CN114464803B

CN114464803B - FeS (FeS) 2 Composite positive electrode and all-solid-state battery device

Info

Publication number: CN114464803B
Application number: CN202210129111.7A
Authority: CN
Inventors: 吴凡; 卢普顺; 李泓
Original assignee: Yangtze River Delta Physics Research Center Co ltd; Institute of Physics of CAS; Tianmu Lake Institute of Advanced Energy Storage Technologies Co Ltd
Current assignee: Yangtze River Delta Physics Research Center Co ltd; Institute of Physics of CAS; Tianmu Lake Institute of Advanced Energy Storage Technologies Co Ltd
Priority date: 2022-01-29
Filing date: 2022-02-11
Publication date: 2023-06-30
Anticipated expiration: 2042-02-11
Also published as: CN114464803A; CN116979062A

Abstract

The invention provides FeS ₂ Composite positive electrode and all-solid-state battery device, which adopt sulfide solid electrolyte with lithium supplementing and moisture absorbing effects and FeS ₂ As a positive electrode active material, the sulfide solid state electrolyte has the following chemical composition: li (Li) _7+y‑ _z M _y As _1‑y S _6‑z X _z Wherein M is at least one of Si, ge, sn, ti, zr, X is halogen element, y is more than or equal to 0 and less than or equal to 1, and z is more than or equal to 0 and less than or equal to 2. The invention provides a positive electrode and an all-solid-state battery which have low cost, high load capacity, long cycle life and capability of charge and discharge under high multiplying power and high current density, and can reduce the consumption of conductive carbon and overcome FeS ₂ A huge volume change problem.

Description

FeS (FeS) 2 Composite positive electrode and all-solid-state battery device

Technical Field

The invention relates to the technical field of battery materials, in particular to sulfide solid electrolyte with functions of supplementing lithium and absorbing moisture, and FeS and a preparation method thereof ₂ The composite positive electrode and the all-solid-state battery device are manufactured.

Background

Lithium ion batteries have been commercially used in consumer electronics and electric vehicles as high efficiency energy storage devices. However, the lithium ion battery has reached a bottleneck in terms of energy density improvement, and the safety problem thereof is also worry. And an all-solid-state battery using a solid electrolyte and a metallic lithium negative electrode is a key technology for realizing a high-safety and high-energy-density battery, and has attracted a wide attention in academia and industry. The solid electrolyte with high thermal stability, compactness and mechanical strength is used as an ion conductor to replace an organic electrolyte and a diaphragm used in a liquid lithium ion battery, so that the problems of short circuit and the like caused by inflammability of the organic electrolyte and puncture of a diaphragm by negative lithium dendrites can be effectively solved, and the safety of the battery is greatly improved. With the advent of ultra-fast solid-state ion conductors in recent years, the problem of long-range migration and transport of lithium ions inside the electrolyte is no longer an obstacle to practical application of all-solid-state batteries. Wherein the sulfide solid state electrolyte is excellent in room temperature ion conductivity (e.g., li ₁₀ GeP ₂ S ₁₂ (LGPS) and Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 (LSiPSCl) room temperature lithium ion conductivities of 12mS/cm and 25mS/cm, respectively, are distinguished from a range of solid state electrolytes (polymer, oxide, sulfide, halide solid state electrolytes).

Sulfide electrolyte systems with high ionic conductivity currently contain almost all P elements, such as Li of LGPS family ₁₀ GeP ₂ S ₁₂ And Li (lithium) _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 Li of sulfur silver germanium ore type ₇ PS ₆ And Li (lithium) ₆ PS ₅ Cl, glass or glass-ceramic Li ₃ PS ₄ And Li (lithium) ₇ P ₃ S ₁₁ Etc. According to the theory of hardness and acidity, the sulfide electrolyte containing the P element has poor air stability, is easy to react with moisture and oxygen in the air, and generates toxic hydrogen sulfide gas, so that the structure of the electrolyte is destroyed, chemical components are changed, the structure and the performance are irreversibly changed, and the performances such as ionic conductivity and the like are rapidly deteriorated. The extremely poor air stability of the sulfide solid electrolyte influences the production, preparation, storage and transportation of the sulfide solid electrolyte material, and various links of production, manufacture, use and the like of the sulfide all-solid-state battery, so that the yield of the sulfide all-solid-state battery is severely limited, the difficulty of preparation and processing is increased, the large-scale application of the sulfide all-solid-state battery in the all-solid-state lithium battery is limited, and the production and processing cost is increased. The idea of the prior art is to dope and modify the material to improve the ion conductivity or wet air stability or stability to metallic lithium, such as Li with better stability to metallic lithium anode ₆ PS ₅ I has an ionic conductivity of only 10 ^-6 S/cm order, ion conductivity is generally 10 through a series of elements such as In, si, ge, sn, F and the like doped materials ^-5 -10 ^-4 S/cm level, at most 1.1X10 ^-3 S/cm, hardly reaches 10 ^-2 S/cm。

Sulfide solid electrolyte free of P element, e.g. Li ₄ GeS ₄ ，Li ₄ SnS ₄ ，Li ₃ SbS ₄ Etc., although having high air stability, it has the following problems: (1) The ionic conductivity is generally very low, well below 1mS/cm; (2) The electrochemical reduction stability is poor due to the high-valence metal ions; (3) Due to the formation of electron and ion conductive alloy byproducts, a kinetically stable interface passivation layer cannot be formed with metallic lithium, resulting in a continuous increase in interface resistance, deterioration of battery performance (rapid decay of capacity).

At the solid-state battery device level, the electrolyte material is limited by low room temperature ion conductivity (< 10 mS/cm), low electron conductivity (< 1 mS/cm) of the positive electrode active material, and problems in chemical and electrochemical stability between the sulfide electrolyte and the positive electrode active material, including space charge layer effect, element interdiffusion, electrochemical interaction and the like existing between the sulfide electrolyte and the oxide positive electrode, result in that the current sulfide all-solid-state battery device cannot reach the level of a liquid lithium ion battery in various performance indexes, especially in the aspects of active material loading, current density, rate performance at room temperature (generally required to work at 0.1C low rate) and the like.

The room temperature ion conductivity of the currently reported sulfide solid electrolyte is generally lower than 10mS/cm, and in addition, the solid electrolyte does not have the fluidity and wettability of the liquid electrolyte, cannot permeate into the pores of primary particles and/or secondary particles of the positive electrode active material, and can conduct lithium ions only by means of limited contact area, so that high active material loading, high surface capacity, high current density or high-rate charge and discharge are difficult to realize.

The initial cycle coulombic efficiency of all-solid-state sulfide batteries reported so far is generally lower than 90%, and the initial efficiency is low mainly because lithium ions are consumed by side reaction forming interface layers. In addition, all solid-state batteries reported so far have serious interface problems, resulting in generally lower cycle life (the reduction of specific capacity to 80% of the initial or reversible specific capacity, corresponding cycle times) even at low rates.

