Method for synthesizing an electrode material and electrode comprising the material

Abstract

A method for synthesizing a material, comprising the steps of: providing a starting mixture containing lithium, a metal, a phosphate ion, and an additive which improves the transport of lithium ions into a material provided by this method compared to a material provided in the absence of these additives; heating this mixture in a reduction atmosphere to produce a material, wherein the material comprises a first phase which is LixMPO4, where M is the metal and x is less than or equal to 1.05, e.g.LiFePO4 in olivine structure, and includes a second phase, wherein the second phase has an ionic conductivity greater than the ionic conductivity of the first phase, wherein the additive replaces at least some of the phosphorus or the metal in the LixMPO4, where M is the metal and x is less than or equal to 1.05, wherein the first phase comprises 80-95 mol percent of the material and the second phase comprises 5-20 mol percent of the material, wherein the metal and the phosphate are provided as FePO4×2H2O in the starting mixture, wherein the process further comprises: introducing the carbon-containing compound polyvinyl alcohol (PVA) into the mixture prior to the reaction.

Description

[0001] This application claims priority from US Provisional Patent Application No. 60 / 649,501, filed on February 3, 2005 with the Title: “Electrod material with improved internal transport properties”. AREA OF INVENTION

[0002] This invention relates generally to materials and methods for synthesizing these materials. More specifically, the invention relates to Methods for synthesizing certain materials containing a metallic phosphate phase. Composite materials which include a The invention includes a metal phosphate phase. In particular, the invention relates to a method for synthesizing a metallic phosphate material which has improved conductivity for lithium ions, as well as for such materials and for electrodes and other devices made from such materials Devices. BACKGROUND OF THE INVENTION

[0003] Lithium-containing transition metal phosphates such as LiFePO4 including various doped and modified versions thereof, They are increasingly used as cathode materials for lithium batteries. In operation, these materials transport electrons and lithium ions. This results in lithium transport through such materials being a crucial factor influencing their performance in lithium batteries. Systems. Therefore, the efficiency of devices containing such materials depends, among other things, on their lithium-ion batteries. Transport properties depend on the materials. Therefore, attempts have been made to improve lithium transport in such materials.

[0004] As explained below, the present invention proposes an electronic material based on lithium metal phosphates, wherein This material combines good electrical conductivity with high internal conductivity. In certain embodiments of the invention, the Materials composed of at least two phases. The materials of the present invention are simple and economical to synthesize. and are ideal cathodes for lithium batteries with high-performance capabilities. BRIEF DESCRIPTION OF THE INVENTION

[0005] This document describes a method for synthesizing a material useful as an electrode for a lithium battery. The method includes the provision of a starting mixture containing lithium, a metal, a phosphate ion, and an additive which facilitates transport. of lithium ions into a material produced according to this process, compared with a material produced in the absence of the additive, improved. The mixture is heated in a reduction atmosphere to produce a material containing LixMPO4, where M is a metal. and x ranges from 0 to approximately 1. In some special cases, x can have values ​​greater than 1.05; it will be understood that such superstoichiometric values ​​are within the range of the definition of "approximately 1" in this disclosure. In special cases, the An additive selected from the group consisting of: V, Nb, Mo, C, and combinations thereof. In some cases, the additive promotes the reduction of Carbon-containing species to form free carbon. In other cases, the additive replaces some of the metal in the material. In others In some cases, it can replace some of the phosphorus.

[0006] In other cases, the additive can act as a nucleation agent, promoting the growth of at least one component of the material. In other cases, the additive can promote the reduction of a carbon-containing element in the starting mixture to generate free carbon, and this free carbon can be at least partially sp2-coordinated. In still other cases, the additive is effective in modifying the lattice structure of the material, so that the transport of lithium ions through the modified lattice is improved compared to the transport of lithium ions through a corresponding unmodified lattice.

[0007] In some cases, the material is a two-phase material comprising a first phase, which includes LixMPO4, and a second phase. The ionic conductivity of the second phase can be higher than that of the first phase. In specific cases, the second phase includes oxygen, and the atomic ratio of oxygen to phosphorus is less than 4:1. In some embodiments, the first phase comprises 80–95 mol percent of the composite material, and the second phase comprises 5–20 mol percent.

