula unit (72 per C6 unit). Thus, a 1C ratecorresponds to the reaction (i.e. insertion or removal) of 1 lithium ion per C6 formula unit inone hour. The high-rate application may also be described by reference to (gravimetric) current density, for example where the current density is at least 800 mA·g-1or 2000 mA·g-1. Current density is related to C-rate by: Thus, for graphite a theoretical current density of 800 mA·g-1 corresponds to a C-rate of2.15C and a current density of 2000 mA g-1 corresponds to a C-rate of 5.38C.All (gravimetric) capacities are quoted based on the mass of the active electrode material. Electrochemical Cell In a first aspect there is provided an electrochemical cell comprising a working electrode, a counter electrode, and an electrolyte, wherein the working electrode comprises a working electrode active material, and the workingelectrode active material comprises graphite particles having a D50 particle length by volume of D50w the counter electrode comprises a counter electrode active material, and the counter electrode active material comprises particles having a D50 particle length by volume of D50c, wherein D50w and D50c satisfy Formula (Ia): D50c = C50 × D50w (Ia) wherein C50 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less. In some embodiments, C50 is 3 or less, preferably 2.5 or less, more preferably 2 or less. The inventors have found that providing a counter electrode with a particulate counter electrode material having a particle length (D50c) which is only slightly larger or similar to the particle length of the graphite anode (D50w) (e.g., C50is 3 or less, more preferably from 1.0 to 2.0) results in improved high-rate cycling and long term cell cycling performance. In some embodiments C50is from 1 to 6, preferably from 1.2 to 4, more preferably from 1.4 to3. In some embodiments C50 is from 1 to 3, preferably from 1.2 to 2, more preferably from 1.4to 1.6. Preferably C50is about 1.6. C50is typically more than 0. In some embodiments C50is 1 or more, preferably 1.2 or more, more preferably 1.4 or more. In some embodiments C50 is 3 or less, preferably 2 or less, more preferably 1.6 or less. In some embodiments the working electrode active material comprises graphite particles having a D10 particle length by volume of D10w, and the counter electrode active material comprises particles having a D10 particle length by volume of D10c, wherein D10wand D10csatisfy Formula (Ib): D10c = C10 × D10w (Ib)wherein C10 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less. In some embodiments, C10 is 3 or less, preferably 2.5 or less, more preferably 2 or less. C10 is typically more than 0. In some embodiments C10 is from 1 to 3, preferably from 1.2 to 2, more preferably from 1.5 to 1.7. Preferably C10is about 1.7. In some embodiments C10is 1 or more, preferably 1.2 or more, more preferably 1.5 or more. In some embodiments C10 is 3 or less, preferably 2 or less, more preferably 1.7 or less. Preferably C10is about 1.7. In some embodiments the working electrode active material comprises graphite particles having a D90 particle length by volume of D90w, the counter electrode active material comprises particles having a D90 particle length by volume of D90c, and wherein D90w and D90csatisfy Formula (Ic): D90c = C90 × D90w (Ic) wherein C90 is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less. In some embodiments, C90is 3 or less, preferably 2 or less, more preferably 1.5 or less. C90is typically more than 0. In some embodiments C90is from 1 to 3, preferably from 1.1 to 2, more preferably from 1.2 to 1.4. Preferably C90is about 1.3. In some embodiments C90is 1 or more, preferably 1.1 or more, more preferably 1.2 or more. In some embodiments C90 is 3 or less, preferably 2 or less, more preferably 1.4 or less. Preferably C90is about 1.3. In some embodiments C10, C50 and C90 are each independently 1 or more, preferably 1.2 or more. In some embodiments C10, C50 and C90 are each independently 2 or less, preferably 1.7 or less.Preferably, C10, C50 and C90 are each independently from 1 to 2, preferably from 1.2 to 1.7.In some embodiments the working electrode active material comprises graphite particles having a calendar density of CDw, and the counter electrode active material comprises particles having a calendar density of CDc, wherein CDw and CDc satisfy Formula (IV): CDc = F × CDw (IV)wherein F is 3 or less, preferably 2.8 or less, more preferably 2.5 or less, yet more preferably2.3 or less. F is preferably 1 or more, more preferably 2 or more, yet more preferably 2.2 ormore. F may be from 1 to 3, preferably from 1.5 to 2.8, more preferably from 1.8 to 2.5, yet more preferably from 2 to 2.5.F is typically more than 0.In some embodiments the working electrode active material comprises graphite particles having a porosity of Pw, and the counter electrode active material comprises particles having a porosity of Pc, wherein Pwand Pcsatisfy Formula (V): Pc = G × Pw (V)wherein G is from 0.5 to 1.5, preferably from 0.7 to 1.3, more preferably from 0.8 to 1.2, yet more preferably about 1.0. Porosity may refer to the porosity of the calendared electrode, as described herein. The electrochemical cell is preferably a secondary electrochemical cell, such as a lithium ion cell. A secondary cell is a cell which is rechargeable. The working electrode may be an anode or cathode during a discharge step, for example in a lithium ion cell. Preferably, the working electrode is the anode during a discharge step. The counter electrode may be an anode or cathode during a discharge step, for example in a lithium ion cell. Preferably, the counter electrode is the cathode during a discharge step. The electrochemical cell may be chargeable and / or dischargeable at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more. The electrochemical cell may be chargeable and / or dischargeable at a current density of 700 mA g-1or more, preferably800 mA g-1 or more, more preferably 900 mA g-1 or more, yet more preferably 1000 mA g-1 ormore. Preferably, the specific discharge capacity retention is 90% or more after 1000 cycles at a C- rate of 1C. Preferably, the specific discharge capacity retention is 80% or more after 2000 cycles at charge rate of 6C and a discharge rate of 1C.In some embodiments the specific discharge capacity at a C-rate of 5C is 140 mAh / g or more.In some embodiments the specific discharge capacity at a C-rate of 20C is 55 mAh / g or more.Working ElectrodeThe working electrode comprises a working electrode active material, and the workingelectrode active material comprises graphite particles having a D50 particle length by volume of D50w.The active material refers to the material involved in the electrochemical reaction within thecell (e.g., hosting the charge carrier). The working electrode may be an anode or cathode during a discharge step, for example in a lithium ion cell. Preferably, the working electrode is the anode during a discharge step. In some embodiments graphite particles have particle length spread, Sw, of 1.6 or more, wherein the spread is defined by formula (IIa): Sw = (D90w – D10w) / (D50w) (IIa)wherein D90w and D10w are the D90 and D10 particle lengths by volume of the graphiteparticles. In some embodiments Sw is 1.65 or more, preferably 1.7 or more, more preferably 1.75 or more. In some embodiments Sw is from 1.6 to 2.0, preferably from 1.7 to 1.9, more preferably from 1.75 to 1.85. Preferably Swis about 1.79. D90w, D50wand D10wmay be measured using any suitable method known to the skilled person. Preferably, D90w, D50w and D10w are measured by laser diffraction, such as set out in ISO 13320:2020.D50w is the 50th percentile by volume of the graphite particles lengths, D50w is the 50thpercentile by volume of the counter electrode active material particle lengths. D90 is 90thpercentile by volume, and D10 is the 10thpercentile volume. In some embodiments the graphite particles have a (i) D50w is from 1 to 20 µm, preferably from 2 to 10 µm, more preferably from 3 to 7 µm,yet more preferably from 3.5 to 4 µm; (ii) D10w is 5 µm or less, preferably 4 µm or less, more preferably 3 µm or less, yetmore preferably 2 µm or less; and / or(iii) D90w is 30 µm or less, preferably 20 µm or less, more preferably 15 µm or less, yetmore preferably 9 µm or less.In some embodiments the graphite particles have a:(i) D50w is from 1 to 8 µm, preferably from 2 to 6 µm, more preferably from 3 to 5 µm,yet more preferably from 3.5 to 4 µm; (ii) D10w is 5 µm or less, preferably 4 µm or less, more preferably 3 µm or less, yetmore preferably 2 µm or less; and / or(iii) D90w is 14 µm or less, preferably 12 µm or less, more preferably 10 µm or less, yetmore preferably 9 µm or less.In some embodiments, the graphite particles have a D50w particle length of from 1 to 8 µm,preferably from 2 to 6 µm, more preferably from 3 to 5 µm, yet more preferably from 3.5 to4 µm.In some embodiments, the graphite particles have a D10w particle length of 5 µm or less,preferably 4 µm or less, more preferably 3 µm or less, yet more preferably 2 µm or less. Thegraphite particles may have a D10w particle length of 0.5 to 5 µm, preferably from 1 to 4 µm,more preferably from 1.2 to 3 µm, yet more preferably from 1.5 to 2 µm.In some embodiments, the graphite particles have a D90w particle length of 14 µm or less,preferably 12 µm or less, more preferably 10 µm or less, yet more preferably 9 µm or less.The graphite particles may have a D90w particle length of 6 to 20 µm, preferably from 7 to15 µm, more preferably from 8 to 10 µm. In some embodiments the electrode active material comprises graphite particles having a bimodal particle length distribution. A bimodal distribution refers to a particle length distribution having at least two maximums (e.g., peaks), such as exactly two maximums. Each of the maximums represents a modal particle length. Each of the maximums are different, and preferably have a difference of from1 to 10 µm, more preferably from 2 to 6 µm, yet more preferably 3 to 4 µm.In some embodiments, the graphite particles have a first modal particle length of 2 µm ormore, more preferably 3 µm or more, yet more preferably 3.5 µm or more and a secondmodal particle length of 6 µm or more, more preferably 7 µm or more, yet more preferably7.5 µm or more. In some such embodiments, the graphite particles have a first modal particlelength of 6 µm or less, more preferably 5 µm or less, yet more preferably 4 µm or less and asecond modal particle length of 10 µm or less, more preferably 9 µm or less, yet morepreferably 8 µm or less.In some embodiments, the graphite particles have a first modal particle length of from 2 to6 µm, more preferably from 3 to 5 µm, yet more preferably from 3.5 to 4 µm and a secondmodal particle length of from 6 to 10 µm, more preferably from 7 to 9 µm, yet more preferablyfrom 7.5 to 8 µm. In a preferred embodiment the graphite particles have a first modal particlelength of about 4 µm and a second modal particle length of about 7.5 µm.It is thought that having a bimodal particle size distribution provides access to a high number of voids in the structure, which allows for increased lithium ion diffusion and good electrolyte- electrode interaction, while still providing a reasonable degree of energy density. In some embodiments a first population of the graphite particles have a first modal particlelength of from 2 to 6 µm, more preferably from 3 to 5 µm, yet more preferably from 3.5 to4 µm and a second population of the graphite particles have a second modal particle lengthof from 6 to 10 µm, more preferably from 7 to 9 µm, yet more preferably from 7.5 to 8 µm.In some embodiments a first population of the graphite particles have D50 particle length by volume of D50w1 and a second population of the graphite particles have a D50 particle length by volume of D50w2, wherein D50w1and D50w2satisfy Formula (IIIa): D50w1 = E50 × D50w2 (IIIa)wherein E50 is 3 or less, preferably 2.5 or less, more preferably 2 or less. E50 is typically more than 0. In some embodiments E50 is from 1 to 3, preferably from 1.5 to 2.5, more preferably from1.8 to 2.2. Preferably E50 is about 2.0. In some embodiments a first population of the graphite particles have D10 particle length by volume of D10w1and a second population of the graphite particles have a D10 particle length by volume of D10w2, wherein D10w1 and D10w2 satisfy Formula (IIIb): D10w1 = E10 × D10w2 (IIIb)wherein E10 is 3 or less, preferably 2.5 or less, more preferably 2 or less. E10is typically more than 0. In some embodiments E10is from 1 to 3, preferably from 1.5 to 2.5, more preferably from1.8 to 2.2. Preferably E10 is about 2.0.In some embodiments a first population of the graphite particles have D90 particle length by volume of D90w1 and a second population of the graphite particles have a D90 particle length by volume of D90w2, wherein D90w1 and D90w2 satisfy Formula (IIIc): D90w1 = E90 × D90w2 (IIIc)wherein E90is 3 or less, preferably 2.5 or less, more preferably 2 or less. E90is typically more than 0. In some embodiments E90is from 1 to 3, preferably from 1.3 to 2.3, more preferably from1.5 to 2.0. Preferably E90 is about 1.75.E10, E50and E90are each independently from 1 to 3, preferably from 1.5 to 2.5. Preferably, E10, E50 and E90 are each independently from 1.7 to 2.1. In some embodiments the working electrode comprises 90 wt.% or more electrode activematerial particles based on the total mass of the working electrode, preferably 94 wt.% ormore, more preferably 96 wt.% or more.In some embodiments the working electrode consists essentially of, such as consists of, electrode active material particles. The graphite particles may have a mean aspect ratio of 2 or more, preferably 3 or more. The aspect ratio is the ratio between the length (the longest dimension of the particle) and the width (the shortest dimension of the particle). The length and width are measured as described above for the particle length. The width may be taken as the shortest dimension of the particle when viewed from above (e.g., in a 2D plan representation). The graphite particles may have a sphericity of 0.9 or less, such as 0.8 or less, such as 0.7 or less. The graphite particles may have a sphericity of 0.4 or more, such as 0.5 or more, such as 0.6 or more.

