WO2022208047A1

WO2022208047A1 - Process

Info

Publication number: WO2022208047A1
Application number: PCT/GB2022/050683
Authority: WO
Inventors: Daniel CAIRNS; Paul Frederick CONNAGHAN; Andrew Diamond; Joshua Andrew HEAPS
Original assignee: Ev Metals Uk Limited
Priority date: 2021-03-31
Filing date: 2022-03-18
Publication date: 2022-10-06
Also published as: GB202104681D0

Abstract

The present invention provides a process for producing a particulate lithium nickel metal oxide material having a composition according to Formula 1: Li_aNi_xM_yA_zO_2+b Formula 1 in which: M is one or more of Co and Mn; A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W; 0.8 ≤ a ≤ 1.2 0.5 ≤ x < 1 0 < y ≤ 0.5 0 ≤ z ≤ 0.2 -0.2 ≤ b ≤ 0.2 x + y + z = 1 the process comprising the steps of: (iv) pre-calcining a mixture of nickel metal precursor particles and a lithium-containing compound at a temperature less than 625 °C to form a pre-calcined intermediate; (v) treating the pre-calcined intermediate with at least one metal-containing compound; (vi) calcining the material obtained after step (ii) at a temperature to form the particulate lithium nickel metal oxide material.

Description

PROCESS

Field of the Invention

The present invention relates to improved processes for making lithium nickel metal oxide materials which have utility as cathode materials in secondary lithium-ion batteries.

Background of the Invention

Lithium nickel metal oxide materials having a layered structure find utility as cathode materials in secondary lithium-ion batteries. High nickel content in such materials can lead to a high discharge capacity but can also lead to reduced capacity retention due to poor electrochemical stability after repeated charge-discharge cycles.

It has been found that increasing or enriching the amount of certain metal elements, such as cobalt, at the particle surface or, in the case of secondary particles, at the grain boundary between adjacent primary particles, can be an effective way to improve capacity retention.

Typically, lithium nickel metal oxide materials are produced by mixing a nickel metal precursor with a source of lithium, and then calcining the mixture at a temperature of at least 700 °C to form the desired layered crystalline structure. Grain boundary enrichment is then achieved by immersion of secondary particles of the lithium nickel metal oxide material in a solution of one of more metal-containing compounds and then removal of the solvent through evaporation, followed by a second calcination step.

For example, WO2013025328A2 (TIAX LLC) describes a particle including a plurality of crystallites including a lithium nickel metal oxide composition having a layered a-NaFeC>2- type structure, and a grain boundary between adjacent crystallites, wherein a concentration of cobalt in the grain boundaries is greater than in the crystallites. Example 2 of WO2013025328 has the composition Li1.01 Mg0.024Ni0.88Co0.12O2.03 and has cobalt-enriched grain boundaries. In order to form this material, a mixture of a nickel cobalt hydroxide precursor, lithium hydroxide, magnesium hydroxide and lithium nitrate is calcined at a temperature of 700 °C for six hours to form a lithium nickel metal oxide base material (Example 1). In order to achieve enrichment of the grain boundaries, particles of the lithium nickel metal oxide base material are then added to an aqueous solution of lithium nitrate and cobalt nitrate and the resulting slurry subsequently spray dried before a second heat treatment step (Example 2). WO2017189887A1 (CAM POWER, L.L.C.) describes a method of manufacturing electrochemically active polycrystalline particles where the method includes a first calcination with a maximum temperature of less than 700 °C and optionally further includes coating the particles and subjecting them to a second calcination to enrich grain boundaries.

The use of surface modification and / or grain boundary enrichment has the drawback that additional process steps are required, leading to higher energy consumption, increased levels of process waste, and higher manufacturing costs. This can impact on the commercial viability of such materials and have environmental impacts.

There remains a need for improved processes for the manufacture of lithium nickel metal oxide materials which have enhanced process efficiency.

Summary of the Invention

The present inventors have surprisingly found that a low temperature pre-calcination step can be used to significantly improve process efficiency, in particular in combination with surface-modification methods that avoid the immersion of intermediate materials in a solution of one or more metal-containing compounds.

It has further been found that the discharge capacity retention of materials produced by immersion-evaporation methods involving two high temperature calcinations may be at least matched by materials produced by the herein described process, with the advantage that a lower temperature pre-calcination can be used during the manufacturing process, significantly reducing energy consumption.

Accordingly, in a first aspect of the invention there is provided a process for producing a particulate lithium nickel metal oxide material having a composition according to Formula 1:

LiaNixMyAzC>2+b Formula 1 in which:

M is one or more of Co and Mn;

A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W;

0.8 £ a £ 1.2 0.5 £ x < 1 0 < y £ 0.5 0 £ z £ 0.2 -0.2 £ b £ 0.2 x + y + z = 1 the process comprising the steps of:

(i) pre-calcining a mixture of nickel metal precursor particles and a lithium-containing compound at a temperature less than 625 °C to form a pre-calcined intermediate;

(ii) treating the pre-calcined intermediate with at least one metal-containing compound;

(iii) calcining the material obtained after step (ii) to form the particulate lithium nickel metal oxide material.

In a second aspect of the invention there is provided a particulate lithium nickel metal oxide obtained or obtainable by a process described herein.

Brief Description of the Drawings

Figure 1 shows an SEM image of particles formed in Example 6.

Figure 2 shows an SEM image of particles formed in Example 7.

Detailed Description

Preferred and/or optional features of the invention will now be set out. Any aspect of the invention may be combined with any other aspect of the invention unless the context demands otherwise. Any of the preferred and/or optional features of any aspect may be combined, either singly or in combination, with any aspect of the invention unless the context demands otherwise.

The present invention provides a process for the production of particulate lithium nickel metal oxide materials having a composition according to Formula I as defined above.

In Formula I, 0.8 £ a £ 1.2. It may be preferred that a is greater than or equal to 0.9, or 0.95. It may be preferred that a is less than or equal to 1.1 , or less than or equal to 1.05. It may be preferred that 0.90 £ a £ 1.10, for example 0.95 £ a £ 1.05, or that a = 0 or about 0. In Formula I, 0.5 £ x < 1. It may be preferred that 0.6 £ x < 1 , for example 0.7 £ x < 1,

0.75 £ x < 1 , 0.8 £ x < 1 , 0.85 £ x < 1 or 0.9 £ x < 1. It may be preferred that x is less than or equal to 0.99, 0.98, 0.97, 0.96 or 0.95. It may be preferred that 0.75 £ x < 1 , for example 0.75 £ x £ 0.99, 0.75 £ x £ 0.98, 0.75 £ x £ 0.97, 0.75 £ x £ 0.96 or 0.75 £ x £ 0.95. It may be further preferred that 0.8 £ x < 1 , for example 0.8 £ x £ 0.99, 0.8 £ x £ 0.98,

0.8 £ x £ 0.97, 0.8 £ x £ 0.96 or 0.8 £ x £ 0.95. It may also be preferred that 0.85 £ x < 1 , for example 0.85 £ x £ 0.99, 0.85 £ x £ 0.98, 0.85 £ x £ 0.97, 0.85 £ x £ 0.96 or 0.85 £ x £ 0.95.