[0008] In some cases, the metal M is initially present in the starting mixture in a first oxidation state and when the When the mixture is heated in a reducing atmosphere, at least some of the metal changes from the first oxidation state to a second. The reduction reaction occurs when the oxidation state is lower than the first oxidation state. In some cases, the reduction atmosphere can... some involve a gaseous reduction atmosphere, while in other cases the reduction atmosphere is created by the insertion of a solid or liquid. A reducing agent can be provided. Heating can be carried out at temperatures in a temperature range of 300–750°C. can be carried out and, in special cases, at temperatures in a temperature range of 650–700°C.

[0009] Also disclosed herein are materials produced by a method of the present invention. In one case, the materials are The present invention is characterized in that, when contained in a cathode of a lithium battery, they increase the lithium-ion conductivity. the material has a density in the range of 10⁻⁶ S / cm to 5 × 10⁻⁴ S / cm. The material may further be characterized by the fact that when it is in contained in the cathode of a lithium-ion battery, its electronic conductivity is in the range of 10⁻⁷ S / cm to 10⁻⁴ S / cm. Also in this Disclosed are electrodes made from the material of the present invention, such as lithium batteries, which comprise these electrodes. BRIEF DESCRIPTION OF THE DRAWING

[0010] Fig. 1 is a graph showing the absorption rate of materials of the present invention and comparison materials in the form of Shows capacity versus number of charge / discharge cycles. DETAILED DESCRIPTION OF THE INVENTION

[0011] Prior art methods for synthesizing lithium metal phosphate materials generally rely on a chemical Reaction of precursor materials, which is typically carried out at elevated temperatures. According to the present invention, the The inventors of this method produced lithium metal phosphate compounds using reacting precursor materials under reduction conditions, wherein the The metal component is typically reduced from a higher to a lower oxidation state, and the inventors have thereby found that the materials produced in this way were significantly improved compared to materials known from the prior art. They have performance characteristics as cathode materials for lithium batteries. In special cases, the metal and the phosphate are both in one. The component of the initial mixture is present. For example, if the metal is iron, the initial mixture may contain FePO4, where the Iron is present in the +3 state. During the synthesis reaction, the iron is reduced to the +2 state. This process The manufactured materials exhibit good electronic and ionic conductivities, and this is thought to be partly due to the fact that It can be attributed to the fact that the metal and the phosphate ion are initially in close proximity in the starting mixture. With the presence of the metal and the phosphate ion in close proximity... With iron and phosphorus, the process time and temperature are reduced because less diffusion in the solid state is required.

[0012] According to the method of the present invention, the starting mixture includes an additive which increases the lithium ion conductivity of the The material produced in this way is improved compared to identically produced materials without the additive. The additive can be one or more This includes metals exhibiting a +5 oxidation state. And in special cases, the metal does not have a +6 oxidation state. Vanadium is one such example. Niobium is a particularly preferred additive material; it is another. In some cases, carbon acts as an additive, and this carbon can originating from a source such as a polymer or other organic compounds, which is reduced during the preparation of the material. In specific cases, an additive, such as the aforementioned metal, can promote or trigger the activity of another additive, such as carbon. How As described in detail below, the additive can act in various ways, such as to promote the ionic conductivity of the material; and in In some cases, it can also promote the electronic conductivity of the material.

[0013] Upon investigation, the inventors found that in special cases the reductive synthesis method of the present The invention produced a two-phase material. This material was analyzed using electron microscopy and EDX, and it was found that The material produced in this way comprises a first phase, which includes a lithium metal phosphate with very good ionic conductivity, and a The second phase, which has a higher electrical conductivity than the first phase, is included. In some cases, the second phase is a A type that contains the least amount of the metal and the phosphate, and may also contain subphosphate levels of oxygen. In certain cases The second phase also has good ionic conductivity. In a given material, the first phase is composed of the general Formula LixMPO4, where M is a metal such as iron and x is less than or equal to approximately 1; and a second phase, which is a reduced form of a It is a metal phosphate. If the metal is, for example, iron, the second phase contains one or more of: Fe2P2O7; FeP; Fe2P and Fe3P.

