SE546073C2 - An electrode material and a battery comprising titanium dioxide bronze - Google Patents

Abstract

The present invention relates to a component material of a battery electrode as well as a battery comprising the component material. The component material comprises a) TiO2 with a fraction of TiO2 (B), titanium dioxide in bronze phase, b) at least one conducting material, and c) at least one binder, wherein the TiO2 comprises metal ions, wherein the Ti to metal ion atomic ratio R fulfils the following condition(0.029*AWmetal - 0.10*X) < R < (0.82*AWmetal - 0.10*X), wherein AWmetal is the atomic weight of the metal and X is the metal valence, wherein the metal ions are at least one type of ion of a metal selected from one of: a) rare earth elements, b) transition metals, which have the ability to form cations with anincomplete d sub-shell, and c) alkaline earth metals. A high fraction of TiO2 (B), titanium dioxide in bronze phase gives a battery with a desirable high capacity.

Description

Technical Field The invention relates to a material intended to be a constituent in a battery electrode, the material comprising titanium dioxide in bronze form. Also a battery comprising such an electrode is encompassed. In particular, it relates to stabilizing the material during manufacture and preventing the formation of titanium dioxide in anatase form thereby increasing the fraction of titanium dioxide in bronze form, which increases the capacity of the battery.

Background In the prior art there is disclosed methods of manufacturing titanate bronze precursor material, which can be used in the manufacture of a battery.

The known methods according to the prior art may require a) an expensive and complicated hydrothermal process step operating at elevated temperature, pressure and high alkalinity, with a limited scale up capacity of the pressure vessels, or b) a very high temperature process step, greater than approx. 800 °C to make a bronze precursor or c) making TiO2(B) from a titanium glycolate precursor which generally involves use of dangerous oxidizers such as hydrogen peroxide. Still there is the problem of anatase formation instead of formation of the desired bronze form of titanium dioxide.

For batteries, some polymorphs of TiO2 are more desirable whereas others are undesirable. Anatase is undesirable as it generally loses half of its capacity relative to the first few cycles, unlike bronze, which retains most of its capacity after an initial approx. 20% loss on first cycle. Thus, the bronze polymorph can more readily achieve high capacities than anatase. For the bronze polymorph, TiO2 (B) the theoretical specific capacity is about 335 mAh/g when used as an electrode material in a lithium battery. with methods In particular, when preparing TiO2(B) involving relatively low temperature and pressure, the prepared TiO2(B) appears unstable. Since methods using relatively low temperature and pressure are more economical it would be desirable to use them, had not the problems with unstable TiO2(B) existed.

In the art there is a problem how to stabilize the material to minimize the formation of anatase, keeping bronze during the manufacturing cycle, while the capacity of the material in a finished battery should not decrease too much, or should decrease as little as possible. On a more general level, a problem in the art is how to provide a more efficient method for manufacturing titanium dioxide in bronze form. On an even more general level a problem in the art is how to improve the manufacture of a material for a battery.

WO 2020/165419 discloses a method for manufacturing a structure of a titanium compound selected from the group consisting of sheets, wires and tubes.

Objects of the Invention It is an object of the present invention to alleviate at least some of the problems in the prior art and to provide a component material of a battery electrode as well as a battery.

Summary It has been discovered that it is possible to improve the manufacture of a TiO2(B) bronze material. It has been discovered that presence of certain metal ions can stabilize the material during the process and in particular stop or at least decrease the transition to the anatase phase of titanium dioxide during the manufacturing process. Anatase is less preferred compared to the bronze form. The material is treated to adjust the content of certain metal ions during the manufacturing process.

In a first aspect there is provided a component material of a battery electrode, the material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, wherein the Ti to metal ion atomic ratio R fulfils the following condition (O.O29*AWmmfi1 O.lO*X) S R S O.lO*X), (O.82*AWmtfl wherein Awmfialis the atomic weight of the metal and X is the metal valence¿ In a second aspect there is provided a battery comprising at least one electrochemical cell, said at least one electrochemical cell comprises at least two electrodes (lQ,2Q) and at least one electrolyte (73), wherein at least one of the electrodes (l§,2§) comprises a) a material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wherein for the material the Ti to metal ion atomic ratio R fulfils the following condition (0.029*AWmetal - O.lO*X) 3 R 3 (O.82*AWmetal - O.lO*X), wherein AWmmfil is the atomic weight of the metal and X is the metal valence, An advantage is that titanium dioxide in bronze form is stabilized during the manufacturing process. The formation of anatase is suppressed and the fraction of titanium dioxide in bronze form is thereby equal to or increased relative to if the stabilizer was not used in the first place.

In particular, it is an advantage that a less expensive manufacturing method involving lower temperature and pressure can be used, while the stability issues with TiO2(B) have been overcome. The present invention provides a more cost efficient material and battery.

Another advantage is that a battery will have an improved capacity since the fraction of TiO2(B) is high. The content of metal ions in the material stabilizes the material so that a high fraction of TiO2(B) is ensured. Further this has the potential to give a much higher charging rate compared to the batteries according to the prior art.

The long term performance of the battery improves compared to the prior art.

Brief description of the drawings The invention is further described by the appended drawings in which: Figure 1 shows representative Raman spectra of hydrogen titanate powders where hydrogen was exchanged for Na in increasingly concentrated NaOH solutions followed by filtering, drying at room temperature and heating to 400 °C in air. The peak at “A' near 150 cm* in the 0 M spectrum is assigned to the anatase Eg(1) vibrational mode (Gariola et al. 174305, 2010).

Physical Review B 81, The peak at “B' near 200 cm* is assigned to the Bg(2) vibrational mode of bronze (or bronze-like) (Ben Yahia et 204501, 2009) phase of titanium dioxide al. The Journal of Chemical Physics 130, The same labelling, A and B are the same in all figures. The bronze stability indicator is plotted in llater Figures at different temperatures and NaOH exchange concentrations.

Figure 2 shows representative Raman spectra of hydrogen titanate powders where hydrogen was exchanged for Na in increasingly concentrated NaOH solutions followed by filtering, drying at room temperature and heating to 400 °C in air. Figure 3 shows representative Raman spectra of hydrogen titanate powders where hydrogen was exchanged for Na in increasingly concentrated NaOH solutions followed by filtering, drying at room temperature and heating to 400 °C in air. This figure also clearly shows the amount of stabilization against the transition to anatase at 500 °C is positively correlated to the amount of Na exchanged into the titanate. This is also seen in figures 4 and 5 below.

Figure 4 shows bronze stability indicator (BSI) value as a function of increasing NaOH concentration in the exchange solution for a range of thermal treatment temperatures applied to the exchanged powders. Note that as the concentration of the exchange solution goes up, the amount of sodium exchanged into the titanates also goes up since there was a complete or nearly complete exchange indicated by drop in pH after exchange (provided the titanate precursor is not saturated with Na), independent of the starting NaOH concentration. Here the BSI clearly goes up as a function of sodium exchange into the titanate.

Figure 5 shows the same data as in Figure 4 was re- plotted to show BSI as a function of temperature for a range of exchange solution concentrations. Clearly, the stability of bronze or bronze-like phase is stabilized in an increasingly positive way as the amount of Na in the exchange solution was increased.

Figure 6 shows a schematic drawing of a battery comprising at least one electrochemical cell, said at least one electrochemical cell comprises two electrodes (1§,2Q) and an electrolyte (7Ü). The battery is according to the invention and comprises a working anode (lg), a counter electrode (ZÄ), a (3), (4), and a gasket (6). In this particular embodiment separator (5), the working anode (18) a lower casing an upper casing comprises an electrode material made by the method according to the invention. The casing (4,5) encloses the electrolyte (7Ü).

Figure 7 shows a flow chart of the method according to the present invention.

O Figure 8 is a graph showing weight 6 of stabilizing metal versus Ti/M ratio. Cnly Li is according to the Figure 9 shows calculated theoretical capacity versus Ti/M atomic ratio R for various stabilizing metals.