[0038] The relatively high aspect ratio and / or the low sphericity further contributes to the low tap density of the graphite particles, and the associated benefits for high rate cycling. The secondary particles are preferably non-spherical, and typically have an aspect ratio 2 or more. This results in non-ideal packing properties that are reflected in the low tap density.

[0039] In some embodiments the graphite particles have a tap density of 0.8 g / cm3or less, preferably 0.7 g / cm3or less, more preferably 0.65 g / cm3or less. The tap density may be from 0.5 to 0.8 g / cm3, preferably 0.55 to 0.7 g / cm3, more preferably from 0.60 to 0.65 g / cm3.

[0040] Tap density may be measured using any suitable method known to the skilled person. Preferably, tap density is measured by ISO 3953:2011.

[0041] In some embodiments the graphite particles have a BET surface area of 4 m2 / g or more, preferably 5 m2 / g or more, more preferably 6 m2 / g or more. The graphite particles may have a BET surface area of from 4 to 10 m2 / g, preferably from 5 to 8 m2 / g, more preferably from 6 to 7 m2 / g.

[0042] BET surface area may be measured using any suitable method known to the skilled person. Preferably, BET surface area is measured using a nitrogen gas adsorption method, such as ISO 9277:2022.

[0043] The working electrode may be adapted to provide a current density of 700 mA g-1or more, preferably 800 mA g-1or more, more preferably 900 mA g-1or more, yet more preferably 1000 mA g-1or more.