[0014] As described above, the incorporation of relatively small amounts of an additive enhances the performance of the resulting Cathode material, presumably by improving the material's lithium ion transport properties. This effect can manifest itself as an increase in the internal conductivity of the main material and / or an improvement in ion transport between particles of the main material. The additive can be incorporated as an additional component of the material, such as a doping substance, modifier, or similar, and in the In such a case, the general formula mentioned above for the material is also understood to represent materials of the general formula. LixM1-yAyPO4, where A is the additive, y is less than 1, and M and x are as described above. In other cases, the additive cannot be directly added to the The material is absorbed and can function as a catalyst or in other ways, altering the physical and / or chemical environment. the material is altered. Among the additives that can be used in this way is vanadium, typically in the form of V2O5 in the The base mixture contains niobium and its compounds, which can be used in the same way. Other additives include other metals. such as molybdenum and carbon. The additive can directly influence the lithium-ion conductivity of the material; or it can serve as a force transmitter. which improves the dispersion of lithium. The additive can also facilitate the formation of other elements such as carbon, metal, or similar substances. promote and this type can then act as an additive to improve the performance of the resulting cathode material, either directly or by promoting the formation of a phase or species with high lithium capacity. Carbon can be removed, for example, by the reduction of in the A reaction mixture can be produced from existing organic molecules, and this carbon can be used as a direct conductivity improver and / or or additive that improves the material, and the additive can influence the amount and / or type of carbon. The additive can Furthermore, it can act as a nucleation agent, promoting the growth of a preferred phase or species. In other cases, the additive will facilitate the formation of surface states on particles of the material, with these states facilitating interparticle transport.

[0015] The additive can play various other roles in the material. It can act as a catalyst, promoting the reduction of phosphate or other elements in the resulting material as discussed above. In other cases, the additive can act as a dopant. For example, an additive such as vanadium can replace some of the phosphate in the material and, in this context, can improve the ionic conductivity of the material. The additive can also replace some of the iron in the olivine structure and, as a result, improve internal transport in the material through effects such as vacancy hopping, modification of the local electron density, and formation of larger tunnels. The additive can also modify the lattice structure of the material, either by doping or by spatial and / or electronic effects; and this modified lattice can have improved ionic conductivity.Accordingly, the additive can have diverse and overlapping functions and can act as a doping substrate and / or as a catalyst for the formation of such advantageous structures. For this, the role of the additive in improving lithium ion capacity and transport must be interpreted more generally.

[0016] According to a further aspect of the present invention, the methods thereof provide for the production of a material containing carbon, wherein the electronic state, morphology, and / or arrangement of the carbon in the material is optimized to provide a cathode material exhibiting improved electronic and ionic transport properties. Carbon is known to possess good electrical conductivity; the presence of even relatively small amounts of carbon can improve the electrical conductivity of materials of the type used in the present invention. It has been found that the electronic and lithium-ion transport properties of sp2-coordinated carbon are superior with respect to the materials of the present invention to the corresponding properties of sp3-coordinated carbon.Although the applicant does not wish to be bound by any assumption, it is assumed that the application of the methods of the present invention produces a material which has a higher concentration of sp2 carbon than in other prior art processes. For example, the presence of the additive and / or the reduction step increases the amount of preferred sp2 carbon and / or improves its distribution. As a result, higher electrical conductivities are achieved.

[0017] In addition, the method of the present invention optimizes the particle size, shape and / or distribution of the carbon to maximize its effect, although any inhibition of internal transport is not possible. The in-situ generation of carbon from a precisely mixed blend of reactive precursors facilitates the distribution of very small particles and / or thin films of carbon on or between particles of ionically active material. These small-dimensional Carbon bodies establish good electrical contact between ionically active particles, while any obstacle to ion transport between them minimized.

[0018] Therefore, according to this particular aspect of the present invention, it was found that steps of the present invention including one or more incorporations of an additive, grinding and mixing, and a reaction under reduction conditions. serve to enhance the electronic and physical properties of carbon, which is incorporated in the materials of the present invention. can be optimized. In this way, both the electronic conductivity and the ionic storage and transport properties of the Materials of the present invention with regard to their use as electrochemical materials and in particular as cathode materials for Optimized lithium batteries.

[0019] In a group of embodiments of the two-phase material of the present invention, the first phase has approximately 80–95 mol- percent of the composite material, and the second phase contains 5–20 mol percent of the composite material. In a special group of In these materials, the first phase comprises 85–90 mol percent of the material and the second phase 10–15 mol percent of the material. Typical Concentrations of additive material in the resulting composite material are generally quite low and typically fall within the range of 0.1–5 atomic percent of the total material. The EDX analysis indicates that concentrations of metals such as vanadium or others are present. The residual additives are somewhat higher at the boundary with the second phase, indicating that the additive material inhibits the formation of the second phase. promotes this. It is also possible that the additive can act as a nucleation site for the growth of the second phase.