Figure 10 shows the measured specific capacity vs the number of cycles for the measurement of example Figure 11 shows representative Raman spectra of hydrogen titanate powders where hydrogen was exchanged for Na in increasingly concentrated NaOH solutions followed by filtering, drying at room temperature and heating to 550 °C in air from example Figure 12 shows the measured specific capacity vs the number of cycles for the measurement of a half cell constructed using an electrode made from the first slurry of example Figure 13 shows the measured specific capacity vs the number of cycles for the measurement of a half cell constructed using an electrode made from the second slurry of example Figure 14 shows the measured specific capacity vs the number of cycles for the measurement of a half cell constructed using an electrode made from the second slurry of example Detailed description The following detailed description discloses by way of examples details and embodiments by which the invention may be practised.

*Bronze precursor' as used in the description and the claims denote layered titanate compounds that are precursors to bronze and have a particular structure, whereas other precursor titanate compounds may transform directly to anatase. Titanate is a titanium dioxide compound. The distinction between these precursors that lead to bronze or anatase has been discussed in detail by Feist and Davies, J. Solid 101, 275-295 (1992) Mater. 17, State Chem. and for example by Zukalova et al., Chem. 1248-1255 (2005), both of which are explicitly incorporated herein by reference. Feist and Davies note that layered bronze precursor titanates of formula A2Ti¿bnH comprise titanate sheets that stack in an ABA sequence. Also considering the water molecules, the general formula is A2TigbnH_mH2O. n is an integer from 3 to 6, m is a number from 0 to 2.5. Those with an AAA sequence cannot transform to bronze. The sheets themselves comprise corrugated ribbons of edge sharing TiO6 octahedra, each ribbon is n octahedral wide and ribbons form stepped sheets by sharing corners of For octahedral. The step size is defined by n. example, Na2Tiflh with n=3 is a step 3 layered titanate with AAA stacking, and H2Tiflh, K2Ti4b, H2Ti4b.H2O and Cs2Ti5OU H2Ti5OU.H2O are step 3, 4 and 5 layered titanates with ABA sequence, respectively.

AAA and ABA refers to the stacking sequence of titanates as normally referred to within the scientific literature involving titanates.

When stacking of the titanate layers is of the variety ABA, 500 °C, calcination in the temperature range about 300- they convert, by a multi-step mechanism, to titanium dioxide bronze, TiO2(B). An intermediate formed at approximately 140 °C in the conversion of H2Ti¶h, is thought to be an ABA stacked (non-layered) tunnel structure with formula H2Ti@h¿, and then a bronze-like structure forms on further heating to which on approximately 225 °C with formula H0¿Ti30@2@ further heating above approximately 280 °C forms TiO2(B). Other ABA stacked intermediates are thought to occur in the heating of step 4 and 5 layered titanates.

*Anatase precursor' as used in the description and the claims denotes anatase precursors including non ABA stacked layered compounds of titanium oxygen and hydrogen, hydrated amorphous titanium oxides or orthorhombic lepidocrocite-like layered titanates of formula HXTi¿¶[ ]XM O4, where [ ] represents a crystal vacancy with sheets of flat rather than corrugated TiO6 octahedra. These transform directly to anatase without first converting to bronze.

In the present invention it is believed that when these anatase precursors are present with bronze precursors, the transition temperature of bronze to anatase is lowered due to the nucleation of anatase from anatase precursors and subsequent destabilization of bronze by these anatase seeds, and that addition of Na or other suitable ions prevent the formation of anatase via formation of stable metal titanates directly from the anatase precursors, and that any excess Na trapped in the bronze precursors transforms to a bronze-like structure. Sodium or other stabilizing ions may not need to be added separately, they may be included as controlled residuals from incomplete ion exchange of the metal titanate precursor. Where the process comprises removal of metal ions such a removal can be incomplete and not full, so that an amount of metal ions remain in the material.

Thus in a battery application where a bronze structure is required, it is desirable to use the minimum amount of stabilizing Na or other metals to just keep the anatase precursors stable as metal titanates which appear to not destabilize bronze at lower temperaturescompared to if no anatase precursors were present. Once anatase forms at about 300-500 °C by heating these anatase precursors, any bronze will be converted to anatase because the anatase can act as a nucleation site and is more stable than bronze.

A *bronze stability indicator' is calculated by dividing the intensity for the Bg(2) bronze peak located in the interval 190 - 205 cm* minus the background intensity by the intensity for the Eg(1) anatase peak located in the interval 140 - 160 cm* minus the background intensity and then the resulting ratio is divided with a normalization factor which is calculated as the intensity of the Eg(1) anatase peak minus the background intensity divided by the intensity for the Bg(2) bronze peak minus the background intensity for pure TiO2(B), wherein the background intensity as calculated as the average intensity in the region with a wavenumber higher than the zero-peak and lower than the intensity originating from the sample. The exact location of the Eg(1) anatase and Bg(2) bronze peaks may vary somewhat depending on the conditions. The peaks can be for instance at 201 and 148 cm* respectively. The skilled person can easily identify the peaks and read the intensity at the peak and use that peak intensity for the calculation. Regarding the background, it is the intensity for the background between the zero-peak and the intensity from the sample, i.e. the wave number is higher than 0 and lower than the first intensity originating from the sample. This background normally corresponds to the intensity at 75 cm*. A corresponding formula would be (Peak heightBgQ) - background)/((Peak heightmnn _ background)*NF). Thevalue is then normalized with a normalization factor NF. The normalization factor is selected so that a pure TiO2 bronze phase has BSI = 1. NF = (Peak heightBg@))/(Peak heightEg@)), for pure bronze. For a common Raman spectrometer with a green laser a normalization factor around 1.3 can be expected. Effects such as fluorescence may complicate the calculation of the BSI, so that the measurements be done without significant influence of fluorescence on the spectra.

A *clear solution' is defined as being nearly or completely transparent to visible light with little or no detectable cloudiness or scattering of visible light by undissolved titanic acid and may be determined by shining a visible light laser through the solution until it passes straight through the solution with little to no detectable scattering of visible light from within the solution to the naked eye. Alternately, it may be detected in practise when ordinary 12 point printed text is resolved through a 10cm path-length of the solution held in a glass pipe. A *ratio' is used to describe a relation between different quantities. A ratio between a and b is expressed as a:b, which is interpreted as a/b, i.e. a divided by b so that the ratio is equal to a divided by b. *Suspension' as used throughout the description are solid particles in a liquid medium. For a suspension, the particles are at least partially so large that they settle after some time due to gravity. The solid llparticles in the suspension can be for instance a precipitate.

*Wt%' denotes percentage by weight. All percentages and ratios are calculated by weight unless otherwise clearly stated. For instance the ratio of Ti:metal ratio is not expressed in wt%, instead the ratio is based on the number of atoms of Ti to the number of atoms of metal. that it is The same applies to the ratio Ti:Nb, i.e. the number of atoms of Ti to the number of atoms of Nb. Mass and weight for the calculation of wt% as well as other quantities are as defined in ISO 80000- 4:20l In the first aspect there is provided a component material of a battery electrode, the material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, wherein the Ti to metal ion atomic ratio R fulfils the O.lO*X) S R S following condition (O.029*AWMtfl (0.82*AWmmfil O.lO*X), wherein Awmmalis the atomic weight of the metal and X is the metal valence.

The word “fraction” means that a part of the TiO2 is in bronze form, i.e. TiO2(B).

The first aspect can be expressed also in Ti/metal ratio (R) in the component material. This ratio R can be calculated from the content of metal ions. The metal ions will be present as a metal oxide in the material. A general formula for the said metal stabilised material is: (TiÛ2)R°MÛ2/X (1)where, R is a real number > O and interpreted as the Ti/metal ratio; and MOQM is a metal oxide, X is the metal valence.