[0044] The working electrode may be adapted to provide a current area density of 3.5 mA / cm2or more, preferably 4 mA / cm2or more, more preferably 5 mA / cm2or more. The working electrode may be adapted to provide a current area density of 10 mA / cm2or less, preferably 8 mA / cm2or less, more preferably 6 mA / cm2or less. The working electrode may be adapted to provide a current area density of 3.5 to 10 mA / cm2, preferably 4 to 8 mA / cm2or more, more preferably 5 to 6 mA / cm2. The current area density for a lithium ion cell may be calculated from the product of current density (mA g-1) x areal loading (g / cm2) of electrode active material. This gives the current area density (mA / cm2).

[0045] The working electrode may comprise a binder to improve adhesion of the electrode active material. Examples of typically binders are PVDF, PTFE, CMC, PAA, PMMA, PEO, SBR and co-polymers or mixtures thereof. In some embodiments, the binder is PVDF, CMC, SBR or a mixture thereof. Preferably the binder comprises a mixture of CMC and SBR. In some embodiments the working electrode further comprises a binder, wherein the binder is PVDF, CMC, SBR or a mixture thereof, preferably wherein the binder comprises a mixture of CMC and SBR.

[0046] The binder may be present at any suitable amount, such as from 1 to 5 wt.% based on the total mass of the electrode. Typically the binder is present at 2.5 wt.% based on the total mass of the electrode.

[0047] The working electrode is typically fixed to a current collector, such as a copper or aluminium collector, which may be in the form of a plate. The working electrode may be applied as a layer on a surface of the current collector.

[0048] In some embodiments the layer of the electrode active material has a coating density of from 1 to 10 mg / cm2, preferably from 3 to 8 mg / cm2, more preferably from 4 to 6 mg / cm2.

[0049] In some embodiments the layer of the electrode active material has a calendar density of from 1.2 to 1.8 g / cm3, preferably 1.3 to 1.6 g / cm3. The calendar density is determined by measuring the weight and thickness of the electrodes after calendaring. The calendaring process is as described below.

[0050] In some embodiments the layer of the electrode active material has a calendared porosity of from 20 to 50%, preferably 30 to 40%. This calendered porosity refers to the fraction of the volume of the calendared electrode which includes a pore or void. The porosity may be calculated based on comparison of the actual density verses the theoretical density of the material.

[0051] In some such embodiments, the layer of the electrode active material has a calendared packing efficiency of the graphite particles of from 53 % to 62 %. In some embodiments, the layer of the electrode has a thickness of from 25 to 50 pm, preferably from 30 to 45 pm, more preferably from 35 to 40 pm.

[0052] The working electrode may comprise a conductivity additive, such as a conductive carbon additive to improve conductivity. The conductive carbon material may be carbon black, nanoparticulate carbon powder, carbon fibre and / or carbon nanotubes. The conductive carbon material may be Ketjen black or Super P carbon, or hard or soft amorphous carbon. Preferably the conductivity additive is carbon black, carbon nanotubes, or a combination thereof.

[0053] The working electrode may comprise 1 wt.% or more of conductivity additive based on the total mass of the electrode. Preferably the conductivity additive comprises 0.95 wt.% or more carbon black, based on the total mass of the electrode. Preferably the conductivity additive comprises 0.05 wt.% or more carbon nanotubes based on the total mass of the electrode. In a particular preferred embodiment, the conductivity additive comprises about 0.95 wt.% carbon black and 0.05 wt.% carbon nanotubes. The working electrode may comprise comprises 90 wt.% or more graphite particles based onthe total mass of the electrode, preferably 94 wt.% or more, more preferably 96 wt.% or more.In some embodiments graphite is the dominant electrode active material in the anode. Thatis, the electrode active material is 50 wt.% or more graphite, based on the total mass of theelectrode active material in the anode. In some embodiments the electrode active material comprises 90 wt.% or more graphiteparticles based on the total mass of the electrode, preferably 94 wt.% or more, morepreferably 96 wt.% or more.In some embodiments the electrode active material consists essentially of graphite particles. In some embodiments the electrode active material consists of graphite particles. In a particular preferred embodiment there is provided a working electrode consisting of96.5 wt.% graphite particles as electrode active material, 0.95 wt.% C65 and 0.05 wt.%carbon nanotubes as conductivity additives, 2.5 wt.% CMC:SBR (1:1) binder. The graphite particles of the working electrode may be prepared using any suitable method,which would be known to the person in the art. For example, by milling (e.g., bead milling,dry milling, wet milling), grinding, electro spraying, sintering, calcination or a combinationthereof. Counter Electrode The counter electrode comprises a counter electrode active material, and the counter electrode active material comprises particles having a D50 particle length by volume of D50c. The active material refer to the material involved in the electrochemical reaction within the cell (e.g., hosting the charge carrier). The counter electrode may be an anode or cathode during a discharge step, for example in a lithium ion cell. Preferably, the counter electrode is the cathode during a discharge step. In some embodiments counter electrode active material comprises particles having a particle length spread, Sc, of 1.6 or less, wherein the spread is defined by formula (IIb): Sc = (D90c – D10c) / (D50c) (IIb)wherein D90cand D10care the D90 and D10 particle lengths by volume of the counter electrode active material particles. D90c, D50c and D10c may be measured using any suitable method known to the skilled person. Preferably, D90c, D50c and D10c are measured by laser diffraction, such as set out in ISO 13320:2020. In some embodiments Scis 1.5 or less, preferably 1.4 or less, more preferably 1.35 or less. In some embodiments Sc is from 1.0 to 1.5, preferably from 1.1 to 1.4, more preferably from 1.2 to 1.4. Preferably, Scis about 1.33. In some embodiments, particles of the counter electrode active material have a: (i) D50cof from 2 to 50 µm, preferably from 3 to 30 µm, more preferably from 4 to20 µm, yet more preferably from 5 to 10 µm;(ii) D10c of 8 µm or less, preferably 6 µm or less, more preferably 5 µm or less, yet morepreferably 4 µm or less; and / or(iii) D90cof from 6 to 80 µm, preferably from 8 to 60 µm, more preferably from 9 to40 µm, yet more preferably from 10 to 15 µm.In some embodiments, the particles of the counter electrode active material have a:(i) D50c of from 2 to 15 µm, preferably from 3 to 10 µm, more preferably from 4 to 8 µm,yet more preferably from 5 to 7 µm; (ii) D10c of 8 µm or less, preferably 6 µm or less, more preferably 5 µm or less, yet morepreferably 4 µm or less; and / or(iii) D90c from 6 to 20 µm, preferably from 8 to 15 µm, more preferably from 9 to 13 µm,yet more preferably from 10 to 12 µm. In some embodiments the particulate counter electrode material has a D10cparticle length, which is the 10thpercentile by volume of the particulate counter electrode material particlelengths, of 8 µm or less, preferably 6 µm or less, more preferably 5 µm or less, yet morepreferably 4 µm or less.In some embodiments the particulate counter electrode material has a D90cparticle length, which is the 90thpercentile by volume of the particulate counter electrode material particlelength, of from 6 to 20 µm, preferably from 8 to 15 µm, more preferably from 9 to 13 µm, yetmore preferably from 10 to 12 µm.Suitable counter electrode materials include lithium-containing or lithium-intercalated material,such as a lithium metal oxide, wherein the metal is typically a transition metal such as Co, Fe,Ni, V or Mn, or combination thereof. The counter electrode material may be doped withadditional metal or non-metal components or may be undoped. Preferably the counterelectrode material is undoped.Some examples of counter electrode materials include lithium cobalt oxide (LiCoO2; LCO),lithium nickel manganese cobalt oxide (NMC, NCM111, NCM532, NCM622 and NCM811),lithium vanadium fluorophosphate (LiVPO4F), lithium nickel cobalt aluminum oxide (NCA,LiNiCoAlO2), lithium iron phosphate (LFP, LiFePO4) and manganese-based spinels (e.g.LiMn2O4). Preferably the counter electrode material is LCO, NMC, NCA or a combinationthereof. Preferably the counter electrode material is LCO, NCM or a combination thereof.The NCM is preferably NCM811.A conductive carbon material (e.g., carbon black, graphite, nanoparticulate carbon powder orcarbon nanotubes) may be admixed with the counter electrode material. In one embodiment,the counter electrode comprises porous carbon, such as porous reduced graphene oxide. In one embodiment, the counter electrode is substantially free of binders. In an alternative embodiment, the counter electrode is admixed with a binder or adhesive. Some examples of binders or adhesives include PVDF, PTFE, CMC, PAA, PMMA, PEO, SBR and co-polymers thereof. The counter electrode is typically fixed to a current collecting substrate, such as an aluminum plate.In preferred embodiments the particulate counter electrode active material is lithium cobaltoxide (LCO).In preferred embodiments the counter electrode further comprises a binder, wherein thebinder is PVDF, CMC, SBR or a mixture thereof, preferably wherein the binder comprises a mixture of CMC and SBR.In preferred embodiments the counter electrode comprises 90 wt.% or more electrode activematerial particles based on the total mass of the working electrode, preferably 94 wt.% ormore, more preferably 96 wt.% or more.In preferred embodiments the counter electrode consists essentially of, such as consists of, electrode active material particles.In some embodiments the layer of the counter electrode active material has a calendaredporosity of from 20 to 50%, preferably 30 to 40%. This calendered porosity refers to the fraction of the volume of the calendared electrode which is includes a pore or void. The porosity may be calculated based on comparison of the actual density verses the theoretical density of the material.In some embodiments the layer of the electrode active material has a calendar density offrom 2 to 4 g / cm3, preferably 3.2 to 3.8 g / cm3. In some embodiments the layer of theelectrode active material has a calendar density of about 3.6 g / cm3. The calendar density isdetermined by measuring the weight and thickness of the electrodes after calendaring. The calendaring process is as described below. The counter electrode may be adapted to provide a current density of 700 mA g-1or more, preferably 800 mA g-1or more, more preferably 900 mA g-1or more, yet more preferably 1000 mA g-1or more.