M is one or more of Co and Mn. In other words, the general formula may alternatively be written as Li_aNi_xCoyiMn_y2A_z0_2+b, wherein y1+y2 satisfies 0 < y1+y2 £ 0.5, wherein either y1 or y2 may be 0. It may be preferred that M is Co alone, i.e. the lithium nickel metal oxide contains no Mn.

In Formula 1 , 0 < y £ 0.5. It may be preferred that y is greater than or equal to 0.01 , 0.02 or 0.03. It may be preferred that y is less than or equal to 0.4, 0.3, 0.25, 0.2, 0.15, 0.1 or 0.05.

It may also be preferred that 0.01 £ y £ 0.5, 0.02 £ y £ 0.5, 0.03 £ y £ 0.5, 0.01 £ y £ 0.4,

0.01 £ y £ 0.3, 0.01 £ y £ 0.25, 0.01 £ y £ 0.20, 0.01 £ y £ 0.1 or 0.03 £ y £ 0.1.

A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo,

Nb, P, Sb, and W. It may be further preferred that A is Mg and / or Al optionally in combination with one or more of V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Sr, Mn, Ca, S, Ce, La, Mo, Nb, P, Sb, and W. It may be further preferred that A is Mg optionally in combination with one or more of Al, B or Zr, or that A is Mg and Al. Where A comprises more than one element, z is the sum of the amount of each of the elements making up A.

In Formula I, 0 £ z £ 0.2. It may be preferred that 0 £ z £ 0.15, 0 £ z £ 0.10, 0 £ z £ 0.05, 0 £ z £ 0.04, 0 £ z £ 0.03, 0 £ z £ 0.02, 0 £ z £ 0.01 or that z is 0 or about 0.

In Formula I, -0.2 £ b £ 0.2. It may be preferred that b is greater than or equal to -0.1. It may also be preferred that b is less than or equal to 0.1. It may be further preferred that - 0.1 £ b £ 0.1 , or that b is 0 or about 0.

It may be preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1, 0 < y £ 0.25, 0 £ z £ 0.2, -0.2 £ b £ 0.2 and x + y + z = 1. It may also be preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1, 0 < y £ 0.25, 0 £ z £ 0.2, -0.2 £ b £ 0.2, x + y + z = 1 , and A = Mg optionally in combination with one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W (it may be further preferred in such cases that M = Co). It may also be preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1, 0 < y £ 0.25, 0 £ z £ 0.2, -0.2 £ b £ 0.2, x + y + z = 1, and A = Al optionally in combination with one or more of V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W (it may be further preferred in such cases that M = Co). It may be further preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1 , 0 < y £ 0.25, 0 £ z £ 0.2, -0.2 £ b £ 0.2, x + y + z = 1, and A = Al and Mg optionally in combination with one or more of V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, W (it may be further preferred in such cases that M = Co). It may also be preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1, 0 < y £ 0.25, 0 £ z £ 0.1, -0.2 £ b £ 0.2, x + y + z = 1 and A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W, or A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W and M = Co. It be further preferred that 0.8 £ a £ 1.2, 0.75 £ x < 1, 0 < y £ 0.25, 0 £ z £ 0.05, -0.2 £ b £ 0.2, x + y + z = 1 and A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W, or A is one or more Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and Wand M = Co.

Typically, the lithium nickel metal oxide material is a crystalline (or substantially crystalline) material with an a-NaFe0₂-type structure.

It may be preferred that the particulate lithium nickel metal oxide material of Formula I is surface-modified. Herein, the term “surface-modified” refers to a particulate material in which the particles comprise a layer of material at or near to the surface of the particles which contains a greater concentration of at least one element than the remaining material of the particle, i.e. the core of the particle. Typically, the surface modification results from contacting the particles with one or more further metal-containing compounds, and then heating the material. For clarity, the discussions of the composition according to Formula I herein when in the context of surface-modified particles relate to the overall particle, i.e. the particle including the modified surface layer.

Typically, the lithium nickel metal oxide particles are in the form of secondary particles which comprise a plurality of primary particles (made up from one or more crystallites). The primary particles may also be known as crystal grains. The primary particles are separated by grain boundaries. It may be further preferred that, in the case that the particulate lithium nickel metal oxide material is in the form of secondary particles, the material comprises enriched grain boundaries, i.e. the concentration of one or more metals at the grain boundaries is greater than the concentration of the one or more metals in the primary particles. It may be preferred that the concentration of cobalt at the grain boundaries between the primary particles of the particulate lithium nickel metal oxide materials is greater than the concentration of cobalt in the primary particles. Alternatively, or in addition, it may be further preferred that the concentration of aluminium at the grain boundaries between the primary particles is greater than the concentration of aluminium in the primary particles.

The concentration of cobalt in the primary particles may be at least 0.5 atom %, e.g. at least 1 atom %, at least 2 atom % or at least 2.5 atom % with respect to the total content of Ni, M and A in the primary particle. The concentration of cobalt in the primary particle may be 35 atom % or less, e.g. 30 atom % or less, 20 atom % or less, atom % or less, 15 atom % or less, 10 atom % or less, 8 atom % or less or 5 atom % or less with respect to the total content of Ni, M and A in the primary particles.

The concentration of cobalt at the grain boundaries may be at least 1 atom %, at least 2 atom %, at least 2.5 atom % or at least 3 atom % with respect to the total content of Ni, M, and A at the grain boundaries. The concentration of cobalt at the grain boundaries may be 40 atom % or less, e.g. 35 atom % or less, 30 atom % or less, 20 atom % or less, atom % or less, 15 atom % or less, 10 atom % or less, or 8 atom % or less with respect to the total content of Ni, M and A in the primary particles.

The difference between the concentration of cobalt in the primary particles and at the grain boundaries may at least 1 atom %, e.g. at least 3 atom % or at least 5 atom % (calculated by subtracting the concentration of cobalt in the primary particles in atom % from the concentration of cobalt at the grain boundaries in atom %).