For example, if the metal is Na with a valence of x=1, and the Ti/Na ratio, R = 2, then the chemical formula of the stabilized material is: (TiO2)2 °NäO1m If La with a valence of x=3 is the metal, the chemical formula then the stabilized material is: (TiO2)2 °LäO3m In any case the weight percent, Mmfi of the metal in the material is: Mmfi = l00*(ÄWmmfii/(ÄWmmfii + R*ÄWTi + (2R+X/2)*ÄWo) (2) where, AWm%al= the atomic weight of the metal AWfi_= the atomic weight of titanium AWO= the atomic weight of oxygen.

The Ti to metal ratio, R can then be solved in terms of weight percent metal.

The expression for R is as follows: R = {ÄWmmfii*[(lOO/NMt%)-1] _ (X/2)* ÄWO }/MWTflfl (3) where, AWm%al= the atomic weight of the metal Mmfi of the metal in the material X is the metal valence AWO= the atomic weight of oxygen MWTflfi the molecular weight of TiO2. When using the limits 1.5 to 30 wt% of metal ions, which can be assumed to be essentially the same as the then we have the wt% of metal in the material, following limits for the Ti to metal ratio. With an atomic weight AWO of 16 for oxygen and a molecular weight MWTMW of 79.87 for TiO2 the upper and lower limits become the following: Upper limit (1.5 wt%): {AWmtæ*[(100/1.5)-1] - (X/2)* 16 }/79.Equals: 0.82*AWmmfil 0.10*X Lower limit (30 wt%): {AWm¶æ%[(100/30)-1] - (X/2)* 16 }/79.Equals: 0.029*AWmfial- 0.10*X Where AWmmalis the atomic weight of the metal and X is the metal valence. An example for sodium is AWmfial which 18. 22.99 u, X = 1, gives 0.571 S R S Thus with an alternative wording of the first aspect there is provided a component material of a battery wherein the electrode, the material comprising TiOh TiO2 comprises a fraction of TiO2(B), titanium dioxidein bronze phase, wherein the material comprises at least one type of metal ion, wherein the Ti to metal ion atomic ratio R fulfils the following condition (0.029*AWmmfii O.10*X) S R S (O.82*AWmmfii O.10*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence. The ratio R is preserved after calcination and is the same in the finished product.

Usually the metal ions which are added according to the present invention are considered very detrimental in TiO2(B) bronze based Li-ion battery anodes, because small amounts of metals decrease performance dramatically in terms of lithium capacity. The metals take up space where lithium would normally fit. Most publications concerning TiO2(B) in Li-ion batteries go to great lengths to obtain the least metal as possible to maximize lithium capacity.

TiO2(B) appears to be unstable when prepared according to some methods according to prior art, in particular this is true of inexpensive methods. Such methods typically involve low temperature and pressure relative to other methods in the prior art with higher temperature and pressure. They can be referred to as low temperature and pressure pathways - or LTP pathways.

In order to achieve bronze stability via LTP pathways, the present inventors have after extensive research discovered that if metal ions are added during an LTP there is an improved bronze yield. pathway, However, if too much is added, then the lithium capacity is reduced more than necessary. Thus there is a trade-off between on one hand improved stability of TiO2(B)during the manufacture with improved yield of TiO2(B) and on the other hand the lithium capacity in a battery with at least one electrode comprising the material with TiO2(B).

The skilled person realizes this trade off and can in the light of the description select a suitable amount of added metal ions so that both the stability during manufacture and the capacity of finished battery becomes as desired.

The range of metal ion content is in the alternative wording of the first aspect formulated as Ti:metal ratio R, not in wt%, but instead based on the number of atoms of Ti to the number of atoms of metal.

In one embodiment for the material comprising TiO2(B), the Ti:metal atomic ratio R in the final product is greater than 4:1 Ti:metal (Giving about 20% loss of theoretical lithium capacity). The final product is for this calculation considered to be the material comprising TiO2. The Ti:metal atomic ratio R in the material is greater than 4:1 Ti:metal, wherein the metal is present as ions, with the proviso that Ti, Ta and Nb are not included as metal. It is only used for the number of atoms of Ti (and Ta and Nb) in the atomic ratio R. The same applies for Nb and Ta since they can replace Ti in the TiO2(B)structure. “metal” denotes stabilizing metals. If only a very small fraction of Nb is present, its contribution to the ratio R is negligible. Thus for small amounts of Nb and/or Ta, such as a few percent (or 0.5-1 wt%) its contribution can be essentially ignored since the effect is small. At larger amounts of either Nb or Ta,their differing valence compared to Ti must be accounted for - see equation Niobium doping of TiO2 bronze can be advantageous in increasing the electrical conductivity of the said bronze material during the cycling of a lithium ion battery and can increase the lithium ion capacity of the resulting electrode constructed from the bronze due to its slightly larger radius. Nb doping can even have a positive impact on the conductivity at relatively low amounts of niobium, this low amount being an advantage over higher amounts since niobium is relatively more expensive than titanium and it is also significantly heavier. Niobium doping can be achieved by addition of appropriate precursor compounds along with the titania precursor compounds normally used to make titania bronze. (2020) According to Xu et al. ChemElectroChem 2020, 7, 4016-4023, niobium doping is generally limited to less than about 10%, however higher amounts can be achieved by a solvothermal process. Regarding metal stabilization of niobium doped TiO2 bronzes, we are here limited, as we are for pure TiO2 bronzes, to approaches whereby metal cations can be incorporated into an intermediate or precursor structure of TiO2 bronze since once the bronze is formed it is difficult to incorporate the stabilizer metal ions into the TiO2 bronze. Such intermediates include but are not limited to various H2Ti4O9, mixtures of H2Tifih, EüTi5OU and their hydrates and Na2Ti$h, Na2Ti4b, Na2Ti¿L1 and their hydrates.

At least under some circumstances the replacement of a part of the Ti with Nb during the manufacturing process lessens the need to add the stabilizing metal ions during the process.The composition of metal stabilized niobium doped titanium dioxide can usefully be described as having a general formula similar to the general formula (1) above for said metal stabilized titanium dioxide material, but now with an added Nbflk component, where Nb2O5 can also be expressed as NbO2¿. (NbO2.5)R/s'(Tj-O2)R° MO2/X/ (4) Where, R is a real number > O and interpreted as the Ti/metal ratio; S is a real number 2 O and interpreted as the Ti/Nb ratio; and MO2M is a metal oxide, X is the metal valence. From this formula, and knowing the atomic weights of the elements we can easily interconvert between atomic O O 6 and weight 6 as we did for metal doped titania in equation (2). Then a number of possible conversions can be done. Firstly the weight %, Mmfi of the stabilizing metal in a niobium doped material is: Mwt% = lOO*(AWmetal/(AWmetal + R*AWTi + S*R*AWNb+(2.5SR+2R+X/2)*AWO )) (5) where, AWm%al= the atomic weight of the metal AWfi_= the atomic weight of titanium AWfi_= the atomic weight of niobium AWO= the atomic weight of oxygen.

In our related patent applications SE 2050954-3 and SE 2050955-O the range of values of metal stabilization was expressed in terms of weight % metal compared to TiO2, and then we can set the value of R/S in formula (4) to be effectively zero, in which case the wt % Na relative to TiO2 for Nb doped TiO2 is found by applying formula (1).

The Ti/M ratio for niobium doped TiO2, R can then be O solved in terms of wt 6 stabilizing metal for a given Ti/Nb ratio, S.

R = {ÄWmetai*[(l00/Mwt%)_l] _ (X/2)* ÄWo }/(MWTio2+S/2*MWNb2o5) (6) A similar approach can be taken for calculating equations 2 and 3 when other elements are substituted or for for oxygen, such as nitrogen or fluorine, accounting for crystal lattice vacancies.

In another embodiment the Ti:metal atomic ratio R in the final product is greater than 5:1 Ti:metal about 16.7% (Giving loss in theoretical lithium capacity).

In yet another embodiment the Ti:metal atomic ratio R in the final product is greater than 7:12.5% (Giving about loss in theoretical lithium capacity).