[0054] The counter electrode may be adapted to provide a current area density of 3.5 mA / cm2or more, preferably 4 mA / cm2or more, more preferably 5 mA / cm2or more. The counter electrode may be adapted to provide a current area density of 10 mA / cm2or less, preferably 8 mA / cm2or less, more preferably 6 mA / cm2or less. The counter electrode may be adapted to provide a current area density of 3.5 to 10 mA / cm2, preferably 4 to 8 mA / cm2or more, more preferably 5 to 6 mA / cm2. The current area density is calculated as described above for the working electrode.

[0055] The counter electrode active material particles may be prepared using any suitable method, which would be known to the person in the art. For example the particles may be prepared by milling (e.g., bead milling, dry milling, wet milling), grinding, electro spraying, sintering, calcination or a combination thereof.

[0056] Electrolyte

[0057] The electrochemical cell also comprises an electrolyte. The electrolyte is for facilitating the flow of ions between the working electrode and the counter electrode. Thus, the electrolyte is present in the interelectrode space. Typically, the electrolyte in the electrochemical cell is suitable for solubilising lithium ions.

[0058] Typically, the electrolyte in a charged and discharged cell contains lithium ions. Typically, the electrolyte comprises lithium salts, such as LiTFSI, (bis(trifluoromethane)sulfonimide lithium salt, LiPFe, LiBF4, l_iCIC>4, LiTF (lithium triflate) or lithium bis(oxalato) borate (LiBOB). In some embodiments, the electrolyte comprises 1.15M LiPFe.

[0059] The electrolyte may be a liquid electrolyte, such as a liquid at ambient temperature, for example at 25°C.

[0060] The electrolyte may be a non-aqueous electrolyte. The electrolyte may comprise a polar aprotic solvent. The electrolyte may comprise an organic solvent. Solvents for dissolving lithium ions are well known in the art.

[0061] Suitable solvents include carbonate solvents. For example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), chloroethylene carbonate, fluorocarbonate solvents (e.g., fluoroethylene carbonate and trifluoromethyl propylene carbonate), as well as the dialkylcarbonate solvents, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC).Suitable solvents also include sulfone solvents. For example, methyl sulfone, ethyl methylsulfone, methyl phenyl sulfone, methyl isopropyl sulfone (MiPS), propyl sulfone, butyl sulfone, tetramethylene sulfone (sulfolane), phenyl vinyl sulfone, allyl methyl sulfone, methyl vinyl sulfone, divinyl sulfone (vinyl sulfone), di phenyl sulfone (phenyl sulfone), dibenzyl sulfone (benzyI sulfone), vinylene sulfone, butadiene sulfone, 4-methoxyphenyl methyl sulfone, 4- chlorophenyl methyl sulfone, 2-chlorophenyl methyl sulfone, 3,4-dichlorophenyl methyl sulfone, 4-(methylsulfonyl)toluene, 2-(methylsulfonyl) ethanol, 4-bromophenyl methyl sulfone, 2-bromophenyl methyl sulfone, 4-fluorophenyl methyl sulfone, 2-fluorophenyl methyl sulfone, 4-aminophenyl methyl sulfone, a sultone (e.g., 1,3-propanesultone), and sulfone solvents containing ether groups (e.g., 2-methoxyethyl(methyl)sulfone and 2- methoxyethoxyethyl(ethyl)sulfone). Suitable solvents also include silicon-containing solvents such as a siloxane or silane. For example hexamethyldisiloxane (HMDS), 1,3-divinyltetramethyldisiloxane, the polysiloxanes, and polysiloxane-polyoxyalkylene derivatives. Some examples of silane solvents include methoxytrimethy lsilane, ethoxytrimethy lsilane, dimethoxydimethylsilane, methyltrimethoxysilane, and 2-(ethoxy)ethoxytrimethylsilane. Typically, an additive may be included in the electrolyte to improve performance. For example vinylene carbonate (VC), vinyl ethylene carbonate, allyl ethyl carbonate, t-butylene carbonate, vinyl acetate, divinyl adipate, acrylic acid nitrile, 2-vinyl pyridine, maleic anhydride, methyl cinnamate, ethylene carbonate, halogenated ethylene carbonate, α-bromo-γ- butyrolactone, methyl chloroformate, 1,3-propanesultone, ethylene sulfite (ES), propylene sulfite (PS), vinyl ethylene sulfite (VES), fluoroethylene sulfite (FES), 12-crown-4 ether, carbon dioxide (CO2), sulfur dioxide (SO2), and sulfur trioxide (SO3). The additive may be present in the electrolyte at any suitable amount. Typically, the additive is present at 0.1 wt.% or more, such as 1 wt.% or more. The additive may be present at10 wt.% or less, such as 5 wt.% or less or 3 wt.% or less. In some embodiments, the additiveis present at from 0.1 to 5 wt.%, preferably 0.5 to 3 wt.%, preferably 1 to 2 wt.%. In some embodiments, the electrolyte comprises EC, EMC and VC solvents. The EC, EMC and VC solvents may be present in a ratio of 30:70:2 v / v / w. The electrochemical cell may also include a separator in the interelectrode space. The interelectrode space is the space between the working electrode and counter electrode. Theseparator is typically a solid porous membrane positioned between the working electrode andcounter electrode. The solid porous membrane may partially or completely replace the liquid electrolyte. The solid porous membrane may comprise a polymer (e.g., polyethylene, polypropylene, or copolymer thereof) or an inorganic material, such as a transition metal oxide (e.g., titania, zirconia, yttria, hafnia, or niobia) or main group metal oxide, such as silicon oxide, which can be in the form of glass fiber.The solid non-porous membrane may comprise a lithium-ion conductor. For example, LLZO(garnet family), LSPO (LISICON family), LGPS (thio-LISICON family), LATP / LAGP (NASICON family), LLTO (perovskite family) and phosphide / sulfide glass ceramics. Preferably the separator comprises a polymer, such as a polyethylene, polypropylene, orcopolymer thereof, or comprises fiberglass.The separator may have a porosity sufficient to facilitate the inter-electrode ion flow requiredby the electrochemical cell. This may be known as the current area density. The current area density for a singly charged ion (e.g., lithium) may be calculated from the product of current density (mA g-1) × areal loading (g / cm2) of electrode active material. This gives the current area density (mA / cm2). For example, where the areal loading of graphite particles is 5 mg / cm2and the current density is 700 mA / g, then the current area density is 3.5 mA / cm2.The separator may be adapted to receive a current area density of 3.5 mA / cm2 or more,preferably 4 mA / cm2 or more, more preferably 5 mA / cm2 or more. The separator may beadapted to receive a current area density of 10 mA / cm2or less, preferably 8 mA / cm2or less,more preferably 6 mA / cm2 or less. The separator may be adapted to receive a current areadensity of 3.5 to 10 mA / cm2, preferably 4 to 8 mA / cm2 or more, more preferably 5 to 6mA / cm2. Battery The present invention also provides a battery comprising one or more electrochemical cells of the invention. The battery may be a lithium ion battery. Where there are a plurality of electrochemical cells, these may be provided in series or parallel. A battery of the invention may be provided in a road vehicle, such as an automobile, bus, moped or truck. Alternatively, a battery of the invention may be provided in a rail vehicle, such as a train or a tram. A battery of the invention may also be provided in an electric bicycle (e-bike), a drone, an electric aircraft, and an electric or hybrid boat. Similarly, batteries of the invention may be provided in power tools such as powered drills or saws,garden tools such as lawnmowers, hedge trimmers, or grass trimmers, or home appliancessuch as toothbrushes, vacuum cleaners or hair dryers. Batteries of the invention may beused in cameras. Batteries of the invention may be used in robots, such as delivery robots or warehouse automation robots. A battery of the invention may be provided in a regenerative braking system. A battery of the invention may be provided in a portable electronic device, such as a mobile phone, laptop or tablet.