The concentration of a metal, such as cobalt or aluminium, at the grain boundaries and in the primary particles may be determined by energy dispersive X-ray spectroscopy (EDX) analysis of the centre of a grain boundary and the centre of an adjacent primary particle for a thinly sliced (e.g. 100-150 nm thick) section of a particle by a sectioning technique such as focused ion beam milling.

It may be preferred that the particles of lithium nickel metal oxide have a cobalt-rich coating on their surface. The concentration of cobalt in the particles may decrease in a direction from the surface to the centre of the particles. The difference between the concentration of cobalt at the surface of the particles and at the centre of the secondary particles may be at least 1 atom %, e.g. at least 3 atom % or at least 5 atom % (calculated by subtracting the concentration of cobalt at the surface of the particles in atom % from the concentration of cobalt at the centre of the particles in atom %). The concentration of cobalt at the grain boundaries and in the primary particles may also be determined using the method as set out above.

The particles of lithium nickel metal oxide typically have a D50 particle size of at least 1 pm, e.g. at least 2pm, at least 4pm or at least 5pm. The particles of lithium nickel metal oxide typically have a D50 particle size of 30pm or less, e.g. 25pm or less or 12pm or less. It may be preferred that the particles of lithium nickel metal oxide have a D50 of 1 pm to 30pm, such as between 2pm and 25pm, or 5pm and 20pm. The term D50 as used herein refers to the median particle diameter of a volume-weighted distribution. The D50 may be determined by using a laser diffraction method (e.g. by suspending the particles in water and analysing using a Malvern Mastersizer 2000).

The process as described herein comprises a step (i) of pre-calcining a mixture of nickel metal precursor particles and a lithium-containing compound at a temperature less than 625 °C to form a pre-calcined intermediate.

The nickel metal precursor is a compound which comprises nickel and one or more additional metals and which may be converted to the desired lithium nickel metal oxide with a layered structure upon heat treatment in the presence of a lithium-containing compound. The nickel metal precursor may be a precipitated nickel metal compound, for example it may be a co-precipitated mixed nickel metal compound.

The nickel metal precursor may be a nickel metal hydroxide, a nickel metal oxyhydroxide or a mixture thereof.

It may be preferred that the nickel metal precursor comprises a compound according to Formula 2:

[Ni_X2M_y2Az2][Op(OH)_q]a,

Formula 2 wherein:

M is one or more of Co and Mn;

A is one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Mn, Ca, S, Ce, La, Mo, Nb, P, Sb, and W;

0.5 £ x2 < 1 0 £ y2 £ 0.5 0 £ z2 £ 0.2 wherein p is in the range 0 £ p < 1 ; q is in the range 0 < q £ 2; x2 + y2 + z2 = 1 ; and a is selected such that the overall charge balance is 0.

Preferably, p is 0, and q is 2. In other words, preferably the nickel metal precursor is a pure metal hydroxide having the general formula [Ni_X2M_y2A_Z2][(OH)2]a.

As discussed above, a is selected such that the overall charge balance is 0. a may therefore satisfy 0.5 £ a £ 1 .5. For example, a may be 1 . Where A includes one or more metals not having a +2 valence state, or not present in a +2 valence state, a may be other than 1.

It will be understood by the skilled person that the values x2, y2, and z2, and the element(s) M and A, are selected so as to achieve the desired composition in Formula 1 after the process as described herein.

It may be preferred that 0.7 £ x2 < 1 , 0 < y2 £ 0.3, 0 £ z2 £ 0.2, or that 0.75 £ x2 < 1 , 0 < y2 £ 0.25, 0 £ z2 £ 0.2. It may also be preferred that 0.75 £ x2 < 1 , 0 < y2 £ 0.25, 0 £ z2 £ 0.2 and A = Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W (it may be further preferred in such cases that M = Co). It may also be preferred that 0.75 £ x2 < 1 , 0 < y2 £ 0.25, 0 £ z2 £ 0.1 , A = Mg optionally in combination with one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W, or that A = Mg optionally in combination with one or more of Al, V, Ti, B, Zr, Cu, Sn, Cr, Fe, Ga, Si, Zn, Mg, Sr, Ca, S, Ce, La, Mo, Nb, P, Sb, and W and M = Co.

For example, the nickel metal precursor may be a compound of formula Ni0.90CO0.05Mg_0.05(OH)2, Ni0.90CO0.06Mg_0.04(OH)2, Ni0.90CO0.07Mg_0.03(OH)2, Nio.9lCOo.08Mgo.Ol(OH)2, Nio.88Coo.o8Mgo.o4(OH)_2, Nio.9oCoo.o8Mgo.o2(OH)₂, or Nio.93Coo.o6Mgo.oi(OH)2.

The nickel metal precursor particles are typically provided in the form of secondary particles comprising a plurality of primary particles.

The nickel metal precursor materials are produced by methods well known to the person skilled in the art. Typically, these methods involve the co-precipitation of a mixed metal hydroxide from a solution of metal salts, such as metal sulfates, for example in the presence of ammonia and a base, such as NaOH. In some cases, suitable nickel metal precursors, such as mixed metal hydroxides, may be obtainable from commercial suppliers known to the skilled person.

The nickel metal precursor materials are mixed with at least one lithium-containing compound to the precursor particles prior to pre-calcination. Suitable lithium-containing compounds that may be mixed with the precursor materials include lithium salts, such as inorganic lithium salts, for example lithium hydroxide (e.g. LiOH or UOH.H2O) or lithium carbonate (U2CO3). Lithium hydroxide may be particularly preferred.

The mixture is then heated at a temperature less than 625 °C to form a pre-calcined intermediate. Typically, the pre-calcination step is carried out at a temperature of at least 250 °C, at least 275°C, or at least 300 °C. It may be preferred that the pre-calcination step is carried out at a temperature of 600 °C or less, 575 °C or less, or 550 °C or less, 525 °C or less, 500 °C or less, 475 °C or less, 450 °C or less, 425 °C or less, 400 °C or less, 375 °C or less, or 350 °C or less. It may be preferred that the mixture may be held at a temperature in the range of and including 275 to 625 °C, 275 to 600 °C, or 275 to 550 °C, or 275 to 525 °C.

Typically, the mixture is heated for a period of at least 1 hour, at least 2 hours, at least 3 hours, at least 4 hours or at least 5 hours. The period may be less than 12 hours, less than 10 hours, or less than 8 hours. Preferably, the pre-calcination step comprises heating to a temperature in the range of and including 275 to 625 °C for a period of 1 to 12 hours, such as 1 to 8 hours, 1 to 6 hours, or 1 to 4 hours. It may be further preferred that the pre-calcination step comprises heating to a temperature in the range of and including 275 to 525 °C for a period of 1 to 8 hours, 1 to 6 hours, or 1 to 4 hours.