[0020] In a typical process for the synthesis of a material of the present invention, a starting mixture is created which Lithium, a metal like iron, is a source of phosphate ions, and the additive contains this mixture. This mixture is typically obtained by grinding, e.g., in a mill. a ball mill, a disc mill, a mortar or similar, mixes the resulting mixture, and this mixture is placed in a reduction environment. heated. In some examples, the milling process can introduce organic compounds into the reaction mixture, such as from solvents or from the kettle in which the grinding takes place. Carbon derived from this source has a promoting effect on the formation of of the material of the present invention. In other cases, carbon-containing compounds can be specifically added to the mixture before the reaction. can be introduced. One such carbon source is polyvinyl alcohol (PVA). A typical reduction environment can be a gaseous atmosphere, which contain one or more hydrogens, ammonia, hydrocarbons and carbon monoxide; and generally the same Results were achieved by using gas. In other examples, the reduction environment can be improved by adding solid or liquid substances. Reducing agents are formed in the mixture.

[0021] In one group of syntheses, the lithium source is a lithium salt such as lithium carbonate. The iron and phosphate ions can both This can be provided by using a material such as iron phosphate, which is subsequently reduced to an iron compound. As above. As mentioned, vanadium is a special additive material and can be used in the form of V₂O₅. As also mentioned above, carbon, Carbon produced, in particular during reduction synthesis, has a beneficial effect on the formation of the materials of the present The invention is therefore possible. Consequently, small amounts of organic material can be added to the reaction mixture, either directly or as artifacts of the manufacturing process. This reaction mixture is produced at atmospheric pressure and under a reduction atmosphere such as As mentioned above, it is heated to a temperature of approximately 550–600°C for 1.5–2.0 hours. After reduction, the material is... Cooled to room temperature, typically under an inert atmosphere. Material produced in this way exhibits excellent performance characteristics. when it is incorporated into cathodes for lithium batteries.

[0022] In a specific procedure, a first material was produced from a starting mixture which contained: Li2CO3, 0.02 M (1.4780 g) and FePO4 × 2H2O, 0.04 M (7.0031 g with an Fe content of 31.9%). A second material was prepared from a mixture which contained: Li₂CO₃, 0.02 M (1.4780 g); FePO₄ × 2H₂O, 0.95 × 0.04 M (6.6530 g with an Fe content of 31.9%) and V₂O₅, 0.05 × 0.02 M (0.1819 g). The mixtures The samples were each ball-milled in acetone for 96 hours using 2 mm and 5 mm YSZ balls. The acetone sludge was separated from the bottle. and air-dried. The powders were then ground with a mortar and pestle and transferred into quartz boats for a reduction reaction. with programming ter temperature.

[0023] In the reaction, the mixtures were heated under a hydrogen atmosphere at a flow rate of 1.26 / min, according to the following schedule: RT→350°C, 2 hours; 350°C→350°C, 2 hours; 350°C→600°C, 3 hours; 600°C→600°C, 1.5 hours. Afterwards, the samples were cooled to 100°C and passivated in an O2 / He atmosphere.

[0024] In the vanadium-free sample, the particles varied in size from 50 nm to several micrometers, and the micrometer-sized particles exhibited nanometer-sized features. EDX analysis of the two 200 nm particles showed an atomic percent ratio of Fe:P:O of 29.4:28:42.6 and 25.8:28.5:45.7, indicating the presence of phosphate and partially reduced phosphate. EDX analysis of a micrometer-sized single-crystal whisker structure showed an atomic percent ratio of Fe:P:O of 49.1:48.9:2.0, indicating the presence of FeP. EDX analysis of a spot onto a micrometer-sized single-crystal whisker structure showed Na spikes with an atomic percent of 11.6. All other EDX on different spots showed an Fe:P ratio of about 1 with an atomic percent of 0 from 1.6 to 49.5, indicating the presence of phosphate, partially reduced phosphate and FeP, however there was no evidence of Fe2P or Fe3P.