[0062] A battery of the invention may be provided in a power grid management system.

[0063] Method of Preparing an Electrochemical Cell

[0064] Generally, the invention also provides a method of preparing an electrochemical cell of the first aspect.

[0065] The method typically comprises a step of providing a working electrode, a counter electrode, an electrolyte, and optionally a separator, and assembling the same into an electrochemical cell.

[0066] There is also provided an electrochemical cell, obtained or obtainable by this method.

[0067] The assembly may be carried out in an oxygen free, and / or moisture free environment. Oxygen free or moisture free typically refers to an oxygen or water concentration below 1 ppm, preferably below 0.1 ppm.

[0068] The cell may be prepared by arranging the working electrode, counter electrode, and optionally a separator, in a container, and adding electrolyte.

[0069] The container may be a pouch.

[0070] The invention provides a method of preparing a working electrode or counter electrode for the electrochemical cell, the method comprising: depositing a layer of electrode active material composition onto a substrate.

[0071] The method may further comprise a step of calendaring the layer of electrode active material to form a working electrode.

[0072] The step of depositing a layer of electrode active material composition according to the second aspect onto a substrate may be known as the “deposition step”.

[0073] Preferably the substrate is a current collector. The current collector may be as described above.

[0074] The deposition step may be by any suitable additive manufacturing method, such as 3D printing, casting, or other methods known in the art. Preferably, the deposition step comprises: preparing a slurry of the electrode active material; casting a layer of the slurry onto the substrate; and drying the slurry to form a layer of the electrode active material.

[0075] The slurry may be prepared by adding a carrier fluid, such as water, to the electrode active material. The slurry is preferably flowable to allow the formation of a layer. The slurry may be about 50 wt.% electrode active material composition.

[0076] The step of casting a layer of the slurry typically includes adding the slurry to a substrate and allowing the slurry to flow across the substrate to form a layer. The slurry may be left to flow under gravity. Alternatively or in addition, the slurry may be spread to form a layer. The spreading may be achieved by mechanical agitation, ultrasound or a mechanical spreader (e.g., a blade run across the surface of the layer). The casting step typically forms a uniform layer of the composition across the substrate surface.

[0077] The step of drying the slurry typically removes the carrier fluid from the slurry to leave a dry layer of the electrode active material. The drying step may use increased temperatures. The drying step may use reduced pressures. The drying step may use a combination of increased temperature and reduced pressure. For example, the electrode may be dried at 100 °C for 3 h under vacuum.

[0078] Drying conditions may vary depending on the cell assembly process, cell type, and dry-room capability. In the case of an electrode jelly-roll or stack, bakeout, the temperature is limited to ~85°C with a duration of several days. If electrodes are able to be baked separately, a temperature range of 100-125°C for a duration of 8-12 hours may be used. The drying conditions may be adapted to suit the binders used.

[0079] The step of calendaring the layer of electrode active material to form a working electrode may be known as the “calendaring step”.

[0080] The calendaring step may be carried out by any suitable calendaring process, such as using rollers to apply pressure to the working electrode layer. The calendaring step typically provides a uniform layer of the working electrode material on the substrate.

[0081] The calendaring step may apply sufficiency pressure to the working electrode layer to provide a density of 1.2-1.4 g / cm3for the working electrode layer.

[0082] The calendaring step may be achieved using a pair of rollers. The rollers apply a pressure at a set inter-roller gap. The substrate is then fed through the rollers and so is subject to the pressure from the rollers. The size of the inter-roller gap may correspond to the desired thickness of the final material. A high pressure is typically used to achieve the desired thickness. In some embodiments, the rollers are heated during calendaring.

[0083] Method of Charging and / or Discharging

[0084] The invention also provides a method of charging and discharging the electrochemical cell or battery of the invention.

[0085] In another aspect there is provided a method of charging and / or discharging the electrochemical cell of the first aspect at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more.

[0086] In some embodiments the method comprises a cycle of charging and discharging the electrochemical cell. Preferably, the specific discharge capacity retention is 90% or more after 1000 cycles at a C-rate of 1C. Preferably, the specific discharge capacity retention is 80% or more after 2000 cycles at charge rate of 6C and a discharge rate of 1C.

[0087] In some embodiments the method comprises charging and / or discharging the electrochemical cell at a current density of 700 mA g-1or more, preferably 800 mA g-1or more, more preferably 900 mA g-1or more, yet more preferably 1000 mA g-1or more.

[0088] In some embodiments the specific discharge capacity at a C-rate of 5C is 140 mAh / g or more.

[0089] In some embodiments the specific discharge capacity at a C-rate of 20C is 55 mAh / g or more.

[0090] Use

[0091] In another aspect of the invention there is provided a use of an electrochemical cell of the fifth aspect for charging and / or discharging at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more.

[0092] The electrochemical cell may find use in the methods described herein.

[0093] Definitions

[0094] The following common definitions are used herein, as determined by the relevant context.

[0095] A dry weight basis refers to the mass without water. Where not otherwise specified, wt.% are provided as dry weights. Other Preferences

[0096] Each and every compatible combination of the embodiments described above is explicitly disclosed herein, as if each and every combination was individually and explicitly recited.