From the aspect of (sulfide) solid electrolyte materials, a technical scheme for indirectly introducing a lithium supplementing agent into a positive electrode to improve battery performance, including first-week coulombic efficiency, rate capability and long-cycle stability, has not been reported.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides FeS ₂ Composite positive electrode and all-solid-state battery device, which adopt sulfide solid electrolyte with lithium supplementing and moisture absorbing effects and FeS ₂ As the positive electrode active material, a positive electrode and an all-solid-state battery which have low cost, high load capacity, long cycle life and capability of charge and discharge under high multiplying power and high current density are obtained, and simultaneously the consumption of conductive carbon can be reduced, and FeS is overcome ₂ A huge volume change problem.

The technical scheme adopted by the invention is as follows.

FeS (FeS) ₂ Composite positive electrode comprising sulfide solid electrolyte and FeS ₂ A positive electrode active material; the sulfide solid state electrolyte has the following chemical composition: li (Li) _7+y-z M _y As _1-y S _6-z X _z Wherein M is at least one of Si, ge, sn, ti, zr, X is halogen element, y is more than or equal to 0 and less than or equal to 1, and z is more than or equal to 0 and less than or equal to 2.

Further, the sulfide solid state electrolyte has a chemical structure with Li _7-z AsS _6-z X _z Diffraction main peaks corresponding to XRD diffraction spectrums of the X-ray diffraction pattern; preferably, with cubic system

Li of space group ₆ AsS ₅ The I diffraction main peaks are uniform, and diffraction peaks of the Li ion conduction phase are provided at 2θ=17.30 °, 24.57 °, 28.90 °, 30.21 °, 43.26 °, and 50.38 °, and the positions of the diffraction peaks may generally have an error within ±1° due to measurement errors, structural shifts, and the like.

Further, the sulfide solid state electrolyte has LiI and Li therein ₂ S impurity phase; liI and Li ₂ The S impurity content is preferably 3% or less, respectively.

Further, in the sulfide solid state electrolyte, when M is Si, the doping amount with respect to As is y=0.3 to 0.9, preferably y=0.5 to 0.8; when M is Sn, the doping amount relative to As is y=0.05 to 0.6; when M is Ge, the doping amount relative to As is y=0.1 to 0.6; when M is Ti, the doping amount relative to As is y=0.1 to 0.6; when M is Zr, the doping amount with respect to As is y=0.1 to 0.5.

Wherein, in the composite positive electrode, feS ₂ And conductive carbon in a mass ratio of (2-5): 1, feS ₂ And the ratio of the total mass of the conductive carbon to the mass of the sulfide solid state electrolyte is 1: (0.6-3).

In the composite positive electrode, the conductive carbon is at least one of conductive carbon black, carbon fiber, carbon nanorod or carbon nanotube, and is preferably ketjen black.

Wherein, in the composite positive electrode, the active material FeS ₂ Load(s)The upper limit of the amount can reach 5mg/cm ² The upper limit is preferably up to 6mg/cm ² Above, it is also preferable that the upper limit is up to 30mg/cm ² The above.

The invention also provides an all-solid-state battery device, which comprises the sulfide solid-state electrolyte and FeS ₂ And (5) compounding the positive electrode. The negative electrode of the all-solid-state battery device adopts a lithium-containing negative electrode, and comprises a metal lithium negative electrode, a lithium alloy negative electrode and a lithium-carbon composite negative electrode, preferably a lithium-indium alloy negative electrode.

FeS of the invention ₂ Advantages of the composite positive electrode and the all-solid-state battery device include:

adopts special solid electrolyte without P sulfide, has ultrahigh ionic conductivity and lower activation energy, and has in-situ generated hetero-phase LiI and Li ₂ S, can exert good lithium supplementing and moisture absorbing effects, and is matched with FeS ₂ The positive electrode active material can maintain long circulation capacity and service life under high multiplying power and high current, can reduce the consumption of conductive carbon, has good deformation resistance and overcomes FeS ₂ A huge volume change defect.

Drawings

The technical scheme of the embodiment of the invention is further described in detail through the drawings and the embodiments.

FIG. 1 is a graph showing Li doping levels of different Sn doping levels _6+x Sn _x As _1-x S ₅ XRD pattern of I.

FIG. 2 is Li at different Si doping levels _6+x Si _x As _1-x S ₅ XRD pattern of I.

FIG. 3 Li at different Si doping levels _6+x Si _x As _1-x S ₅ I electrochemical impedance spectrum. (A) 0%, 10%, 20%, 100% doped, and (B) 30% -90% doped.

FIG. 4 is a diagram of Sn and Si doped Li ₆ AsS ₅ Ion conductivity of I as a function of doping ratio x.

Fig. 5 is a graph showing ionic conductivity versus temperature and activation energy for different sulfide electrolytes.

FIG. 6 is a DC polarization test of Li _6.8 Si _0.8 As _0.2 S ₅ Electron conductivity of I.

Fig. 7 is a graph showing hydrogen sulfide gas production after exposure of various electrolyte samples to humid air.

FIG. 8 is Li _6.8 Si _0.8 As _0.2 S ₅ XRD patterns of I exposure to humid air vary with the duration of exposure and after heat treatment.

FIG. 9 is Li ₆ PS ₅ XRD patterns of I exposure to humid air vary with the duration of exposure and after heat treatment.

FIG. 10 is raw Li _6.8 Si _0.8 As _0.2 S ₅ I Li with heat treatment after exposing to air _6.8 Si _0.8 As _0.2 S ₅ I electrochemical impedance spectroscopy.

FIG. 11 is a schematic illustration of TiS prepared from different electrolyte materials ₂ First week charge-discharge curve of solid-state battery.

FIG. 12 is a diagram of TiS prepared from different electrolyte materials ₂ Rate performance of solid state batteries.

FIG. 13 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Charge and discharge curves for 1 st, 100 th, 200 th, 300 th and 400 th turns of the I/Li-In all-solid-state battery at 1C,30℃.

FIG. 14 is a schematic view of TiS prepared from different electrolyte materials ₂ Comparison of long cycle performance of solid state battery 1C at 30 ℃ for 1000 cycles.

FIG. 15 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ And the capacity of the I/Li-In all-solid-state battery is obtained by cycling the battery more than 7000 times at 10C and 30 ℃.

FIG. 16 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ The rate performance of the I/Li-In all-solid-state battery at 30 ℃.

FIG. 17 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Fast charge and fast discharge curves of I/Li-In all-solid-state batteries at 30 ℃.

FIG. 18 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Fast charge and slow discharge curves of the I/Li-In all-solid-state battery at 30 ℃.

FIG. 19 is TiS at high loadings ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Charge and discharge curves for 1 st and 40 th turns of the I/Li-In all-solid-state battery.

FIG. 20 is TiS at high loadings ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In all-solid-state battery long cycle stability curve.