In a further embodiment the Ti:metal atomic ratio R in the final product is greater than 9:1 10% (Giving about loss in theoretical lithium capacity) It has turned out that a highly competitive material for battery electrodes can be made with very lO 2l competitive Li capacity although a certain fraction of the Li capacity is lost due to the addition of metal ions.

Both one metal as well as mixtures of metals are encompassed for the addition of metal ions.

The weight 6 of metal would vary a lot if it is calculated as a weight 6 of the final product depending on which metal is used.

The atomic ratio R can be readily determined by skilled persons using standard chemical analyses of materials and allows the ranges given above to be independent of the type of metal.

For metals the wt% can be calculated as a function of atomic ratio, R assuming the formula (TiOfiR,Na2O from equation (l) if the metal is sodium. See Figure 8. For the calculation of the Ti:metal atomic ratio R standard dopants such as niobium are in one embodiment neglected if their amount is small compared to the amount of Ti. (3-4 wt%) Up to a total amount of a few percent their contribution can in one embodiment be neglected for the calculation of the atomic ratio R. For a more accurate result, all standard dopants such as niobium are taken into account. Apart from Nb, at least one of Ta, W, Zr, Mo, Fe, V, In and Sn can be used as a dopant, substituting for Ti in the bronze or metal titanate or hydrogen titanate precursor Ti-O framework.

Nb can be incorporated in the process using NbCl@ Nb2O5 or KNbO3. Niobium may significantly improve the 22 results of these metal-stabilised bronzes. Niobium substitutes for Ti in the bronze structure.

In one embodiment the material comprises Nb ions so The limit in (Ti/Nb) = (8/1) 8, calculated based on the number of atoms of Ti and that the Ti:Nb ratio is 8:1 or higher. this embodiment corresponds to a ratio Nb in the finished material. In an alternative embodiment, the material comprises Nb in an amount in the range 0.1 - 20 wt%. In another alternative embodiment the material comprises Nb in an amount in the range O - 20 wt%. In yet another embodiment the amount of Nb is even higher so that the ratio Ti:Nb is lower than 8. The amount of Nb or other dopant is calculated based on the finished material, or on the precursor hydrogen or metal titanate since the Ti:Nb (or Tizdopant) ratio of the bronze framework is the same as in its precursors.

In figure 8 there is a graph showing weight 6 of stabilizing metal versus Ti/M atomic ratio. It is easy to see that for an equivalent atomic ratio, a stabilizing metal represents a greater fraction of the weight if it is a heavier metal.

Figure 9 shows calculated theoretical capacity versus Ti/M atomic ratio for various stabilizing metals. Lighter stabilizing metals are predicted to have less impact on the theoretical capacity at a given Ti/M if a Ti/M ratio needs be above ratio. In other words, a certain value to achieve stabilization (say at an index >O.8), then the lighter stabilizing metals will yield higher theoretical capacities in mAh/g. Also note this diagram is applicable to all stabilizingmetals since the curves are calculated from atomic weights. The curves for metals with intermediate atomic weights simply fall in between the curves shown. AW = 107.9 will fall For example, for silver, between that for Rb and Cs. For mixed metals, simply use the average atomic weight, for example a mixture of Na and K will fall between the Na and K curves. the metal ions In one embodiment of the second aspect, are at least one type of ion of a metal selected from rare earth elements.

Any cations can be added as metal ions, providing that the metal can substitute for Na ions between the TiO sheets in the layered Na2TinO2ÛH layered sodium titanate phase from aqueous solution. In one embodiment, the metal ions are at least one type of ion of a metal selected from transition metals, which have the ability to form cations with an incomplete d sub-shell. The definition of transition metals follow the IUPAC definition that there is an incomplete d sub-shell. In one embodiment, the metal ions are at least one type of ion of a metal selected from alkaline earth metals. in :no cmbçiimigi, In one embodiment complex ions such as charged clusters comprising more than one atom can be the stabilizing ion provided it can substitute for Na ions between the TiO2 sheets inthe layered Na2Ti¿bnH layered sodium titanate phase from aqueous solution.

In one embodiment, a BSI value is above 0.8 for the TiO2, wherein the BSI value is calculated from laser Raman spectroscopy of the TiO2, according to the following method: the instrument is calibrated against a silicon wafer standard, the intensity for the bronze Bg(2) peak located in the interval 190 - 205 cm* minus the background intensity is divided by the intensity for the Eg(1) anatase peak located in the interval 140 - 160 cm* minus the background intensity and then the resulting ratio is divided with a normalization factor which is calculated as the intensity of the Eg(1) anatase peak minus the background intensity divided by the intensity for the bronze Bg(2) peak minus the background intensity for pure TiO2(B), wherein the background intensity is calculated as the average intensity in the region with a wavenumber higher than the zero-peak and lower than the intensity originating from the sample. The anatase Eg(1)and bronze Bg(2) peaks used in the BSI may be at slightly different wavenumbers for different materials and peaks in the given intervals should be used since the peaks are intervals. expected to be within the That is the Bg(2) peak position for a pure bronze near 200c m* should be determined as should that of the Eg(1) peak nearcm* of anatase made by destabilizing the bronze by heating to 600 °C for 2 hours. For example, a pure bronze is found to have a moderate to strong Bg(2) peak at 202 cm* and when heated to 600 °C for 2 hours, has a strong anatase Eg(1) peak at 148 cm*. These should be the positions used to determine the peak the intensities for the BSI calculation. Similarly, position at which the background intensity is calculated may vary depending on the optical configuration of the Raman spectrometer. Importantly this value be taken at a position where the trace of the spectrum is flat or nearly flat in the range from just above O cm* to where the spectrometer starts to have a response from the sample in question.

In addition to the metal ions mentioned above, the material may comprise further ions. In one embodiment, the material comprises at least one type of ion selected from the group consisting of calcium, magnesium, strontium and barium. In one embodiment, the material comprises at least one type of ion selected from the group consisting of silver, copper, and cadmium. In one embodiment, the material comprises at least one type of ion selected from the rare earth metals.

In one embodiment, the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-m2/g. In one embodiment, the BET specific surface area according to ISO 9277 of the TiO50 m2/g. is in the range 30- In one embodiment, the BET specific surface area according to ISO 9277 of the TiO2 is in the range50-100 m?/g. In one embodiment, the BET specific surface area according to ISO 9277 of the TiO2 is in the range 100-200 m?/g.

In one embodiment, the TiO2 comprises 1.5 to 6 wt% of metal ions, calculated by weight of the material. Using the above formula this can be expressed as 0.10*X) S R S 0.10*X) (0.20*AWmetal - (0.82*AWmetal In one embodiment, the TiO2 constitutes 70-90 wt% of the electrode material.

In the second aspect there is provided a battery comprising at least one electrochemical cell, said at least one electrochemical cell comprises at least two electrodes (10,20) and at least one electrolyte (70), wherein at least one of the electrodes (10,2Q) comprises a) a material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wherein for the material the Ti to metal ion atomic ratio R fulfils the following condition (0.029*AWmetal - 0.10*X) S R S (0.82*AWmetal - 0.10*X), wherein Awmfial is the atomic weight of the metal and X is the metal valence.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from rare earth elements.In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from transition metals, which have the ability to form cations with an incomplete d sub-shell. The definition of transition metals follow the IUPAC definition that there is an incomplete d sub-shell.

In one embodiment of the second aspect, the metal ions are at least one type of ion of a metal selected from alkaline earth metals.