[0097] Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

[0098] “and / or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example “A and / or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

[0099] Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described.

[0100] Certain aspects and embodiments of the invention will now be illustrated by way of example and with reference to the figures described above.

[0101] Examples

[0102] The following examples are provided to further illustrate the present invention and are not intended to limit the scope of the invention.

[0103] Example 1 - Anode Testing

[0104] The graphite particles were used to prepare seven samples (Samples A to G) of dry graphite powder.

[0105] Physio-chemical Characterization of Graphite Particles

[0106] The physio-chemical properties of the graphite particles in each of Samples A to G were analysed.

[0107] Samples A and F were characterised by SEM microscopy at 2,000 x magnification. SEM images of the samples A and F are shown in Figure 6. The particles in sample F have a higher aspect ratio and a lower sphericity than Sample A. The small, non-spherical shape of the particles is suspected to be the reason for the very low tap density.

[0108] The BET surface area for Samples A to G was measured using ISO 9277:2022. The results of the BET surface area measurements are shown in Table 1. The D10, D50 and D90 particle diameters were measured using laser diffraction according to ISO 13320:2020. The length of the particles were measured and analysed to give a particle size distribution, from which the D10, D50 and D90 values were calculated. The particle size distribution is calculated on a volume basis. The results are shown in Table 1.

[0109] The tap density for Samples A to F were measured using ISO 3953:2011. The results of the tap density measurements are also shown in Table 1.

[0110] Table 1. Physio-chemical Properties of Graphite Samples

[0111] Sample F has the greatest BET surface area. Sample F has the lowest tap density. This is thought to be because the particles of Sample F have the poorest packing, and so have the greatest number of voids between particles. This leads to a low tap density and high specific surface area of the graphite particles.

[0112] The D90, D50 and D10 particle diameters were also compared using formula (II). The value of ‘S’ in Formula (II) is shown in Table 2.

[0113] S = (D90 - D10) / (D50) (II)

[0114] ‘S’ represents the distribution of the particle diameters (the difference between D90 and D10 particle diameters) as a proportion of the D50 particles diameter. If the distribution of particle diameters is large compared to the D50 particle diameter, then S is higher. However, if the distribution of particle diameter is small compared to the D50 particle diameter, then S is lower. Table 2. Particle Diameter of Graphite Samples and Value of ‘S’

[0115] The value of S is greatest for Sample F at 1.79. This indicates that Sample F has the greatest distribution of particle diameters compared to the D50 particle diameter. In other words, based on the average particle diameter the distribution of particle diameters is larger than the other samples.

[0116] Preparation of Electrodes

[0117] Graphite electrode active material slurries were prepared using 96.5 wt.% dry graphite powder (samples A to G), 1 wt.% C65 / CNT (0.95 / 0.05 w / w) and 2.5 wt.% CMC:SBR (1:1.5) binder, where the wt.% is a dry weight. These components were dispersed in about 50 ml of deionised water to give 50 wt.% of solid dispersion in water. The slurry was mixed.

[0118] The slurries were coated on a copper foil current collector, at a coat weight of 5 mg / cm2(dry weight). The electrodes were then dried under ambient conditions. The dried electrodes were calendared at room temperature to give a calendar density of 1.2-1.4 g / cm3, to give a graphite working electrode.

[0119] Electrochemical Characterization

[0120] The working electrodes were evaluated using 2025-type stainless steel coin cells in a half cell configuration. The graphite working electrode and lithium counter electrode were dried at 100 °C for 3 h under vacuum, then transferred into an argon-filled glove box without exposure to air. The cells were assembled in the glove box with an electrolyte including 1.15M LiPFe in EC, EMC and VC solvent (30:70:2 v / v). A fiberglass separator was used, after drying at 40 °C for 2 h under vacuum and transferring to the glove box.

[0121] Electrochemical performance was tested, by measuring intercalation and deintercalation capacity at 0.1 , 0.2, 0.5, 1, 2, 5, 10, 20C rates. The electrochemical performance results are summarized in Table 3. 5mV vs Li was taken as fully charged and 2.0V vs Li was taken as fully discharged.

[0122] The direct current internal resistance (DC-IR) of the cells was measured for the first charge and discharge cycle. The DC-IR was measured by setting the cell to a certain state of charge and allowing the cell to rest for ~15 minutes. A 1 second to 10 second current pulse is then applied through the cell. The difference in open circuit voltage (OCV) and load voltage is then divided by the current at the end of the pulse to give the DC-IR value.

[0123] The first cycle efficiency (FCE) was measured by comparing the first specific discharge capacity and the first specific charge capacity at a C-rate of C / 10. The first specific discharge capacity (FDC) is also provided in Table 3.

[0124] The specific charge capacity at a range of different C-rates were also measured. The delithiation between each test charge was carried out at a C-rate of C / 2.

[0125] Table 3. Electrochemical properties of graphite samples tested in 2025 half coin-cells with CMC:SBR binder

[0126] Sample F shows the lowest DC-IR value, as well as the highest specific capacity across all C- rates. At high C-rates the specific capacity of Sample F is proportionally much higher than the other samples. For example, at 0.2C the specific capacity of Sample F is on average only 20% higher than the other samples, whereas at 5C, 10C and 20C the specific capacity of Sample F is 37%, 38% and 42% higher respectively, compared to the other samples.

[0127] A multivariate correlation analysis between the physical and electrochemical properties of the graphite samples A to F indicates an excellent correlation between fast charge capability and DC-IR of the cells with the tap density of the graphite powder used to prepare the electrodes. Figure 1 plots the specific capacity at a rate of 20C compared to the tap density (top graph) and the first DC-IR against tap density (bottom graph).

[0128] Graphite particles which have a tap density lower than 0.8 g / cm3are shown to be best suited for enabling very fast cell cycling rates (e.g., 10C or 20C), as electrodes including these particles have a low DC-IR and high specific capacity at high C-rates.

[0129] The charge voltage profile was also analysed using a cell including Sample A and Sample F, at a range of C-rates. The results are shown in Figure 2, which plot the cell voltage against specific charge capacity for Sample A and Sample F. It can also be seen that the voltage profiles for Sample F are much flatter, and more consistent at different C-rates, indicating that the barrier to lithium intercalation is less dependent on the extent or rate of lithium intercalation. Comparing the lithium intercalation profiles of high tap density graphite to low tap density graphite, it is thought that the lithium diffusion in the low tap density electrodes is easier because the electrode potential is less dependent on lithium concentration in the electrode.

[0130] Without wishing to be bound by theory, it is thought that the low tap density graphite powder provides more voids for the electrolyte to transport lithium through the bulk of the electrode, resulting in improved lithium diffusion.

[0131] In addition, anisotropic particle orientation in the electrode may be responsible for higher rate capability, while isotropic orientation (e.g., the presence of large flakes parallel to the current collector) will cause ion transport hinderance in the direction normal to the current collector. For the same pore volume (i.e. same electrode density), the tortuosity would be higher in the direction normal to the current collector plane for the larger particles.

[0132] Particle Dso, size distribution and aspect ratio are responsible for the low tap density. Anisotropy of the particles orientation in the electrodes is the likely reason for high rate cycling performance.

[0133] Further Anode Particle Mixtures

[0134] Further graphite electrode active material slurries were prepared using 96.5 wt.% dry graphite powder, 1 wt.% C65 / CNT (0.95 / 0.05 w / w) and 2.5 wt.% CMC:SBR (1:1.5) binder, where the wt.% is a dry weight. In this example, the dry graphite powder used was a 1:1 weight ratio mixture of Sample F and Sample G (as described above). These components were dispersed in about 50 ml of deionised water to give 50 wt.% of solid dispersion in water. The slurry was mixed.