The pre-calcination step is preferably carried out under a CC free atmosphere. For example, CC>2-free air may be flowed over the materials to be calcined during calcination and optionally during cooling. The CC>2-free air may, for example, be a mix of oxygen and nitrogen. Preferably the CC>2-atmosphere comprises at least 90 vol% oxygen, or more preferably the CC>2-free atmosphere may be oxygen (e.g. pure oxygen). Preferably, the atmosphere is an oxidising atmosphere. As used herein, the term “CC>2-free” is intended to include atmospheres including less than 100 ppm CO2, e.g. less than 50 ppm CO2, less than 20 ppm CO2 or less than 10 ppm CO2. These CO2 levels may be achieved by using a CO2 scrubber to remove CO2.

The pre-calcination may be carried out in any suitable furnace known to the person skilled in the art, for example a static kiln (such as a tube furnace or a muffle furnace), a tunnel furnace (in which static beds of material are moved through the furnace in a ceramic saggar or other container) such as a roller hearth kiln or push-through furnace, or a rotary furnace (including a screw-fed or auger-fed rotary furnace). In general, a rotary furnace (also known as a rotary kiln or rotary calciner) is a piece of kiln equipment comprising a cylindrical or tubular drum into which the material to be heated is loaded. The drum tends to be heated by a heater external to the drum. During calcination the drum is rotated slowly to agitate the material.

Preferably, the pre-calcination is carried out using a rotary furnace. It has been found by the current inventors that the distribution of lithium compound(s) in the pre-calcined intermediate is significantly improved through the use of a rotary furnace for the pre-calcination in comparison with pre-calcination of a static bed of material. The use of a rotary furnace also provides a more efficient process in terms of both cost and energy consumption in comparison to a tunnel furnace and also saves on materials since there is no need to use saggars during the calcination.

Optionally, the process may include the step of milling or sieving the pre-calcined intermediate prior to step (ii). For example, the particles of the pre-calcined intermediate may be sieved or milled until they have a particle size distribution such that the D50 particle size is 20 pm or less, 15 pm or less, e.g. 14 pm or less or 13 pm or less, for example between 3 and 20 pm.

In step (ii) of the process the pre-calcined intermediate is treated with at least one metal- containing compound to provide a treated intermediate which is then then subjected to calcination in step (iii) to form the lithium nickel metal oxide particles.

It will be understood by the skilled person that the metal-containing compounds are selected to include those elements which are desired to be present in the surface layer of the particulate lithium nickel metal oxide material. The metal-containing compounds are typically metal salts, inorganic metal salts, for example metal oxides, hydroxides, nitrates, sulfates, citrates or acetates. Nitrates may be particularly preferred.

In some embodiments, the or each metal-containing compound present is independently selected from an M-containing compound and an A-containing compound (and optionally a Li-containing compound). The pre-calcined intermediate may be treated with one or more of each of these options, e.g. one or more A-containing compounds, wherein the identity of A is different within each compound. In some embodiments, the pre-calcined intermediate is treated with at least one metal- containing nitrate, wherein each metal-containing nitrate present is independently selected from an M-containing nitrate and an A-containing nitrate (and optionally a Li-containing nitrate).

In some embodiments, the pre-calcined intermediate is treated with at least one M- containing compound and at least one A-containing compound and, optionally at least one Li-containing compound. In some embodiments, the pre-calcined intermediate is treated with a single M-containing compound, a single A-containing compound, and optionally a single Li-containing compound. In some embodiments, the pre-calcined intermediate is treated with a single M-containing nitrate, a single A-containing nitrate and a single Li- containing nitrate.

Preferably, the pre-calcined intermediate is treated with an aluminium-containing compound. The aluminium-containing compound is typically an aluminium salt, such as an inorganic aluminium salt, for example aluminium nitrate. The use of an aluminium-containing compound can lead to an increase in the concentration of aluminium at the grain boundaries and/or at or near to the surface of the lithium nickel metal oxide particles.

Alternatively, or in addition, it is preferred that the pre-calcined intermediate is treated with a cobalt-containing compound. The cobalt-containing compound is typically a cobalt salt, such as an inorganic cobalt salt, for example cobalt nitrate. The use of a cobalt-containing compound in the coating liquid can lead to an increase in the concentration of cobalt at the grain boundaries and/or at or near to the surface of the lithium nickel metal oxide particles.

Alternatively, or in addition, the pre-calcined intermediate is treated with a zirconium- containing compound. In some embodiments, the pre-calcined intermediate is treated with a zirconium-containing compound alongside one or both of a cobalt-containing compound and an aluminium-containing compound. In some embodiments, the pre-calcined intermediate is treated with zirconium-containing compound but does not contain either of a cobalt- containing compound and an aluminium-containing compound. In some embodiments, the pre-calcined intermediate is treated with a zirconium-containing compound as the sole metal-containing compound.

Optionally, the pre-calcined intermediate is treated with a lithium-containing compound in addition to one or more other metal-containing compounds. It proposed that this may be beneficial in order to avoid voids or defects in the structure of the particulate lithium nickel metal oxide material which may lead to a reduced lifetime.

The treatment of the pre-calcined intermediate may be achieved by any suitable method.

In some embodiments, the treatment is achieved by immersing the particles of the pre calcined intermediate in a solution of one or more metal-containing compounds, then removing solvent from the solution, for example by spray drying. It may be preferred that the treatment of the pre-calcined intermediate is achieved by mixing the particles of the pre calcined intermediate with the one or more metal-containing compounds in the absence of any liquid medium (i.e. dry mixing).