In one embodiment of the second aspect, the Tizmetal atomic ratio R in the material is greater than 4:Tizmetal, wherein the metal is present as ions. efitassiams In one embodiment of the second aspect, the metal ions comprise Nb ions. In one embodiment of the second aspect, the material comprises at least one type of ion selected from the group consisting ofcalcium, magnesium, strontium and barium. In one embodiment of the second aspect, the material comprises at least one type of ion selected from the and cadmium. In group consisting of silver, copper, one embodiment of the second aspect, the material comprises at least one ion selected from the group of rare earth metals, including yttrium and scandium. In one embodiment of the second aspect, the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-30 m?/g. In one embodiment of the second aspect, the BET specific surface area according to ISO 9277 of the TiO50 m2/g. is in the range 30- In one embodiment of the second aspect, the BET specific surface area according to ISO 9277 of the TiO2 is in the range 50-100 m?/g. In one embodiment of the second aspect, the BET specific surface area according to ISO 9277 of the TiO200 m2/g. is in the range 100- In one embodiment of the second aspect, the TiOcomprises 1.5 to 6 wt% of metal ions, calculated by weight of the TiO2. Using the above formula this particular amount of metal ions in TiO2 can be expressed as: (O.20*AWmfial- 0.10*X) S R S (0.82*AWmmfil 0.10*X).

In one embodiment of the second aspect, the conducting material is carbon black. In one embodiment of the second aspect, the conducting material is graphene. lIn one embodiment of the second aspect, the conducting material is conductive carbon nanotubes. In one embodiment of the second aspect, the TiO2 constitutes 70-90 wt% of the electrode material.

In one embodiment of the second aspect, the wt% ratio between the conducting material and the binder is in the range lzl to 7: The embodiments of the first aspect are also applicable to the second aspect with appropriate modifications and vice versa.

The titanate is a compound comprising Ti covalently bound to O, where cations are associated and bound by electrostatic forces. In the general formula for the titanate A2Ti¿bnH mH2O, it is thus conceived that A is in ionic form, whereas Ti and O are covalently bound. The hydrogen or a metal in cationic form is thus a proton or a positively charged metal ion. Such cations including protons can be exchanged by ion exchange. For instance, a proton can be exchanged for another cation such as a sodium cation. n is an integer from 3 to 6. The resulting titanates H2T13O7, H2T14O9, H2T15O11, and H2T16O13 aIG knOWn in thG aIt.

As can be seen from the experimental data, if the temperature is higher more cations are required for the stabilization, but if the temperature is kept low, a lower amount of cations is required. In one embodiment, the temperature in step b is in the interval 300 - 500 °C and content of metal ions is in the range 1.5 - 30 wt%. In an alternative embodiment, the temperature in step b is in the interval 300 - 400 °C and content of metal ions is in the range 1.5 - 6 wt%. In yet another alternative embodiment the temperature in step b is in the interval 350 - 450 °C. In still another alternative the temperature in step b is in the interval 400 - 500 °C. In even a further alternative the temperature in step b is in the interval 500 - 600 °C. The content of metal ions can be adjusted to the desired value in several ways. In one embodiment the content of metal ions is adjusted during the manufacture of the titanate by use of suitable 3l amounts of the desired ions. This has the advantage the desired amount of metal ions is achieved directly without an additional ion exchange step. Alternatively, the content of metal ions is adjusted by an ion exchange step, where for instance protons are exchanged with the desired metal ions. Also a combination of adjustment methods is envisaged. The term addition of stabilizing metal ions includes the case where metal ions such as Na- ions are added in some context and where an ion exchange step is such that a fraction of metal ions remain after the ion exchange step.

The titanate starting material, i.e. the material with the general formula A2Ti¿bnfl 0nfi2O can be provided in several ways. There are commercially available titanates, which can be purchased. Alternatively, the titanate can be made from other substances. In one embodiment, the titanate is obtained by providing an aqueous solution comprising TiOCl2, and HCl, and thereafter increasing the pH and/or the temperature of the solution until a precipitate comprising the titanate is obtained. In one embodiment, the precipitate is washed in water. In another embodiment, the precipitate is dried. In a further embodiment, the precipitate is dried and ground.

In one embodiment, the aqueous solution comprises an alpha hydroxy acid in addition to TiOCl2, and HCl. In one embodiment the aqueous solution is clear.

In another embodiment, the aqueous solution comprising TiOCl2 is provided by at least partial hydrolysis of TiCl In another embodiment the aqueous solution comprising TiOCl2 is provided by dissolving at least one titanic acid with the general formula TiOX(OH)44X, wherein x is O or l, lin an aqueous solution comprising at least one compound selected from the group consisting of TiOCl2, TiCl4, and HCl so that a clear solution is obtained, while keeping the temperature below 30 °C. In one embodiment, the at least one titanic acid is made from TiOCl2 by addition of an aqueous solution of a base until precipitation. The latter approach has the advantage that the process is easier to control, in particular in large scale. More in particular it is possible to measure and control the acidity with high accuracy. The acidity is the ability to donate protons in an aqueous solution, i.e. the acidity is the amount of acids.

The calcination, i.e. a heat treatment is carried out so that the organic material including the alpha- hydroxy acid is removed. Water is also removed during heating. Further, the calcination should be carried out so that a rearrangement occurs in the material in such a way that the fraction of anatase is minimized and the fraction of titanium dioxide in bronze form is maximized. This is normally done by choosing a lower temperature in the interval such as in the interval 300-400 °C together with a longer calcination time, or a higher temperature in the interval 300-500 °C together with a shorter calcination time. A skilled person can in the light of the description and the appended examples choose a suitable temperature and time for the calcination. A time range for the calcination is in one embodiment, 5 minutes tohours. The Ti to metal ion atomic ratio R does not change during the calcination. The ratio of Ti: metal is assumed to be constant from the time of mixing the air dried H-titanate with the appropriate metal to the solution, through the ion exchange process,collection and drying of the titanate through to the final calcined material. The assumption is that all of the metals in solution end up in the final, dry exchanged titanate and then in the final calcined product. The ratios of Ti:metal assume 100% uptake during the ion exchange step. Elemental analysis can be used as feedback to adjust the process to achieve the desired metal uptake required.

In one embodiment, the method is carried out at a pressure p being ambient pressure f20%. In a variant embodiment, the method is carried out at ambient pressure. Ambient pressure is the atmospheric pressure at which the method is carried out. The standard atmosphere is normally taken as ambient pressure, i.e. 1013.25 mbar.

In one embodiment, the at least one alpha hydroxy acid is citric acid.

In one embodiment, no transition metal ions are added as stabilizing ions. Although the metal-oxygen framework does comprise titanium, which is a transition metal, the titanium is not a stabilizer as it is in the framework. Stabilizer metals always are sandwiched between framework layers in the layered pIGCllISOIS .

Lighter ions are suitably chosen if the final material is to be made lightweight. Thus, for instance sodium ions are preferred over caesium ions if the weight of the final material is the most important factor.In one embodiment, Nb-ions are added at any point before or during the chemical reaction leading to the the Nb ions titanate layered precursor structure. I.e. are added before the material is finished. The Nb-ions have the advantage of improving the conductivity.

In one embodiment, the pH is increased during an ion exchange process during the manufacture and wherein the pH is increased to a value in the range 7-10. This has the effect that the charge of certain groups of the material is reversed to become negative so that cations are more attracted to the material. The reason to increase the pH is to increase the rate of stabilizing metal uptake because the metals are not competing with protons for the negatively charged binding sites on the titanate.

In order to obtain an electrode material for use in a battery, in one embodiment, of the method at least one conducting material and at least one binder are added to the calcined material to obtain an electrode the material for a battery. In one embodiment, conducting material is carbon black. In another embodiment the conducting material is graphene. In yet another embodiment, the conducting material is carbon the electrode material 6-nanotubes. In one embodiment, comprises about 90 wt% of the calcined material, wt% carbon black and 4-3 wt% binder.

Two or more of all embodiments can be freely combined with each other in any combination. It will be appreciated that two or more selected ones of the mentioned embodiments can be combined.

Examples The invention is further described by the following non-limiting examples.