[0135] The slurries were coated on a copper foil current collector, at a coat weight of 5 mg / cm2(dry weight). The electrodes were then dried at 85°C. The dried electrodes were calendared at room temperature to give a calendar density of 1.2-1.4 g / cm3, to give a graphite working electrode.

[0136] A lithium foil counter electrode was prepared as described above.

[0137] The working electrodes were evaluated using 2025-type stainless steel coin cells in a half cell configuration, as described above. Electrochemical performance was tested as described above. The electrochemical performance results are summarized in Table 3 and shown graphically in Figures 3a and 3b.

[0138] Figure 3a shows that the anode formed from the mixture of Sample F and G had a charge rate capacity very similar to Sample F at rates from 0.2 to 10C. The anode formed from a mixture of Sample F and G also had a charging rate capacity greater than Sample G across all C- rates tested.

[0139] Figure 3b shows that the anode formed from the mixture of Sample F and G had a discharge rate capacity at rates from 0.1 to 20 slightly higher than both Sample F and G when used separately. At higher discharge rates of 5C and 100, the discharge rate capacity of the anode of the mixture of Samples F and G was similar to Sample F, but still greater than Sample G.

[0140] The mixture of Sample F and G has the benefit of similar or superior charge / discharge capacity, while having an overall lower BET surface area and tap density than sample F. As a result, the bimodal mixture of Samples F and G provides similar or better electrochemical properties with greater volumetric capacity and energy density.

[0141] Further Anode Binders

[0142] An alternative graphite electrode was prepared using the method described above for graphite samples A to F, but with 2.5 wt.% of a PVDF binder instead of the CMC:SBR binder. This electrode was assembled into a 2025-type stainless steel coin cells in a half cell configuration as described above.

[0143] The electrochemical performance of the cell was tested, by measuring intercalation and deintercalation capacity at 0.1 , 0.2, 0.5, 1, 2, 5, 10 and 20C rates, to determine the specific discharge capacity at these different rates. The results are shown in Table 4.

[0144] Table 4. Electrochemical properties of graphite samples tested in 2025 half coin-cells with PVDF binder

[0145] A multivariate correlation analysis between the tap density and specific discharge capacity was carried out, and the results for the electrode with the CMC:SBR binder and the PVDF binder are shown in Figure 4.

[0146] Figure 4 shows that the correlation observed was found to increase with charging rate capability, i.e. the faster charging rate is required from the graphite, the lower tap density is needed. This correlation is shown to occur for a PVDF binder and a CMC:SBR binder. Without wishing to be bound by theory, it is thought that ion transport becomes the limiting factor at high charging rates, so it is understood that lower tap density of the powders has a beneficial effect on the ion transport capability of the electrodes, hence the stronger correlation when charging rate increases. Different binders and binder systems may have varying degrees of adhesive and cohesive strength, electrolyte swelling, and insulative properties which may affect the resistance or impedance of the cell. Some binders and binder systems may also affect the electrode porosity and the availability of the electrolyte in contact with the particle surface. Anode particles can become electrically isolated during cycling if cohesive and adhesive strength is poor, resulting in loss of capacity and increase in impedance.Example 2 - Cathode TestingLithium cobalt oxide (LCO) particles were used to prepare two samples (Samples LCO-A and LCO-B) of dry LCO powder. NCM811 particles were also prepared. Physio-chemical Characterization of LCO ParticlesThe physio-chemical properties of the particles in each of Samples LCO-A, LCO-B andNCM811 were analysed.The BET surface area for Samples LCO-A, LCO-B and NCM811 was measured using ISO9277:2022. The results of the BET surface area measurements are shown in Table 5.The D10, D50 and D90 particle diameters for Samples LCO-A, LCO-B and NCM811 weremeasured using laser diffraction according to ISO 13320:2020. The lengths of particles weremeasured and analysed to give a particle size distribution, from which the D10, D50 and D90values were calculated. The size distribution is calculated on a volume basis. The results areshown in Table 5. The D90, D50 and D10 particle diameters were also compared using formula (II), which represents the distribution of the particle diameters (the difference between D90 and D10particle diameters) as a proportion of the D50 particles diameter. The value of ‘S’ inFormula (II) is shown in Table 5 for each of the Samples.Table 5. Physio-chemical Properties of Graphite Anode (Sample F) and LCO CathodeSamples (LCO-A and LCO-B) The Sample LCO-A has a much larger D50 than LCO-B, and accordingly also has a much lower BET surface area. LCO-A has a D50 over 4 times greater than the D50 of graphite Sample F. LCO-B has a D50 under 2 times greater than the D50 of graphite Sample F. NCM811 has a D50 about 2.7 times greater than the graphite D50 of Sample F. Preparation of Electrodes A graphite anode of Sample F was prepared as described above for Example 1.An LCO cathode was prepared by combining 95 wt.% LCO, 3 wt.% conductive carbon,2 wt.% PVdF to form a slurry, and then coating the slurry onto aluminium foil. The electrodeswere dried at room temperature. The dried electrodes were calendared at room temperatureto give a calendar density of 3.6 g / cm3.An NCM811 cathode was prepared in the same way. Electrochemical CharacterizationThe LCO electrodes were evaluated using 2025-type stainless steel coin cells in a half cellconfiguration. The graphite working electrode (Sample F) and LCO counter electrodes(LCO-A or LCO-B) were dried at 100 °C for 3 h under vacuum, then transferred into an argon-filled glove box without exposure to air. The cells were assembled in the glove box with anelectrolyte including 1.15M LiPF6 in EC, EMC and VC solvent (70:30:2 v / v / w). A fiberglassseparator was used, after drying at 40 °C for 2 h under vacuum and transferring to the glovebox. Electrochemical performance was tested, by measuring intercalation and deintercalationcapacity at 0.2, 0.5, 1, 2, 5, 10, 20C rates. 4.3V was taken as fully charged and 2.8V wastaken as fully discharged. The capacity retention was determined as a % of the initial charging capacity at 0.5C and the initial discharging capacity at 0.2C. The electrochemical performance results are summarized in Table 6.Table 6. Capacity Retention at high rates of LCO-A and LCO-B cathodes and Sample Fgraphite anode tested in 2025 half coin-cells

[0147] The capacity retention (%) during charging and discharging at 0.1 , 0.2, 0.5, 1, 2, 5, 10, 20C rates is also shown in Figure 5. The capacity retention is measured by comparing the initial charge / discharge capacity (at a C-rate of 0.2) with the charge / discharge capacity at the new C-rate.

[0148] Figure 5 shows that the charge and discharge capacity retention for LCO-B is superior to LCO-A across all charge rates. The difference between LCO-B and LCO-A is greatest at high rates, especially high charge rates.

[0149] The NCM811 cathode and Graphite Sample F anode were tested in a single-layer 12 mAh pouch cell. Long term electrochemical performance was tested, by measuring intercalation and deintercalation capacity at a charge rate of 12C and a discharge rate of 1C.

[0150] Figure 8 shows the capacity retention (compared to the initial cell capacity) over about 1 ,200 cell cycles. The cell retains a capacity of about 85% over 1 ,000 cycles at high charge rates.

[0151] It is thought that it is advantageous if the cathode fast charging rate capability matches the fast-charging rate capability of the graphite anode. This example shows that using a LCO or NCM cathode particles having a smaller particle size are better suited for fast charging. Specifically, LCO cathode with particle size Dso smaller than three times the Dso of the graphite anode material provides particularly fast charging and good capacity retention at high (dis)charge rates.