It may be further preferred that the pre-calcined intermediate is mixed with the one or more metal-containing compounds using acoustic resonance. The use of acoustic resonance involves the application of acoustic energy of a selected frequency to a mixing vessel to cause macroscopic and microscopic turbulence within the mixture. The mixing is typically achieved without the use of impellors, blades, rotors, or paddles. It may be preferred that the mixture is subjected to acoustic energy at a frequency that causes resonance of the materials to be mixed. In this case, the frequency is selected to match the resonant frequency of the mixing vessel and the materials to be mixed. This causes rapid mixing of the pre-calcined intermediate with the or each metal-containing compound. Typically, the frequency of the acoustic energy applied during mixing is at a much lower frequency than ultrasonic mixing, i.e. it is preferred that the mixing is not ultrasonic mixing. It may be preferred that the acoustic energy applied is in the range from about 15 Hz to about 1000 Hz. It may be further preferred that the frequency range for the acoustic energy is from about 15 Hz to 500 Hz, 15 Hz to 200 Hz, 15 Hz to 100 Hz, 20 Hz to 100 Hz, more preferably 25 Hz to 100 Hz, 30 Hz to 100 Hz, 40 Hz to 100 Hz, 50 Hz to 100 Hz, 50 Hz to 90 Hz, 50 Hz to 80 Hz, 50 Hz to 70 Hz, 55 to 65 Hz, or 58 and 62 Hz. The level of application of acoustic energy into the mixture is measured in units of acceleration of gravity or “g”( 1 g = 9.81 m/s²). Typically, the acoustic energy is applied in the range 30 g to 100 g, preferably in a range from 60 g to 100 g, or from 60 g to 90 g. Use of a level of acoustic energy between 30 and 100 g has been found to achieve sufficient mixing of the pre-calcined intermediate and the or each metal-containing compound without the use of extended mixing times. The mixing step is typically carried out over a period of between 30 seconds and 10 minutes, preferably between 1 and 10 minutes, more preferably between 1 and 5 minutes. It may be preferred that the mixing step is performed by applying an acoustic energy in the range of 30 g to 100 g for a period between 30 seconds and 10 minutes. The acoustic energy may be applied to a mixer configured as a batch mixer or the mixer may be configured to operate in a semi-continuous or continuous manner. It will be understood by the skilled person that if the mixing process is carried out in a semi-continuous or continuous manner the relevant time period for the mixing step is the residence time of the materials to be mixed, and that the residence time is typically between 30 seconds and 10 minutes.

Alternatively, in preferred embodiments the step of treating the pre-calcined intermediate with at least one metal-containing compound comprises (a) providing a coating liquid, the coating liquid comprising at least one metal-containing compound, and (b) adding the coating liquid to the pre-calcined intermediate to form an impregnated powder, the volume of coating liquid added corresponding to 50 to 150 % of the apparent pore volume of the pre- calcined intermediate. The inventors have surprisingly found that the electrochemical performance (such as capacity retention) of materials produced using a controlled volume of coating liquid may at least match materials produced prior art immersion-evaporation methods, with the advantage that solvent evaporation is significantly reduced during manufacture, considerably reducing energy consumption and industrial waste.

The specific combination of the addition of a controlled volume of a coating liquid during the treatment step with the pre-calcination step (in particular if pre-calcination is carried out in a rotary furnace) provides significantly improved efficiency and reduced energy consumption of the overall process.

The coating liquid comprises at least one metal-containing compound. It will be understood by the skilled person that the coating liquid comprises those elements which are desired to be present in the surface layer of the particulate lithium nickel metal oxide material. The metal-containing compounds are typically metal salts, such as nitrates, sulfates, citrates or acetates. It may be preferred that the metal containing compounds are inorganic metal salts. Nitrates may be particularly preferred.

In some embodiments, the coating liquid comprises at least one metal selected from M, A and Li (where M and A are as defined above). In some embodiments, the coating liquid comprises at least one metal-containing compound, wherein the or each metal-containing compound present is independently selected from an M-containing compound, an A- containing compound and a Li-containing compound. The coating liquid may include one or more of each of these options, e.g. one or more A-containing compounds, wherein the identity of A is different within each compound. In some embodiments, the coating liquid comprises at least one metal-containing nitrate, wherein each metal-containing nitrate present is independently selected from an M- containing nitrate, an A-containing nitrate and a Li-containing nitrate.

In some embodiments, the coating liquid comprises at least one M-containing compound, at least one A-containing compound and at least one Li-containing compound. In some embodiments, the coating liquid comprises a single M-containing compound, a single A- containing compound and a single Li-containing compound. In some embodiments, the coating liquid comprises a single M-containing nitrate, a single A-containing nitrate and a single Li-containing nitrate.

Preferably, the coating liquid comprises an aluminium-containing compound. The aluminium-containing compound is typically an aluminium salt, such as an inorganic aluminium salt, for example aluminium nitrate. The use of an aluminium-containing compound in the coating liquid can lead to an increase in the concentration of aluminium at the grain boundaries and/or at or near to the surface of the lithium nickel metal oxide particles.

Alternatively, or in addition, it is preferred that the coating liquid comprises a cobalt- containing compound. The cobalt-containing compound is typically a cobalt salt, such as an inorganic cobalt salt, for example cobalt nitrate. The use of a cobalt-containing compound in the coating liquid can lead to an increase in the concentration of cobalt at the grain boundaries and/or at or near to the surface of the lithium nickel metal oxide particles.

The coating liquid may comprise a zirconium-containing compound. In some embodiments, the zirconium-containing compound is present in the coating liquid alongside one or both of a cobalt-containing compound and an aluminium-containing compound. In some embodiments, the coating liquid comprises a zirconium-containing compound but does not contain either of a cobalt-containing compound and an aluminium-containing compound. In some embodiments, the zirconium-containing compound is present in the coating liquid as the sole metal-containing compound.

Optionally, the coating liquid comprises a lithium-containing compound. It proposed that this may be beneficial in order to avoid voids or defects in the structure of the particulate lithium nickel metal oxide material which may lead to a reduced lifetime. It may be preferred that the one or more metal-containing compound(s) are provided as hydrates of metal salts, for example a hydrate of a metal nitrate, such as a hydrate of cobalt nitrate and / or aluminium nitrate, optionally in combination with lithium nitrate, or a hydrate of lithium nitrate.

It may be particularly preferred that the one or more metal salt hydrates are heated to form the coating liquid. Advantageously, such materials dehydrate upon heating leading to a phase change and formation of a liquid suitable for coating with a high metal concentration. Furthermore, metal salt hydrates are typically more economical than de-hydrated equivalents. Optionally, and if required, further water may be added to achieve the required volume of coating liquid.

In some embodiments, the coating liquid is provided at a temperature of at least 50°C. This reduces the likelihood of crystallisation of the one or more metal-containing compound(s) during addition which would lead to poor mixing and an inhomogeneous coating. Furthermore, the use of an elevated temperature allows for the use of metal salts at high concentration and for the coating liquid to be prepared by heating metal salt hydrates.

Typically, the coating liquid is provided at a temperature of from 50 to 80 °C, such as from 50 to 75 °C, 55 to 75 °C, 60 to 75 °C, or 65 to 75 °C.