FIG. 21 is TiS at ultra high loadings ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ 0.05C rate charge-discharge curve for I/Li-In all-solid-state battery.

FIG. 22 is FeS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In all-solid-state battery charge-discharge curves of 1 st, 2 nd and 5 th turns at 0.1C and 30 ℃.

FIG. 23 is FeS ₂ Charge-discharge curves of 1 st, 2 nd and 5 th turns of the LSPSC/Li-In all-solid-state battery at 0.1C and 30 ℃.

FIG. 24 is a FeS prepared from different electrolyte materials ₂ Long cycle performance of the solid-state battery 1C at 30 ℃ for 600 cycles.

FIG. 25 is FeS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Impedance change before and after cycling of the I/Li-In all-solid-state battery.

FIG. 26 is a FeS prepared from different electrolyte materials ₂ Rate performance of all-solid-state batteries.

FIG. 27 is a high load FeS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Cycling at 1C rate for I/Li-In all-solid-state batteries.

FIG. 28 is FeS under ultra-high load ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In all-solid-state battery cycling.

Detailed Description

The invention is further illustrated by the drawings and the specific examples, which are to be understood as being for the purpose of more detailed description only and are not to be construed as limiting the invention in any way, i.e. not intended to limit the scope of the invention.

1. Development of sulfide solid state electrolytes

The invention firstly develops a novel sulfur silver germanium ore system sulfide solid electrolyte material without P element, li _7+y-z M _y As _1-y S _6-z X _z (M= Si, ge, sn, ti, zr, X= F, cl, br, I, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.2). The ionic conductivity of the material can be improved to 10 ^-2 S/cm or more, the wet air stability is good (the hydrogen sulfide generation amount is low, the structure and the property can be restored by heating), and meanwhile, the lithium supplement agent (Li) generated in situ in the structure is carried ₂ S, liI), different from the lithium supplementing agent material which is independently added, can improve the first week coulombic efficiency, the rate capability and the long-cycle stability of the all-solid-state battery.

Firstly, the technical proposal uses As element to completely replace P element to obtain Li _7-z AsS _6-z X _z (X= F, cl, br, I, 0.ltoreq.z.ltoreq.2) electrolyte, e.g. Li ₆ AsS ₅ I, and studied for its wet air stability, including in particular hydrogen sulfide production, crystal structure (XRD) change, and heat recoverability. Although compared with Li _7-z PS _6-z X _z ，Li _7-z AsS _6-z X _z The hydrogen sulfide production is significantly reduced and the heating is resumed after exposure to humid air, but the electrolyte material is exposed to low ionic conductivity (only 10 ^-6 S/cm grade). According to low-price substitution, the number of interstitial lithium ions can be increased, so that the concentration of carriers is increased, and Li can be screened out _7- _z AsS _6-z X _z And carrying out As-site substitution on the element, thereby realizing the aim of improving the ion conductivity of the material.

By doping element M, S in the crystal structure is improved ^2- /I ^- The disorder degree and interstitial lithium ion concentration of anions reduce the activation energy of lithium ion migration, thereby leading to the room temperature ion conductivity of the material from 10 ^-6 The S/cm level is increased to 10 ^-3 S/cm grade or higher (cold press test). After M element dopingThe phase stability of the material is reduced, and in-situ generated lithium-containing halides LiX and Li are generated ₂ S phase. On the other hand, since the impurity LiX is more hygroscopic than the electrolyte material, the absorption of moisture by LiX occurs when the material is left in humid air for a long time, and lix·nh is generated ₂ The compound containing crystal water consumes water molecules around the electrolyte material, thereby avoiding chemical reaction between the electrolyte material and water in the air and indirectly improving the wet air stability of the electrolyte material. On the other hand, liX and Li ₂ S can generate a lithium supplementing effect on the positive electrode material, and compared with a lithium supplementing agent which is independently added, the in-situ generated lithiated phase material can better overcome the problems of interface, migration, intercalation and deintercalation, precipitation and the like, thereby more effectively playing roles of first-week coulomb efficiency, rate capability, long-cycle stability and the like.

The selection of the doping element M of the invention takes into account the following aspects:

(1) The highest valence is 4 and there are generally no intermediate lower valence (1, 2, and 3);

(2) The chemical coordination number is generally 4, and MS can be formed ₄ Tetrahedron;

(3) Ion radius and As ⁵⁺ Proximity.

Through screening elements meeting the principle and combining experiments, the M element obtained through final screening is one or more of Si, ge, sn, ti, zr, and the doping proportion can be more than 0% and not equal to 100%.

2. Preparation of sulfide electrolyte

Weighing proper element raw materials according to a metering ratio, and placing the raw materials into ball milling tanks, wherein the mass of powder in each ball milling tank is 2g in total. Wherein the Li source may be Li ₂ S or LiX, the As source may be As ₂ S ₃ The S source can be S powder, the M source can be M powder or M sulfide, and the X source (halogen source) can be LiX.

The ball milling pot filled with the raw materials is sealed and placed in a planetary ball mill for ball milling for 60 hours. After ball milling, the mixed powder in the ball milling tank is scraped off and placed in an alumina crucible. Placing the material placed in an alumina crucible in a muffle furnaceHeating, heating to 550 ℃ from room temperature at 5 ℃/min, preserving heat for 12 hours, and naturally cooling. Taking out the sintered material, grinding with a mortar, and refining the particles to obtain Li _7+y-z M _y As _1-y S _6-z X _z An electrolyte material. Control experiments other corresponding electrolyte materials, e.g. Li, were obtained using the same preparation method ₆ PS ₅ I、Li ₆ PS ₅ Cl、Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 Etc.

3. Development of all-solid-state battery devices

Based on the good lithium supplementing and moisture absorbing effects of the sulfide electrolyte, the sulfide electrolyte is applied to the preparation of a composite positive electrode material and forms an all-solid-state battery, and is expected to form a battery device with high capacity, long cycle life and high multiplying power.

Generally, lithium ions are consumed in the first-week charge and discharge, and stable interface layers are formed at the interfaces or pores are filled, so that the first-week coulomb efficiency is low. Sulfide electrolyte Li developed above _7+y-z M _y As _1-y S _6-z X _z Not only has ultra-high ionic conductivity, but also is self-contained (generated in situ during synthesis) with Li ₂ The S and LiI impurity phases are used as lithium supplementing agents to improve the first-week coulombic efficiency, so that the battery shows higher reversible capacity. Li (Li) ₂ The theoretical specific capacities of S and LiI are 1166 and 200mAhg respectively ^-1 。

(1)TiS ₂ Battery development as lithium-free positive electrode active material

The sulfide all-solid-state battery disclosed and reported at present is characterized in that an electrode material, particularly a positive electrode material, of the sulfide all-solid-state battery is at least composed of three parts, wherein the three parts comprise a positive electrode active material, a sulfide electrolyte and a conductive agent (conductive carbon). Even further, if slurry coating or film forming is performed, a binder is required. Sulfide electrolytes can be considered as ionic conductors, electronic insulators, conductive carbon as an electronic conductor, ionic insulator, while binders generally do not conduct either ions or electrons. In order to construct an effective conductive network with good connectivity, the types and proportions of three inactive ingredients, namely electrolyte, conductive carbon and binder, need to be accurately regulated and controlled, and a large number of experiments are explored, so that an effective ionic and electronic conductive network is constructed and good solid-solid contact is maintained.