[0152] References

[0153] A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art. Full citations for these references are provided below. The entirety of each of these references is incorporated herein.

[0154] CN110649256B

[0155] CN111725485B

[0156] CN112397691A

[0157] CN 113140697

[0158] US 2023 / 0016746

[0159] CN 107910483

[0160] KR 1020230131294

[0161] US 7749659

[0162] WO 2021 / 125755

Claims

Claims:

1. An electrochemical cell having a working electrode, a counter electrode, and anelectrolyte, wherein the working electrode comprises a working electrode active material, and the workingelectrode active material comprises graphite particles having a D50 particle length by volumeof D50wthe counter electrode comprises a counter electrode active material, and the counterelectrode active material comprises particles having a D50 particle length by volume of D50c,wherein D50wand D50csatisfy Formula (Ia): D50c = C50 × D50w (Ia)wherein C50 is 6 or less, preferably 4 or less, more preferably 3 or less, yet morepreferably 2 or less.

2. The electrochemical cell of claim 1, wherein C50 is from 1 to 6, preferably from 1.2 to 4,more preferably from 1.3 to 3, yet more preferably from 1.4 to 2.

3. The electrochemical cell of claim 1 or 2, wherein the working electrode active materialcomprises graphite particles having a D10 particle length by volume of D10w, and the counterelectrode active material comprises particles having a D10 particle length by volume of D10c,wherein D10w and D10c satisfy Formula (Ib): D10c = C10 × D10w (Ib)wherein C10is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less.

4. The electrochemical cell of claim 3, wherein C10 is from 1 to 6, preferably from 1.2 to 4,more preferably from 1.3 to 3, yet more preferably from 1.5 to 2.

5. The electrochemical cell of any one of claims 1 to 4, wherein the working electrodeactive material comprises graphite particles having a D90 particle length by volume of D90w,the counter electrode active material comprises particles having a D90 particle length byvolume of D90c, and wherein D90w and D90c satisfy Formula (Ic):D90c = C90 × D90w (Ic)wherein C90is 6 or less, preferably 4 or less, more preferably 3 or less, yet more preferably 2 or less.

6. The electrochemical cell of claim 5, wherein C90 is from 1 to 6, preferably from 1.1 to 4,more preferably from 1.2 to 3, yet more preferably from 1.2 to 2.

7. The electrochemical cell of any one of claims 1 to 6, wherein graphite particles haveparticle length spread, Sw, of 1.6 or more, wherein the spread is defined by formula (IIa): Sw = (D90w – D10w) / (D50w) (Iia)wherein D90w and D10w are the D90 and D10 particle lengths by volume of the graphiteparticles.

8. The electrochemical cell of claim 7 wherein Sw is 1.65 or more, preferably 1.7 or more,more preferably 1.75 or more.

9. The electrochemical cell of any one of claims 1 to 8, wherein counter electrode activematerial comprises particles having a particle length spread, Sc, of 1.6 or less, wherein the spread is defined by formula (Iib): Sc = (D90c – D10c) / (D50c) (Iib)wherein D90c and D10c are the D90 and D10 particle lengths by volume of the counterelectrode active material particles.

10. The electrochemical cell of claim 9 wherein Sc is 1.5 or less, preferably 1.4 or less,more preferably 1.35 or less.

11. The electrochemical cell of any one of claims 1 to 10, wherein for the graphite particles:(i) D50w is from 1 to 20 µm, preferably from 2 to 10 µm, more preferably from 3 to 7 µm,yet more preferably from 3.5 to 4 µm; (ii) D10w is 5 µm or less, preferably 4 µm or less, more preferably 3 µm or less, yetmore preferably 2 µm or less; and / or(iii) D90w is 30 µm or less, preferably 20 µm or less, more preferably 15 µm or less, yetmore preferably 9 µm or less.

12. The electrochemical cell of any one of claims 1 to 11, wherein the graphite particleshave: (i) a tap density of 0.8 g / cm3 or less, preferably 0.7 g / cm3 or less, more preferably0.65 g / cm3 or less; and / or(ii) a calendar density of from 1.2 to 1.8 g / cm3, preferably 1.3 to 1.6 g / cm3.

13. The electrochemical cell of any one of claims 1 to 12, wherein the graphite particleshave a BET surface area of 4 m2 / g or more, preferably 5 m2 / g or more, more preferably6 m2 / g or more, wherein BET surface area is measured according to ISO 9277:2022.

14. The electrochemical cell of any one of claims 1 to 13, wherein the electrode activematerial comprises graphite particles having a bimodal particle length distribution.

15. The electrochemical cell of claim 14, wherein a first population of the graphite particleshave a first modal particle length of from 2 to 6 µm, more preferably from 3 to 5 µm, yet morepreferably from 3.5 to 4 µm and a second population of the graphite particles have a secondmodal particle length of from 6 to 10 µm, more preferably from 7 to 9 µm, yet more preferablyfrom 7.5 to 8 µm.

16. The electrochemical cell of either claim 14 or 15, wherein a first population of thegraphite particles have D50 particle length by volume of D50w1 and a second population ofthe graphite particles have a D50 particle length by volume of D50w2, wherein D50w1 andD50w2satisfy Formula (IIIa): D50w1 = E50 × D50w2 (IIIa)wherein E50 is 3 or less, preferably 2.5 or less, more preferably 2 or less.

17. The electrochemical cell of claim 16, wherein E50 is from 1 to 3, preferably from 1.5 to2.5, more preferably from 1.8 to 2.2.

18. The electrochemical cell of any one of claims 1 to 17, wherein for the particles of thecounter electrode active material: (i) D50c is of from 2 to 50 µm, preferably from 3 to 30 µm, more preferably from 4 to20 µm, yet more preferably from 5 to 10 µm;(ii) D10c is 8 µm or less, preferably 6 µm or less, more preferably 5 µm or less, yet morepreferably 4 µm or less; and / or(iii) D90c is from 6 to 80 µm, preferably from 8 to 60 µm, more preferably from 9 to40 µm, yet more preferably from 10 to 15 µm.

19. The electrochemical cell of any one of claims 1 to 18, wherein the counter electrodeactive material particles are lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide(NMC), nickel cobalt aluminum oxide (NCA) or a combination thereof, preferably LCO, NCMor a combination thereof.

20. The electrochemical cell of any one of claims 1 to 19, wherein working electrode and / orthe counter electrode comprises a binder, wherein the binder is PVDF, CMC, SBR, or amixture thereof, preferably wherein the binder comprises a mixture of CMC and SBR.

21. The electrochemical cell of any one of claims 1 to 20, wherein the working electrodeand / or the counter electrode comprises 90 wt.% or more electrode active material particlesbased on the total mass of the working electrode, preferably 94 wt.% or more, more preferably 96 wt.% or more.

22. The electrochemical cell of any one of claims 1 to 21 , further comprising a separator.

23. The electrochemical cell of any one of claims 1 to 22, wherein the electrochemical cell is chargeable and / or dischargeable, such as chargeable, at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more24. A method of charging and / or discharging the electrochemical cell of any one of claims 1 to 23 at a C-rate of 5C or more, preferably 10C or more, more preferably 20C or more.

25. The method of claim 24 wherein the method comprises a cycle of charging and discharging the electrochemical cell, and(i) the specific discharge capacity retention is 90% or more after 1 ,000 cycles at a C-rate of 1 C, and / or(ii) the specific discharge capacity retention is 80% or more after 2,000 cycles at charge rate of 6C and a discharge rate of 1C.

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