Example l An acidic, 10 wt% TiO2 dispersion of pH <1 was prepared by mixing 2.5 parts of titanic acid suspended (22-24 wt % in water with 1 part of TiOCl2 solution TiO2, density 1.5-1.6 g.cm*) to obtain a clear solution and adding citric acid as stabilizer in mass ratio of 10:1 TiO2: citric acid prior to raising the temperature to 80 °C and holding for 75 minutes and subsequent rapid cooling. The said titanic acid suspended in water was pH 5.5 and was prepared by mixing 2 parts of said TiOCl2 solution with 1 part of water and 8.8 parts 10% NaOH, keeping the temperature in the range 25-40 °C. In this example, the ratio of two masses, i.e., the mass of Ti in the aqueous TiOCl2 solution used to prepare the titanic acid suspended in water and the mass of Ti in the aqueous solution of TiOCl2 that was mixed with titanic acid to form a clear solution was 3: The ion and water content were adjusted to pH 1 to 1.and 20 wt% TiO2 so that an acidic sol of TiO2 was obtained. The acidic sol of TiO2 was adjusted towt% to arrive at a 37 wt% dispersion of particles. An amount corresponding to 5.2773 g TiO2 was taken.

Total 10 M KOH 130.56 g was added to adjust the concentration of hydroxide ions to well above 8 M.

The mixture stirred for 1 hour using a magnetic stirrer. Subsequently the mixture was divided evenly between 4 Teflon® (polytetraflouroethene) lined autoclaves and then heated for 56 hours at 145 °C with no stirring.

After 56 hours of heating, the autoclaves were cooled ambiently to room temperature in the closed oven for 23 hours. The product in each Teflon® liner were mixed together.

To this was added 0.1 M HCl and allowed to settle, decanting the clear supernatant. This was repeated three times. After this, an excess of 0.1 M HCl was mixed with the decanted product and filtered. By this procedure at least a part of the K*-ions was replaced by H*-ions.

The sample was then filtered slowly over several days, washing with milliQ water until pH > 3. The sample was then air-dried.

The air-dried powders were then stirred in solutions of 0.001, 0.005, 0.01 and 0.05 M NaOH to exchange the hydrogen for sodium. The amount of solution was controlled so that the calculated amount of sodium, when fully exchanged would yield the following sodiumcontents of the exchanged titanates: 0.001 M - 1.6%; 0.005 M - 2.7%; 0.01 M - 6.0%; and 0.05 M - 26.9%.

The four samples exchanged at these four different concentrations plus the unexchanged titanate were then divided and heated to 500 °C. After heating, the powders were then subject to Raman spectroscopy. The Raman spectra are shown in the figures below. From these spectra, a bronze stability indicator, BSI was calculated. First, a background was subtracted from all spectra according to the average spectral intensity above the zero-peak and the first intensity from the sample. This background average was flat and equal to the intensity at 75 cmfl. Next the peak height of a bronze indicator peak, B at 201.69 cm* was divided by the peak height of an anatase indicator peak, A at 148.68 cmfl. These peaks could easily be identified as inside the ranges of wavenumbers. This is the bronze/anatase ratio value or BAR = B/A. The BAR value was normalized to a value of 1.3, which was obtained by making the same procedure for a pure bronze phase. This gave the bronze stability indicator value or BSI, which was found to be a representative value of BAR for pure or nearly pure bronzes made using this hydrothermal method. Therefore, higher values of BAR or BSI indicate higher levels of bronze compared with anatase. Please note this is not quantitative in terms of exact amount of bronze, but systematically increases with increasing bronze to anatase, or systematically decreases with increasing anatase fraction.

This method of stabilization can be performed on small fractions of a batch of samples in order to find theBSI as a function of Na exchange and temperature. Such information will likely vary somewhat depending upon the quality and nature of the starting titanate material.

In the case where one would prefer to find an optimized stability condition as a function of temperature and Na content, say for use in a lithium ion battery anode material, the desire for thermal stability of bronze is high (high BSI) since full conversion of the titanate to TiO2 is best achieved above 300-350 °C, but the desire for high sodium content is low, since it will impact the capacity of the anode. So one can use this method to find an optimum amount of stabilizer that is high enough to give stability at a desired temperature, say 400 °C, but not too high that the capacity for lithium is negatively affected. The capacity of a battery is negatively affected by a high content of other metal ions such as Na because the other metal ions take the place of Li-ions contributing to the capacity of the battery.

Using the same titanate powder as in example 1, other ions of were exchanged in place of the H, by ZnCl2 and LaCl0.01 and exchanging in solutions of LiOH, CsOH, respectively at approximately 0.001, 0.005, 0.05 M concentrations each.

The corresponding ratios R for each case, i.e. for Li, Cs, Zn and La at the four different concentrations of 0.001 M 0.005 M (low), 0.01 M (high) (very low), and0.05 M In the (very high) of the metal solutions. experiments these were target concentrations and the actual concentrations differed slightly from the target concentrations. Since the concentrations are not exact they are given as very low, low, high, and very high instead of actual values.

Metal Very high. High Low Very low Li 0.81 1.62 8.53 15.Cs 0.81 1.62 7.27 9.Zn 0.79 1.57 7.57 16.La 0.83 1.53 7.79 14.80 The underlined values fall within the formula (0.029*AWmmfil 0.10*X) S R S (0.82*AWmmfil 0.10*X), wherein Awmfialis the atomic weight of the metal and X is the metal valence.

Each solution contained 0.35 f 0.03 g of the dry titanate, and 10 g of solution, and 10 g solution of varying metal content. Exact weights were recorded and the following weight and atomic ratios (relative to the air-dried titanate) were used. For each concentration of Li 0.49, 0.91, of Li solution, the weight-% relative to the air-dried titanate was: 4.60 and 13.8, 17.1, 8.81 wt% respectively. For the Cs solution: 48.0 and 64.9 wt% 4.32, 8.86, respectively. For the Zn 31.88 and 48.32 wt%, 9.55, 16.7, solution: respectively. For the La solution: 50.and 65.3 wt%, respectively. For the ion exchange, all solutions were stirred magnetically together with the titanate samples for 20 minutes at room temperature and then transferred to an oven heated to 70 °C for an additional 30 minutes without stirring. The exchanged powders were collected by triple decantation and centrifugation with deionized water in 45 ml centrifuge tubes, and air-dried. All of the air-dried, exchanged samples were then heated in air at 350 °C °C for 1 hour. for 2 hours plus 400 The samples were then split, and the splits subjected to an additional 1 hour of heating in air at 450 °C. Raman spectroscopy was run on all 32 samples. Additionally, the non- exchanged titanate was also heated in air at 350 °C for 2 hours plus 400 °C for 1 hour at the same time as the other samples. Most samples displayed Raman spectra characteristic of bronze or a bronze-like phase with either zero or trace anatase when measured in multiple spots. Two exceptions were found, one being that a consistent albeit small amount of anatase The was detected in the heated, non-exchanged sample. other was the Li exchanged samples. These displayed 1- 5% anatase when heated to 400 °C (as judged by the size of the anatase peak near 150 cmfl), although no anatase was detected in the sample exchanged in the highest concentration. For the higher temperature run, the anatase fraction increased from 1-5% to 10-20% at high exchange concentration, for the lowest exchange concentrations. Taken together these results indicate that Li is not effective in stabilizing bronze from transitioning to anatase in these samples whereas Cs, Zn and La do have a stabilizing effect. Example 3 Stabilised anode material preparation A stabilised bronze material was prepared by an exchange reaction similar to example 1 but now usingg of air dried hydrogen titanate and adding it to approximately 125g of 0.01M NaOH.

The so obtained titanate/NaOH dispersion was stirred magnetically at room temperature for 30 minutes followed by 30 minutes heating without stirring, in an oven preheated to 65 °C, followed by a second stirring of approximately 15 minutes.

The sample was then washed in deionized water to remove excess ions and subsequently air dried.

Chemical analysis showed the atomic ratio of titanium to alkali metal (R) in the stabilized material to be 6.5, with the Na/K atomic ratio of 0.9, the potassium being unremoved alkali metal during the initial acid exchange.

The material was used in an electrode of a coin cell and its electrochemical properties were measured.