Existing TiS ₂ All-solid-state battery prepared and assembled as positive electrode active material and having general load capacity of 2.57mg/cm ² The area capacity is 0.92mAh/cm ² The upper limit of the multiplying power is 20C, and the corresponding current density of 20C is 12mA/cm ² . As in literature (Bum Ryong Shin et al, comparative Study of TiS) ₂ /Li-In All-Solid-State Lithium Batteries Using Glass-Ceramic Li ₃ PS ₄ and Li ₁₀ GeP ₂ S ₁₂ Solid Electrolytes, electrochimica Acta 146 (2014) 395-402).

Using TiS having electron conductivity (greater than 10S/cm) comparable to that of conductive carbon ₂ As a lithium-free positive electrode active material, the present invention is used together with Li having an ultrahigh ionic conductivity _7+y-z M _y As _1-y S _6-z X _z As an electrolyte, a composite positive electrode material is composed of only these two components. Conductive carbon and a binder are not needed, and the optimization process of the electrode component proportion is greatly simplified.

Since the positive electrode does not contain lithium, it is necessary to match a negative electrode containing lithium, such as a metallic lithium negative electrode, a lithium alloy negative electrode, a lithium-carbon composite negative electrode, or the like. The lithium-indium alloy cathode has very good electron conductivity and better lithium ion transmission kinetics.

Li with the ionic conductivity of more than 10mS/cm _6.8 Si _0.8 As _0.2 S ₅ I electrolyte is exemplified by TiS which is excellent in electron and ion transport kinetics ₂ The composite anode is prepared, and the lithium-indium cathode is combined to be assembled into an all-solid-state battery, so that high active material loading (95.49 mg/cm) ² ) The ultra-long cycle life (more than 7000 circles) can also be realized at ultra-high multiplying power (200C) and ultra-high current density (24.44 mA/cm) ² ) Charging and discharging are performed.

These excellent properties can be attributed primarily to:

i.TiS ₂ as a sulfide positive electrode, li with high ion conductivity _7+y-z M _y As _1-y S _6-z X _z The electrolyte has good chemical stability, and no element interdiffusion and space charge layer effect exist;

ii.TiS ₂ the operating voltage range of (2) is 1.5-3V (vs. Li) ⁺ Li) is matched with an electrochemical window of the sulfide electrolyte, so that good interface electrochemical stability can be realized, and the good interface stability is favorable for realizing long-cycle stability of the battery, thereby obtaining an all-solid-state battery with ultra-long service life;

due to Li _7+y-z M _y As _1-y S _6-z X _z Electrolyte is provided with LiI and Li ₂ The S lithium supplementing agent (generated in situ in the synthesis process, rather than being introduced from a stoichiometric ratio) can provide additional capacity in the charging process, so that the first-week coulomb efficiency and the reversible specific capacity are improved;

the positive electrode, the electrolyte and the negative electrode all have good lithium ion transmission dynamics, so that the battery can exert more capacity under high multiplying power and high current.

(2)FeS ₂ Battery development as lithium-free positive electrode active material

Compared with the traditional positive electrode material, the lithium-free positive electrode FeS relies on Co and Ni resources with high price and low storage quantity, such as lithium cobaltate, ternary NMC, lithium-rich manganese base and the like (the specific capacity is 140-300 mAh/g) ₂ Is the main component of the abundant mineral pyrite existing in the nature, has been commercialized at present, has low cost, and has a theoretical specific capacity as high as 894mAh/g (3 to 6 times the specific capacity of the positive electrode of the oxide). But FeS ₂ The method is applied to a liquid lithium ion battery system, has a polysulfide ion shuttle effect and slow first-week reaction kinetics, and needs to use a large amount of conductive carbon and solid electrolyte to respectively improve the electronic conductivity and the ionic conductivity so as to construct an effective conductive network, thereby causing the problem of low capacity or surface capacity. The mass ratio of conductive carbon used by the positive electrode plate in the liquid lithium ion battery is generally 2-3%, and FeS in the sulfide solid state full battery ₂ The mass ratio of the powder to the conductive carbon (conductive carbon black, carbon fiber, carbon nano-rod or carbon nano-tube) is generally (2-4) 1, feS ₂ After the powder is compounded with conductive carbon andthe mass ratio of the solid electrolyte is 1: (1-3), and in addition, a high-temperature melting method is sometimes adopted in the preparation process to improve the contact of the positive electrode material with the solid electrolyte. Simultaneous FeS ₂ As a conversion type positive electrode, there was a large volume change (159%) during charge and discharge. These drawbacks severely limit FeS ₂ As a lithium-free positive electrode active material.

Existing FeS ₂ All-solid-state battery prepared and assembled as positive electrode active material and having general load capacity of 3.17mg/cm ² The area capacity is 2.37mAh/cm ² The cycle life was 220 cycles (0.1C, 30 ℃ C.). As reported in the literature (Sun et al, operando EDXRD Study of All-Solid-State Lithium Batteries Coupling Thioantimonate Superionic Conductors with Metal Sulfide, adv. Energy Mater.2020, 2002861).

Use of commercial micron-sized FeS without any treatment ₂ As the positive electrode material, li having an ultrahigh ion conductivity according to the present invention is used _7+y-z M _y As _1-y S _6-z X _z As the electrolyte, ketjen black conductive carbon of a branched structure extremely high in specific surface area and electron conductivity is simultaneously used as the electron conductive agent. The sulfide solid electrolyte and the ketjen black conductive agent have good deformability, and the FeS in the charge and discharge process is relieved ₂ Bringing about a large volume change.

Li with the ionic conductivity of more than 10mS/cm _6.8 Si _0.8 As _0.2 S ₅ I electrolyte is exemplified by FeS which is low in cost and high in specific capacity and Ketjen black ₂ The composite anode is prepared, and the lithium-indium cathode is combined to be assembled into an all-solid-state battery, so that high active material loading (31.83 mg/cm) ² ) Long cycle life (600 cycles) at higher magnification (1C) is maintained stable whileIs capable of adapting to FeS ₂ The ultra-large volume change of the material reaches higher material density.