Typically, the total molar concentration of metal in the coating liquid (i.e. the sum of the molar concentration of each metal in the coating liquid) is at least 0.5 mol/L. The skilled person will understand that the total metal concentration of the coating liquid used will depend on the amount of metal that is required to be applied to the base material and also the apparent pore volume of the base material. However, total metal concentrations less than 0.5 mol/L may not provide a consistent treatment of the pre-calcined intermediate. Preferably, the total molar concentration of metal in the coating liquid is at least 0.75 mol/L, 1.0 mol/L, 1.25 mol/L, 1.5 mol/L, 1.75 mol/L, 2.0 mol/L, 2.5 mol/L or 3 mol/L.

The skilled person will understand that the total molar concentration will be limited by the solubility of the metal-containing compounds in the required volume of coating liquid. Typically, the total molar concentration of metal in the coating liquid is less than 7 mol/L. Typically, the total molar concentration of metal in the coating liquid is from 0.5 mol/L to 7 mol/L, such as from 1 mol/L to 7 mol/L, 2 mol/L to 7 mol/L, 3 mol/L to 7 mol/L, or 4 mol/L to 7 mol/L. The coating liquid is added to the particles of the pre-calcined intermediate. Typically, the particles of the pre-calcined intermediate are loaded into a mixing vessel prior to the addition of the coating liquid. Typically, the particles are mixed during the coating liquid addition, for example through stirring or agitation. This ensures an even distribution of the coating liquid. It may be preferable that the addition step may be carried out under a controlled atmosphere, such as an atmosphere free of CC>2and / or moisture, which may reduce the level of impurities, such as lithium carbonate, in the formed lithium nickel metal oxide particles.

The addition may be carried out by a number of means, such as portionwise addition to a mixing vessel via an inlet pipe, or by spraying the coating liquid onto the particles of the pre- calcined intermediate. It is considered that spraying the coating liquid may lead to a more consistent distribution of the coating liquid, a more reproducible coating process, and a shorter mixing time following complete addition of the coating liquid.

The addition step may be carried out at an elevated temperature, i.e. the temperature at which the vessel containing the particles of the pre-calcined intermediate is heated to is higher than ambient temperature prior to addition of the coating liquid, such as a temperature greater than 25°C, preferably greater than 30°C, or greater than 40°C. The use of an elevated temperature during the addition step reduces the likelihood of solidification or crystallisation of the components of the coating liquid during the addition step, therefore helping to ensure a homogenous coating.

It may be preferable to carry out the addition step at a temperature of from 40 °C to 80 °C, such as from 50 °C to 70 °C, or from 55°C to 65 °C.

In the process as described herein the coating liquid is added to the particles of the pre- calcined intermediate in a volume corresponding to 50 to 150 % of the apparent pore volume of the particles of the pre-calcined intermediate. The use of a volume of coating liquid less than 50 % of the apparent pore volume of the particles may lead to an inhomogeneous surface-modification. It has been found that the use of a volume of coating liquid greater than 150% of the apparent pore volume of the particles is not required in order to achieve surface-modification, and detrimentally leads to an increased need for solvent removal and / or drying and associated energy consumption.

Preferably, the coating liquid is added to the particles of the pre-calcined intermediate in a volume corresponding to 70 to 150 %, or more preferably 90 to 150 %, of the apparent pore volume of the lithium nickel metal oxide particles. The use of a volume of coating liquid greater than 70 %, or greater than 90% of the available pore volume, enables the use of use of higher amounts of the one or more metal-containing compound, which may lead to enhanced grain boundary enrichment.

Preferably, the coating liquid is added to the particles of the pre-calcined intermediate in a volume corresponding to 70 to 125%, or more preferably 90 to 125 % of the apparent pore volume of the particles of the pre-calcined intermediate. Use of a volume of coating liquid less than 125% of the apparent pore volume leads to a lower requirement for drying and evaporation. It has also been observed that the use of a volume of coating liquid greater than 125% of the apparent pore volume of the particles can lead to pooling of the coating liquid in the vessel containing the particles of the pre-calcined intermediate once the coating liquid has been added which may be detrimental to achieving a homogeneous surface- modification. It may be preferred that the volume of coating liquid added corresponds to 95 % to 120 % of the apparent pore volume of the particles, or 95 % to 115 %, or 95 % to 110 %, or 95 % to 105 %.

It may also be preferred that the volume of coating liquid added corresponds to 100 % to 150 % of the apparent pore volume of the particles of the pre-calcined intermediate, or 100 to 125 %, 100 to 120 %, 100 to 115 % or 100 to 110 %.

The apparent pore volume per unit mass of the pre-calcined intermediate is determined using a torque measurement system, such as a Brabender Adsorptometer “C”. This method involves the measurement of torque during a mixing process. Water is added to the particles of the pre-calcined intermediate whilst mixing, leading to a torque peak on a volume added-torque curve. The volume of water added per unit mass of particles at the point of onset of the torque peak is the apparent pore volume per unit mass of particles.

Following complete addition of the coating liquid the particles may be mixed for a period of time. Typically, the particles may be mixed for a period of from 1 to 60 minutes following complete addition of the coating liquid. It may be preferred that, after complete addition of the coating liquid, the treated particles are subjected directly to the calcination step, without the requirement for additional drying. Advantageously, the treated particles may be transferred directly from the vessel used for the addition of the coating liquid to a calciner.

In step (ii), the treated mixture is then calcined to form the particulate lithium nickel metal oxide material. The calcination step is typically carried out at a temperature of less than or equal to about 800 °C. In cases in which surface-modification of the lithium nickel metal oxide particles is desired the use of calcination temperatures greater than 800 °C helps to control the distribution of metal elements within the lithium nickel metal oxide particles.

It may be further preferred that the calcination step is carried out at a temperature less than or equal to about 750 °C, less than or equal to 740 °C, less than or equal to 730 °C, less than or equal to 720 °C, or less than or equal to 710 °C.

Preferably, the calcination step comprises heating the mixture to a temperature of at least about 600 °C, or at least about 650 °C, for example heating the mixture to a temperature of between about 600 °C and about 800 °C, about 600 and about 750 °C, or about 650 and about 750°C. It may be further preferred that the calcination step comprises heating the mixture to a temperature of at least about 600 °C, or at least about 650 °C for a period of at least 30 minutes, at least 1 hour, or at least 2 hours. The period may be less than 8 hours.

Preferably, the calcination comprises the step of heating the mixture to a temperature of 600 to 800 °C for a period of from 30 mins to 8 hours, more preferably a temperature of 600 to 750 °C for a period of from 30 mins to 8 hours, even more preferably a temperature of 650 to 750 °C for a period of from 30 mins to 8 hours.