Anode preparation A dispersion was made with the material as follows: Samples were prepared using 1.002g third structure comprising TiO2 0.124g Super C 65 carbon black (Imerys®) 0.126g Kynar® PVDF(polyvinylidene fluoride). 2.377g n-methylpyrrolidone (NMP) All slurries were homogenised using a RETCH Mixer Mill MM 200 with stainless steel jars.

First the carbon black was dispersed in a 5 wt% PVDFsolution for 10 min. Afterwards the active material and additional NMP was added and the slurry was homogenised for 30 min.

The slurries were coated using a K control coater with a meter bar designed to leave a wet film deposit of 100 um.

After coating the electrode sheets were dried at 60 °C, roll pressed and dried again at 100 °C under vacuum for 10 hours. 12 mm ø electrodes were punched and transferred to an Ar filled glovebox. 2016 coin-cells (6 cells per sample) were assembled using Li as counter electrode a Celgard 2400 PP separator and 40 uL LP40 electrolyte (1M LiPF6 in EC/DEC 1:1 wt.) EC/DEC is Ethylene Carbonate:Diethyl Carbonate.

Electrochemical characterisation Electrochemical charge and discharge experiments were carried out on a Maccor 4200 and a LANHE CT2001A in a 1C was defined voltage window of 1-2.5 V vs. Li/Li+. as 330 mA/g (TiOfi.

Two different test programs were applied. In the first program, the rate acceptance was assessed.

C/10, C/3, The cells were charged and discharge at C/2, 1C, 2C, 5C, 1OC and C/10 again for 5 cycles each. The last step at low currents was applied to analysed the capacity recovery.

In the second program, the cycle-life at C/2 wasassessed for 200 cycles. Prior to the cycle life analysis the cells underwent 3 cycles at a low current of C/ Electrochemical results All results are given in mAh per gram TiO2. The coulombic efficiency is calculated by dividing the delithiation capacity by the lithiation capacity. The lowest applied current was 33 mA/g (C/10) and the highest 3300 mA/g (10C). This would translate to about 20C for LTO.

A diagram from a test cycle is shown in Figure Initial capacity at C/10 cycle 3: 175 mAh/g Capacity at 5C (cycle 30): 95 mAh/g Capacity at 10C (cycle 35): 65 mAh/g Recovered capacity: 170 mAh/g Capacity after 500 cycles at 3C: 130 mAh/g (160 mAh/g initial) Coulombic efficiency in both tests: 99.5% converged to > after initial cycling.

Example 4 Niobium doped TiO2(B) was prepared with a composition identical to Example 1, except with the addition of 0.5g Nb2O5 stirred into the 37% TiO2 dispersion until well homogenised, prior to addition of 10 M KOH.

The sample was divided equally into four 30 ml Teflon- lined steel autoclaves and heated at 145 °C for 44.5 hours. The sample was acid exchanged by repeated centrifugation, decantation and re-suspension in distilled water.A niobium-doped bronze material was obtained by heating 2.065 g of the washed and dried acid exchanged material from example 4. The sample was calcined by heating at 140°C for 20 minutes, °C for 1 hours, °C for 30 minutes and 450 °C for one hour in air. The cooled sample was weighed and the weight loss during heating was 17.5%. The sample was hand ground in a mortar and pestle and subject to x-ray diffraction and Raman spectroscopy. The sample was found to be consistent with the bronze phase of TiOh with no detectable anatase The calcined R value of this niobium-doped TiO2 bronze materials was 13.5. The potassium present due to incomplete removal during the acid exchange step.

Four 0.042g samples of the air-dried hydrogen titanate obtained prior to the conversion to bronze were re- exchanged with 0.05M, 0.01M, 0.005M and 0.001M NaOH, respectively to obtain four metal stabilised, niobium doped titanates in the same way as example 1, with the same final target Na con tents for each as was targeted in example These sodium exchanged, niobium doped titanates were calcined by heating at 140 °C for 20 minutes, 300 °C for 45 minutes, 350 °C for one hour and 450 °C for 30 minutes, 500 °C for 30 minutes and 550 °C forminutes. The cooled samples were then subject to Raman spectroscopy.

The Ti/Nb ratio of the input mixture was determined as 17 and the measured ratio in the so-made bronze was also determined to be 17 by electron dispersive x-ray analysis on three separate areas of the sample indicating a homogeneous reaction of Ti and Nb oxides with KOH. A Ti:Nb ratio of 17 is within the limitation that Nb ions are added up to a Ti:Nb ratio of 8. So the Ti/K ratio and Ti/Nb ratio is considered identical in the metal stabilised niobium-doped bronzes and the niobium doped bronze with residual potassium.

A result from the example can be seen in fig 11 showing Raman spectra corresponding to metal stabilised niobium-doped bronze materials with very high to very low contents of sodium stabilisation.

It appears that with metal stabilization of niobium doped TiO2(B) at 17:1 Ti:Nb, the thermal stability of the unstabilised (or minimally stabilized) material is so improved that the need for stabilizing metal ions becomes less the more Nb is present in the precursor bronze structure likely due to a separate thermal stabilisation of the bronze arising through niobium doping. Nonetheless stabilisation originating from sodium and or potassium ions is still readily apparent in the 17:1 Ti:Nb metal stabilised bronze material of but this example, only at relatively high Na content.

It is likely that the destabilization of bronze to anatase can occur for longer thermal treatments for a given temperature, therefore metal stabilization of niobium doped bronzes made by hydrothermal processing is best taken advantage at longer heating times than for non-doped bronzes, the exact temperature depending on the intrinsic thermal stability of the non- stabilised niobium-doped bronze, which is likely to be a higher temperature than for a non-niobium-doped bronze.Example 5 Niobium doped bronze anode preparation and electrochemical characterization Anode preparation Anodes were prepared using the niobium-doped TiObronze of example 5, of 450 °C. calcined at a maximum temperature Two electrode slurries were prepared using the following: O.7000 g of the active material component (TiOfi. 0.2000g Super C65 carbon black 2.000 g of a 5wt% (Imerys®) solution of Kynar® PVDF polyvinylidene fluoride) 5% in n- methylpyrrolidone(NMP) and extra NMP to adjust viscosity.

These would yield a final dry cast composition of 70:20:10, TiO2:carbon black: binder calculated by weight.

To form the first slurry: i) A first mixture was made by combining O.2g of carbon black dispersed in the 2.0 g of binder solution in a mixing cup using a vacuum centrifugal mixer running at 2000rpm for 10 minutes and then degassing under vacuum for 30 seconds. ii) A second mixture was obtained by adding 3.0 g of NMP solvent and O.70g of active Nb-doped TiO2 material to the mixing cup containing thefirst mixture, followed by mixing for 5 minutes at 2000 rpm followed by degassing for 30 seconds under vacuum.

The second mixture was then transferred into a with 1 ball iii) stainless-steel vial (10ml volume) (6.5g mass) and mixed in a Retsch MM 400 mixer mill at 25Hz for 10 minutes iv) Extra NMP was added to adjust viscosity for casting in 1.5g steps, with a further 2 minutes mixing at 25Hz.

To form the second slurry: i. A first mixture was made by combining 0.2g of carbon black, 0.7g of the active Nb-doped TiOand 3.0g NMP solvent in a stainless steel vial (10 ml). One ball(6.5g mass) was added to the stainless steel vial and the vial shaken in a Retsch MM 400 mixer mill at 25 Hz for 5 minutes. ii. A second mixture was obtained by adding 2.0g of binder solution to the first mixture contained in the stainless steel vial obtained after(i) above and the vial was shaken in a Retsch MM 400 mixer mill at 25 Hz for 10 minutes. iii. Extra NMP was added to adjust viscosity for casting in 1.5g steps, with a further 2 minutes mixing at 25Hz.

Coating Procedure The freshly made slurries were coated onto 20 micron thick Al foil using a K control coater with a Zhentner applicator frame designed to leave a wet film deposit of 200 micrometers.After coating the electrode sheets were dried at 60 °C for 48 hours. For testing, 14 mm ø electrodes were punched from the dry electrode sheet and dried at 120 °C under vacuum for 14 hours in a glove box mini chamber and transferred to an Ar filled glove box.