These excellent properties are mainly due to:

i.FeS ₂ as a sulfide positive electrode, li with high ion conductivity _7+y-z M _y As _1-y S _6-z X _z The electrolyte has good chemical stability, and no element interdiffusion and space charge layer effect exist;

li of the invention _7+y-z M _y As _1-y S _6-z X _z The electrolyte has strong deformability and can be matched with ketjen black with the same strong deformability to greatly relieve FeS in the charge and discharge process ₂ Is a huge volume change of (a);

the positive electrode, the electrolyte and the negative electrode have good lithium ion transmission dynamics, the composition of the ketjen black conductive agent and the sulfide solid electrolyte can also reduce the duty ratio and improve the load, and the battery can exert more capacity under high multiplying power and high current.

4. Preparation of all-solid-state battery device

(1)TiS ₂ Preparation of battery as lithium-free positive electrode active material

Li synthesized by the method _7+y-z M _y As _1-y S _6-z X _z Sulfide solid state electrolytes, e.g. Li _6.8 Si _0.8 As _0.2 S ₅ I, etc., untreated or ball milled TiS ₂ As the positive electrode active material, li-In alloy was used as the negative electrode active material.

Active material TiS ₂ Solid electrolyte Li _7+y-z M _y As _1-y S _6-z X _z Weighing according to a certain proportion (such as 1:1, 7:3, etc.), and performing mortar grindingGrinding and mixing to obtain the positive electrode material.

And taking the Li sheet and the In sheet, respectively calendaring and punching the Li sheet and the In sheet to obtain the indium foil with the thickness of 50um and the diameter of 10mm, and the lithium foil with the thickness of 30um and the diameter of 8mm, wherein the mass ratio of the indium foil to the lithium foil is 17-33.

100mg of solid electrolyte material is weighed and put into a battery mould with the inner diameter of 10mm, trowelling is performed by using a stainless steel mould, then 2mg of positive electrode material is weighed and put into the battery mould, and trowelling is performed by using the stainless steel mould. The electrolyte and positive electrode materials were pressurized to 7t (t is a unit ton, this value is an indication of the press, corresponding to an actual pressure of about 873 MPa) using a press. And then In foil and Li foil are sequentially put on the other side of the electrolyte layer, a battery shell mold screw is screwed, and a press is used for pressurizing three layers of materials of the cathode, the electrolyte and the anode to 1t (t is a unit ton, the numerical value is a press indication, and the actual pressure is about 124 MPa). A vacuum silicone grease seal is applied to isolate the water oxygen in the air.

The assembled all-solid-state battery is connected with a blue electric testing channel, and electric performance tests are carried out under different conditions, wherein the test standard is 1C=0.24A/g.

(2)FeS ₂ Preparation of battery as lithium-free positive electrode active material

Li synthesized by the method _7+y-z M _y As _1-y S _6-z X _z Sulfide solid state electrolytes, e.g. Li _6.8 Si _0.8 As _0.2 S ₅ I et al, untreated commercial micron-sized (d90=14-18 μm) FeS ₂ As a positive electrode active material, ketjen black KB was used as an electron conductive agent, and a Li-In alloy was used as a negative electrode active material.

100mg of solid electrolyte material is weighed and put into a battery mold, trowelling is performed by using a stainless steel mold, then 5mg of positive electrode material is weighed and put into a battery mold with the inner diameter of 10mm, and trowelling is performed by using the stainless steel mold. The electrolyte and positive electrode materials were pressed together to 7t using a press. And then In foil and Li foil are sequentially put on the other side of the electrolyte layer, a battery shell mold screw is screwed, and a press is used for pressurizing three layers of materials of the cathode, the electrolyte and the anode to 1t. A vacuum silicone grease seal is applied to isolate the water oxygen in the air.

The assembled all-solid-state battery is connected with a blue electric testing channel, and electric performance tests are carried out under different conditions, wherein the test standard is 1C=0.75A/g.

5. Testing and characterization

1、Li _7+y-z M _y As _1-y S _6-z X _z XRD structural test of (2)

For the M element doped sulfide solid state electrolyte of the present invention, since the relative difference between the doping elements Sn and Si is the largest, the products of the two doping elements are selected for structural diffraction analysis. As shown in FIGS. 1-2, li at different doping levels ₆₊ _x Sn _x As _1-x S ₅ I and Li _6+x Si _x As _1-x S ₅ I are respectively corresponding to Li ₆ AsS ₅ Comparison of PDF cards 98-038-0389 of I shows that the main peaks of the structures are consistent (the peaks at 21.5 degrees come from PE preservative films used in XRD tests) and all belong to a cubic crystal system

(No. 216) a space group, belonging to sulfur silver germanium ore type materials. Li without M element ₆ AsS ₅ I is substantially free of LiI and Li ₂ S impurity phase or content is relatively very little, liI and Li are formed in situ in the structure along with the increase of doping amount ₂ The S impurity phase increases. Can be used for explaining that the instability caused by the doping of M element promotes LiI and Li ₂ And S impurity phase formation. Also, as seen from XRD patterns, the electrolyte of the present invention has a high Li ion-conducting phase with the strongest peak at 6 of 2θ=17.30 °, 24.57 °, 28.90 °, 30.21 °, 43.26 °, 50.38 ° (half width of 0.51 ° or less).

2. Influence of M element doping on electrochemical properties of electrolytes

100mg of each prepared electrolyte material is pressed into compact powder cakes by a pressure die under 873MPa, and the diameter of each electrolyte sheet is equal to that of a batteryThe shell mold diameter is 10mm. Stainless steel posts of the battery case mold act as stopper electrodes. Then testing the alternating current impedance spectrum under the frequency range of 100mHz-8MHz on a Zahniumpro electrochemical workstation with 20mV perturbation, reading the corresponding impedance value, and according to the formula

The ionic conductivity can be calculated.

FIG. 3 shows Li at different Si doping levels _6+x Si _x As _1-x S ₅ I, it can be seen that the sulfide electrolyte has typical ionic conductor characteristics and can be continuously varied in the 0% -100% doping range, with optimal impedance results in a region of appropriate doping levels.

FIG. 4 further shows Li at various doping levels _6+x Sn _x As _1-x S ₅ I and Li _6+x Si _x As _1-x S ₅ The ion conductivity curve of I, thus more clearly showing the optimal range of doping amount under different doping elements M. Meanwhile, table 1 lists the ion conductivities of electrolytes doped with Ge, ti, zr in numerical form.

TABLE 1 Ge doping ⁴⁺ 、Ti ⁴⁺ 、Zr ⁴⁺ Post Li _6+x M _x As _1-x S ₅ Ionic conductivity of I

As can be seen from fig. 4 and table 1, si is the optimal doping element, and the doping amount x is preferably in the range of 30% -90%, more preferably in the range of 50% -80%, and most preferably in the range of 80%. Other elements all make 10 ^-6 The ionic conductivity of the order of S/cm is improved to different extents. When the doping element is Sn, the preferable range of the doping amount x is 5% -60%; when the doping element is Ge, the preferable range of the doping amount x is 10% -60%; when the doping element is Ti, the preferable range of the doping amount x is 10% -60%; when the doping element is Zr, the doping amount x is preferably 10% -50%. Therein as an illustrative example，Li ₆ AsS ₅ I、Li _6.3 Sn _0.3 As _0.7 S ₅ I、Li _6.8 Si _0.8 As _0.2 S ₅ I has an ionic conductivity of 3.92×10 respectively ^-6 S/cm、2.00×10 ^-4 S/cm and 1.04X 10 ^-2 S/cm。

From the ion conductivity results at each temperature, an Arrhenius curve can be drawn, and activation energy can be calculated. As shown in FIG. 5, li _6.3 Sn _0.3 As _0.7 S ₅ I、Li _6.8 Si _0.8 As _0.2 S ₅ I. Li (lithium ion battery) ₆ PS ₅ The Cl activation energy values are 0.36eV, 0.20eV and 0.33eV respectively, and the M element doping has little influence on the activation energy of the sulfide electrolyte material.