[0025] Similar analyses of the V-containing material showed particle sizes ranging from 50 nm to several micrometers, with nanometer-sized features on the micrometer-sized particles. The EDX of a 150 nm particle showed an atomic percent ratio of Fe:P:O:V of 2.68:25.1:47.2:1.0, indicating the presence of phosphate and partially reduced phosphate. The EDX of a 30 nm particle showed an atomic percent ratio of Fe:P:O:V of 59.4:33.9:3.9:2.9, indicating the formation of Fe₂P with the presence of V. The EDX of three differently sized single-crystal filament structures showed the presence of Fe₂P. The EDX of round particles showed no difference in phosphate formation in the main body and at the edges. The deflection pattern of LiFePO₄ indicates the olivine crystal structure.

[0026] Electronic and ionic conductivities were measured for a number of materials produced according to the present invention, as well as for a number of reference materials. Table 1 below specifies particularly representative measurement parameters for these properties. Sample 1 in the table comprises a lithium iron phosphate material which does not contain any additive of the present invention and which was produced according to the prior art non-reductive synthesis process. Conductivity was measured using impedance spectroscopy of the dry granules of the material, although other methods for measuring conductivity, such as a galvanostatic intermittent titration method (GIPT), could be used.Sample 2 comprises a lithium ion phosphate material which also contains vanadium, but which was prepared without a non-reductive process according to Sample 1. Sample 3 is a lithium iron phosphate material which contains no vanadium additive at all, but which was prepared using a reduction synthesis according to the present invention, and as such, the material of Sample 3 corresponds to the first synthesized material described above. Sample 4 corresponds to the second synthesized material described above and, as such, contains vanadium, and was prepared using a reductive synthesis. Sample 5 is representative of a commercially available, high-capacity material containing lithium cobalt oxide. Sample number Sample content Precursor Electronic conductivity (S / cm) Ionic conductivity (S / cm) 1 LiFePO4 without V Fe (II) < 7 × 10–7 7 × 10–5 2 LiFePO4 with V Fe (II) 4 × 10–9 5 × 10–5 3 LiFePO4 without V Fe (III) 7 × 10–3 < 7 × 10–5 4 LiFePO4 with V Fe (III) 1 × 10–4 5 × 10–4 5 LiCoO2 From FMC 5.4 × 10–4 1 × 10–4

[0027] Samples 3 and 4 from the preceding table were processed in electrodes and recorded in half-cells and evaluated with respect to their rate capability. The electrolyte used was 1 M LiPF6 in a 1:1 EC / DEC ratio. The half-cells were subjected to flux densities of 13 mA / g, 60 mA / g, 250 mA / g, and 800 mA / g for two, five, five, and ten cycles, respectively. The results of this evaluation are summarized graphically in Fig. 1. Sample 3 and Sample 4 have similar electronic conductivities. while the ionic conductivity of sample 4 is seven times higher than that of sample 3. As can be seen from the figure, the charge capacity of Sample 3's conductivity is relatively low compared to that of Sample 4, even though its electronic conductivity is slightly better. This is especially true at high temperatures. Current densities are considerable. The charge capacity of probe 4 is significantly improved, and this is not only due to its good electronic conductivity. attributable to, but also to their improved ionic conductivity.

[0028] From the foregoing it will be understood that the principles of the present invention significantly improve lithium-ion Provide materials exhibiting conductivity. These materials can be used to manufacture electrodes for lithium and lithium-ion batteries. They can be used, and these batteries will demonstrate good current carrying capacity.

[0029] The preceding description was primarily directed towards materials containing iron; however, it is to be understood that Composite materials based on other metals can likewise be produced according to the principles of the present invention. Since the preceding description generally describes two-phase materials, the present invention can also be used for the production of Single-phase materials as well as multi-phase materials can be used. The material of the present case was also The invention is described with primary reference to its use as a cathode material for lithium batteries. It is understood that this Due to its electronic and ionic properties, the material is also used in other electrochemical applications, such as chemical reactors, other battery systems, electronic devices, and the like will be found. The material of the present The invention can be used in various catalytic applications both as an electrocatalyst and as a non-electrical catalyst. Accordingly, it should be understood that the preceding description and discussion serve as an illustration for various versions of the The invention is, but its application is not limited. The following claims, including all equivalents, which define the invention, are: Determine the scope of the invention. SUMMARY

[0030] Materials useful as electrodes for lithium batteries have very good electronic and ionic conductivities. They are made from a starting mixture which contains a metal, a phosphate ion and an additive which facilitates the transport of lithium ions in the resulting material improved, includes. The mixture is heated in a reduction atmosphere to produce the material. The additive can be a pentavalent metal. or include a carbon component. In certain formulations, the material is a two-phase material. It also includes electrodes, which the materials and lithium batteries which contain these electrodes.