The calcination step may be carried out under a CC free atmosphere. For example, CC>2-free air may be flowed over the materials during heating and optionally during cooling. The CC>2-free air may, for example, be a mix of oxygen and nitrogen. Preferably, the atmosphere is an oxidising atmosphere. As used herein, the term “CC>2-free” is intended to include atmospheres including less than 100 ppm CO2, e.g. less than 50 ppm CO2, less than 20 ppm CO2 or less than 10 ppm CO2. These CO2 levels may be achieved by using a CO2 scrubber to remove CO2. It may be preferred that the CC>2-free atmosphere comprises a mixture of O2 and N2. It may be further preferred that the mixture comprises N2 and O2 in a ratio of from 1:99 to 90:10, for example from 1 :99 to 50:50, 1 :99 to 10:90, for example about 7:93. High oxygen levels in the calcination (such as greater than 90% oxygen) may provide benefits in enhancing the discharge capacity of the formed lithium nickel metal oxide material. The CC>2-free atmosphere may also be an oxygen atmosphere.

The process may include one or more milling steps, which may be carried out after the calcination step. The nature of the milling equipment is not particularly limited. For example, it may be a ball mill, a planetary ball mill or a rolling bed mill. The milling may be carried out until the particles reach the desired size. For example, the particles of the lithium nickel metal oxide material may be milled until they have a particle size distribution such that the D50 particle size is at least 3 pm, e.g. at least 5 pm, at least 5.5 pm, at least 6 pm or at least 6.5 pm. The particles of lithium nickel metal oxide material may be milled until they have a particle size distribution such that the D50 particle size is 15 pm or less, e.g. 14 pm or less or 13 pm or less.

The process of the present invention may further comprise the step of forming an electrode comprising the lithium nickel metal oxide material. Typically, this is carried out by forming a slurry of the lithium nickel metal oxide material, applying the slurry to the surface of a current collector (e.g. an aluminium current collector), and optionally processing (e.g. calendaring) to increase the density of the electrode. The slurry may comprise one or more of a solvent, a binder, carbon material and further additives.

Typically, the electrode of the present invention will have an electrode density of at least

2.5 g/cm³, at least 2.8 g/cm³ or at least 3 g/cm³. It may have an electrode density of

4.5 g/cm³ or less, or 4 g/cm³ or less. The electrode density is the electrode density (mass/volume) of the electrode, not including the current collector the electrode is formed on. It therefore includes contributions from the active material, any additives, any additional carbon material, and any remaining binder.

The process of the present invention may further comprise constructing a battery or electrochemical cell including the electrode comprising the lithium nickel metal oxide material. The battery or cell typically further comprises an anode and an electrolyte. The battery or cell may typically be a secondary (rechargeable) lithium (e.g. lithium ion) battery.

The present invention will now be described with reference to the following examples, which are provided to assist with understanding the present invention and are not intended to limit its scope.

Examples

Example 1 - An example method of calculation of the volume of a coating liquid to be applied to a lithium nickel metal oxide particle.

(A) Calculation of the apparent pore volume 92.7g of a lithium nickel metal oxide material of formula Li1.03Ni0.91Co0.08Mg0.01O2 (was loaded into a Brabendar absorptometer B torque measurement system and demineralised water added at 4 ml/min. The torque readings were plotted against the amount of liquid added per mass of solid material. The torque readings showed a peak value at 0.14 ml / g. The onset of the torque increase leading to this peak was then taken as the apparent pore volume per unit mass of the lithium nickel metal oxide material (0.12 ml / g).

(B) Calculation of volume of coating liquid to be used

Based on a desired composition after coating of Lii.oiNio.867Coo.n5Alo.oo6Mgo.oi202, the amounts of Co, Al and Li that were required to be added to a 500g sample of lithium nickel metal oxide base material were calculated (as set out below), and hence the amounts of the nitrate crystals to be used.

Mass of base: 500g

Mass of cobalt to be added: 11.96 g Weight of Co(NC>₃)₂.6H₂0: 59.04 g

Mass of aluminium to be added: 0.88 g Weight of AI(NC>₃)₂.9H₂0: 12.18 g

Mass of lithium to be added: 1.65 g Weight L1NO3: 16.39 g

(1) The volume of liquid obtained when the mixed nitrate crystals were heated to 60 °C was measured as 52 mL.

(2) The apparent pore volume of the lithium nickel metal oxide Base Material A (500g) was calculated as 60 mL (0.12 mL/g * 500 g).

(3) The amount of water to be added to the nitrate crystals to achieve a volume of coating liquid corresponding to approximately 120% of the apparent pore volume was calculated as 20 mL

Example 2 - Example method of treatment of a pre-calcined intermediate using a controlled volume of coating liquid.

The pre-calcined intermediates were contacted with the coating liquid using a Winkworth z- blade mixer. The hearing jacket of the mixer was set at 60 °C. The pre-calcined intermediate (250-300g) was added to the mixing chamber of the Z-blade. The mixing speed set to 50 rpm. Cobalt (II) nitrate hexahydrate (ACS, 98 - 102%, from Alfa Aesar), aluminium nitrate nonahydrate (98% from Alfa Aesar) and lithium nitrate (anhydrous, 99%, from Alfa Aesar) were combined with water (amounts of nitrates used dependent on the desired final composition, amount of water calculated according to the method of Example 1 ) and then heated to approximately 60°C to form the coating liquid. The coating liquid was added to the mixing chamber by pipette over a period of 5 minutes. After complete addition, the mixture was left to mix for 10 minutes before being discharged from the unit.

Example 3 - Example method of treatment of a pre-calcined intermediate using resonant acoustic mixing.

Pre-calcined intermediate was placed into a plastic container with cobalt (II) nitrate hexahydrate, aluminium nitrate nonahydrate and lithium nitrate amounts of nitrates used dependent on desired final composition). The materials were mixed using a LabRAM (RTM) resonant acoustic mixer for 5 min at 80 g operating at 58-62 Hz.

Example 4 - Pre-calcination using a rotary furnace

A precursor of Nio_.92Coo_.o₈Mgo_.oiOH₂ was mixed with lithium hydroxide (21 parts per 79 parts of precursor) and then calcined using a rotary kiln (feed rate: 0.5 kg/h, tube angle: 0.3 °, rotation speed: 4 rpm, residence time: Example 4A: 90 minutes at 300 °C, Example 4B: 90 minutes at 500 °C).