As shown in FIG. 6, li was measured by DC polarization _6.8 Si _0.8 As _0.2 S ₅ I has an electron conductivity of 5.03X10 ^-9 S/cm ^-1 . It can be seen that the doped solid electrolyte of the present invention has extremely low electron conductivity.

3. Electrolyte air stability test

Respectively to Li ₆ AsS ₅ I、Li ₆ PS ₅ I、Li ₆ PS ₅ Three Cl samples were exposed to 25% rh humidity air to test the change in hydrogen sulfide gas concentration over time. Specifically, 3mg of each of the three samples was weighed, placed in a sample bottle, sealed and transferred. And (3) performing atmosphere adjustment on the hydrogen sulfide gas detection device, and after the atmosphere adjustment is finished, connecting a sample bottle into a gas path of the detection device to enable the device to start working, and recording the concentration value of the hydrogen sulfide gas according to a time interval of 5 s. After 180min of electrolyte exposure, the whole device was stopped. And (3) deriving the recorded data, calculating the total hydrogen sulfide gas accumulated before a certain moment according to the formula of the total hydrogen sulfide gas generation amount, and drawing a total hydrogen sulfide gas generation amount-time curve. As a result, as shown in FIG. 7, compared with P-containing Li ₆ PS ₅ I (LPSI) and Li ₆ PS ₅ Cl(LPSC)，Li ₆ AsS ₅ Hydrogen sulfide gas production of I (LASI)Significantly reduced, indicating higher air stability.

FIGS. 8 and 9 show Li, respectively _6.8 Si _0.8 As _0.2 S ₅ I and Li ₆ PS ₅ XRD patterns of the two electrolytes exposed to humid air (25% rh humidity) were varied with the exposure time and the change after recovery of heat (heat treatment at 100 ℃ for 6 h). FIG. 10 shows the original Li _6.8 Si _0.8 As _0.2 S ₅ I Li with heat treatment after exposing to air _6.8 Si _0.8 As _0.2 S ₅ I electrochemical impedance spectroscopy. The results show that the crystal structure of the electrolyte doped with M element is hardly changed (figure 8), the LiX hetero-phase generated in situ can be recovered by simple low-temperature (80 ℃ and above) heating (figure 8), and the ionic conductivity of the electrolyte material after heating recovery is hardly changed (figure 10). While Li is ₆ PS ₅ I after exposing the electrolyte to air, li is generated ₃ PO ₄ Etc., and the structure is not recoverable after heat treatment (fig. 9).

4、TiS ₂ Solid state battery device performance test as lithium-free positive electrode active material

FIG. 11 shows TiS prepared using different electrolyte materials ₂ First-round charge-discharge curve of solid-state battery. Wherein Li using the electrolyte of the present invention _6.8 Si _0.8 As _0.2 S ₅ I is solid line, li without doping is used ₆ PS ₅ Cl is a long line, and is independently added with LiI and Li ₂ S Li as lithium supplementing agent ₆ PS ₅ Cl is a dashed line. The results show that Li is used at 1C _6.8 Si _0.8 As _0.2 S ₅ I an all-solid-state battery using Li as an electrolyte having a first cycle coulombic efficiency of 99.06% ₆ PS ₅ Cl, the first effect is only 80.39%. The great difference of first effect mainly comes from the large difference of specific charge capacity. By comparing the charge curves of the two, it was found that Li _6.8 Si _0.8 As _0.2 S ₅ The slope of the charging curve corresponding to I is relatively gentle, and the charging curve is bent at about 2.1V. To demonstrate that the high first effect is due to Li _6.8 Si _0.8 As _0.2 S ₅ I in situ generated LiI and Li ₂ S hetero-phase induced, liI and Li were experimentally determined ₂ S is mixed into TiS in a proportion of 3% ₂ And Li (lithium) ₆ PS ₅ In the composite anode of Cl as a contrast (dashed line), the contrast material maintains the active material TiS ₂ Is constant, liI and Li ₂ S exists as a separate external lithium supplement, and the electrolyte does not contain LiI and Li ₂ S impurity phase. As a result, it was found that LiI and Li were mixed alone ₂ After S, the initial effect can be increased from 80.39% to 89.19%, and the curve is likewise curved (arrow) at about 2.1V. But mixed LiI and Li ₂ S is still not comparable to Li _6.8 Si _0.8 As _0.2 S ₅ I lithium supplementing agents LiI and Li generated in situ in electrolyte synthesis process ₂ S exerts its effect, probably due to the mixed LiI and Li ₂ Poor uniformity of S dispersion and large particle size result in slow reaction kinetics and limited capacity. If lithium supplementing agents LiI and Li are used ₂ Li with lower S ratio and slightly lower ionic conductivity _6.5 Si _0.5 As _0.5 S ₅ I, the improvement effect on the first effect and the multiplying power performance is limited.

FIG. 12 shows TiS prepared using different electrolyte materials ₂ Rate performance of solid state batteries. Wherein, tiS ₂ +LPSC of 0.5TiS ₂ +0.5Li ₆ PS ₅ Cl；TiS ₂ +LPSC+Li ₂ S-0.03、TiS ₂ +LPSC+LiI-0.03、TiS ₂ +LPSC+LiI-0.06 is respectively independently added with lithium supplementing agent LiI or Li ₂ 0.5TiS of S ₂ +0.47Li ₆ PS ₅ Cl+0.03Li ₂ S、0.5TiS ₂ +0.47Li ₆ PS ₅ Cl+0.03LiI、0.5TiS ₂ +0.44Li ₆ PS ₅ Cl+0.06LiI；TiS ₂ +LASI-50Si、TiS ₂ +LASI-80Si is the invention with different LiI and Li respectively ₂ Li of S hetero-phase content _6.5 Si _0.5 As _0.5 S ₅ I and Li _6.8 Si _0.8 As _0.2 S ₅ I，Li _6.5 Si _0.5 As _0.5 S ₅ The electrolyte I contains LiI 1.81% and LiI 1.33% by mass respectivelyLi of (2) ₂ S，Li _6.8 Si _0.8 As _0.2 S ₅ I electrolyte contains 2.98% LiI and 2.64% Li, respectively ₂ S, S. The results show that the electrolyte TiS of the invention ₂ +LASI-50Si and TiS ₂ +LASI-80Si, with the increase of M element doping amount, liI or Li ₂ The S miscellaneous content is increased to be less than 3 percent of LiI and Li ₂ The generation of S impurity phase significantly increases the cycle rate performance of the solid electrolyte. Separately adding a certain (3%) of LiI and Li ₂ Li of S lithium supplementing agent ₆ PS ₅ Cl can also improve the rate capability (TiS) ₂ +LPSC+Li ₂ S-0.03、TiS ₂ +LPSC+LiI-0.03), but a higher (6%) level of lithium supplement addition, instead, leads back to a reduction in the rate performance (0.5 TiS) ₂ +0.44Li ₆ PS ₅ Cl+0.06LiI)。