Claims

[1] Method for synthesizing a material, comprising the steps: Provision of a starting mixture containing lithium, a metal, a phosphate ion, and an additive which facilitates the transport of lithium ions into a material produced using this method is improved compared to a material produced in the absence of these additives; Heating this mixture in a reduction atmosphere to produce a material containing LixMPO4, where M is the metal and x less than or equal to 1.

05. [2] Method according to claim 1, wherein x is greater than 0. [3] Method according to claim 1, wherein the additive promotes the reduction of the phosphate ion. [4] Method according to claim 1, wherein the additive is selected from the group consisting of V, Nb, Mo, C and combinations thereof. [5] Method according to claim 1, wherein the step of heating the material in a reduction atmosphere produces a composite material comprising a first phase which is comprised of the LixMPO4 and a second phase. [6] Method according to claim 5, wherein the second phase has an ionic conductivity which is greater than the ionic conductivity of the first phase. [7] The method of claim 5, wherein the second phase also includes oxygen and the atomic ratio The oxygen to phosphorus ratio is less than 4:

1. [8] Method according to claim 1, wherein M is iron. [9] Method according to claim 8, wherein at least some of the iron in the starting mixture is in the form of Fe3+. [10] Method according to claim 5, wherein the second phase is a member selected from the group consisting of Fe2P2O7; FeP; Fe2P; Fe3P and combinations thereof. This includes... [11] Method according to claim 5, wherein the first phase comprises 80–95 mol percent of the composite material and the second phase comprises 5–20 comprises mol percent of the composite material. [12] The method of claim 1, wherein the catalyst promotes the reduction of a carbon-containing species such that free carbon is formed. [13] The method of claim 12, wherein the carbon is at least partially sp2-coordinated [14] Method according to claim 6, wherein the ratio of spe to sp3-coordinated carbon produced in the presence of the additive is greater, than it would be in the absence of the additive. [15] The method of claim 1, wherein the reduction environment comprises a gas environment containing one or more hydrogens, Contains carbon monoxide, hydrocarbons and ammonia. [16] Method according to claim 1, comprising the further step of grinding the mixture before heating the mixture in the Reduction environment. [17] The method of claim 1, wherein the step of heating the mixture comprises heating the mixture to a temperature in a range of 300–750°C. [18] Method according to claim 1, wherein the step of heating the mixture is heating the mixture to a temperature of approximately 650–750°C [19] The method of claim 1, wherein the catalyst is a nucleating agent which promotes the growth of at least one component of the material promotes. [20] The method of claim 1, wherein the starting mixture includes a carbon source. [21] The method of claim 20, wherein the carbon source is a polymer. [22] Method according to claim 1, wherein the additive replaces at least some of the phosphorus in the material. [23] Material according to claim 22, wherein at least some of the phosphate groups are reduced by the additive replaced therein. [24] Method according to claim 1, wherein the additive replaces part of the metal in the material. [25] The method of claim 1, wherein the metal M in the starting mixture is in a first oxidation state, wherein when When the mixture is heated in the reduction environment, at least a portion of the metal M changes from the first oxidation state to a second. The oxidation state is reduced to a lower state than the first oxidation state. [26] The method of claim 1, wherein the additive is effective in modifying the lattice structure of the material; wherein the transport of The transport of lithium ions through the modified lattice is improved compared to the transport of lithium ions through the corresponding non-modified lattice. is. [27] Material manufactured according to claim 1. [28] Electrode comprising the material of claim 27. [29] Material characterized in that when connected to a cathode of a lithium battery, the lithium-ion conductivity of the Materials in the range of 10–6 S / cm to 5 × 10–4 S / cm. [30] Material according to claim 29, further characterized in that when it is embedded in a cathode of a lithium-ion battery, its The electronic conductivity is in the range of 10–7 S / cm to 10–4 S / cm. [31] Material according to claim 29, wherein the material comprises lithium, iron, phosphorus and oxygen. [32] Material according to claim 29, wherein the material includes an additive which increases the lithium ion conductivity of the material compared to a Improves material that does not contain the additive.

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