Example 5 - Treatment of the pre-calcined intermediate and calcination

The pre-calcined intermediates from Example 4 (4A and 4B) were then treated with a mixture of cobalt (II) nitrate hexahydrate, aluminium nitrate nonahydrate and lithium nitrate (amounts selected to achieve a target composition of Lii.oiNio.867Coo.n5Alo.oo6Mgo.oi202) using a coating process according to Example 2 (IW) or Example 3 (RAM) and then calcined using different calcination profiles in a static oven as set out below in Table 1. The lithium nickel metal oxide materials formed were then tested for electrochemical performance using an analogous protocol to that set out below and the results are also included in Table 1.

Table 1 - Treatment and then calcination of the pre-calcined intermediates formed in Example 4

The data shows that the herein described process provides materials with a good combination of discharge capacity and capacity retention upon repeated cycling, despite the use of a low temperature pre-calcination step. The most promising electrochemical performance corresponds to the material pre-calcined at 500 °C and then coated using a controlled volume of coating liquid, and calcined with a longer dwell at an intermediate temperature (500°C) and shorter dwell at 700°C.

Example 6 - Pre-calcination using a static kiln A precursor of Nio_.92Coo_.o₈Mgo_.oiOH₂ was mixed with lithium hydroxide (21 parts per 79 parts of precursor) and then calcined using a static kiln for the times and temperatures set out in Table 2. The formed pre-calcined intermediate were then treated with a mixture of cobalt (II) nitrate hexahydrate, aluminium nitrate nonahydrate and lithium nitrate (amounts selected to achieve a target composition of Ui.oiNio.867Coo.n5Alo.oo6Mgo.oi202) using a coating process according to Example 2 (IW) or Example 3 (RAM) and then calcined using different calcination profiles as set out below in Table 2. The lithium nickel metal oxide materials formed were then tested for electrochemical performance using an analogous protocol to that set out below and the results are also included in Table 2. Table 2 - Experimental conditions and results of electrochemical testing from Example 6

The data shows an increase in 0.1 C discharge capacity when performing the calcination 93% O2. The SEM images of the material produced after the pre-calcination in a static kiln at either 500 or 600°C show significant amount of lithium on the surface. This suggests that the lithium is not fully incorporated into the structure after the pre-calcination.

For example, Figure 1 shows SEM images of particles formed after pre-calcination. Figure 1A - Example 6A; Figure 1B - Example 6F; Figure 1C - Example 6G; Figure 1D - Example 6H.

Example 7 - Pre-calcination using a rotary kiln

A precursor of Nio_.92Coo_.o₈Mgo_.oiOH₂ was mixed with lithium hydroxide (21 parts per 79 parts of precursor) and then pre-calcined using a rotary kiln (ramp rate 60 mins to 600 °C, rotation speed: 4 rpm, hold time at 600 °C, gas flow 5 L/min/Kg, 20% oxygen in nitrogen).

Figure 2 shows SEM images of the pre-calcined intermediate particles. These images show improved incorporation of lithium into the particle structure. Electrochemical Protocol

The electrodes were prepared by blending 94%wt of the lithium nickel metal oxide active material, 3%wt of Super-C as conductive additive and 3%wt of polyvinylidene fluoride (PVDF) as binder in N-methyl-2-pyrrolidine (NMP) as solvent. The slurry was added onto a reservoir and a 125 pm doctor blade coating (Erichsen) was applied to aluminium foil. The electrode was dried at 120 °C for 1 hour before being pressed to achieve a density of 3.0 g/cm³. Typically, loadings of active is 9 mg/cm². The pressed electrode was cut into 14 mm disks and further dried at 120 °C under vacuum for 12 hours. Electrochemical test was performed with a CR2025 coin-cell type, which was assembled in an argon filled glove box (MBraun). Lithium foil was used as an anode. A porous polypropylene membrane (Celgard 2400) was used as a separator. 1M LiPF₆ in 1:1:1 mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with 1% of vinyl carbonate (VC) was used as electrolyte.

The cells were tested on a MACCOR 4000 series using C-rate and retention tests using a voltage range of between 3.0 and 4.3 V. The C-rate test charged and discharged cells at 0.1 C and 5 C (0.1C = 200 mAh/g). The capacity retention test was carried out at 1C with samples charged and discharged over 50 cycles.

Claims

1. A process for producing a particulate lithium nickel metal oxide material having a composition according to Formula 1:

LiaNixMyAzC>2+b Formula 1 in which:

M is one or more of Co and Mn;

(iii) calcining the material obtained after step (ii) at a temperature to form the particulate lithium nickel metal oxide material.

2. A process according to claim 1 wherein step (i) is carried out in a rotary kiln.

3. A process according to claim 1 or claim 2 wherein the treatment in step (ii) comprises the addition a coating liquid comprising the at least one metal- containing compound to the pre-calcined intermediate to form an impregnated powder, the volume of coating liquid added corresponding to 50 to 150 % of the apparent pore volume of the pre-calcined intermediate.

4. A process according to claim 3 wherein the coating liquid is provided at a temperature in the range of and including 50 to 80 °C.

5. A process according to claim 1 or claim 2 wherein the treatment in step (ii) comprises dry mixing the pre-calcined intermediate with at least one metal- containing compound, preferably using acoustic resonance.

6. A process according to any one of the preceding claims wherein the nickel metal precursor is a nickel metal hydroxide or oxyhydroxide precursor.

7. A process according to any one of the preceding claims wherein A includes Al and / or Mg, or is A and / or Mg.

8. A process according to any one of the preceding claims wherein M is Co.

9. A process according to any one of the preceding claims wherein z is 0 £ z £ 0.05.

10. A process according to any one of the preceding claims wherein M includes Co and the metal-containing compound is a cobalt-containing compound, preferably cobalt nitrate.

11. A process according to any one of the preceding claims wherein A includes Al and the metal-containing compound comprises an aluminium-containing compound, preferably aluminium nitrate.

12. A process according to any one of the preceding claims wherein the calcination step (iii) comprises heating to a temperature of less than 800 °C.

13. A process according to any one of the preceding claims wherein the calcination step (iii) comprises heating to a temperature in the range of and including 600 to 800 °C, preferably for a period of 30 mins to 8 hours.

14. A process according to any one of the preceding claims wherein the calcination step (i) is carried out in an atmosphere comprising at least 90 vol% oxygen.

15. A process according to any one of the preceding claims further comprising the step of forming an electrode comprising the lithium nickel metal oxide material.

16. A process according to any one of the preceding claims further comprising the step of forming an electrochemical cell comprising an electrode according to claim 13.