FIG. 13 shows TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Charge and discharge curves for 1 st, 100 th, 200 th, 300 th and 400 th turns of the I/Li-In all-solid-state battery at 1C,30℃. The first cycle charge curve has obvious bending behavior around the 2.2V position, which corresponds to the result of FIG. 11, and illustrates LiI and Li generated in situ ₂ The S-phase plays a capacity contributing role, thereby increasing the first week coulomb efficiency.

FIG. 14 shows TiS prepared from different electrolyte materials ₂ The long cycle performance of the solid-state battery 1C at 30 ℃ for 1000 cycles was compared, and specific values are shown in table 2. Wherein LPSC is Li ₆ PS ₅ Cl, LSPSC is Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 LASI-80Si is Li _6.8 Si _0.8 As _0.2 S ₅ I. The results show that the electrolyte of the invention exhibits higher initial cycle coulombic efficiency, higher specific capacity, and longer cycle life than other electrolyte materials.

TABLE 2 TiS prepared from different electrolyte materials ₂ Long cycle performance contrast for solid state batteries

FIG. 15 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ And the capacity of the I/Li-In all-solid-state battery is obtained by cycling the battery more than 7000 times at 10C and 30 ℃. Specifically, the charge-discharge cycle program was set to charge-discharge cycle at 1C rate for 2 cycles, followed by cycle at 10C rate for 7000 cycles or more, with each 100 cycles (10C) interval, the rate was reduced to 5C cycle for 2 cycles to reduce polarization. It can be seen that after a long cycle of high magnification above 7000 cycles, the capacity is still as high as above 150 mAh/g.

FIG. 16 is TiS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ The rate performance of the I/Li-In all-solid-state battery at 30 ℃ is shown In table 3. Wherein LPSC is Li ₆ PS ₅ Cl, LSPSC is Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 LASI-80Si is Li _6.8 Si _0.8 As _0.2 S ₅ I. The results show that the electrolytes of the present invention exhibit higher specific capacities from 1C, 2C, 5C to 10C relative to other electrolyte materials.

TABLE 3 TiS prepared from different electrolyte materials ₂ Rate performance contrast of solid state battery

FIGS. 17 and 18 show TiS, respectively ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Fast charge and fast discharge and fast charge and slow discharge curves of the I/Li-In all-solid-state battery at 30 ℃. The limit multiplying power of 1C to 100C quick charge and quick discharge can reach 100C, and the limit charging multiplying power of 1C to 200C quick charge and constant 1C multiplying power discharge can reach 200C.

FIG. 19 shows TiS at high loadings ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Charge and discharge curves for 1 st and 40 th turns of the I/Li-In all-solid-state battery, fig. 20 shows TiS at high load ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In all-solid-state battery long cycle stability curve. As can be seen, the active material loading was 31.83mg/cm ² TiS of (C) ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ The specific capacity of the I/Li-In all-solid-state battery can still reach more than 220mAh/g (close to the theoretical specific capacity 239 mAh/g) after 40 circles of charge and discharge at 30 ℃ and constant 0.1C multiplying power, and the battery has excellent long-cycle stability.

FIG. 21 shows TiS at ultra high loadings ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ 0.05C rate charge-discharge curve for I/Li-In all-solid-state battery. Wherein, tiS ₂ The ratio of the active material to the LASI-80Si electrolyte is 1:1, and the active material loading amounts are 44.56mg/cm respectively ² (solid line), 63.66mg/cm ² (dashed line), 95.49mg/cm ² (dot-dash line) and TiS ₂ The ratio of the active material to the LASI-80Si electrolyte is 7:3, and the active material loading is 44.56mg/cm ² (dotted line). It can be seen that the all-solid-state battery of the present invention shows a higher specific capacity even at an ultra-high load.

5、FeS ₂ Solid state battery device performance test as lithium-free positive electrode active material

Fig. 22 and 23 show FeS, respectively ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In and FeS ₂ Charge-discharge curves of 1 st, 2 nd and 5 th turns of the LSPSC/Li-In all-solid-state battery at 0.1C and 30 ℃. LSPSC is Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 . FIG. 22 shows that there is a pronounced bending behavior around the 2.2V position of the first week charging curve, corresponding to in situ hetero-phases LiI and Li ₂ S plays a role in contributing capacity, consistent with the results of fig. 11, thereby improving first week coulomb efficiency; in addition, as the cycle number increases, the capacity exerted by the battery also increases significantly, and FeS is known ₂ The theoretical specific capacity of the lithium ion battery is 894mAh/g, the first-week discharge capacity is only 790mAh/g, and the discharge capacity after 5 circles is higher than the theoretical specific capacityFeS (FeS) ₂ Is a theoretical specific capacity of (c). In contrast, an all-solid-state battery using LSPSCs with lower ionic conductivity and no lithium supplement (fig. 23) was initially less efficient and the capacity was gradually decayed with increasing number of cycles without significant back-up.

FIG. 24 is a FeS prepared from different electrolyte materials ₂ The long cycle performance of the solid-state battery 1C at 30 ℃ for 600 cycles was compared, and specific values are shown in table 4. Wherein the first 5 turns are 0.1C activation process, and LPSC is Li ₆ PS ₅ Cl, LSPSC is Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 LASI-80Si is Li _6.8 Si _0.8 As _0.2 S ₅ I. Likewise, the electrolyte of the present invention exhibits higher initial cycle coulombic efficiency, higher specific capacity, and longer cycle life than other electrolyte materials.

TABLE 4 FeS prepared from different electrolyte materials ₂ Long cycle performance comparative table for solid state battery

FIG. 25 shows FeS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Impedance change before and after cycling of the I/Li-In all-solid-state battery. It can be seen that the impedance of the battery increases little significantly with increasing number of cycles.

FIG. 26 shows FeS produced from different electrolyte materials ₂ The rate performance of the all-solid battery is shown in table 5. Likewise, compared with other electrolytes (LPSC is Li ₆ PS ₅ Cl, LSPSC is Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 ) The electrolyte Li of the invention _6.8 Si _0.8 As _0.2 S ₅ I shows higher specific capacities from 1C, 2C, 5C to 10C. And contains Li ₂ LASI-80Si with higher S and LiI impurity ratio has obvious advantages over LASI-50Si, and the Li in the electrolyte of the invention is verified again ₂ Important roles of S and LiI heterophases.