Coin cell assembly 2016 coin-cells (9 cells per sample) were assembled using Li metal (16 mm ø) as counter electrodes.

Additionally in each cell, a Celgard 2400 PP was used as a separator, 35 uL LP40(1M LiPF6 in EC/DEC 1:1 wt. from Sigma Aldrich) as the electrolyte and a pre- weighed punched electrode comprising the Nb-doped TiO2 bronze. The mass of the coated electrode material was determined by subtracting an average mass value for 10 punched disks of the uncoated Al foil sheet from which the electrodes were cast.

Electrochemical characterisation A LANHE CT2001A tester was used in cycling the half cells. 1C was defined as 330 mA/g (TiOfi.

Two different test programs were applied. In the first program, operating on several coin cells made from electrodes obtained from the first slurry, cells were charged and discharged for 32 cycles at C/ In the second program, operating on several coin cells from the second slurry, cells were charged and discharged at C/10 C/2 (cycles 13-22), 2C (cycles 23-32),5C and 10C (cycles 43-52) (cycles 1-2), (cycles 3-12), 1C (cycles 33-42) and then back to C/2 (cycles53-62) and C/10 (cycles 63-64) to assess recovered capacity after iterated cycling and then to 1C (cycles 65-264)for assessing capacity for extended further cycling.

Electrochemical results All results are given in mAh per gram (mAh/g) of the active Nb-doped bronze material. The coulombic efficiency is calculated by dividing the delithiation capacity by the lithiation capacity. The lowest applied current was 33 mA/g (C/10) and the highest 3300 mA/g (1OC). 2OC for LTO.

The latter would translate to about Diagrams of the electrochemical characterisation results from two representative cells made as described above are given in Figures 12, 13 and 14. A diagram from a test cycle for a cell made from the first slurry is shown in Figure 12. 242 mAh/q 216 mAh/q 89.9%; Capacity at C/10 cycle 3: Capacity at C/10 cycle 32: Coulombic efficiency: 32M1cycle: 98.8% lfi-cycle: A diagram of the rate cycling for a cell made from the second slurry is shown in Figures 13 and 14. Figure 14 is a zoomed out view of Figure Initial capacity at C/10 (cycle 2): 257 mAh/g Capacity at C/2 (cycle 12): 226 mAh/g Capacity at 1C (cycle 22): 213 mAh/g Capacity at 2C (cycle 32): 195 mAh/g Capacity at 5C (cycle 42): 151 mAh/g Capacity at 1OC (cycle 52): 109 mAh/g Recovered Recovered Recovered Recovered Initial coulombic efficiency: Converged Coulombic efficiency: capacity capacity capacity capacity at at at at C/2 (cycle 62): 218 mAh/g C/lO (cycle 64): 229 mAh/g lC (cycle lOO): 203 mAh/g lC (cycle 264): 195 mAh/g (cycle l): 84.3% cycle 264: 99.8%

Claims (24)

Claims

1. A component material of a battery electrode, the material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion the Ti to metal ion atomic ratio R fulfils the following condition (0.029*AWmmfil O.10*X) S R S (O.82*AWmmfil O.10*X), wherein Awmmalis the atomic weight of the metal and X is the metal valence, wherein the metal ions are at least one type of ion of a metal selected from one of: a.rare earth elements, b.transition metals, which have the ability to form cations with an incomplete d sub-shell, and c.alkaline earth metals. f: ëy wherein the Tizmetal atomic ratio R in the material is greater than 4: \mmThe material according to any one of claims 1- “w, wherein a BSI (Bronze stability indicator) value is above 0.8 for the TiO2, wherein the BSI value is The material according to asyweee calculated from laser Raman spectroscopy of the TiOh according to the following method: the instrument is calibrated against a silicon wafer standard, the intensity for the Bg(2) bronze peak located in the interval 190 - 205 cm* minus the background intensity is divided by the intensity for the Eg(1) anatase peak located in the interval 140 - 160 cm* minus the background intensity and then the resulting ratio is divided with a normalization factor which is calculated as the intensity of the Eg(1) anatase peak minus the background intensity divided by the intensity for the Bg(2) bronze peak minus the background intensity for pure TiO2(B), wherein the background intensity as calculated as the average intensity in the region with a wavenumber higher than the zero-peak and lower than the intensity originating from the sample. mmïhe material according to any one of claims 1- wherein the material comprises Nb ions. The material according to any one of claims 1- fis, wherein the material comprises Nb ions so that the Ti:Nb ratio is 8:1 or higher. The material according to any one of claims 1- åä, wherein the material comprises at least one type of ion selected from the group consisting of calcium and magnesium. The material according to any one of claims l- wherein the material comprises at least one type of ion selected from the group consisting of silver, copper, and cadmium. The material according to any one of claims l- ~s, wherein the material comprises at least one rare earth metal. The material according to any one of claims l- wherein the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-30 m2/g. The material according to any one of claims l- f, wherein R fulfils: The material according to any one of claims l- wherein the TiO2 constitutes 70-90 wt% of the electrode material. A battery comprising at least one electrochemical cell, said at least one electrochemical cell comprises at least two electrodes (lï,2fl) (7§), comprises a) a and at least one electrolyte wherein at least one of the electrodes (l§,2Q) material comprising TiO2, wherein the TiO2 comprises a fraction of TiO2(B), titanium dioxide in bronze phase, wherein the material comprises at least one type of metal ion, b) at least one conducting material, and c) at least one binder, wše§e§$»§haractæriæeü in that for the material the Ti to metal ion atomic ratio Rfulfils the following condition (0.029*AWmmfil 0.10*X) 3 R S 0.10*X), (0.82*AWmmai wherein Awmmalis the atomic weight of the metal and X is the metal valence, wherein the metal ions are at least one type of ion of a metal selected from one of: a.rare earth elements, b.transition metals, which have the ability to form cations with an incomplete d sub-shell, and c.alkaline earth metals. The battery according to any wherein the Ti:metal atomic ratio R in the material is greater than 4:1 Ti:metal, wherein the metal is present as ions. The battery according to any one of claims 1%» J, wherein a BSI value is above 0.8 for the TiO2, wherein the BSI value is calculated from laser Raman spectroscopy of the TiO2, according to the following method: the instrument is calibrated against the intensity for the Bg(2) 205 cm* a silicon wafer standard, bronze peak located in the interval 190 - minus the background intensity is divided by the intensity for the Eg(1) anatase peak located in the interval 140 - 160 cm* minus the background intensity and then the resulting ratio is divided with a normalization factor which is calculated as the intensity of the Eg(1) anatase peak minus the background intensity divided by the intensity for the Bg(2) bronze peak minus the background intensity for pure TiO2(B), wherein the background intensity as calculated as the average intensity in the region with a wavenumber higher than the zero-peak and lower than the intensity originating from the sample. The battery according to any one of claims %ë« e- 1 L, wherein the material comprises Nb ions so that the Ti:Nb ratio is 8:1 or higher. The battery according to any one of claims èš~ wherein the material comprises at least one type of ion selected from the group consisting of calcium and magnesium. The battery according to any one of claims ëš« wherein the material comprises at least one type of ion selected from the group consisting of and cadmium. silver, copper, The battery according to any one of claims %š~ wherein the material comprises at least one rare earth metal. The battery according to any one of claims lä» wherein the BET specific surface area according to ISO 9277 of the TiO2 is in the range 2-m2/g. The battery according to any one of claims lä» wherein R fulfils: (0.20*AWmmal- 0.l0*X) 3 R 3 (0.82*AWmmfil 0.l0*X). The battery according to any one of claims %ë~ wherein the conducting material is carbon wherein the TiO2 constitutes 70-90 wt% of the electrode material. The battery according to any one of claims g, wherein the wt% ratio between the conducting material and the binder is in the range lzl to 7:3.