TABLE 5 FeS prepared from different electrolyte materials ₂ Multiplying power of solid-state battery

FIG. 27 shows a higher load FeS ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ Cycling at 1C rate for I/Li-In all-solid-state batteries. The composite positive electrode comprises FeS in proportion of each component ₂ : LASI-80Si: kb=50:40:10, using 10mg of positive electrode, corresponding to an active material loading of 6.37mg/cm ² The area capacity is 4.77mAh/cm ² FeS (calculated as 750 mAh/g) ₂ the/LASI-80 Si/Li-In all-solid-state battery was charged and discharged at 30℃for 5 cycles at 0.1C rate, and then cycled for 100 cycles at 1C rate while being charged and discharged at LPSC (Li ₆ PS ₅ Cl)，LSPSC(Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 ) As a comparison. It can be seen that FeS under high magnification and high load conditions ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ The I/Li-In all-solid-state battery still exhibits high capacity and long-cycle stability.

FIG. 28 shows FeS at ultra high load ₂ /Li _6.8 Si _0.8 As _0.2 S ₅ I/Li-In all-solid-state battery cycling. The mass of the composite electrode is 50mg, and the active material loading capacity is 31.83mg/cm ² The surface capacity is 23.87mAh/cm ² FeS (calculated as 750 mAh/g) ₂ The capacity of the LASI-80Si/Li-In all-solid-state battery at the 2 nd turn under the multiplying power of 0.1C at 30 ℃ can still reach 550mAh/g.

To examine the electrolyte of the present invention in FeS ₂ The capacity of the positive electrode material for adapting to volume change adopts Li _6.8 Si _0.8 As _0.2 S ₅ The electrolyte I is used as a research sample, and the thickness and the density of the electrolyte I are explored along with the change of pressure, so that the electrolyte I has good deformation property. The specific method comprises the following steps: 100mg of Li is weighed _6.8 Si _0.8 As _0.2 S ₅ I powder is uniformly placed in a stainless steel die with the inner diameter of 10mmIn (a) and (b); placing the die in the center of a press, and applying a pressure of 1t (124.8 MPa) to form electrolyte powder into an electrolyte sheet; measuring the thickness d1 of the electrolyte sheet, and weighing the mass m1 of the electrolyte sheet again, wherein the diameter of the electrolyte sheet is 10mm; the applied pressure was increased from 1t (124.8 MPa) to 3t (374 MPa), 5t (624 MPa), 7t (873 MPa), respectively, and the electrolyte sheet thickness di at the corresponding pressure was measured, and the mass mi (i=1, 2,3, 4) was weighed, and the volume and the density of the electrolyte sheet at the corresponding pressure were calculated from the measured data. The results are shown in Table 6.

TABLE 6 deformation of electrolyte sheets after application of various pressures

Note that: known to have a diameter of 10mm and a true density of 2.215g/cm ³

As can be seen from the test results of Table 6, the electrolyte of the present invention was used in FeS ₂ In the positive electrode material, the volume and the density can change along with the change of the external pressure, and can bear the pressure of up to 7t, which can indicate that the electrolyte has good deformation capability and can buffer FeS in the charge and discharge process ₂ Bringing about a large volume change.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims

1. FeS for battery ₂ Composite positive electrode comprising sulfide solid electrolyte and FeS ₂ A positive electrode active material; the sulfide solid state electrolyte has the following chemical composition: li (Li) _7+y-z M _y As _1-y S _6-z X _z Wherein M is at least one of Si, ge, sn, ti, zr,x is halogen element, z is more than 0 and less than or equal to 2;

the sulfide solid state electrolyte has LiI and Li therein ₂ S impurity phase; liI and Li ₂ The S impurity phase content is respectively below 5%;

in the sulfide solid electrolyte, when M is Si, y=0.3-0.9; when M is Sn, y=0.05 to 0.6; when M is Ge, y=0.1 to 0.6; when M is Ti, y=0.1 to 0.6; when M is Zr, y=0.1 to 0.5.

2. FeS for a battery according to claim 1 ₂ A composite positive electrode characterized in that the sulfide solid state electrolyte has a composition similar to Li _7-z AsS _6-z X _z Wherein X is a halogen element, and z is more than 0 and less than or equal to 2.

3. FeS for a battery according to claim 1 ₂ The composite positive electrode is characterized in that the sulfide solid electrolyte and the cubic system

Li of space group ₆ AsS ₅ The main peaks of I diffraction are consistent, and diffraction peaks are formed at 2 theta = 17.30 DEG + -1 DEG, 24.57 DEG + -1 DEG, 28.90 DEG + -1 DEG, 30.21 DEG + -1 DEG, 43.26 DEG + -1 DEG and 50.38 DEG + -1 deg.

4. FeS for a battery according to claim 1 ₂ A composite positive electrode characterized in that LiI and Li in the sulfide solid state electrolyte ₂ The S impurity phase content is 1% -3% respectively.

5. FeS for a battery according to claim 1 ₂ The composite positive electrode is characterized in that FeS in the composite positive electrode ₂ And conductive carbon in a mass ratio of (2-5): 1, feS ₂ And the ratio of the total mass of the conductive carbon to the mass of the sulfide solid state electrolyte is 1: (0.6-3).

6. FeS for a battery according to claim 1 ₂ A composite positive electrode, characterized in thatIn the composite positive electrode, the conductive carbon is at least one of conductive carbon black, carbon fiber, carbon nanorod or carbon nanotube.

7. FeS for a battery according to claim 1 ₂ The composite positive electrode is characterized in that conductive carbon is ketjen black in the composite positive electrode.

8. FeS for a battery according to claim 1 ₂ A composite positive electrode characterized in that, in the composite positive electrode, an active material FeS ₂ The upper limit of the load is 5mg/cm ² The above.

9. FeS for a battery according to claim 1 ₂ A composite positive electrode characterized in that, in the composite positive electrode, an active material FeS ₂ The upper limit of the load is 6mg/cm ² The above.

10. FeS for a battery according to claim 1 ₂ A composite positive electrode characterized in that, in the composite positive electrode, an active material FeS ₂ The upper limit of the load is 30mg/cm ² The above.

11. An all-solid-state battery device comprising the FeS for a battery according to any one of claims 1-10 ₂ And (5) compounding the positive electrode.

12. The all-solid-state battery device according to claim 11, wherein the negative electrode of the all-solid-state battery device is a lithium-containing negative electrode, including a metallic lithium negative electrode, a lithium alloy negative electrode, and a lithium-carbon composite negative electrode.

13. The all-solid-state battery device according to claim 11, wherein the negative electrode of the all-solid-state battery device is a lithium-indium alloy negative electrode.